Understanding ultrasound physics Exam Review

89. What happens when the power in an beam is unchanged, and at the same time, the beam area doubles? A. doubles B. is halved C. is quartered D. remains the same

divided by beam power is unchanged doubled. Therefore, B. Intensity is equal to power area. In this case, the while the beam area is the beam's intensity is halved. For example, if the original power was 2 watts and the initial beam area was 2 cm?, then the starting intensity was 2 watts divided by 2 cm2, or 1 wattcm2. Now, beam area is doubled, from 2 to 4 cm2. The new intensity is 2 watts divided by 4 cm? or 0.5 watts cm2. The initial intensity was 1, and the final intensity is 0.5 watts/cm2; therefore, the intensity has been halved.

411. What is a typical pulser output voltage that excites a piezoelectric crystal? A. 0.1 volts B. 500 millivolts C. 40 volts D. 10 microvolts

of an ultrasound system, used to excite the C. The signal typically produced by the pulser transducers's piezoelectric crystals, may be in the range of tens of volts.

554. Which process causes mirror image artifact? A. reflection B. refraction C. propagation speed error D. attenuation

A. Mirror imaging is created by an unexpected and uncorrected reflection of the ultrasound pulse off a strong reflector.

28. Sound is best described as ______ A. a series of compressions and rarefactions B. a transverse wave C. a wave that humans can hear D. an oblique displacement of acoustic energy

A. Sound is composed of a series of Molecules in the compressions and rarefactions. medium are alternately together (compressed) and stretched apart squeezed (rarefied).

210. The attenuation of an acoustic wave traveling through bone is ____ its attenuation through soft tissue. A. greater than B. less than C. equal to

A. The attenuation of ultrasound in bone is greater than its attenuation in soft tissue.

140. What determines the pulse duration? A. the source of the wave B. the medium in which the pulse travels C. both A and B D. neither A nor B

A. The pulse duration is the actual time that a transducer is creating one sound pulse and is determined by the ultrasound system. Pulse duration does not include the listening time.

490. What happens to venous flow in the legs when an individual exhales? A. increases B. decreases C. remains the same

A. Venous flow in the legs increases when an individual exhales.

557. Which artifact is created by sound moving A. through a medium with a propagation speed less than soft tissue? A. vertical misregistration B. horizontal misregistration C. lateral resolution D. ring down

A. Vertical misregistration occurs when pulses do not travel at the speed of sound in soft tissue (1,540 m/sec.) The reflections on the image will be placed at depths deeper than the actual position of the reflector in the body.

189. What is the decibel representation when an acoustic signal is amplified? A. positive B. negative C. equal to zero

A. When a signal is amplified, its magnitude increases and it becomes stronger. In decibel notation, an increase in signal strength is described with positive decibels. Positive dB means "getting bigger."

58. What establishes the frequency of an ultrasound wave? A. the transducer B. the medium through which the sound travels C. both A and B D. neither choice A nor B

A. When created by a transducer, an ultrasound wave has a specific frequency. The frequency is not determined by the medium through which the sound travels. Only the sound source (the transducer) establishes the wave's frequency.

450. Which of these is a binary number? A. 12211221 B. 10000000 C. 98765432 D. 01010102

B. A binary number is a string of zeroes and ones only. Binary numbers are based on two choices. Digital numbers are based on ten choices.

24. As sound travels through a medium, what term describes the effects of the medium on the sound wave? A. toxic effects B. acoustic propagation properties C. bioeffects D. transmission properties

B. Acoustic propagation properties describe the effects of the medium on the wave traveling through it. Acoustic means "sound." Propagation means "to travel"

167. What are the units of pulse repetition frequency (PRF)? A. seconds B. 1/seconds C. mm/us D. seconds?

B. Pulse repetition frequency is the number of pulses that are produced by the ultrasound system in one second. PRF has the same units as frequency, and these units are hertz, Hz, or per second.

124. Compared to soft tissue, the speed of an acoustic wave through lung tissue is _____ A. faster B. slower C. equal D. cannot be determined

B. The speed of sound in lung tissue is slower than in soft tissue. Sound travels at speeds in the range of 0.5 to 1.0 km/sec in lung tissue.

216. To calculate the acoustic impedance of a medium, one should ____ the ____ by the ____ A. divide, propagation speed, density B. multiply, density, propagation speed C. divide, density, propagation speed D. multiply, stiffness, density

B. To obtain the value of acoustic impedance, multiply the density of a medium by its propagation speed.

192. The power in a wave is increased to ten times its original value. How many decibels describe this change? А. З В. 6 С. 10 D. 20

C. An increase of ten times the original power of a wave is reported as +10 dB.

220. Which of the following describes an angle of 123 A. orthogonal B. acute C. obtuse D. normal

C. Any angle that measures greater than 90° is an obtuse angle.

616. Research has indicated that cavitation A. never occurs B. cannot occur with long pulses C. can be lethal to living things D. effects are purely theoretical

C. Cavitation resulting from ultrasound exposure is lethal to the fruit fly. Cavitation has the potential for significant and harmful bioeffects under specific circumstances.

324. Two ultrasound systems are identical except for the pulse repetition period (PRP) of the emitted pulse. Which system will have the deeper focus? A. the system with the lower PRP B. the system with the higher PRP C. their foci will be at the same depth

C. Changes in the pulse repetition period do not affect the depth of the focus. The frequency of the sound and the piezoelectric crystal's diameter help to determine the focal depth.

513. All of the following are associated with a CW Doppler transducer except:. A. narrow bandwidth B. increased sensitivity C. backing material D. high Q-factor

C. Compared to pulsed transducers, continuous wave transducers do not use backing material. As a result, CW has increased sensitivity and is more able to detect small Doppler shifts.

424. Which receiver function creates an image of comparable brightness from top to bottom? A. receiver gain B. output power C. swept-gain compensation

C. Compensation establishes images of uniform brightness from top to bottom. Compensation adjusts for the attenuation of sound with increasing path length.

551. Unexpectedly low attenuation results in which of the artifacts listed below? A. refraction B. attenuation C. enhancement D. shadowing

C. Enhancement occurs with unexpectedly low rates of attenuation.

491. The Doppler effect is observed as a change in ______ and has units of _____ A. amplitude, watts B. power, watts C. frequency, per second D. wavelength, millimeters

C. The Doppler effect is a change in a wave's frequency when the sound source and the receiver of the sound are in motion relative to each other. Frequency may be expressed as hertz, Hz, cycles/sec, or per second.

138. Two sound waves with frequencies of 5 and 3 MHz travel to a depth and then reflect back to the of 8 cm in a medium surface of the body. Which arrives first at the surface of the body? acoustic wave A. the 5 MHz wave B. the 3 MHz wave C. neither D. cannot be determined

C. They both travel at the same speed and reach the surface of the body at exactly the same time. All sound waves, regardless of their features, travel at the same speed in a specific medium. The fact that these waves have different frequencies is irrelevant.

79. Mathematically, when a number is squared, the number is multiplied by: A. 2 B. 0.5 C. itself D. 1.5

C. To square a number means to multiply the number by itself. Hence, the term "five squared" means 5 times 5, or 25. Ten squared is 10 times 10, or 100.

418. Which of the following tasks is not performed by the receiver of an ultrasound system? (More than one answer may be correct.) A. rectification B. smoothing C. compression D. degaussing

D. Degaussing is the only task listed above that is not performed by the system's receiver.

433. Which of the following best describes the demodulation process? A. changing the gray scale of an image B. changing the frequency of a signal C. changing the form of a sound pulse D. changing an electrical signal's form

D. Demodulation alters the form or shape of electrical signals within the receiver.

397. Which two controls determine a system's temporal resolution? A. frame rate and sector size B. focal zones and sector depth C. propagation speed and frame rate D. depth of view and pulses per image

D. Depth of view and number of pulses per image determine the frame rate (and temporal resolution) of an ultrasound system. The sonographer can alter both of these factors.

564. Grating lobes are most common with which type of transducer technology? A. annular array B. continuous wave C. mechanical scanners D. linear arrays

D. Grating lobe artifacts are associated with linear array transducers.

327. Huygens' Principle is based on. A. refraction B. constructive indices C. transverse waves D. interference

D. Huygens' Principle explains the difference between the beam shape from tiny pieces of PZT and disc crystals of a larger dimension. The hourglass-shaped beam is caused by the interference of spherical waves.

580. Which artifact is not related to the unexpected reflection of an acoustic wave? A. multipath B. comet tail C. reverberation D. lateral resolution

D. Lateral resolution is an artifact that is not associated with abnormal reflection. Lateral resolution artifacts are related to beam diameter.

622. Epidemiologic studies of in utero exposure to ultrasound have included all of the following findings except. A. birth weight B. cancer C. structural abnormalities D. none of the above

D. Many epidemiologic studies on the effects of ultrasound have been reported. End points of birth weight, cancer, and structural abnormalities have all been studied. There is no correlation between ultrasound exposure and these events.

253. Sound propagates from one medium with a density of 1.16 kg/m to a second medium with a density of 1.02 kg/m3, If the angle of transmission is 49°, what can be correctly stated about the angle of incidence? A. it is less than 49° B. it is equal to 49° C. it is greater than 49° D. it cannot be determined

D. No definite statement can be made about propagation speeds of the media are unknown, we cannot make any conclusions about the incident angle. The density of a medium helps to determine the propagation speed, but knowledge of only the density without knowledge of a tissue's stiffness is insufficient to deduce which of the two media has a higher propagation speed.

323. As sound travels deeply into the far zone, the beam diverges, or spreads will result in the greatest beam divergence out. Which deep in the far zone? A. small diameter, high frequency B. high frequency, large diameter C. large diameter, low frequency D. low frequency, small diameter

D. Small diameter crystals of low frequency tend to produce sound beams that diverge most in the deep far zone.

244. Which of the following best describes the process described by Snell's law? A. reflection with normal incidence B. reflection with oblique incidence C. transmission with normal incidence D. transmission with oblique incidence

D. Snell's Law defines the physics of refraction. Refraction describes the behavior of sound beams that transmit after striking a boundary obliquely. Refraction is "transmission with a bend."

27. Which of the following describes the characteristics of a sound wave? A. longitudinal, non-mechanical B. mechanical, transverse C. transverse, acoustic D. mechanical, longitudinal

D. Sound is a mechanical, longitudinal wave. A mechanical wave, such as sound, actually imparts energy to the molecules of the medium through which it travels. The molecules of the medium vibrate, striking their neighbors, which in turn vibrate. This chain reaction results in the acoustic energy traveling through the medium.

541. Which of the following is not a potential cause of artifact in diagnostic imaging? A. operator error B. equipment malfunction C. patient motion D. ultrasound physics E. none of the above

E. The four choices, A through D, represent the primary explanations of artifacts commonly seen in diagnostic ultrasound.

56. Which of the following cannot be considered a unit of frequency? A. per day B. cycles/sec C. Hz D. hertz E. cycles

E. The term cycles informs us of the number of events, but does not inform us of the duration of time required for those events to occur.

607. True or False? A bioeffect identified through the mechanistic approach rather than the empirical approach is more likely to have clinical significance.

False. A bioeffect identified only by a mechanistic methodology is not likely to have greater clinical significance than a bioeffect identified empirically. The most clinically relevant bioeffect would be one identified both mechanistically and empirically.

267. True or False? The more cycles there are in a pulse, the greater the detail that will be visualized in the ultrasound scan.

False. A pulse with many cycles is long. Systems with long pulses cannot produce images with fine detail. When many cycles are in a pulse, less detail is presented on the scans. Transducers with pulses composed of more cycles can be described as "more ringing."

410. True or False? The pulser of a mechanical the pulser of a phased array transducer. transducer is typically more complex than

False. A single electrical signal excites the PZT are excited nearly simultaneously to phased array technology, many crystals crystal of a mechanical transducer. With produce an acoustic pulse. Phased array focus sound beams. Thus, systems use this technique to steer and phased array systems have more complex pulsers.

144. A sonographer can adjust the duration of an acoustic pulse since it depends upon the maximum imaging depth. T/F

False. A sonographer cannot change the pulse duration. It has a constant value, and is not dependent on imaging depth.

143. A sonographer can adjust the duration of an acoustic pulse since it depends upon the pulse's propagation speed. T/F

False. A sonographer cannot change the pulse duration. It is a fixed feature of the transducer and ultrasound system. It does not depend upon propagation speed.

519. True or False? The higher the pulse repetition frequency of a Doppler exam, the more likely aliasing is to occur.

False. Aliasing is less likely to occur with high PRF. Aliasing occurs when the Doppler frequency exceeds half of the PRF. If the PRF is high, it is less likely that the Doppler shift will reach a value that is greater than half the PRF.

583. True Fals All artifacts are errors in imaging that do not represent the true anatomy of the imaged organ. Therefore, they are all undesirable and should be eliminated if possible.

False. All artifacts are indeed errors in imaging. However, they may provide useful information. An artifact can provide insight into the physical characteristics of a structure, and help the clinician make a definitive diagnosis. Eliminating all artifacts may exclude important information from appearing on the exam.

109. The ultrasound wave travels much faster than the audible wave. T/F

False. All sound waves, regardless of their frequencies, travel at exactly the same speed in a particular medium. Both waves propagate at the same speed. In soft tissue, sound propagates at a speed of 1,540 m/sec.

59. True or False? With standard ultrasound pulses, the frequency of the ultrasound changes significantly as the wave propagates through the body.

False. In diagnostic imaging, the frequency of the sound wave generally remains constant and does not routinely change as the sound propagates through the body. Slight changes in frequency occur when sound strikes moving structures. This forms the basis for Doppler ultrasonography

317. The thicker a continuous wave transducer's piezoelectric crystal, the longer the near zone length is.

False. Increasing the thickness of a piezoelectric crystal does not alter the length of the near zone of a continuous wave ultrasound beam.

313. The near zone is the only region where the diameter of the sound beam decreases as depth increases.

True. In the near zone, the sound beam actually tapers down until it reaches the focus. At depths greater than the near zone, the beam diverges, or spreads out.

526. True or False? Color flow Doppler exams tend to have lower temporal resolution than traditional two-dimensional, real-time imaging.

True. Temporal resolution is the ability to accurately locate moving structures. Color flow technology reduces the number of pictures produced each second. Color flow Doppler suffers from poor temporal resolution because of this low frame rate.

518. True or False? In a pulsed Doppler exam, the use of a higher transducer frequency increases the likelihood that aliasing will appear.

True. The Doppler shift depends on the frequency of the incident sound wave. The statement is true because a higher emitted frequency produces a higher Doppler shift, and a high Doppler shift is more likely to alias.

289. The backing material decreases the quality factor. T/F

True. The backing material that is attached to the back of the piezoelectric crystal will decrease the transducer's Q-factor.

566. True or False? Grating lobes are a result of substantial acoustic energy directed outward from a linear array transducer, but not along the main axis of the sound beam.

True. This is the exact definition of a grating lobe.

606. True or False? The empirical approach to the study of bioeffects and ultrasonic safety surveys data involves finding a relationship between exposure and toxic effects.

investigators look for a relationship True. An empirical study is one where between two events without necessarily understanding the fundamental cause and effect that relates the two factors. An example of an empirical study is examining the possibility that changes in fetal birth weight and ultrasound exposure are associated. Note that no specific mechanism for this relationship is postulated. The empirical approach is considered "exposure-response.

74. Which of the following are acceptable units for the amplitude of an acoustic wave? (More than one answer may be correct.) A. cm B. pascals C. gauss D. watts

A and B. The acoustic variables are pressure, density, and particle motion. The units of acoustic wave amplitude are cm for particle motion and pascals for pressure.

596. Which two of the following devices convert ultrasound energy into heat? A. a calorimeter B. a thermocouple C. a hydrophone D. a Schlieren

A and B. The calorimeter and the thermocouple are two devices that use the principle of converting acoustic energy into thermal energy to estimate the energy in a sound beam. A hydrophone converts acoustic energy into pressure. A Schlieren uses the interaction of sound and light to evaluate a sound beam profile.

53. Which of the following units are appropriate to describe the period of an acoustic wave? (More than one answer may be correct.) A. minutes B. microseconds C. meters D. mm/us E. cubic centimeters

A and B. The period of a wave is defined as the time that elapses as a wave oscillates through a single cycle. The units for period must be a measure of time, such as minutes or seconds. A and B are units of time. The incorrect selections C, D, and E are units of distance, speed, and volume, respectively.

156. A sonographer adjusts the maximum imaging depth of an ultrasound system. Which of the following also changes? (More than one answer may be correct.) A. pulse repetition period B. wavelength C. pulse repetition frequency D. frequency

A and C. As imaging depth is altered, the PRF and pulse repetition period change. The wavelength and frequency remain describe the constant, as these terms attributes of a single cycle and are not affected by alterations in within the pulse, imaging depth.

432. The process of demodulation incorporates which of the following tasks? (More than one answer may be correct.) A. smoothing B. amplification C. rectification D. decompression

A and C. Demodulation is a two-step process. These steps are rectification and smoothing.

278. The main purposes of a transducer's case are (more than one may be correct): A. to protect the patient from shock B. to protect the patient from heat C. to protect the internal components of the transducer D. to protect the patient from radiation

A and C. The case of a transducer protects the patient from electrical shock and also protects the internal components of the transducer from damage.

417. Which of these functions are performed by the receiver of an ultrasound system? (More than one answer may be correct.) A. amplification B. threshold C. compensation D. demodulation

A, B, C, and D. All of the functions listed above are performed by the ultrasound system's receiver,

38. What are the units of a pressure measurement of an acoustic wave? (More than one answer may be correct.) A. atmospheres (atm) B. pascals (Pa) C. millimeters of mercury (mm Hg) D. pounds sq. inch (Ibin?)

A, B, C, and D. All of these terms are appropriate to represent pressure (just as weight can be reported with units of pounds, ounces, tons, or grams). However, the pressure of sound waves is most often reported in units of pascals.

540. Acoustic artifacts include: (More than one answer may be correct.) A. images of reflectors in an inappropriate position B. images of reflectors with improper shape C. images of reflectors with incorrect brightness D. images that do not correspond to anatomical structures

A, B, C, and D. An artifact is an error in imaging. All of the choices indicate a type of error, and therefore, are artifacts.

118. Propagation speed can be correctly recorded with which of the following units? (More than one may be correct.) A. miles per hour B. mm/mseç C. km/sec D. inches per year

A, B, C, and D. Speed is recorded as a distance per unit of time, such as miles per hour, or feet/sec. Any relationship of distance per time is an acceptable answer.

593. Which of the following statements are true of a tissue equivalent phantom? (More than one answer may be correct.) A. it has the same propagation speed as that of soft tissue B. it attenuates ultrasound at a rate similar to soft tissue C. embedded in it are solid masses and cystic structures D. it is the device of choice for quality assurance studies

A, B, C, and D. Tissue equivalent phantoms have characteristics that allow for the optimal evaluation of ultrasound systems. They are quite similar to soft tissue and are the preferred device to evaluate system performance.

26. Which of the following types of waves do not require a medium in order to propagate? (More than one answer may be correct.) A. light B. heat C. sound D. television

A, B, and D. Sound cannot travel through a vacuim; it requires a medium in order to propate. Other waveforms such as light, hea and TV waves are capable of traveling through a vacuum.

179. While using the same ultrasound machine and transducer, which of the following can a sonographer alter? (More than one answer may be correct.) A. pulse repetition period B. PRF C. frequency D. duty cycle E. pulse duration

A, B, and D. While adjusting the desired maximum imaging depth in an exam, the sonographer adjusts the pulse repetition period and the PRF. The duty factor is also altered. Unlike choices A, B and D, the frequency of the ultrasound and the pulse duration are fixed once a transducer is selected. These parameters cannot be altered.

388. What is the advantage of using a 12 dimensional array transducer? A. improved elevational resolution B. improved lateral resolution C. improved axial resolution D. improved temporal resolution

A. A 1½ dimensional array transducer creates a thinner imaging plane. Thin imaging planes have superior elevational, or slice thickness, resolution.

196. What does a 3 dB change in a value intensity mean? A. the value has doubled B. the value has tripled C. the value has increased 30% D. the value has increased ten times

A. A 3 decibel change in the intensity indicates that the value has doubled.

514. The information that is processed by a standard duplex ultrasound system includes all of the following except. A. attenuation B. amplitude C. frequency D. time of arrival

A. A duplex ultrasound system provides both image and Doppler information. Included in the data processing is the amplitude of the reflected signal, its time of arrival, and its frequency content. The pulse's attenuation is not recorded or processed.

520. A system has three transducers with frequencies of 7.5 MHz, 5 MHz, and 3.25 MHz. Aliasing appears while using the 5.0 MHz transducer during a pulsed Doppler exam. What should the sonographer do? A. use the 3.25 MHz transducer B. use the 7.5 MHz transducer C. nothing; the other transducers do not provide solutions to the problem

A. A transducer producing ultrasound at a lower frequency will produce smaller Doppler shifts, which are less likely to alias. Thus, one potential solution for aliasing is to use a lower frequency transducer.

352. Which imaging technique usually displays a single jagged line of varying heights? A. A-mode B. B-mode C. C-mode D. I-mode

A. A-mode displays reflected echoes as spikes of varying height. Echo amplitude appears on the y-axis, and reflector depth on the x-axis. The spike's location on the x-axis is based on the pulse's time of flight. The height of the peak is determined by the reflection's strength. Stronger reflections create higher spikes.

414. Which one of the following does not belong in the group below? A. receiver gain B. energy output C. pulser power D. acoustic power E. transmitter output F. output gain

A. All of the terms listed as answers, except for choice A, refer to the strength of the signal produced by the transducer and transmitted into the body. Receiver gain is not synonymous with the other five choices.

81. The amplitude of an acoustic wave decreases from 27 pascals to 9 pascals. If the initial power in the wave was 27 watts, what is the wave's final power? A. 3 watts B. 9 watts C. 1 watt D. none of the above

A. Alterations in a wave's power are proportional to changes in its amplitude squared. The power is reduced to one-third of its previous value (from 27 to 9 pascals). One-third squared equals one-ninth. Thus, only one-ninth of the wave's original power remains. The initial power in the wave was 27 watts, one-ninth of that is 27/9, or 3 watts.

73. As an ultrasound wave travels through the body, its amplitude usually: A. decreases B. increases C. remains the same D. cannot be determined

A. As a sound wave travels in the body, its strength or amplitude diminishes. This process is called attenuation. We experience attenuation when walking away from a person who is speaking. The further away we are from a speaker, the weaker that person's voice becomes.

77. Typically, as an ultrasound wave travels through soft tissue, the power of the wave: A. decreases B. increases C. remains the same

A. As a sound wave travels through the body, its power diminishes. This process is called attenuation. Amplitude and power are boih measures of the strength of an acoustic wave, and tend to decrease as sound travels.

88. What are the units of the transmitted intensity of a sound wave? A. W/cm? B. watts C. dB D. none; it is unitless

A. As sound propagates, one of the ways to measure its strength is to record its intensity. The intensity of the part of a beam that continues to propagate in the forward direction as it reaches a boundary is called the transmitted intensity. It is reported in units w/cm2.

258. Axial resolution describes the accuracy related to visualizing two structures that are _____ to a sound beam's main axis. A. parallel B. perpendicular C. oblique D. normal

A. Axial resolution is related to structures that are parallel to the beam's main axis. In other words, the structures are arranged front to back.

478. What is the primary reason blood moves from one location to another? A. energy gradient B. anemia C. pressure gradient D. systole E. friction

A. Blood flows from one location to another when an energy gradient exists. Blood moves from regions of higher energy to regions of lower energy. Although choice C, pressure gradient, is attractive, it is not the best answer.

585. What is a comet tail artifact's fundamental mechanism of formation? A. reflection B. rarefaction C. refraction D. attenuation

A. Comet tail artifacts appear on an image as a result of numerous reflections between two closely spaced reflectors.

511. All of the following are related to dedicated continuous wave Doppler transducers except A. wide bandwidth B. high quality factor C. higher sensitivity D. range ambiguity

A. Continuous wave transducers have a narrow bandwidth. Backing material in pulsed wave transducers creates a wide bandwidth. Since dedicated continuous wave transducers do not use backing material, they have a narrow bandwidth.

390. What is the use of a greater number of channels to receive echoes from ever increasing depths called? A. dynamic aperture B. apodization C. dynamic frequency tuning D. subdicing

A. Dynamic aperture is a technique of receive focusing that uses fewer crystals to identify echoes from superficial depths and many more crystals to monitor echoes from greater depths. Dynamic aperture is also known as variable aperture.

589. What is true of acoustic speckle? A. its effects are mild and it tends to slightly degrade images B. it is a rare artifact that does not occur in real-time imaging C. its effects are dramatic D. it is eliminated with apolarization

A. Even though it does not accurately represent reflectors in the medium, acoustic speckle is often considered "tissue texture." It tends to contribute to overall image degradation.

344. All of the following occur with focusing except. A. lower intensity at the focus B. shorter near zone length C. more compact focal zone D. smaller diameter beam diameter at the end of the near zone

A. Focusing does not lower the beam's intensity at the focus. With focusing, the near zone is shallower, the focal zone is smaller, and the beam is narrower at the focus.

341. Which of the following techniques is external focusing? A. lens B. curved crystal C. electronic

A. Focusing with a lens is known as external focusing.

295. All of the following are true about transducers except. A. it is necessary to sterilize transducers before use B. most transducers simply require disinfection as they do not penetrate mucous membranes C. sterilization could depolarize PZT D. they are unlikely to transmit infection

A. Generally, it is unnecessary to sterilize most ultrasound transducers since they do not penetrate mucous membranes. Typically, simple disinfection is all that is needed.

524. Which of the following determines the gray scale in a Doppler spectrum? A. number of reflectors B. velocity C. frequency shift D. laminar flow

A. Gray scale in a Doppler spectrum is related to the number of red blood cells creating the reflection.

326. Which of the following explains the difference in sound beam shape created by a disc-shaped crystal from that of a small chip of PZT? A. Huygens' Principle B. Snell's Law C. Bernoulli's Law D. Murphy's Law

A. Huygens' Principle explains the difference between the beam shape from tiny chips of PZT and disc crystals of a larger dimension.

483. The arterial blood pressure of a standing individual is 120 mmHg. What is the hydrostatic pressure at the subject's ankle? A. 100 mmHg B. 0 mmHg C. 40 mmHg D. -100 mmHg E. -120 mmHg

A. Hydrostatic pressure is related to the difference between heart level and the site of measurement. Since the ankle is substantially lower than heart level, the hydrostatic pressure is 100 mmHg.

254. How long does it take for sound to make a round trip to and from the skin's surface to a reflector depth of 1 cm in soft tissue? A. 13 us B. 150 ms C. 15 us D. 2 seconds

A. In soft tissue, sound can travel to and return from a depth of 1 cm (a total distance of 2 cm) in 13 microseconds (13 millionths of a second).

601. Some ultrasonic bioeffects studies are performed in vivo. What is the meaning of the term in vivo? A. observable in a living body B. observations based on an experiment C. discernible in a test tube D. estimated in a computer simulation

A. In vivo observations are made in a living body. For example, increased tissue temperatures in patients following exposure to ultrasound are considered in vivo observations.

396. Which two factors determine temporal resolution? A. speed of sound and depth of view B. pixel size and sector size C. focal zones and sector depth D. propagation speed and frame rate

A. Of the 4 choices, propagation speed and depth of view have the greatest effect upon frame rate and temporal resolution. Frame rate is high with shallow imaging. Frame rate is high when sound travels quickly in a medium.

467. Which of the following components typically has the lowest dynamic range? A. display B. pulser C. amplifier D. demodulator

A. Of the four choices, the component of an ultrasound system with the lowest dynamic range is the display.

301. Which properties of the piezoelectric crystal of an imaging transducer result in the highest emitted acoustic wave frequency? A. thin, high propagation speed B. thick, slow propagation speed C. thin, slow propagation speed D. none of the above

A. Only pulsed wave transducers can create images. The crystal's thickness and propagation speed determine the frequency of sound created by these transducers. Highest frequency sound is created by thin crystals in which sound travels quickly.

477. Which of the following is not associated with turbulent flow? A. parabolic B. eddy C. vortex D. swirling E. spectral broadening

A. Parabolic flow is a bullet-shaped flow pattern associated with laminar flow. The remaining terms, B, C, D, and E are all related to turbulent flow.

269. Which transducer has the best axial resolution? A. 2 cycles/pulse, 4 MHz B. 4 cycles/pulse, 4 MHz C. 4 cycles/pulse, 2 MHz D. 2 cycles/pulse, 2 MHz

A. Pulses with the fewest cycles and the highest frequency have the best axial resolution.

462. All of the following are true of read zoom except. A. preprocessing function of a receiver B. same number of pixels are in the original ROI and the zoomed image C. on the screen, the pixels in the zoomed image are larger than those in the ROI D. the same number of ultrasound pulses are used to create the original ROI and the zoomed image

A. Read zoom is a postprocessing function of the receiver. The data originally in the region of interest (ROI), before zoom, remains intact. New information is not acquired.

240. An ultrasound wave strikes an interface between two media at a 90° angle. The propagation speeds of the media are identical. However, the densities of the media are different. Which is true? A. reflection will definitely occur B. reflection will definitely not occur C. refraction may occur D. none of the above

A. Reflection will definitely occur. With normal incidence, reflection will occur when the impedances of the media on either side of the boundary are different from each other. In this example, the densities of the media are different while their propagation speeds are the same. Since impedance is propagation speed multiplied by density, it follows that the acoustic impedances of the media bordering the interface are indeed different. Reflection will occur.

543. Six distinct, equally spaced reflections appear on an image at ever increasing depths. What type of artifact is this? A. reverberation B. ring down C. mirror imaging D. longitudinal resolution

A. Reverberations are multiple, equally spaced reflections.

565. Grating lobes are produced by the same mechanism as which other artifact? A. side lobes B. reverberation C. transaxial lobes D. acoustic speckle

A. Side lobes and grating lobes are similar in that they represent acoustic energy transmission in a direction other than the main axis of an acoustic beam.

155. On what does the pulse repetition period depend? A. the source of the sound wave B. the medium through which the pulse travels C. both A and B D. neither A nor B

A. Similar to the PRF, the pulse repetition period depends only on the ultrasound system. The pulse repetition period is the time from the start of one pulse to the start of the next pulse and includes the pulse duration and the receiving time. When the sonographer adjusts the depth of view, the pulse repetition period is altered. To be more exact, the listening time is lengthened with deeper imaging and shortened with shallower imaging.

573. How does slice thickness artifact commonly express itself? A. fill in of cystic structures B. improper brightness of reflectors C. absence of reflectorsob D. strong linear echoes

A. Slice thickness artifact results in reflections placed on the image that do not correlate with the anatomical position of the reflector. Therefore, anechoic structures in the imaging plane are filled in with echoes from structures above or below the image slice.

135. The characteristics of four media are described below. Which of the media has the slowest propagation speed? A. high density and high elasticity B. low density and high stiffness C. low stiffness and low density D. low compressibility and low stiffness

A. Speed is determined by density and stiffness of a medium (the opposite of stiffness is elasticity). When a medium has high elasticity, its speed is slow. A medium with a high density also has a slow speed. The medium described in choice A has the lowest propagation speed.

579. Two small cysts, positioned perpendicular to the main axis of a sound beam, are 2.4 mm apart. What determines whether they appear as two distinct images on the system's display? A. the beam width B. the pulse length C. the PRF D. the TGC

A. The ability to correctly image structures that lie close to each other in a direction perpendicular to the main axis of the ultrasound beam is called lateral resolution. Lateral resolution is primarily determined by the width of the acoustic pulse.

449. What is the smallest amount of digital storage called? A. bit B. byte С. pіхel D. fractel

A. The bit is the smallest amount of digital storage or computer memory. The term bit is derived from the words "binary digit." A combination of eight bits makes a byte. Computer memory is called random access memory, or RAM.

488. What happens to the diaphragm when an individual breathes out? A. it ascends into the thorax B. it descends into the abdomen

A. The diaphragm moves upward into the chest cavity (the thorax) when a subject exhales.

281. The impedance of a transducer's matching layer is 2.6 MRayls and the impedance of the piezoelectric crystal is 3.4 MRayls. If this is assumed to be a good imaging system, what is the best estimate for the impedance of the skin? A. 1.5 MRayls B. 3.8 MRayls C. 3.4 MRayls D. 2.8 MRayls

A. The impedance of a transducer's matching layer should be between the impedance of skin and the impedance of the piezoelectric crystal.

71. What determines the initial amplitude of an ultrasound wave? A. the transducer B. the medium through which the sound travels C. both A and B D. neither choice A nor B

A. The initial strength or amplitude of a sound wave is determined by the vibration of the piezoelectric crystal in the transducer. The greater the vibration of the crystal, the larger the amplitude of the ultrasound wave.

90. What happens to an acoustic beam's intensity when the power in the beam increases by 25% while the cross- sectional area of the beam remains the same? butigmA A. it increases by 25% B. increases by 75% C. it increases by 50% D. decreases by 25%

A. The intensity is equal to the power divided by the beam area. If the power increases by 25% while the beam's area is unchanged, then the intensity is also increased by 25%.

226. What are the units of the intensity reflection coefficient? A. none B. W/cm? C. watts D. dB

A. The intensity reflection coefficient is defined as the percentage or proportion of an ultrasound beam's intensity that is reflected as the sound wave strikes a boundary between two media. The intensity reflection coefficient is reported as percentage and therefore is unitless.

329. The lateral resolution of an ultrasound system is primarily determined by the. A. width of the sound pulse B. length of the ultrasound pulse C. duration of the sound pulse D. none of the above

A. The lateral resolution achieved by an imaging system is approximately equal to the width of the ultrasound pulse.

609. Which of the following terms best describes the mechanistic investigation of bioeffects? A. cause-effect B. exposure-response C. cause-response D. exposure-cure

A. The mechanistic approach to the study of bioeffects is properly called cause and effect. For example, a researcher might propose that vibration causes harmful bioeffects and then conducts research to see whether this is indeed the case.

46. A particle within a transverse wave is traveling vertically. What is the direction of the wave's propagation? A. horizontal B. vertical C. diagonal; both horizontal and vertical D. cannot be determined

A. The particles within a transverse wave travel in a direction that is perpendicular to the direction of propagation of the wave. If a transverse wave is traveling vertically, the particles in the wave are traveling horizontally. A water wave is a primarily a transverse wave. The wave propagates sideways along the surface of the water, while a ball floating on top of the water moves up and down as the wave passes.

369. The pattern of electrical signals exciting the piezoelectric crystals of a linear phased array transducer A. typically changes from one acoustic pulse to the next B. changes every fourth or fifth acoustic pulse C. changes only when the maximum imaging depth changes D. none of the above

A. The pattern of the electrical signals that excite the PZT crystals of a linear phased array transducer changes from one pulse to the next. The electrical patterns determine the direction and focusing of each acoustic pulse. Each sound wave is directed in a slightly different direction to create a two-dimensional imaging plane. Thus, the electrical signals vary for each acoustic pulse. The electronics that creates the varying patterns is called the beam former.

445. What happens to a digital image when the pixel density increases? A. spatial detail improves B. temporal resolution increases C. the field of view expands D. there are more shades of gray

A. The pixel density, the number of pixels per inch, determines the detail that a digital picture can illustrate. With greater pixel density, spatial detail improves. Alternatively, the image has less detail with fewer pixels per inch.

468. Why is it necessary for the receiver to perform compression on the electrical signals that it processes? A. the dynamic range of the system's electronics is less than the dynamic range of the received sound reflection B. the display's dynamic range exceeds the transducer's dynamic range C. the dynamic range of the receiver is less than the dynamic range of the image processor D. the dynamic range of the display exceeds the dynamic range of all other components of the ultrasound system.

A. The process of compression decreases the dynamic range of a signal. Ultrasound systems compress signals because the dynamic range of the reflected signals received by the transducers is far greater than the dynamic range of any of the other components of the system. Thus, compression matches the dynamic range of the signal to the dynamic range of the system's electrical components.

123. The speed of sound traveling through bone is _____ soft tissue. A. higher than B. lower than C. equal to D. cannot be determined

A. The propagation speed of sound in bone is higher than in soft tissue. Sound travels at a speed of 3 to 5 km/sec in bone. This is two to three times faster than soft tissue.

142. The pulse duration is expressed in the same units as the ____ A. period B. PRF C. wavelength D. density

A. The pulse duration and the period are measured in units of time, such as seconds, minutes, or hours. PRF has units of hertz. Wavelength has units of distance. Density has units of mass per volume.

168. The pulse repetition frequency of ultrasound produced by a transducer typical of diagnostic imaging systems ______ A. can be changed by the sonographer B. depends on the medium through which the sound travels C. is unchanged as long as the same ultrasound system is used D. has nothing to do with clinical imaging

A. The pulse repetition frequency (PRF) is inversely related to the maximum imaging depth that is achieved during an exam. As the sonographer increases the maximum imaging depth, the PRF must decrease. This occurs because the transducer must wait a longer time for echoes to return from deeper depths. Sonographers, therefore, alter the PRF when they adjust the maximum imaging depth.

187. Which of the following reports the relative strength of an ultrasound wave? A. decibels B. watts C. W/cm2 D. pascals

A. The relative strength of a sound beam may be reported in decibels. The term "relative" indicates a comparison between two values, such as a beam has decreased in strength by 50%. Choices B, C. and D are not comparisons, but absolute measurements.

444. Two digital scan converters are undergoing evaluation. Both produce images of the same size. System A has 1,000,000 pixels, with 10 bits assigned to each. System B has 250,000 pixels, with 12 bits assigned to each. Which system is more likely to have the capability to display very small details in an image? A. System A B. System B C. both are the same D. cannot be determined

A. The scan converter with the greatest number of pixels assigned to an image of fixed size will provide the viewer with the greatest spatial detail. In this case, system A has a higher pixel density, and therefore has the ability to display greater detail.

536. While using a linear sequential array transducer during a color Doppler exam, the shape of the gray scale image is most often _____ whereas the shape of the color Doppler portion of the image is _____ A. rectangular, parallelogram B. rectangular, sector C. sector, trapezoid D. square, rectangular

A. The shape of a gray scale image using a linear sequential array is rectangular. However, the sound beams used for Doppler are steered at an angle, creating a parallelogram-shaped region.

202. A sound wave reaches a rough or irregular explicit circumstances, which process is most likely to occur? A. backscatter reflection B. specular reflection C. Rayleigh scattering D. refraction

A. The smoothness or roughness of a boundary will help to determine what form of reflection takes place. Backscatter is likely to occur when the boundary has irregularities that are larger than the wavelength of the incident acoustic pulse. Diffuse reflection is another name for backscatter.

169. In diagnostic imaging, what establishes the pulse repetition frequency? A. the source of the sound B. the medium through which the sound travels C. both A and B D. neither A nor B

A. The sole determinant of the pulse repetition frequency is the source of the acoustic wave, the ultrasound system. The medium through which the sound travels does not directly affect the pulse repetition frequency.

52. What determines the period of an ultrasound wave? A. the transducer B. the medium through which the sound travels C. both A and B D. neither choice A nor B

A. The sound source (the transdlcor) that produces an acoustic signal deemines the period of a wave. The wave's priod is unrelated to the medium througn which the sound travels, and will not change as the wave moves from one medium to another.

86. What determines the initial intensity of an ultrasound beam? A. the source of the sound wave B. the medium through which the sound travels C. both A and B D. neither A nor B

A. The source of the acoustic wave determines the initial intensity (as well as the wave's amplitude and power). At its point of origin, the strength of an acoustic wave will not be related to the medium that the sound is about to enter.

594. All of the following may be used to evaluate Doppler systems except: A. tissue equivalent phantom B. moving belt phantom C. vibrating string phantom D. Doppler phantom

A. The tissue equivalent phantom is not suitable for evaluating Doppler systems because all the reflectors within it are stationary. Doppler evaluations require moving reflectors.

98. What is the wavelength of 2 MHz sound in soft tissue? A. 0.77 mm B. cannot be determined C. 1.54 mm D. 2 mm

A. The wavelength of sound in soft tissue is defined by the following relationship: wavelength (mm) = 1.54 / frequency (MHz) For 2 MHz sound, the wavelength is 1.54/2 or 0.77 MHz.

441. Which of the following is best described as an analog number? A. the weight of a person B. the number of people in a room C. the number of stars in the sky D. the number of tires on a car

A. The weight of a person can be considered an analog number because it is continuous and can achieve an unlimited number of values. On the other hand, the number of people in a room or the number of tires on an automobile can be represented only by discrete, whole, or integer values.

75. The maximum value of the density of an acoustic wave is 60 lb/in? while the minimum density is 20 lb/in?. What is the amplitude of the wave? A. 20 lb/in? B. 40 lb/in2 C. 60 lb/in2 D. none of the above

A. To calculate the amplitude of a wave, subtract the minimum value of the acoustic variable from its maximum and then divide that number in half. In this case, the maximum minus the minimum is 60 - 20 = 40 lb/in?. Half of 40 is 20 lb/in?.

211. Ultrasound waves traveling through lung tissue attenuate to a ____ extent than when traveling through soft tissue. A. greater B. lesser C. nearly equal

A. Ultrasound attenuates more when traveling through lung tissue than when traveling through soft tissue.

227. A wave strikes an interface between two media and intensities are measured at the interface. What results when the reflected intensity is divided by the incident intensity? A. intensity reflection coefficient B. intensity transmission coefficient C. beam uniformity coefficient D. none of the above

A. Under these circumstances, when we divide the reflected intensity by the incident intensity, the result is the intensity reflection coefficient. The intensity reflection coefficient is the percentage of the incident intensity that is reflected as a wave strikes a boundary between two media.

486. What happens to venous return to the heart when an individual inhales? A. increases B. decreases C. remains the same

A. Upon inspiration, venous return to the heart increases.

470. A signal with a 120 dB dynamic range was previously compressed by 40 dB. What is the dynamic range of the original uncompressed signal? A. 160 dB В. 120 dB C. 3 dB D. 80 dB

A. When a signal is already compressed, the original dynamic range is obtained by adding the decibels of compression. In this case, 120 + 40 = 160 dB.

93. If the power of the beam is tripled while the cross-sectional area of the beam remains the same, the intensity A. triples B. increases ninefold C. remains the same D. none of the above

A. When the cross-sectional area of a beam remains unchanged, the change in the intensity of a beam is proportional to the change in the power. The question states that the power is tripled. If the power is tripled, then the intensity is also tripled.

248. An acoustic wave is traveling from medium X into medium Z. Medium X has a propagation speed of 1,457 m/sec and an impedance of 1.44 MRayls. Medium Z has a propagation speed of 1,644 m/sec and an impedance of 1.26 MRayls. The angle of incidence is 32°. What is true of the angle of the transmitted wave? A. it is greater than 32° B. it is equal to 32° C. it is less than 32° D. cannot be determined

A. With refraction, the relationship between the angle of incidence and the angle of transmission is defined by Snell's Law. When the propagation speed of the medium that the sound is entering exceeds the propagation speed of the medium that the sound is currently in, the angle of transmission is greater than the incident angle.

375. What is the shape of the elements in an annular phased array transducer? A. rectangles B. squares C. wedges D. circles

Answers D. Annular array transducers have piezoelectric crystals that are donut or ring shaped. They are arranged as a collection of concentric rings.

94. The amplitude of an acoustic wave is increased. Which of the following will most likely remain unchanged? (More than one answer may be correct.) A. power B. frequency C. period D. intensity

B and C. Amplitude relates to the strength of a wave. The frequency of a wave describes the number of cycles in one second. A wave's period is the time an acoustic variable oscillates though one complete cycle. Frequency and period are not related to amplitude, and remain unaltered when the amplitude changes.

364. Which two of the following terms are associated with phased array transducers? A. lens B. multi-focus C. mirror D. adjustable E. external

B and D. Phased array is always associated with adjustable or multi-focusing.

92. What happens to the intensity of an sectional area remains unchanged while ultrasound beam when the beam's cross- the amplitude of the wave triples? A. it triples B. increases ninefold C. remains the same D. none of the above

B. A change in the intensity of a wave is proportional to the change in the amplitude of the wave squared. When the amplitude of a wave is tripled, the intensity is increased ninefold (3 x 3 = 9).

623. Which of the following epidemiologic studies is considered most likely to produce meaningful results? A. retrospective and prospective B. prospective and randomized C. retrospective and empirical D. prospective and mechanistic

B. A clinical trial that is both prospective and randomized is most likely to reach a valid and meaningful endpoint.

319. For a disc-shaped PZT crystal producing continuous sound, which design will create a beam with the deepest focus? A. large diameter, low frequency B. large diameter, high frequency C. small diameter, low frequency D. small diameter, high frequency

B. A continuous wave transducer producing the longest near zone (the deepest focus) will have a large diameter and a high frequency.

41. A longitudinal wave propagates from east to west at a speed of 2 miles per hour. What is the direction of motion of the particles within the wave? A. from east to west only B. alternately from east to west and then from west to east C. from north to south only D. alternately from south to north and then from north to south

B. A longitudinal wave is defined as a wave whose particles vibrate back and forth in the same direction that the wave is propagating. Since the wave is traveling from east to west, the particles in this wave will move alternately from east to west and then from west to east.

365. The minimum number of active elements in a mechanical transducer is: A. 0 B. 1 C. 2 D. none of the above

B. A mechanical transducer may be constructed with a minimum of a single piezoelectric crystal. An imaging plane is created by mechanically steering the single crystal with a motor.

458. What is the number of binary digits required to store 29 levels of gray? A. 4 В. 5 С. 6 D. 29

B. A minimum of 5 bits are required to display 29 shades of gray. Actually, 5 bits can display a maximum of 32 shades of gray. Because only 16 shades of gray can be represented by 4 bits, a fifth bit must be added to achieve adequate memory to display more than 16 shades.

555. Where is a mirror image artifact located? A. Sometimes shallower on the image than in the body B. always deeper on the image than in the body C. sometimes the same depth on the image as in the body D. never deeper on the image than in the body

B. A mirror image artifact occurs when a pulse bounces off a strong reflector (such as the diaphragm) and then strikes a second reflector. The pulse's path is lengthened by the mirroring, and the second reflection (artifact) is always displayed at an abnormally great depth.

401. Which choice will result in increased frame rate and temporal resolution? A. decreased propagation speed B. decreased sector size C. decreased lateral resolution D. decreased pulse repetition frequency

B. A narrower sector diminishes the number of pulses required to produce each image. Frame rate and temporal resolution improves when fewer pulses make each image.

452. A byte is composed of ______ bits. A word is composed of ______ bytes. A. 2, 2 В. 8,2 C. 16, 16 D. 8, 16

B. A string of eight bits of computer memory is a byte. Two bytes of computer memory make a word. Since a byte is 8 bits, a word is 16 bits.

438. A video display that is limited to black and white only, with no shades of gray, is called A. binary B. bistable C. monochrome D. inchworm

B. A video display with the ability to show black and white only, without any intermediate shades of gray, is called bistable.

193. How many decibels represent a 100-fold increase in the intensity of an acoustic pulse? A. 10 В. 20 C. 100 D. 6

B. An increase of 100 times the intensity of a wave is equal to 20 dB. Each 10 dB indicates a tenfold increase. Therefore, 20 dB (two 10 dB increases) means a pair of tenfold increases, 10 x 10 = 100.

219. Which of the following describes an angle with a measure of 45°? A. orthogonal B. acute C. obtuse D. normal

B. Any angle that measures less than 90° is an acute angle.

158. What happens to the pulse repetition period if the sonographer decreases the maximum imaging depth achieved in an ultrasound scan? A. increases B. decreases C. remains the same D. cannot be determined

B. As the maximum imaging depth, or depth of view, is decreased, the interval of time during which the ultrasound machine listens for returning echoes is diminished. As a result of this shorter listening time, the pulse repetition period is shortened. Simply stated, pulse repetition period and depth of view are directly related.

334. Two ultrasound systems have near zone lengths of 8 cm. At their foci, System Q's lateral resolution is 3.0 mm and System H's is 5.0 mm. Which system will correctly display two small structures at a depth of 8 cm? The objects are side by side and are 0.4 cm apart. A. System H B. System Q C. both produce similar quality pictures

B. At a depth of 8 cm, System Q will produce a more accurate picture of two structures that are 0.4 cm apart. A system's lateral resolution is approximated by the beam diameter at that depth. System Q's beam diameter is 3.0 mm at its focus and will display this pair of reflectors accurately. System H's beam, with a diameter of 5 mm, is too wide to display this pair of reflectors as distinct and separate.

182. What is the importance of describing sound beam intensities in a variety of ways with regard to space and time? A. it allows better transducer design B. it's important when studying bioeffects C. it optimizes image quality D. harmonics can be measured

B. Describing the intensity of sound beams as they vary in time and in space is important in the study of bioeffects.

500. Two ultrasound transducers are used to perform Doppler exams on the same patient. The exams are identical except that the transducer frequencies are 5 and 2.5 MHz. Which exam will measure the highest Doppler shift? A. the 2.5 MHz exam B. the 5 MHz exam C. neither D. cannot be determined

B. Doppler shifts are directly related to the transmitted frequency. Higher frequency transducers produce a greater Doppler shift. Using lower frequency ultrasound will result in lower Doppler shifts. For a specific velocity, the Doppler shift produced will depend on the frequency of the incident sound wave, with higher frequencies yielding higher Doppler shifts.

176. While using a particular imaging system, what happens to the duty factor when the depth of view increases? A. increases B. decreases C. unchanged

B. Duty factor is inversely related to depth of view. As the system images to a greater depth, the system requires more time to listen for reflections, and the duty factor decreases. The duty factor is the fraction or percentage of time that an imaging system is transmitting. It is equal to the pulse duration divided by the pulse repetition period. Under normal operation, the pulse duration never changes. However, as depth of view increases, the pulse repetition period increases.

374. All of the following describe dynamic receive focusing except: A. delay pattern changes continuously throughout reception B. may be used by single crystal transducers C. focusing occurs at many depths D. automatically performed by system

B. Dynamic receive focusing is used only with systems using array transducers. Focusing is accomplished automatically during reception and is outside the control of the sonographer.

366. Which best describes the elements in a linear phased array transducer? A. rectangular, 1/4 wavelength thick B. rectangular, 1/2 to 1/4 wavelength wide C. circular D. squares, 1/2 wavelength thick

B. Each element of a linear phased array is rectangular. There are approximately 100 to 200 elements, each having a width of 1/4 to 1/2 wavelength.

552. When enhancement occurs, where does it appear on the image? A. in the near field B. deeper than a weak attenuator C. in the far field D. shallower than a weak reflector

B. Enhancement occurs after an ultrasound pulse has traveled through a low attenuating tissue and appears on the image deeper (distal) than that structure.

621. What is epidemiology the study of? A. large groups B. the prevalence of disease C. acoustic bioeffects on the fetus D. in vitro effects

B. Epidemiology is a division of medicine that is devoted to the study of the prevalence of diseases or pathology in a defined population.

340. Which of the following techniques is internal focusing? A. lens B. curved crystal C. electronic techniques

B. Focusing with a curved PZT crystal is known as internal focusing.

613.Which of the following is not a potential mechanism for production of bioeffects from ultrasound exposure to the body? A. temperature elevation B. fractionation C. cavitation D. vibration

B. Fractionation means "to separate a mixture into its ingredients" and has nothing to do with bioeffects. The other choices are potential mechanisms for acoustic bioeffects.

100. Which sound wave has a longer period? A. the 10 MHz pulse B. the 2 MHz pulse C. neither pulse D. cannot be determined

B. Frequency and period are reciprocals. The wave with a higher frequency has a shorter period. Lower frequencies have longer periods. The 2 MHz wave has a period five times longer than the 10 MHz wave.

estimate for the lateral resolution at a zone length is 8 cm. What is the best piezoelectric crystal is 1.2 cm. The near 349. The diameter of a disc-shaped, unfocused depth of 16 cm? A. 0.6 cm B. 1.2 cm C. 8 cm D. 16 cm

B. Generally, unfocused sound beams produced by a disc-shaped crystal have a profile where the beam tapers to a minimum diameter at the focus and then starts to diverge. At a distance of twice the near zone length, the beam diameter is approximately equal to the piezoelectric crystal diameter. The beam diameter at a depth of 16 cm (which is twice the near zone length) is equal to the crystal diameter, 1.2 cm. Thus, 1.2 cm is the lateral resolution at that depth.

348. The diameter of a disc-shaped, unfocused piezoelectric crystal is 1 cm. What is the best estimate for the minimum lateral resolution of the ultrasound system? A. 1 mm B. 5 mm C. 1 cm D. 5 cm

B. Generally, unfocused sound beams produced by a disc-shaped crystal have an hourglass shape. The beam tapers to a minimum diameter at the focus. At the focus, the beam diameter is approximately one-half the diameter of the PZT crystal. In this example, the minimum beam diameter is 5 mm, and this represents the lateral resolution of the system.

451. Two digital scan converters are undergoing evaluation. System A has 1,000,000 pixels, with 4 bits assigned to each. System B has 250,000 pixels, with 12 bits assigned to each. Which system is more likely to display images with very subtle differences in grayscale? A. System A B. System B C. both are the same D. cannot be determined

B. Gray scale levels are determined by the number of bits assigned to each pixel in an image. Since system B has 12 bits assigned to each pixel and system A has only 4, system B will display more gray shades and, thus, display subtle differences.

321. Two systems are identical except for the frequency of the emitted pulse. Which system will have the deeper focus? A. the lower frequency system B. the higher frequency system C. both foci will be at the same depth

B. High frequency piezoelectric crystals tend to produce ultrasound beams with deeper foci. Frequency and focal depth are directly related. Higher acoustic frequencies create deeper foci. Lower frequency crystals produce beams with shallow foci.

481. The arterial blood pressure of a supine individual is 120 mmHg. What is the hydrostatic pressure at the subject's ankle? A. 100 mmHg B. 0 mmHg C. 40 mmHg D. 120 mmHg E. -120 mmHg

B. Hydrostatic pressure is related to the difference between heart level and the site of measurement. In the supine patient, hydrostatic pressure is zero.

482. The arterial blood pressure of a supine individual is 120 mmHg. What is the hydrostatic pressure at the subject's hips? A. 100 mmHg B. O mmHg C. 40 mmHg D. 120 mmHg E. -120 mmHg

B. Hydrostatic pressure is related to the of measurement. In the supine patient, difference between heart level and the site hydrostatic pressure is zero.

101. Which pulse has a longer wavelength? A. the 10 MHz pulse B. the 2 MHz pulse C. neither pulse D. cannot be determined

B. In any specific medium, the wave with the lower frequency has the longer wavelength. The 2 MHz sound's wavelength is five times longer than the 10 MHz wave.

584. With standard diagnostic imaging instrumentation, which has the higher numerical value? A. axial resolution B. lateral resolution C. neither; they have identical values

B. In terms of image accuracy, axial resolution is usually better than lateral resolution. The number assigned to lateral resolution is higher than to axial resolution.

180. Which of the following terms does not belong with the others? A. increased depth of view B. increased duty factor C. increased pulse repetition period D. decreased pulse repetition frequency

B. Increased duty factors are related to shallower imaging. The other three selections are consistent with deeper imaging.

480. Which of the following causes the greatest amount of inertial energy loss? A. pulsatile flow B. flow through a stenosis C. phasic flow D. steady flow E. parabolic flow

B. Inertial loss is substantial when a fluid's velocity increases or decreases. Flow through a stenosis causes the greatest velocity changes, and the greatest inertial loss.

62. Infrasound is defined as a sound with frequency of _____ A. greater than 20,000 kHz B. less than 20 Hz C. greater than 10 MHz D. less than 0.02 MHz

B. Infrasound is defined as an acoustic wave with a frequency so low that it is not audible to humans. Infrasound is an inaudible wave with a frequency of less than 20 Hz.

563. Side lobe artifact usually results in all of following except A. hollow structures appearing "filled in" on the image B. reflectors not appearing on an image C. reflectors appearing in improper locations on the image D. reflectors appearing in multiple locations on the image

B. It is unlikely that a side lobe artifact would result in the absence of a reflector on an image. With side lobes, it is more likely that additional reflections will appear on the image.

322. As sound travels deeply into the far zone, the beam diverges, or spreads out. Which of the following will result in a minimum beam divergence deep in the far zone? A. small diameter, high frequency B. high frequency, large diameter C. large diameter, low frequency D. low frequency, small diameter

B. Large diameter crystals of high frequency tend to produce sound beams that diverge less in the deep far zone. In contrast, waves from small diameter, low frequency crystals are more divergent in the deep far zone.

320. Two ultrasound systems are identical except for the diameter of the transducer's piezoelectric crystal. Which system has the deepest focus? A. the system with the smaller diameter crystal B. the one with the larger diameter crystal C. their foci will be at the same depth

B. Large diameter crystals tend to produce ultrasound beams with more distant foci. The larger the crystal diameter, the deeper the focus. Smaller diameter crystals produce beams with shallower foci.

275. Which component of an ultrasound system is made of lead zirconate titanate (PZT)? A. transducer's matching layer B. transducer's active element C. transducer's damping material D. scan converter's computer chips

B. Lead zirconate titanate, abbreviated P2T, is a man-made piezoelectric material commonly used as the active element of ultrasound transducers.

271. Two ultrasound systems produce pulses. One pulse is 0.4 usec in duration and the other is 0.2 usec long. Which pulse is most likely to provide the best radial resolution? A. 0.4 usec system B. 0.2 usec system C. they are the same D. cannot be determined

B. Radial (or axial) resolution is determined by the pulse duration or the spatial pulse length. The shorter the time span that a pulse exists (or the shorter the length of the pulse), the better the radial resolution. The device producing the shorter pulse, 0.2 psec, has the best radial resolution. Radial resolution is also called axial, depth, longitudinal, or range resolution.

260. The axial resolution of an imaging system is reported to be 0.85 mm at the beam's focus. What is the closest estimate of the system's radial resolution at a location that is 5 cm deeper than the focus? A. less than 0.85 mm B. equal to 0.85 mm C. greater than 0.85 mm

B. Radial resolution is determined by the spatial pulse length or the pulse duration. These variables remain constant, regardless of the depth of the pulse. The radial resolution is the same at all imaging depths.

259. You are purchasing a diagnostic ultrasound system. System X has axial resolution of 0.7 mm whereas System D's is 0.4 mm. Based on this information, which system will produce the better quality picture? A. System X B. System D C. they have the same quality D. cannot be determined

B. Resolution is reported in units of distance, such as cm or mm. Higher image quality is achieved by systems with lower numerical values for resolution. System D has a lower numerical value for longitudinal resolution, and will produce more detailed, higher quality pictures.

578. The lateral resolution of four ultrasound systems appear below. Which will produce the finest quality picture? A. 2 cm B. 4 mm C. 6 mm D. 8 hm

B. Resolution is reported in units of distance, with smaller values producing higher quality pictures. Choice B is the smallest number and therefore represents the system with the best images based on lateral resolution.

332. Two ultrasound systems have near zone lengths of 8 cm. At the focus, System G's lateral resolution is 3.0 mm, whereas System P's is 5.0 mm. Which system will produce higher quality pictures at their foci? A. System P B. System G C. both will be of similar quality

B. Since System G has a narrower beam than System P at the end of the near field (which is the location of the foci), System G will produce higher quality images at that depth.

152. Two transducers send ultrasound pulses into soft tissue. One transducer emits sound with a 4 MHz frequency, and the other produces sound at a 6 MHz frequency. Each pulse contains 4 cycles. Which has a greater spatial pulse length? A. the 6 MHz pulse B. the 4 MHz pulse C. they are the same D. cannot be determined

B. Since both pulses have the same number of cycles, the pulse whose individual cycles have a longer wavelength will have the greater overall length. In a given medium, waves with lower frequencies have longer wavelengths. The 4 MHz wave has a longer wavelength than the 6 MHz wave and therefore will have a longer spatial pulse length.

256. In soft tissue, sound travels to a reflector and back to the transducer in 39 us (39 microseconds or 39 millionths of a second). What is the total distance that the pulse traveled? A. 2 cm B. 6 cm C. 3 cm D. cannot be determined

B. Since the pulse traveled round trip, the total distance is 6 cm. Imuiben For each 13 us, sound travels a round trip depth of 1 centimeter. Thus, in 39 us, sound travels to and returns from a depth of 3 cm.

243. What event does Snell's Law govern? A. transmission B. refraction C. impedance

B. Snell's Law defines the physics of refraction.

29. All of the following are true about sound waves except ______ A. they are mechanical B. they are transverse C. they carry energy from place to place D. they generally travel in a straight line

B. Sound waves are not transverse, they are longitudinal.

130. If sound travels at exactly 1,540 m/sec in a particular medium, then the medium ____ A. must be soft tissue B. may be soft tissue C. cannot be soft tissue

B. Sound waves travel exactly 1,540 m/sec in soft tissue. However, other media have the same propagation speed as that of soft tissue. The medium in question could be soft tissue, or it could be something else.

133. The speed at which a wave travels through a medium is determined by: A. the sound wave's properties only B. the medium's properties only C. properties of both wave and medium D. none of the above

B. Speed is and power travel at the same speed in a waves of any frequency, period, intensity, the wave do not affect its speed. All sound of the medium only. The characteristics of determined by the characteristics particular medium.

446. Two digital scan converters are undergoing evaluation. System A has 1,000,000 pixels and the picture size is 100 square inches. System B has an image size of 10 square inches composed of 250,000 pixels. Which image is more likely to display very small details? A. System A B. System B C. both are the same D. cannot be determined

B. System B has a greater ability to display small detail in an image in comparison to system A. System B has 25,000 pixels per square inch, whereas system A only has 10,000 pixels per square inch. System B has a greater pixel density, and this determines the degree of spatial resolution.

425. Which transducer system is most likely to have the longest delay in its TGC curve? A. a 5 MHz linear array B. a 2.5 MHz annular array C. a 7.5 MHz mechanical transducer D. a 5 MHz annular array

B. The 2.5 MHz transducer will have a longer delay in the TGC curve. Low frequency ultrasound waves attenuate to a lesser extent than high frequency waves. Since choice B has the lowest frequency, it will have the least amount of attenuation and will require less compensation in the near zone. The type of transducer (e.g., annular, linear) does not affect the TGC.

538. The analysis of Doppler spectra using _____ is most accurate. A. zero-crossing detectors B. Fast Fourier Transforms C. time interval histograms D. Chirp-Z transforms

B. The Fast Fourier Transform, or FFT, is the most accurate spectral analysis technique. Techniques such as zero-crossing, time interval histograms, and Chirp-Z were initially used to assess Doppler spectra, but are now obsolete. Fast Fourier analysis became popular when computers were incorporated into ultrasound systems.

618. Which of the following is related to cavitation bioeffects? A. TIS B. MI C. cavitation index D. pulsatility index

B. The MI, or mechanical index, is related to cavitation bioeffects. Higher values of MI are associated with increased likelihood of cavitation.

307. What is the point or location where a beam reaches its smallest dimension? A. near zone B. focus C. penetration depth D. focal zone

B. The actual location where an ultrasound beam reaches its minimum diameter and cross-sectional area is called the focus.

251. A wave of acoustic energy is leaving soft tissue and transmitting into fat with an 86° incident angle. What is true of the angle of transmission? A. it is equal to 86° B. it is less than 86° C. it is greater than 86° D. cannot be determined

B. The angle of transmission will be less than the angle of incidence. Fat's propagation speed is less than that of soft tissue. The angle of transmission is less than the angle of incidence when a wave travels into a second medium that reduces the wave's propagation speed. In this example, the incidence is oblique, and fat has a lower speed than soft tissue.

208. What is the amount of attenuation per centimeter that a sound wave undergoes called? A. beam uniformity coefficient B. attenuation coefficient C. attenuation D. duty factor

B. The attenuation coefficient reports a sound beam's decibels of attenuation per centimeter. This is a useful tool as its value remains constant, regardless of the actual path length.

266. An ultrasonic pulse has a pulse repetition period of 1.2 msec, a spatial pulse length of 2.0 mm, and a wavelength of 0.4 mm. What is the axial resolution of the system? A. 2.0 mm B. 1.0 mm C. 0.4 mm D. 1.8 mm

B. The axial resolution of an ultrasound system is equal to half of the spatial pulse length produced by the system. In this example, the spatial pulse length is equal to 2.0 mm, and the axial resolution is 1.0 mm. Image accuracy is best when the numerical value of axial resolution is small.

207. As a pulse passes through soft tissue, a certain amount of acoustic energy remains in the tissue as heat. What is this constituent attenuation called? A. scattering B. absorption C. refraction D. rarefaction

B. The conversion of acoustic energy into heat is called absorption. This process deposits a portion of the energy from the beam into the soft tissues.

610. Which of these terms best describes the empirical investigation of bioeffects? A. cause-effect B. exposure-response C. cause-response D. exposure-cure

B. The empirical approach to the study of bioeffects searches for a biologic response following an exposure to ultrasound. An example of an empirical study is the assessment of a newborn child following an ultrasound study performed while in utero.

428. What does the far gain of a depth gain compensation curve represent? A. the median amplification related to compensation B. the maximum amplification related to compensation C. the minimum amplification related to compensation D. the maximum attenuation related to compensation

B. The far gain setting of a TGC curve represents the maximum amplification that a reflected wave undergoes during the compensation process.

328. The focus of an ultrasound beam is the location where the A. beam is the broadest B. optimum transverse resolution is C. frequency is the highest D. finest depth resolution is obtained

B. The focus of an ultrasound beam is the location where the beam is most narrow The narrowest portion of the beam provides the optimal transverse or lateral resolution.

439. What is the approximate number of frames that must be presented each second for the human eye to perceive the display without flickering? А. 2 В. 30 C. 100 D. 500

B. The frame rate required to perceive smooth, flicker-free motion is in the range of 30 frames/sec. When the frame rate is significantly below this value, the viewer experiences flicker. Flicker increases fatigue and discomfort and diminishes the perceptive ability of the observer.

303. You are asked to fabricate a pulsed ultrasound transducer with the lowest possible frequency. Which piezoelectric crystal would you select? A. 6 mm thick, 4 cm diameter, 4.0 mm/us propagation speed B. 8 mm thick, 2 cm diameter, 2.0 mm/us propagation speed C. 4 mm thick, 9 cm diameter, 5.0 mm/us propagation speed D. 2 mm thick, 6 cm diameter, 6.0 mm/us propagation speed

B. The frequency is lowest when the crystal is thick and its propagation speed is low, so the active element listed in B is the proper choice. The diameter of the active element does not affect the frequency of the pulse.

298. With pulsed wave ultrasonic imaging, what helps to establish the primary frequency of the acoustic energy discharged by the transducer? A. piezoelectric crystal diameter B. piezoelectric crystal thickness C. damping material density D. ultrasound system electronics

B. The frequency of sound produced by a standard pulsed wave imaging instrument is partly determined by the thickness of the piezoelectric element. Just as different tones are produced when a musician plays different bars on a xylophone, piezoelectric crystals of various thicknesses produce acoustic pulses of different frequencies.

494. In standard Doppler, what is true about the reflected frequency produced by blood cells traveling away from the transducer? A. it is in the audible range B. it is ultrasonic C. it exceeds the transmitted frequency D. it equals the transmitted frequency

B. The frequency of the sound wave reflecte by red blood cells back to the transducer is ultrasonic (having a frequency greater than 20,000 hertz). Although the difference between the transmitted and reflected frequencies is audible, the reflected waye has a frequency in the ultrasonic range.

355. The mode that produces lines related to the changing position of reflectors in the body with respect to time is called A. A-mode C. B-mode B. M-mode D. a la mode

B. The imaging mode that displays the position of reflectors throughout time is M-mode, or motion mode. M-mode is the only display that provides reflector position throughout time.

83. As sound travels in the body, what typically happens to the intensity of the wave? A. increases B. decreases C. remains the same

B. The intensity of a sound beam decreases as it travels through the body because of attenuation. Amplitude, power, and intensity are three different ways to measure the strength of an ultrasound beam. They all decrease as sound propagates.

387. When looking at images produced by these transducer systems, which one can be distinguished from all the others? A. linear phased array B. linear switched array C. annular phased array D. mechanical transducer

B. The linear switched arrays (or linear sequential arrays) produce an image of rectangular shape. The other three transducers generate sector-shaped images that are essentially indistinguishable from each other.

560. If a sound pulse travels through a large mass at a speed of 1.2 mm/us, what happens to the position of echoes from reflectors deeper than the mass? A. they are placed in too shallow a location on the image B. they are placed in too deep a location on the image C. they are likely to be placed at the correct depth

B. The mass has a slow propagation speed when compared with soft tissue. All structures distal to the mass will be placed at too great a depth on the image. The reflections on the image will be farther than the reflector's true anatomical position.

413. The output of an ultrasound pulser determines the ____ of the acoustic pulse. A. imaging depth B. intensity C. duration D. pulse repetition period

B. The output of the pulser determines the strength or the intensity of the sound beam produced by the transducer. When greater electrical voltages from the pulser strike the PZT crystal of the transducer, pulses with greater intensity are created.

436. The process of eliminating low amplitude signals from further processing is called all of the following except A. reject B. subordination C. threshold D. suppression

B. The process of removing low-level signals from further processing or display by an ultrasound system is called reject, threshold, or suppression. The term subordination does not describe this process.

567. Which technique of linear array transducer design has virtually eliminated the appearance of grating lobe artifact on modern ultrasound systems? A. demodulation B. subdicing C. deconvolution D. none of the above

B. The process of subdicing has almost eliminated the appearance of grating lobe artifact on linear array transducer systems. Subdicing consists of dividing each of the crystals in the array into smaller pieces. The subdiced pieces are then fired simultaneously as if they were a single crystal. This minimizes grating lobes.

345, In which region of a sound beam is focusing most effective? A. the very shallow near zone B. the end of the near zone C. very deep in the far zone D. throughout its entire length

B. The region of a beam that is most affected by focusing is close to the end of the near zone and at the beginning of the far zone. This region is called the focal zone.

127. What is the speed of sound in air? A. 1,540 m/s B. 330 m/s C. 100 m/s D. 3,010 m/s

B. The speed of sound in air is 330 m/s, substantially lower than the speed of sound in soft tissue.

132. The propagation waves in muscle, liver, kidney, and blood speeds of ultrasound are ______ A. exactly the same B. very similar to each other C. vastly different

B. The speed of sound in these media are characteristics of muscle, kidney, liver, and blood that determine the wave's speed in the media are quite similar.

106. What is the wavelength of 10 MHz sound in soft tissue? A. 0.77 mm B. 0.15 mm C. 1.54 mm D. 10 mm

B. The wavelength of sound in soft tissue is defined by the following relationship: wavelength (mm) = 1.54 / frequency (MHz) For 2 MHz sound, the wavelength is 1.54/10 or 0.15 mm.

624. What is the highest SPTA intensity of an unfocused ultrasound wave where there have been no observed bioeffects? A. 1 mW/cm2 B. 100 mW/cm2 C. 1000 mW/cm2 D. 1 W/cm?

B. There have been no independently confirmed significant bioeffects in mammalian tissue exposed to unfocused ultrasound with intensities below 100 mW/cm2.

241. An acoustic wave is traveling from medium X to medium Z. Medium propagation speed of 1,457 m/sec and an X has a impedance of 1.44 MRayls. Medium Z's m/sec and its propagation speed is 1,644 impedance is 1.26 MRayls. The angle of incidence is 32°. What is true of the angle of reflection? A. it is greater than 32° B. it is equal to 32° C. it is less than 32° D. cannot be determined

B. This is a tricky question. In cases of oblique incidence, the angle of reflection is always equal to the angle of incidence. Simply put, if the incident angle is 32°, then the reflection angle is 32°. All information regarding the propagation speeds and acoustic impedances of media X and media Z are irrelevant in this question.

55. What term describes the number of cycles that an acoustic variable completes in a second? A. period B. frequency C. pulse repetition period D. variable rate

B. This is the definition of the term frequency. Frequency can also be thought of as the number of regularly occurring events in a specific time.

617. Which of the following statements regarding cavitation is true? A. it has never been observed in any biologic media B. stable cavitation relates to ocillating bubbles while transient relates to bursting bubbles C. it is a nonlethal bioeffect produced in animal experiments D. waves with peak pressures less than 100 MPa can never induce cavitation

B. This is the principal difference between the two forms of cavitation: stable cavitation means that the microscopic gas bubbles in the tissues are rhythmically swelling, whereas transient cavitation means the microscopic gas bubbles burst.

217. Which two attributes help establish the acoustic impedance of a medium? A. density and temperature B. density and stiffness C. stiffness and elastance D. elasticity and compressibility

B. To calculate the acoustic impedance, multiply the propagation speed of the medium by the density of the medium. A medium's propagation speed is determined by the density and the stiffness of the medium. Therefore, acoustic impedance is a property of both density and stiffness.

532. The two most common color maps used in color flow imaging are: A. variance and direct B. variance and velocity C. turbulence and variance D. power and velocity

B. Two common modes of color Doppler are velocity and variance modes.

252. An acoustic wave is in medium A and traveling toward medium B. The sound beam's angle of transmission into medium B with relation to the boundary is 79°. Sound's propagation speed is 1,547 m/ sec in medium A and 1,745 m/sec in medium B. If reflection and transmission both occur at the boundary, what can be said of the reflection angle? A. it is greater than 79° B. it is less than 79° C. it is equal to 79° D. cannot be determined

B. Two steps are required to determine that the angle of reflection is less than 79°. 1. We know that the transmission angle is 79° and that the propagation speed of medium A is less than that of medium B. From this, we can derive information about the angle of incidence. Since the speed of medium B is greater than the speed of medium A, the angle of transmission is greater than the angle of incidence. Thus, the angle of incidence must be less than 79°. 2. The angle of reflection is equal to the angle of incidence. Since the angle of incidence is less than 79°, the angle of reflection is also less than 79°.

50. What is the range of periods commonly found in waves produced by ultrasound systems? A. 0.001 to 1s B. 0.06 to 0.5 us C. 0.2 to 1 ms D. 10 to 100 ns

B. Ultrasonic imaging waves have a period in ps. The period is the range of 0.06 to 0.5 the time of a single cycle. Period is the loolto reciprocal of frequency. A wave with a frequency of 2 MHz has a period of 0.5 usec. A wave with a frequency of 15 MHz has a period of 0.06 us.

423. What is the process of adjusting for path length related attenuation called? A. compression B. compensation C. time-gain compensation D. reconfirmation

B. Ultrasound experiences attenuation as it travels in soft tissue. The deeper that sound travels, the weaker the reflected pulse is. Compensation is the process of adjusting for path length attenuation.

212. Sound traveling through blood attenuates to a ______ extent than when traveling through soft tissue. A. greater B. lesser C. relatively equal

B. Ultrasound waves attenuate less when traveling through blood than when traveling through soft tissue.

229. An ultrasound wave strikes an interface results when the transmitted intensity is measured directly at the interface. What between two media. All intensities are divided by the incident intensity? A. intensity reflection coefficient B. intensity transmission coefficient C. beam uniformity coefficient D. none of the above

B. Under these circumstances, when the transmitted intensity is divided by the incident intensity, the result is the intensity transmission coefficient. The intensity transmission coefficient is the percentage of the incident intensity that continues to incident wave strikes a boundary between propagate in the forward direction when the two media.

485. What happens to the diaphragm when an individual breathes in? A. it ascends into the thorax B. it descends into the abdomen

B. Upon inspiration, the diaphragm moves downward into the abdomen.

487. What happens to venous flow in the legs when an individual inhales? A. increases B. decreases C. remains the same

B. Upon inspiration, venous flow in the legs decreases.

489. What happens to venous return to the heart when an individual exhales? A. increases B. decreases C. remains the same

B. Venous return to the heart decreases when an individual exhales.

96. The wavelength of a cycle in an ultrasound wave can be reported with which units? A. units of time (sec, min, etc.) B. units of distance (feet, etc.) C. units of area (m2, etc.) D. mm only

B. Wavelength is the distance from the beginning to the end of one cycle. It has units of distance. In soft tissue, and with frequencies typical of diagnostic imaging, wavelengths range from 0.15 to 0.75 mm. Although it may be impractical to record wavelengths in miles or meters, it can be done since they are distances.

25. Which of the following is true of all waves? A. they travel through a medium B. all carry energy from one site to another C. their amplitudes do not change D. they travel in a straight line

B. Waves carry energy from one place to another. A is incorrect because some waves, such as light, can travel through a vacuum. C is incorrect because many waves get weaker as they travel. Certain waves do not travel in a straight line, so D is also incorrect.

49. A pair of waves are in phase. What occurs A. reflection B. constructive interference C. refraction D. destructive interference

B. Waves that are in phase constructively interfere with each other. The that results from the combination single wave of the two have a higher in-phase waves will always amplitude than either of the original waves.

294. Which of the following cause a PZT crystal to lose its special actions would properties? A. breaking it in pieces B. exposing it to high temperatures C. exposing it to electrical current D. exposing it to low pressures

B. When a piezoelectric crystal is exposed to high temperatures, it will depolarize and permanently lose its piezoelectric properties. This temperature is known as the Curie temperature or Curie point.

190. What is the decibel notation for an acoustic signal that is attenuated? A. positive B. negative C. equal to zero

B. When a signal is attenuated, its magnitude decreases and it becomes weaker. In decibel notation, a decrease in signal strength is described with negative decibels. Negative dB means "getting smaller."

496. When red blood cells move away from a transducer, the frequency of the wave reflected from the red cells is ______ the frequency emitted by the transducer. A. greater than B. less than C. equal to

B. When red blood cells are moving away from a transducer, the Doppler shift is negative. The reflected frequency is less than the originally transmitted frequency from the transducer.

170. When a sonographer increases the maximum imaging depth during an exam, what happens to the PRF? A. PRF increases B. PRF decreases C. remains unchanged

B. When the depth of view is increased, the system waits and listens a longer time for reflections. This reduces the system's ability to send out as many pulses per second. Hence, as imaging depth increases, the pulse repetition frequency decreases. Imaging depth and PRF are inversely related.

399. What is the primary disadvantage of multiple focal zones along each scan line of a two-dimensional image? A. improved temporal resolution B. decreased temporal resolution C. improved lateral resolution D. improved longitudinal resolution

B. With multiple foci along each scan line, the ultrasound system uses many pulses to create each image. This reduces the number of frames created per second. A low frame rate results in decreased temporal resolution.

249. An acoustic wave in medium B is traveling strikes the toward medium A. The sound beam boundary at a 45° angle. The propagation speed is 1,547 m/sec for medium A and 1,745 m/sec for medium B. What is true of the angle of transmission? A. it is greater than 45° B. it is less than 45° C. it is equal to 45° D. cannot be determined

B. With refraction, when the medium that the sound is in has a greater propagation speed than the propagation speed of the medium that the wave is entering, the angle of transmission is less than the angle of incidence. In this case, the angle of transmission is less than 45° because the sound wave is entering a slower medium than the one through which it is currently propagating.

463. All of the following are true of write zoom except: A. preprocessing function of the receiver B. the same number of pixels are in the original ROI and the zoomed image C. the pixel size in the zoomed image and the ROI are the same D. in comparison to the zoomed image, fewer uitrasound pulses are used t create the original ROI

B. Write zoom is a preprocessing function of the receiver where new information is acquired from the region of interest (ROI). The data originally in the scan converter, before zoom, is discarded. All the pixels in the image are now concentrated into the ROI, thereby increasing the pixel density and image quality of the zoomed portion.

234. A sound beam with an intensity of 45 Wcm strikes a boundary and 70% of the wave's intensity is reflected. How much is transmitted? A. 45 W/cm2 B. 25 W/cm2 C. 30% D. 100%

C. 30% of the wave's intensity is transmitted. The law of conservation of energy states that the sum of the percentage of transmitted sound and the reflected sound equals 100%.

473. Which of the following terms is not associated with a wide dynamic range image? A. low contrast B. many shades of gray C. bistable

C. A bistable image contains only black and white. An image described as wide dynamic range contains many shades of gray and may be called "low contrast."

194. The intensity of an ultrasound wave is changed by -6 dB. This means that the current intensity is ____ as much as its original level. A. one-tenth B. four times C. one-fourth D. one-sixth

C. A change in intensity of -6 dB indicates that only one-fourth of the initial intensity remains. The minus sign indicates a decrease in signal magnitude. Each -3 dB change means that one-half of the original intensity remains. Since there are two sets of -3 dB, one-half multiplied by one-half indicates that there is only one-fourth remaining.

318. For a disc-shaped PZT crystal producing continuous sound, which design will create a beam with the shallowest focus? A. large diameter, low frequency B. large diameter, high frequency C. small diameter, low frequency D. small diameter, high frequency

C. A continuous wave transducer producing the shortest near zone (the most shallow focus) will have a small diameter and a low emitted frequency.

185. What is a decibel? A. the absolute value of a number B. a range of values C. a relationship between two numbers D. none of the above

C. A decibel represents a relationship between two numbers. A decibel is a relative measure of intensity or power. The term "relative" indicates that we are not dealing with an absolute power (such as 600 watts), but rather with how the power is related to a reference level (for example, the current signal is 50% as strong as the reference level).

471. Which display is limited to a single pair of brightness or display levels? A. CRT B. binary C. bistable D. gray scale

C. A display that presents data in one of only two colors bistable. Each dot on the image is either white or black, bright or dark, on or off. Bistable images are considered high contrast.

512. A duplex ultrasound system displays _______ information. A. M-mode, two-dimensional image, and A-mode B. A-mode and B-mode C. two-dimensional image and Doppler D. two-dimensional image and M-mode

C. A duplex scanner displays both Doppler and two-dimensional image data.

456. With 6 bits, what is the largest number of different gray shades that can be stored? А. 8 В. 16 C. 64 D. 256

C. A maximum number of 64 shades can be stored with the use of 6 bits. We multiply 2 by itself a total of 6 times to calculate the answer to this question: 2 x 2 x 2 x 2 x 2 x 2 = 64 shades.

380. What image is created with a two- dimensional array transducer? A. two-dimensional static image B. two-dimensional real-time image C. three-dimensional real-time image D. B-mode

C. A two-dimensional array transducer creates a three-dimensional image.

215. Acoustic impedance is a property of the _____ and has units of ____ A. source and medium, Imps B. medium, dB C. medium, Rayls D. medium, Ohms

C. Acoustic impedance is a property of the medium through which sound travels. It is unaffected by the sound source or the characteristics of the wave itself. The units of impedance are Rayls.

588. What is the cause of acoustic speckle? A. refraction B. attenuation C. interference of tiny acoustic wavelets D. resonance of particles in the near field

C. Acoustic speckle is produced by the constructive and destructive interference of small acoustic waves reflected from small reflectors in the near field.

472. All of the following are consistent with an image containing black and white only with no shades of gray except: A. bistable B. high contrast C. wide dynamic range

C. An image described as wide dynamic range contains many shades of gray. Wide dynamic range (also called high dynamic range) means "many choices."

602. Certain studies of bioeffects are performed in vitro. What is the meaning of in vitro? A. visible in a living organism B. observations based on experiments C. discernible in a test tube D. perceptible in a living human being

C. An in vitro experiment is performed out of the body and in an artificial environment. The observations may be described as "in a test tube."

614. Which of the following ultrasound beams has a characteristic that is most likely to cause temperature elevation in soft tissue? A. strongly focused B. medium focused C. unfocused

C. An unfocused beam is most likely to cause temperature elevation in soft tissues. Temperature elevation with unfocused beams results from the broad area over which the beam spreads. With narrower, focused beams, the area insonated by the beam smaller and therefore heats a smaller mass of tissue.

475. Which of the following terms does not belong with the others? A. phasic B. spontaneous C. pulsatile D. venous

C. Arterial flow is often described as pulsatile. Phasic or spontaneous flow patterns describe blood moving at a variable velocity as a result of the mechanics of breathing. Phasic flow is observed in venous circulation.

197. As sound propagates through a medium, the total power in the wave decreases, What is this entire process called? A. absorption B. scattering C. attenuation D. reflection

C. As a wave propagates through a medium, its power diminishes. This is attenuation. Choices A, B, and D are all components of or contributors to attenuation.

539. Spectral analysis of color flow Doppler is most commonly performed by which of the following techniques? A. zero-crossing detectors B. Fast Fourier transforms C. autocorrelation D. Chirp-Z transforms

C. Autocorrelation is the technique of choice for spectral analysis of color Doppler. Although the most accurate technique is the FFT, autocorrelation is better suited to process the enormous amount of data acquired in a color Doppler study.

137. When the elasticity of a medium is high, the _____ is high. A. stiffness B. propagation speed C. compressibility D. reflectivity

C. Both elasticity and compressibility describe- the ability of a medium to reduce its volume when affected by a force. High elasticity means the same as high compressibility.

354. Which imaging modality places dots of dissimilar gray scale on the display? A. A-mode C. B-mode B. I-mode D. M-mode

C. Brightness mode, or B-mode, displays reflected echoes as spots of varying brightness. The depth of the dot is based on the time of flight. Stronger reflections create brighter dots. Weaker reflections create darker dots.

51. With standard ultrasonic imaging, what happens to the period of a wave as it propagates? A. increases B. decreases C. remains the same

C. Certain parameters of a wave change as the wave travels through the body. However, the period and the frquency of a wave typically remain constan as a sound wave propagates.

188. The scale associated with decibel notation is _____ A. linear B. discrete C. logarithmic D. additive

C. Decibel notation is based on the mathematical relationship of logarithms.

574. With depth resolution, A. too many reflectors appear on the image B. reflectors are placed too deep on the image C. too few reflectors are on the image D. reflectors appear too shallow on the image

C. Depth resolution is the ability to distinguish two reflectors that lie close to each other along the main axis of the beam. Most errors in depth resolution result in fewer reflections placed on the image than are actually in the body. Depth resolution is another name for axial resolution.

203. Which of the following is true of diffuse reflections? A. they're created by smooth boundaries B. they're created by large reflectors C. sound reflects in many directions D. they do not appear in soft tissue

C. Diffuse reflections, also called backscatter, are dispersed in multiple directions.

501. When using a 4 MHz transducer, a Doppler shift of 3,000 Hz is recorded. What will the Doppler shift be when a 2 MHz transducer is used? A. 3,000 Hz B. 2 Hz C. 1,500 Hz D. 6,000 Hz

C. Doppler shifts are directly related to transducer frequency. When the frequency is halved, the Doppler shift will be halved.

495. What is the range of Doppler shifts commonly measured in clinical exams? A. -10 kHz to 1 MHz B. -0.5 MHz to 0.5 MHz C. -0.02 MHz to 0.02 MHz D. none of the above

C. Doppler shifts in clinical imaging typically range from -20,000 Hz to +20,000 Hz. Choice C has units of megahertz, but when we examine the values of -0.02 to +0.02 MHz closely, we see that this means exactly the same as -20,000 Hz to +20,000 Hz.

497. What information does the Doppler shift furnish concerning the blood cells that produce it? A. frequency B. speed C. velocity D. density

C. Doppler shifts produce information regarding velocity. What is the difference between speed and velocity? Speed is purely a number such as 400 m/s. Velocity is both a number and a direction, such as 200 m/s away from the transducer. Doppler shifts indicate direction and a magnitude.

465. The relationship between the largest and the smallest signal amplitudes processed by a component of an ultrasound system called the ______ and has units of ______A. decibels, watts B. intensity, W/cm? C. dynamic range, dB D. proportionality, dB

C. Dynamic range are decibels, dB. a device can process. The units of dynamic largest to the smallest signal amplitude that range is defined as the ratio of the

379. Which best describes the elements in a linear sequential array transducer? A. rectangular, 1/4 wavelength thick B. rectangular, 1/4 to 1/2 wavelength wide C. rectangular, 1 wavelength wide D. squares, 1 wavelength thick

C. Each element of a linear sequential array is rectangular. There are many elements, each with a width of one wavelength.

343. Which of these techniques is consistent with variable or multi-focusing? A. lens B. curved crystal C. electronic

C. Electronic focusing is achieved with phasing of electronic signals. Electronic focusing, unlike internal or external focusing, is adjusted by the sonographer. In addition, it is multi-focus.

550. What causes enhancement artifact? A. sound beams bending B. linear array transducer architecture C. unexpectedly low acoustic attenuation D. acoustic energy radiating in a direction other than the beam's main axis

C. Enhancement artifact appears directly below structures with atypically low attenuation. Cystic structures often create enhancement artifact since fluids within the cyst often attenuate sound to a lesser extent than surrounding tissues.

200. Which of the following is not one of the physical processes that contributes to attenuation of ultrasound waves passing through soft tissue? A. reflection B. redirection of sound in many directions C. focusing D. conversion of acoustic energy to heat

C. Focusing does not contribute to the attenuation process. In contrast, choices A, B, and D reduce the intensity of a wave as it propagates.

255. In soft tissue, sound travels to a reflector and back to the transducer in 39 us. How deep is the reflector? А. 2 ст B. 6 cm С. 3 ст D. cannot be determined

C. For each 13 us, sound travels a round trip depth of 1 centimeter. Thus, in 39 us, sound travels to and returns from a depth of 3 cm.

69. Compare two sound waves, A and B. The frequency of wave A is one-third that of wave B. How does the period of wave A compare with the period of wave B? A. A is one-third as long as B B. A is the same as wave B C. A is three times as long as B D. cannot be determined

C. Frequency and period are reciprocals. If the frequency of one wave is one-third as large as another, then the period of the wave will be three times longer than the other.

70. ______ is the reciprocal of period. A. inverse period B. pulse repetition period C. frequency D. propagation period

C. Frequency is the reciprocal of piod. Reciprocals are related in two vrys: • As one increases, the other decreases. • When they are multiplied together, the result is unity. For example, a wave with a period of one- hundredth of a second has a frequency of 100 per second or 100 Hz.

The frequency of a continuous acoustic is 5MHz. The wave is then pulsed with a duty factor of 0.1. What is the new frequency? A. 0.5 B. 0.5 MHz C. 5 MHz D. 10 MHz

C. Frequency is the reciprocal of the period The fact that a wave is pulsed rather than continuous does not alter the frequency the signal. The new and old frequencies are the same, 5 million/second.

525. Which choice relates to the presence of gray shades in a Doppler spectrum? A. velocity B. frequency shift C. amplitude of the echo D. laminar flow

C. Gray scale in a Doppler spectrum is related to the number of red blood cells creating the reflection. The number of red blood cells determines the amplitude of the reflected signal.

60. When a sonographer increases the maximum imaging depth during an exam, what happens to the frequency? A. frequency increases B. frequency decreases C. remains unchanged

C. Imaging depth and frequency are unrelated. When the depth of view is increased, the frequency of sound remains the same.

571. With standard diagnostic imaging instrumentation, which has the higher numerical value? A. axial resolution B. lateral resolution C. elevational resolution

C. In terms of image accuracy, elevational resolution, determined by slice thickness, is the cause of greatest image degradation. The numerical value assigned to elevational resolution is higher than the others.

502. Doppler does not always provide a valid estimate of the speed of blood cells because the shift is related to the of the angle between the direction of the beam and the direction of blood flow. A. sine B. tangent C. cosine D. cotangent

C. Included in the Doppler equation is the cosine of the angle between the direction of motion and the direction of the sound beam.

416. Which of the following actions will improve the signal-to-noise ratio? A. increase dynamic range B. increase receiver gain C. increase output power D. increase time-gain compensation

C. Increasing output power will improve the signal-to-noise ratio. When the pulse's strength is increased, reflections arriving at the transducer are stronger as well, Strong reflections are less susceptible to the image degrading effects of noise.

577. With which of the following pulses would lateral resolution be worst? A. 10 MHz, 4 mm beam diameter, 4 cycles per pulse B. 4 MHz, 4 mm beam diameter, 2 cycles per pulse C. 7.5 MHz, 8 mm beam diameter, 2 cycles per pulse D. 6 MHz, 2 mm beam diameter, 2 cycles per pulse

C. Lateral resolution artifact is related to the diameter of the ultrasound beam. Narrow beams have the best lateral resolution. Wide beams have the worst lateral resolution. Choice C, with a beam diameter of 8 mm, is most likely to produce a lateral resolution artifact.

620. Which sound wave is least likely to create cavitation? A. 5 MHz, 2 MPa B. 2 MHz, 4 MPa C. 6 MHz, 2 MPa D. 2 MHz, 2 MPa

C. Low values of mechanical index indicate low likelihood of cavitation. Derived mathematically from a sound wave's frequency and pressure, mechanical index is lowest with high frequency and low pressure.

505. A maximum Doppler shift is obtained when the angle between the direction of blood flow and the direction of the sound beam is A. 10 degrees B. 90 degrees C. 180 degrees D. 270 degrees

C. Maximum Doppler shifts occur when red blood cells travel directly toward or directly away from a transducer. An angle of 180° between the sound source and the direction of motion exists when the cells travel directly away from the transducer.

503. Two otherwise identical Doppler studies are performed, except that the angle between flow and the sound beam is 0 degrees in the first study and 60 degrees in the second. The velocity measured in the first study is 2 m/s. What velocity will be measured in the second study? A. 2 m/s B. 4 m/s C. 1 m/s D. cannot be determined

C. Maximum velocities are measured at a zero degree angle. Only one-half of the true velocity is measured when the angle is 60 degrees.

586. In diagnostic imaging, how does multipath artifact affect the image? A. poor angular resolution B. creation of hyperechoic regions C. mild image degradation D. gross horizontal misregistration

C. Multipath artifact does not manifest itself in a pronounced manner. The primary result of this artifact is mild image degradation.

400. What is the primary advantage of multiple focal zones along each scan line of a two- dimensional image? A. improved temporal resolution B. decreased temporal resolution C. improved lateral resolution D. improved longitudinal resolution

C. Multiple foci along a single scan line creates a composite beam that is extremely narrow. Narrow sound beams create images with superior lateral resolution at all depths. Single focus systems use a single sound beam to create each scan line, and lateral resolution is optimal at only one depth.

556. Which artifact is not affected by the shape or dimensions of an ultrasound pulse? A. lateral resolution B. slice thickness C. mirror imaging D. longitudinal resolution

C. Of the artifacts listed, only mirror imaging is unrelated to the size, shape, or geometry of the ultrasound pulse. The others depend in some way on the pulse's characteristics.

405. Of the following, which imaging modality has the poorest temporal resolution? A. two-dimensional, real-time B. A-mode C. color flow imaging D. M-mode

C. Of the choices, color flow imaging has the lowest temporal resolution. Many pulses are required to create a single color flow image. The large number of pulses required for each image results in a low frame rate and poor temporal resolution.

466. Which of these components typically has the greatest dynamic range? A. display B. pulser C. amplifier D. demodulator

C. Of the four choices, the component of an ultrasound system with the greatest dynamic range is the amplifier.

403. An ultrasound system with a 4.0 MHz transducer is used to image structures as deep as 15 cm. Twenty images are produced each second, each requiring 100 acoustic pulses. What is the PRF of the system? A. 1,500 Hz B. 300 Hz C. 2,000 Hz D. 4 MHz

C. Pulse repetition frequency is defined as the number of pulses produced by anultrasound system in one second. In this example, 100 pulses are required to construct a single image, and 20 images are displayed each second. Thus, a total of 2,000 pulses are each second to meet the imaging requirements of this system; this is the PRF. In this question, frequency and imaging depth are unimportant.

270. Which transducer has the worst axial resolution? A. 2 cycles/pulse, 4 MHz B. 4 cycles/pulse, 4 MHz C. 4 cycles/pulse, 2 MHz D. 2 cycles/pulse, 2 MHz

C. Pulses with the most cycles and the lowest frequency have the worst axial resolution.

561. What type of artifact causes a reflection to be placed at an incorrect depth? A. lateral incertitude B. shadowing C. range ambiguity D. indeterminate relaxation

C. Range ambiguity means that uncertainty exists regarding the depth of a structure in the body.

268. Two ultrasound systems produce acoustic pulses. A pulse from System 1 has a wavelength of 0.5 mm, 4 cycles per pulse, and a pulse repetition period of 1.2 msec. The pulses from System 2 have a wavelength of 1.0 mm, 2 cycles per pulse, and a pulse repetition period of 1.8 msec. Which ultrasound system will have a lower numerical value of axial resolution? A. System 1 B. System 2 C. both are the same D. cannot be determined

C. Range resolution is equal to one-half the spatial pulse length. Spatial pulse length is equal to the number of cycles in the pulse multiplied by the wavelength. System 1's pulse length is 4 x 0.5 mm = 2.0 mm. System 2's pulse length is 2 x 1.0 mm = 2.0 mm. Since both systems have identical pulse lengths, their axial resolutions are also identical.

204. What is the uniform dispersion of a sound wave in many different directions after striking a very small particle? A. microscattering B. backscattering C. Rayleigh scattering D. total absorption

C. Rayleigh scattering is the redirection of an acoustic wave in many different directions as a result of striking a small particle. When Rayleigh scattering occurs, the dimension of the reflecting particle is usually less than the wavelength of the ultrasound wave. The amount of Rayleigh scattering also depends on the frequency of the ultrasound.

201. An acoustic smooth boundary where the irregularities pulse reflects from a very on the surface of the boundary are much under these circumstances? type of reflection is most likely to occur smaller than the pulse's wavelength. What A. partial B. Rayleigh C. specular D. total

C. Reflections from a smooth boundary are The waves strike this smooth boundary specular. A mirror is a specular reflector. and reflect in an organized, systematic manner. the wavelength of the incident ultrasonic irregularities in its surface are smaller than A boundary is considered smooth when beam.

569. Which artifact results in improper side-by- side positioning of reflectors? A. multipath B. comet tail C. refraction D. reverberation

C. Refraction artifact results from an acoustic pulse bending and changing direction. This change of direction is not corrected by the ultrasound system and results in an improper lateral location of reflectors on the image.

544. Which situation will commonly produce reverberation artifact? A. two masses that lie perpendicular to the sound beam's main axis B. two weak reflectors that lie close to each other along the axis of the beam C. two strong reflectors that lie along the main axis of the beam D. a single highly reflective mass

C. Reverberations are commonly produced by a pair of strong reflectors that lie along the main axis of an ultrasound beam.

378. How are the piezoelectric crystals excited when using an ultrasound system with a sequential linear array transducer? A. singly and in order: the first crystal, second, then the third, etc. B. in pairs: the first two crystals, the 3rd and 4th, the 5th and 6th, etc. C. in a specific order D. in a random sequence

C. Sequential linear array transducers fire small groups of piezoelectric crystals in a specific succession or progression. The order of firing is determined by the manufacturer, and is chosen to produce the highest quality image. There is, however, no specific order that all linear arrays use. The firing pattern is best described as "in a specific order."

547. Where are shadowing artifacts commonly seen on an acoustic scan? A. deeper than a structure with a high impedance B. shallower than a structure with a low propagation speed C. deeper than a structure with a high attenuation D. alongside of a structure with a low elastance

C. Shadowing occurs on an image at locations beneath strong attenuators. For example, a region deeper than a gallstone may be affected by shadowing.

576. Which of these pulses is least likely to produce an axial resolution artifact? A. 10 MHz, 8 mm beam diameter, 6 cycles per pulse B. 4 MHz, 4 mm beam diameter, 2 cycles per pulse C. 9 MHz, 8 mm beam diameter, 2 cycles per pulse D. 6 MHz, 2 mm beam diameter, 2 cycles per pulse

C. Short pulses are least likely to produce an axial resolution artifact. Short pulses are those with a high frequency and few cycles per pulse. Although choice C does not have the highest frequency, it has only 2 cycles per pulse, and therefore is the shortest of the 4 pulses.

572. What artifact results from an ultrasound beam having a finite and measurable three-dimensional profile? A. acoustic speckle B. multipath artifact C. slice thickness artifact D. grating lobe artifact

C. Slice artifact occurs because a sound beam has a thickness. Although the sonographer imagines that the imaging plane is extremely thin, the beam actually has a measurable thickness. Thickness artifact results in some reflectors appearing in the image even though they are positioned above or below the idealized imaging plane.

39. Sound can be characterized as: A. energy flowing through a vacuum B. a variable C. cyclical oscillations in certain variables D. a principle of acoustics

C. Sound is a wave. A wave is the rhythmical variation throughout time.

125. What is the best estimate for the speed of sound in tendon? A. 1,000 m/s B. 1,540 m/s C. 1,754 m/s D. 5,400 m/s

C. Sound slightly faster in tendon than in soft tissue.

120. What is the best estimate of the distance that sound can travel in soft tissue in one second? A. one yard B. one hundred yards C. one mile D. ten miles

C. Sound travels at a speed of 1,540 meters per second in soft tissue. This is approximately one mile per second.

131. If sound doesn't travel at 1,540 m/sec in a medium, then the medium ______ A. must be soft tissue B. may be soft tissue C. cannot be soft tissue

C. Sound waves travel exactly 1,540 m/sec in soft tissue. Since the propagation speed of sound in this medium is not 1,540 m/sec, the medium cannot be soft tissue.

149. The spatial pulse length describes certain characteristics of an ultrasound pulse. What are its units? A. time B. hertz C. meters D. none; it is unitless

C. Spatial pulse length is the distance that a pulse occupies in space. Its length is measured from the beginning to the end of the pulse. It can be reported in any unit of distance.

429. At which imaging depth is the slope of the TGC curve most effective? A. the region very close to the transducer B. the far zone C. the focal zone

C. TGC is most effective in improving image quality in the focal zone. Compensating for attenuation in the focal zone allows the ultrasound system to produce high-quality scans with detailed information.

629. A comprehensive and scholarly review of bioeffects is performed by the American Institute of Ultrasound in Medicine for all of the following reasons except: A. ultrasound is a versatile technique B. ultrasound has proven widespread clinical utility C. ultrasound is considered highly toxic D. applications of ultrasound are growing considerably

C. The AIUM examines bioeffects research because diagnostic ultrasound is a clinically relevant, popular, and widely used imaging technique. Diagnostic ultrasound is not, however, considered highly toxic or likely to expose patients to substantial risks.

504. What is true of the Doppler shift when the sound beam is normally incident to the velocity of the red blood cells? A. it is at maximum B. it is half of maximum C. it is absent D. it is at minimum

C. The Doppler shift is related to the angle between the directions of the blood flow and the sound wave. The cosine of this angle indicates the percentage of the true velocity that is measured by Doppler. Normal incidence indicates a 90° angle between blood flow and the sound beam. The cosine of 90° is zero. Therefore, zero percent of the velocity is measured; the Doppler shift is absent.

276. How thick is the active element of a 3 MHz pulsed wave transducer? A. 1.54 mm B. 0.51 mm C. half the wavelength of the sound wave in the PZT D. one-quarter the wavelength of sound in the matching layer

C. The PZT is half a wavelength thick. That is, the thickness is equal to one-half the wavelength of sound in the PZT.

183. Which intensity is most closely correlated to tissue heating? A. SPTP B. SATP C. SPTA D. SATA

C. The SPTA intensity relates most closely to tissue temperature elevation.

522. During a pulsed Doppler exam, aliasing is observed. All of the following may eliminate aliasing except: A. selection of another imaging view with a shallower sample volume B. selection of another transducer with a lower frequency C. selection of another imaging view that provides a greater pulse repetition period D. use of a continuous wave system

C. The actions that will reduce the likelihood of aliasing are: 1. selecting a shallower imaging depth to increase the PRF 2. using a transducer with a lower frequency, and 3. using a continuous wave Doppler system that cannot alias If the sonographer selects an imaging view with a greater pulse repetition period, the pulse repetition frequency will decrease and the likelihood of aliasing will increase.

300. What is the best estimate of the propagation speed of the ferroelectric element of a transducer used in a typical diagnostic imaging laboratory? A. 1.2 mm/usec B. 4.0 m/sec C. 4.0 mm/usec D. 1.0 km/sec

C. The active element of a typical diagnostic imaging transducer has a propagation speed that is approximately three to five times greater than the speed of ultrasound through soft tissue. This range is approximately 4 to 8 km/sec. Other ways of stating this are 4 to 8 mm/usec, or 4,000 to 8,000 m/sec. Choices A, B, and D are all too low to be the speed of sound in an imaging crystal.

422. Which of the following is a typical value for the amplification of a signal by the receiver? A. 50 to 100 watts B. -50 to -100 dB C. 50 to 100 dB D. 5 to 25 W/cm2

C. The amplification of the weak electrical signals that first reach the receiver range from 50 to 100 decibels. This prepares the signals for further processing.

279. Which component of an ultrasound transducer is made from a slab of epoxy embedded with tungsten particles? A. the matching layer B. the piezoelectric crystal C. the damping material D. the computer chips

C. The backing material, or damping material, of a transducer assembly is often fabricated of tungsten-embedded epoxy.

447. What is the smallest part of a digital picture called? А. bit B. byte С. pixel D. fractel

C. The basic element of a digital representation of an image is the pixel. The term is derived from the words "picture element".

404. Which of the following sector imaging systems will have the best image detail if all other parameters are identical? A. a 90° sector with 100 pulses/image B. an 80° sector with 40 pulses/image C. a 70° sector with 84 pulses/image D. a 60° sector with 60 pulses/image

C. The best image detail is provided by the system with the highest line density. Line density is defined as the number of acoustic lines per degree of sector angle. The more lines per sector degree, the closer together the scan lines are, and the greater the anatomic detail displayed. Choice C has 1.2 acoustic pulses per degree (84/70), choice A has a line density of 1.11 (100/90) lines/degree, choice B has 0.5 (40/80) lines/degree, and choice D has 1 (60/60) line/degree. Choice C has the highest line density and the best spatial resolution.

47. Waves that exist at the same location and time will combine. What is this called? A. inference B. rarefaction C. interference D. longitudinal interaction

C. The combination of many waves into a single wave is called interference.

136. Compressibility describes a characteristic of a medium. Which two terms describe the same property as compressibility? A. density and stiffness B. density and conductance C. stiffness and elasticity D. elastance and impedance

C. The compressibility of a medium describes its ability to reduce its volume when a force is applied to it. For example, a marshmallow is compressible because when it is squeezed, it gets smaller. Elasticity has the same meaning as compressibility. Stiffness describes this same characteristic; however, stiffness is the opposite of compressibility.

293. Damping material is secured to piezoelectric material during the fabrication of an ultrasonic imaging transducer. Which of the following is not a consequence of this attachment? A. bandwidth increases B. quality factor decreases C. sensitivity increases D. transducer case is longer

C. The damping material of an imaging transducer decreases the transducer's sensitivity. The backing material increases bandwidth, decreases the Q-factor, and lengthens the transducer case.

206. To which of the following is Rayleigh scattering related? A. half of the wavelength B. square root of propagation speed C. frequency^4 D. PRF2

C. The degree to which a wave exhibits Rayleigh scattering is related to frequency raised to the fourth power. That is, if the frequency is twice as high, Rayleigh scattering is increased 16-fold: 24 = 2 x 2 x 2 x 2 = 16

612. Of the following choices, which is considered the most important for the sonographer with regard to bioeffects? A. pulse repetition frequency B. frequency C. duration of the study D. imaging mode

C. The exam duration is most significant because the sonographer directly controls it. Exams should always be of high quality and should provide relevant diagnostic information with a secondary goal of minimizing output power level and time exposure to the patient.

389. Which transducer possesses the best slice thickness resolution? A. linear phased arrays B. 2-D arrays C. 12 dimensional arrays D. linear sequential arrays

C. The greatest advantage of 12 dimensional arrays is that they create very thin ultrasound slices.

587. Which of the following determines the spatial resolution of an image on a monitor? A. strength of the electron beam B. form of phosphor coating of the screen C. number of lines of the monitor's display D. the pulse duration

C. The image displayed on a monitor is composed of a number of horizontal lines. The detail within the image, called spatial resolution, is determined by the number of TV lines on the screen.

84. What are the units of intensity? A. watts B. watts/cm C. watts/cm2 D. dB

C. The intensity of a beam is the power in the beam divided by its cross-sectional area. Power has units of watts and beam area has units of square cm. Intensity has units of watts/cm2.

82. The intensity of an ultrasound beam is defined as the ____in a beam ______by the _____of the beam. A. power, multiplied, diameter B. amplitude, divided, area C. power, divided, area D. amplitude, multiplied, circumference

C. The intensity of an ultrasound beam is the concentration of the power within the beam area. It is calculated by dividing the power in a beam by its area. The units of intensity are watts per centimeter squared, w/cm2.

559. If an ultrasound pulse travels through a large mass in the body at a speed of 1.2 mm/us, what happens to the position of all echoes produced from reflectors shallower than the mass? A. they are placed in too shallow a location on the image B. they are placed in too deep a location on the image C. they are likely to be placed at the correct depth

C. The mass has a propagation speed different than that of soft tissue. Only structures deeper than the mass will be affected. However, this question asks about reflectors that are shallower than the mass. Reflections from structures shallower than the mass are not affected by this speed difference.

232. What is the maximum permissible value for both the intensity reflection coefficient and the intensity transmission coefficient? A. 100 B. 1% С. 1 D. infinity

C. The maximum percentage of the incident intensity that either reflects or transmits is 1.0 or 100%. At the extremes, total reflection occurs (intensity reflection coefficient = 1.0) or complete transmission occurs (intensity transmission coefficient = 1.0). The upper limit of both of these coefficients is 1.0.

619. Which selection has the highest mechanical index? A. high frequency, high power B. high PRF, high intensity C. low frequency, high pressure D. high spatial pulse length, high PRF

C. The mechanical index is derived mathematically from the pressure in a sound beam and the sound's frequency. Mechanical index is highest with a high pressure sound beam of low frequency.

102. Which pulse has a lower propagation speed? A. the 10 MHz pulse B. the 2 MHz pulse C. neither pulse D. cannot be determined

C. The propagation speeds of all sound waves are identical while traveling in a specific medium.

139. What are the units of pulse duration? A. units of frequency (Hz, etc.) B. msec only C. units of time (sec, years, etc.) D. units of distance (feet, etc.)

C. The pulse duration is the actual time that a transducer is creating one pulse. Hence, it has units of time. The typical range of pulse durations found in diagnostic imaging equipment is 0.3 to 2 usec, but it is valid to report pulse duration in any unit of time.

157. Which of the following correctly describes pulse repetition period? A. the product of wavelength and propagation speed B. the reciprocal of the frequency C. the sum of the pulse's "on" time and the listening "off" time D. the time that the transducer is pulsing

C. The pulse repetition period is the actual time from the start of one pulse to the start of the next pulse. It is equal to the time that the transducer is pulsing (the pulse duration) plus the time that the ultrasound system is listening for reflected echoes.

408. A sonographer reduced the sector size from 90 degrees to 30 degrees. Frame rate, however, did not change. What else happened? A. imaging depth decreased B. pulse duration increased C. multi-focus was turned on D. PRF was increased

C. The question states that sector size was decreased. By itself, this would increase frame rate. Thus, the correct answer to this question is something that would decrease frame rate. The only selection that decreases frame rate is the use of multiple focal points, choice C.

304. What is the smallest cross sectional area region from the transducer to sound beam called? A. focus B. half-value thickness C. near zone D. Fraunhofer zone

C. The region from the transducer to the narrowest portion of an ultrasound beam is defined as the near zone, or Fresnel zone.

427. Which term best describes the region of minimum amplification on a standard TGC curve? A. far field B. focus only C. area close to the transducer D. focal zone

C. The region of minimum amplification on a TGC curve, often called the "delay," is always associated with the area close to the transducer.

305. The area that starts at the beam's smallest diameter and extends deeper is: A. the distant zone B. the Fresnel zone D. the depth of penetration C. the Fraunhofer zone

C. The region that extends deeper from an deeper is called the far zone, or Fraunhofer ultrasound beam's narrowest diameter and zone.

87. What determines the intensity of an ultrasound beam after it has traveled through the body? A. the sound wave's source B. the medium through which the sound travels C. both A and B D. neither A nor B

C. The source and the medium both ultimately determine the residual intensity of an ultrasound beam after it passes through the body. Sound waves attenuate as they propagate. The initial intensity of a sound beam is established by the source of the sound, the transducer. The frequency, which is also determined by the transducer, affects the rate of attenuation. In addition, the characteristics of the medium help to determine attenuation. For example, bone and lung have a greater attenuation rate than soft tissue. In contrast, water has a lower attenuation rate than soft tissue.

153. Using a specific transducer, what happens to the spatial pulse length as the sonographer increases the maximum imaging depth? A. increases B. decreases C. remains the same D. cannot be determined

C. The spatial pulse length is determined by the number of cycles in the pulse and the wavelength of each cycle. With the same system, these factors are unchanged, and the spatial pulse length remains the same.

150. In diagnostic imaging, what determines the spatial pulse length? A. the ultrasound system B. the medium through which the pulse travels C. both A and B D. neither A nor B

C. The spatial pulse length is the distance, or length, of a pulse. It depends, in part, upon the wavelength of each cycle in the pulse. Wavelength depends upon both the source of the sound and the medium through which the sound travels. The length of the entire pulse also depends upon both the source and the medium.

119. The propagation speed of continuous wave ultrasound is 1.8 kilometers per second. The wave is then pulsed with a duty factor of 50%, What is the new propagation speed? A. 0.5 km/sec B. 0.9 km/sec C. 1,8 km/sec D. 3.6 km/sec E. cannot be determined

C. The speed of sound in a medium is determined only by the medium. There is no difference in sound's speed whether the wave is continuous or pulsed. Thus, the new and old speeds will be identical, 1.8km/sec.

537. What is the meaning of the term "analysis" in the context of spectral analysis of Doppler signals? A. building a sophisticated signal from components B. building a simplified signal from components C. identifying the building blocks or components of a complex signal D. measuring a complex signal, then modifying its information content

C. The term analysis defines the act of scrutinizing an object to determine what individual components are incorporated within it. In Doppler analysis, the complex signal is broken down into its more basic ingredients.

597. The_____ measures beam intensity at specific locations, whereas a _____measures the entire energy in a sound beam. A. calorimeter, thermocouple B. Schlieren, thermocouple C. thermocouple, calorimeter D. thermometer, hydrometer

C. The thermocouple is a small electronic thermometer that measures the sound beam's energy at specific locations. The calorimeter absorbs all the beam's energy, converting it to heat. The calorimeter measures all the beam's energy.

148. What happens to the pulse duration when a sonographer decreases the maximum imaging depth in an ultrasound scan? A. increases B. decreases C. remains the same D. cannot be determined

C. The time that a transducer is "pulsing" does not change with alterations in depth of view.

151. Which of the following best describes the spatial pulse length? A. frequency multiplied by wavelength B. PRF multiplied by wavelength C. wavelength multiplied by the number of cycles in the pulse D. duty factor multiplied by the wavelength

C. The total length of a pulse equals the length of each cycle in the pulse multiplied by the number of cycles in the pulse. Imagine the pulse as a train made up of a number of boxcars. The train's length (the spatial pulse length) equals the length of each car (the wavelength) multiplied by the number of cars in the train (the number of cycles in the pulse).

246. What conditions are necessary for refraction to occur at a boundary between two media? A. unequal acoustic impedances and normal incidence at the boundary B. unequal densities of the media and normal incidence at the boundary C. dissimilar propagation speeds and oblique incidence at the boundary D. different elasticities of the media and oblique incidence

C. The two conditions required for refraction are: 1. a sound wave must be obliquely incident to the border between two media, and 2. the media on either side of the border must have dissimilar propagation speeds. Refraction occurs during transmission of a wave from one medium to another.

76. The power of an ultrasound wave can be reported with which of the following units? (More than one answer may be correct.) A. watts/square centimeter B. dB/cm C. watts D. kg/cm2

C. The units of power are watts. This is the same measure of power as for light bulbs, stereo systems, and curling irons.

499. Two ultrasound transducers are used to perform Doppler exams on the same patient. The exams are identical except that the transducer frequencies are 5 and 2.5 MHz. Which exam will measure the highest velocities? A. the 2.5 MHz exam B. the 5 MHz exam C. neither D. cannot be determined

C. The velocities measured by Doppler exams are the same, regardless of the frequency of the transducer. Although the Doppler shifts associated with the velocities may vary with different transmitted frequencies, the measured velocities are identical.

175. In the case of pulsed ultrasound, what is the maximum value of the duty factor? A. 100% В. 1 C. less than 100% D. none of the above

C. This question is a bit tricky. When dealing with a pulsed ultrasound system, at least a tiny bit of time must be spent listening rather than transmitting. Therefore, the percentage of time transmitting must be less than 1 or 100%. If the percentage equals 100%, the system is continuous wave. The correct choice, C, distinguishes between pulsed and continuous wave by stating that the maximum value of the duty cycle must be less than 100% for a pulsed system.

209. A sound beam travels 9 cm in soft tissue. The attenuation coefficient is 3 dB/cm. What is the total attenuation that the sound beam experienced? A. 9 dB B. 3 dB C. 27 dB D. 18 dB

C. To calculate total attenuation, multiply path length by attenuation coefficient. In this example, the overall attenuation is 3 x 9 =27 dB.

392. Which of the following will improve a system's temporal resolution? A. increased sector angle B. increased line density C. increased PRF D. increased frequency

C. To improve temporal resolution, increase the number of images produced each second. If the number of pulses emitted per second is increased (choice C) then the system can increase the frame rate. Increased PRF is obtained by decreasing the maximum imaging depth. A, B, and D all decrease frame rate and decrease temporal resolution.

542. Ultrasound systems are designed to automatically A. display similar structures with equal brightness, regardless of depth B. position structures at the correct depth, regardless of the medium C. display all reflections on a line corresponding to the main axis of the sound beam, regardless of refraction D. select the optimal beam width based on the clinical application

C. Ultrasound systems assume that all reflections are created from reflectors that lie directly along the main axis of the ultrasound beam. An artifact is created when pulses refract and change direction.

570. What assumption is violated when a refracted sound wave is processed? A. waves travel directly to and from a reflector B. sound travels at an average speed of 1.54 mm/us C. sound travels in a straight line D. the acoustic imaging plane is very thin

C. Ultrasound systems create images on the basis of certain assumptions. Artifacts occur when these assumptions are invalid. Refraction artifact results from sound traveling in a crooked or bent line while the ultrasound system assumes a straight path.

235. If the_____ of two media are different and sound strikes a border between the media at 90° incidence, then reflection will occur. A. conductances B. densities C. impedances D. propagation speeds

C. Under the conditions of orthogonal or normal incidence, reflection depends on differences in the acoustic impedances of the media either side of the boundary. With normal incidence, as long as the impedances are dissimilar, reflection will always occur.

97. The wavelength of an ultrasonic wave is determined by: A. the sound source B. the medium through which the wave travels C. both A and B D. neither A nor B

C. Wavelength is determined by both the sound source and the medium through which it travels. Wavelength is determined, in part, by the wave's frequency (which is established by the sound source). Wavelength is also affected by the speed of the sound wave, which is established by the medium. In a particular medium, higher frequency waves have shorter wavelengths. With a particular frequency, faster propagation speeds create longer wavelengths.

199. An acoustic wave is traveling through soft tissue. Its intensity undergoes six decibels of attenuation. How does the final intensity of the wave relate to the intensity of the wave when it started its journey? A. it is now four times larger B. it is now six times larger C. it is now one-fourth as large D. it is now one-tenth as large

C. When a wave undergoes 6 dB of attenuation, the intensity of the wave is decreased to one-fourth of its initial value. The term attenuation means "to weaken, or reduce." Attenuation always describes a reduction in the intensity of the wave. Six decibels of attenuation is made up of two groups of -3 dB. Each -3 dB indicates a halving of intensity. One-half multiplied by one-half means that only one-fourth of the original intensity remains.

493. If red blood cells are traveling toward a transducer is the frequency reflected transducer, the frequency emitted by the from the red blood cells. A. greater than B. equal to C. less than

C. When red blood cells approach a transducer, a positive Doppler frequency shift results. The emitted frequency is lese than the reflected frequency.

335. The lateral resolution of an ultrasound system is 4 mm. Two structures are separated by 3 mm and lie side by side in relation to the sound beam's main axis. What will most likely appear on the system's display? A. two weak echoes, 4 mm apart B. two bright echoes, 3 mm apart C. one echo D. two bright echoes, 7 mm apart

C. When two structures are closer together than the resolution of an ultrasound system, the images of the structures will blur together. Since these structures are 3 mm apart and the lateral resolution is 4 mm, only a single echo representing both reflectors will appear on the image.

353. With B-mode, on which axis is the strength of the reflection input? A. X-axis В. у-аxis C. z-axis

C. With B-mode, reflection strength is input into the z-axis.

205. Which of the following is considered a Rayleigh scatterer? A. bone B. liver C. muscle D. blood cell

D. A blood cell is a Rayleigh scatterer. A red blood cell is smaller than the wavelength of the typical acoustic wave used in diagnostic imaging. When an acoustic wave strikes a blood cell, the energy within the pulse is scattered in many directions.

45. The direction of motion of a particle in a wave is perpendicular to the direction of propagation of the wave. What type of wave is this? A. longitudinal B. acoustic C. mechanical D. transverse

D. A characteristic of transverse waves is that the direction of propagation is perpendicular to the direction of particle motion in the wave. Sound waves are not transverse, but rather longitudinal.

545. What are the characteristics of a medium that produces comet tail artifact? A. weak reflectors, closely spaced, low propagation speeds B. strong reflectors, widely spaced, high propagation speeds C. strong reflectors, closely spaced, low propagation speed D. strong reflectors, closely spaced, high propagation speed

D. A comet tail artifact is similar to a reverberation except that the reflection is a solid hyperechoic line. The comet tail is a solid jet because of strong reflectors with high propagation speeds lying close to each other.

297. What helps to determine the frequency of the sound produced by the transducer of a continuous wave ultrasound system? A. piezoelectric crystal diameter B. piezoelectric crystal thickness C. damping material density D. ultrasound system electronics

D. A continuous wave (CW) transducer produces an acoustic wave with a frequency equal to the frequency of the electrical signal that excites the crystal. When the pulser's electrical signal has a frequency of 6 MHz, then the emitted acoustic wave is also 6 MHz. The electronics of a CW system determine the frequency of the sound wave.

191. The intensity of a signal declines from 1.5 mW/cm2 to 0.75 mW/cm2. How many decibels is this change in intensity? A. 3 dB B. 0.75 dB C. -0.75 dB D. -3 dB

D. A decline in intensity to one-half of the original level is a change of -3 dB. When the new level is less than the reference level, the reported decibels must be negative. When the new intensity is greater than the reference level, the change in decibels is positive.

455. What is the maximum number of shades of gray that are represented with 4 bits? A. 4 В. 8 С. 12 D. 16

D. A maximum of 16 shades of gray can be represented with 4 bits. To calculate this. multiply 2 by itself the same number of times that there are bits. In this example, multiply 2 by itself a total of 4 times (there are 4 bits): 2 x 2 x 2 x 2 = 16 shades.

474. Which of the following flow patterns is associated with cardiac contraction? A. phasic B. spontaneous C. steady D. pulsatile E. continuous

D. A pulsatile flow pattern describes blood moving at a variable velocity as a result of contraction of the heart. As a result, arterial flow is often described as pulsatile.

548. How is shadowing artifact expressed? A. positioning structures too deep on the image B. locating structures in improper lateral position C. placing reflections in multiple locations D. reflectors being absent on the image

D. A shadow artifact results from unexpectedly high attenuation. The ultrasound beam deeper than the strong attenuator is so weak that significant anatomical information does not appear on the image.

562. What causes side lobe artifact? A. sound beams bending B. linear array transducer architecture C. unexpectedly low acoustic attenuation D. acoustic energy radiating in a direction other than the beam's main axis

D. A side lobe is produced when a significant amount of acoustic energy is directed along a line other than the main axis of the acoustic pulse.

350. Which imaging modality places time-of- flight information on the x-axis and echo amplitude on the y-axis? A. M-mode B. L-mode C. J-mode D. A-mode

D. A-mode, or amplitude mode, displays reflector depth on the x-axis. Reflector depth is determined by a pulse's time of flight. The strength of the reflection is displayed on the y-axis.

351. Which imaging mode accurately displays reflector depth? A. I-mode B. L-mode C. C-mode D. A-mode

D. A-mode, or amplitude mode, displays the reflector depth accurately. A-mode is used in ophthalmology, which requires precise measures of depth or thickness.

342. Which of these terms means adjustable focusing or multi-focusing? A. dynamic aperture B. harmonics C. frequency agility D. phased array

D. All phased array transducers share one of these two features: 1. they have multi-focus capabilities or 2. the focal depth can be changed by the sonographer.

356. To which of the following do the x-axis of a B-mode, the y-axis of an M-mode and the x-axis of an A-mode all relate? A. depth of view C. echo amplitude B. go time D. time of flight

D. All three of these measurements report the reflector depth. Reflector depth is determined by a pulse's time of flight.

603. Which component of an ultrasound system exposes a patient to greatest risk? A. the CRT B. the electric cord C. the pulser D. the transducer

D. Although the risk is small, the transducer exposes the patient to the greatest risk during an ultrasound scan. However, the risk will be substantially greater if the system is not functioning properly or being used in a responsible manner.

409. Which of the following is not considered a component of an ultrasound system? A. master synchronizer B. pulser C. receiver D. image intensifier

D. An ultrasound system is considered to have six components: transducer, pulser, receiver, image processor, display, and master synchronizer. An image intensifier is part of an x-ray imaging system.

377. What is true of the electrical pulses that excite the active elements of an annular phased array transducer? A. they arrive at each piezoelectric crystal at exactly the same time B. they vary in amplitude based on the direction of the steering and focusing C. they excite the crystals at different times, nanoseconds apart D. they arrive at each PZT crystal at different times, microseconds apart

D. Annular array technology fires the piezoelectric crystals in a particular sequence to produce a focused ultrasound beam. The electrical pulses that excite the ringed elements of the array arrive at slightly different times, separated by only very small fractions of a second.

306. Which of these terms have the same meaning? 1) far zone 2) near zone 3) Fresnel zone 4) focal zone 5) Fraunhofer zone 6) lateral zone A. 1 and 2, 3 and 4 B. 1 and 4, 2 and 3 C. 4 and 6, 5 and 1 D. 2 and 3, 5 and 1

D. Another name for the Fresnel zone is the near zone. The Fraunhofer zone can also be called the far zone. (Hint: Fresnel is the short name-it is the near zone. Fraunhofer is the long name-it is the far zone.)

391. The excitation of array elements with dissimilar voltages is called ______ and is used to _____ A. dynamic aperture, reduce refraction B. subdicing, eliminate lobes C. apodization, remove flash artifact D. apodization, reduce lobe artifact

D. Apodization describes the excitation of a number of PZT elements with different voltages. This acts to decrease the strength of off-axis sound beams and reduce lobe artifact.

95. A sonographer adjusts the output power of the wave emitted by the transducer. Which of the following also changes? (More than one answer may be correct.) A. pulse repetition period B. PRF C. propagation speed D. intensity

D. As a sonographer adjusts the output power, the intensity will change. The PRF and pulse repetition period will change only when the maximum imaging depth (also called depth of view) changes. The sound's propagation speed will change only if the medium changes.

231. What remains when the reflected intensity is subtracted from the incident intensity? A. 1.0 B. incident intensity C. transmitted intensity coefficient D. transmitted intensity

D. At any point in time and space, there must be conservation of energy. In other words. all energy must be accounted for. The intensity in a wave as it reaches a border between two media is called the incident intensity. As the wave strikes the boundary, a portion of the wave's intensity is redirected toward the sound source. This is called the reflected intensity. The remainder of the energy continues to propagate and is called the transmitted intensity.

195. What units are used to describe attenuation? A. watts B. watts/cm2 C. macro D. decibels

D. Attenuation is measured in decibels. Attenuation is reported as a relative change in strength, not an absolute change.

611. When studying bioeffects, which research approach is more important? A. empirical B. mechanistic C. neither is important D. both are equally important

D. Both the empirical and the mechanistic approaches are important. The strongest bioeffects conclusions are reached when the results of both approaches are in agreement.

80. The final reduced to one-half amplitude of an acoustic wave is of its original value. The final power is _____ the original power. A. the same as B. one-half C. double D. none of the above

D. Changes in the power of a wave are proportional to changes in the wave's amplitude squared. One-half squared equals one-quarter (1/2 x 1/2 = 1/4). When one-half of the wave's original amplitude remains, then only one-fourth of the original power remains.

186. Decibel notation is a _____ between two numbers. A. difference B. sum C. product D. ratio

D. Decibels are calculated by dividing the final strength of a signal by the starting strength. Thus, decibel notation is a ratio between two numbers.

498. Blood moving at a velocity of 2 m/s creates a Doppler frequency of 3,000 Hz. What will the Doppler shift be if the velocity increases to 4 m/s? A. 3,000 Hz B. 2 Hz C. 1,500 Hz D. 6,000 Hz

D. Doppler shifts are directly related to reflector velocity. Higher velocities create higher Doppler shifts. Lower velocities create lower Doppler shifts. When the velocity doubles, the Doppler shift doubles.

173. What is a typical value for the duty factor (also called the duty cycle) of pulsed sound waves used in diagnostic imaging? A. 0.001 msec B. 0.001 kg/cm3 C. 0.75 D. 0.001

D. Duty factor, or duty cycle, is the percentage or fraction of time that an ultrasound system produces an acoustic signal, or is transmitting. Typically, ultrasound transducers spend the vast majority of time receiving, and only a small fraction of time transmitting an acoustic signal.

373. Which of the following forms of focusing is different from the others? A. lens B. mirror C. phased D. dynamic receive

D. Dynamic receive focusing is accomplished during reception of reflected sound. The other three techniques are forms of focusing during transmission.

615. According to the AIUM, at what in situ tissue temperature is there danger to a fetus? A. 100° C B. 98.6° F C. 1° F over normal temperature D. 41° C

D. Elevation of fetal tissue in excess of 41° C is considered potentially harmful.

553. Acoustic focusing of an ultrasound beam may create which artifact? A. side lobes B. refraction C. speckle D. enhancement

D. Focusing of an ultrasound beam may result in very strong reflections from anatomic structures at the depth of the focus. The powerful reflections result in a hyperechoic band that is called focal enhancement or focal banding.

457. How many bits are required to display 10 different shades of gray? 14 shades? 15 shades? A. 4 bits, 5 bits, 6 bits B. 10 bits, 14 bits, 15 bits C. 4 bits, 4 bits, 2 bits D. 4 bits, 4 bits, 4 bits

D. Four bits of memory are required to display 10, 14, or 15 shades of gray. Three bits can display a maximum of 8 gray shades (2 x 2 x 2 = 8). Adding a single bit to the collection increases the number of gray shades to 16 (2 x 2 x 2 x 2 = 16).

57. What is the range of frequencies emitted by transducers used in ultrasonic imaging? A. 1 to 3 MHz B. 1 to 1,000 kHz C. -10,000 to +10,000 Hz D. 2,000,000 to 15,000,000 Hz

D. Frequencies commonly used in diagnostic imaging range from approximately 2 to 15 megahertz or 2 to 15 million cycles per second.

126. As a general rule, which of the following lists media in increasing order of propagation speeds? A. gas, solid, liquid B. liquid, solid, gas C. solid, liquid, gas D. gas, liquid, solid

D. Generally, sound travels slowest in gases, faster in liquids, and fastest in solids.

454. What happens to an image when the number of bits allocated to each pixel increases? A. spatial detail improves B. frame rate increases C. field of view expands D. more shades of gray

D. In a digital representation of an image, as the number of bits assigned to each pixel increases, the number of different shades of gray in the image increases.

492. In clinical imaging, which reflectors produce most relevant Doppler shifts? A. blood vessels B. blood plasma C. platelets D. red blood cells

D. In clinical imaging, red blood cells are the primary reflectors that produce Doppler shifts. Blood cells constantly move through the circulatory system and make up nearly 45% of the volume of the blood.

516. With pulsed Doppler, what term is used to describe a very high positive Doppler shift that is displayed as a negative waveform? A. attenuation B. filtering C. demodulation D. aliasing

D. In pulsed Doppler exams, the phenomenon where high velocities are displayed as negative velocities is called aliasing. The term alias means "having a false identity".

407. All of the following reduce temporal resolution by increasing the number of pulses per image except: A. increasing the number of foci B. increasing line density C. increasing field of view D. increasing depth of view

D. Increasing the depth of view does not alter the number of pulses per image. Increasing depth of view decreases temporal resolution by changing the pulse repetition period while leaving the number of pulses in each image unchanged.

600. Under which condition is it permissible to perform a diagnostic ultrasound exam? A. when the patient will benefit B. when the patient has insurance C. when the exam is perfectly safe D. when the benefits outweigh the risks

D. It is proper to perform a diagnostic ultrasound exam when the benefit to the patient outweighs the risks that may be present.

339. Which of the following focusing techniques is different from the others? A. lens B. curved crystal C. fixed D. phased

D. Phased focusing is achieved with the electronics of an ultrasound system. Phased focusing is adjustable. Focusing with either a lens or curved crystal is fixed.

546. What is the most likely cause of ring down artifact? A. refraction B. inversion C. reabsorption D. reflection

D. Ring down artifact is thought to result from multiple reflections.

549. Which of these produces shadowing? A. reverberation B. multipath C. reflection D. attenuation

D. Shadowing results from atypical attenuation, the weakening of ultrasound pulses.

181. Which of the following terms does not belong with the others? A. increased depth of view B. decreased duty factor C. increased pulse repetition period D. decreased spatial pulse length

D. Spatial pulse length is unrelated to alterations in depth of view. The other three selections are all related to deeper imaging.

406. Which ultrasound imaging modality has the best temporal resolution? A. B-scanning B. duplex imaging C. color flow imaging D. M-mode

D. Temporal resolution is the ability to accurately record the position of moving reflectors. With M-mode, the ultrasound pulse tracks reflector position in only a single dimension (depth only) and delivers extremely fine temporal resolution. The remaining choices all operate in two dimensions and do so by compromising temporal resolution.

395. Two imaging systems produce acoustic pulses; one pulse is 0.4 usec long and the other is 0.2 usec long. Which is most likely to provide the best temporal resolution? A. 0.4 usec system B. 0.2 psec system C. they are the same D. cannot be determined

D. Temporal resolution is unrelated to pulse duration. Temporal resolution is determined by the number of frames, or images, that are produced each second. There is insufficient information to answer the question.

517. The highest Doppler frequency without the appearance of aliasing is called the _____ and is equal to _____ A. aliasing limit, half of the emitted frequency B. pulse repetition frequency, the pulse repetition frequency C. Nyquist limit, half of the emitted frequency D. Nyquist limit, half of the emitted PRF

D. The Nyquist limit is the highest Doppler shift that can be displayed without aliasing. The Nyquist limit is equal to half of the pulse repetition frequency (PRF).

172. The pulse repetition frequency is the _____ A. product of the wavelength and propagation speed B. reciprocal of the period C. sum of pulse duration and listening time D. reciprocal of pulse repetition period

D. The PRF and the pulse repetition period are reciprocals. For example, if the PRF is 100 per second, then the pulse repetition period is one-hundredth of a second. If the system creates five hundred pulses per second, then the pulse repetition period is 1/500 of a second.

291. Assume that the frequency of sound with the greatest power emitted by a transducer is 5 MHz. However, the pulse contains acoustic energy with frequencies as low as 3.5 MHz and as high as 6.5 MHz. What is the bandwidth of the transducer? A. 6.5 MHz B. 5.0 MHz C. 3.5 MHz D. 3.0 MHz

D. The bandwidth of a pulse is defined as the range of frequencies that are present within the pulse. To calculate bandwidth, subtract the lowest frequency from the highest frequency in the acoustic signal (6.5 - 3.5 = 3.0 MHz). The bandwidth is 3.0 MHz. The natural or center frequency of this transducer is 5 MHz.

228. An ultrasound wave strikes a boundary between two media. All intensities are measured directly at the boundary. What results when the transmitted intensity is divided by the reflected intensity? A. intensity reflection coefficient B. intensity transmission coefficient C. beam uniformity coefficient D. none of the above

D. The choices of A, B, and C are all incorrect. When the transmitted intensity is divided by the reflected intensity, a number is obtained. This number has no special meaning in ultrasound physics, and is not identified by a special name.

575. Axial resolution artifacts are due to which of the following? A. multiple reflections B. beam width C. attenuation D. pulse length

D. The critical factor that influences axial resolution is pulse length. Shorter pulses produce more accurate images than longer pulses. Shorter pulses have improved axial resolution.

330. Two ultrasound systems produce acoustic pulses. One pulse is 0.4 usec in duration and the other is 0.2 usec. Which pulse will most likely provide the best lateral resolution? A. 0.4 psec pulse B. 0.2 usec pulse C. they are the same D. cannot be determined

D. The duration of a pulse is unrelated to the lateral resolution. Pulse duration affects axial (longitudinal) resolution. It is not possible to answer the question with the information provided.

174. What is the value of the duty cycle for continuous wave ultrasound? А. 100 В. 1% C. 1000% D. none of the above

D. The duty factor for continuous wave ultrasound is 1.0 or 100%. This means that the transducer is producing an acoustic signal at all times. None of the answers indicate this: 100 is not 100%, 1% means one-hundredth and is incorrect, and 1000% means 10 times and is also false.

198. Attenuation is determined by which of the following factors? A. density and stiffness of the medium B. frequency of sound and propagation speed C. PRF of sound and path length D. path length and frequency of sound

D. The factors that determine the degree to which a sound beam weakens are: 1. the distance that the sound travels, and 2. the frequency of the sound.

239. An ultrasound wave approaches an interface between two media at a 90° angle. The propagation speeds and the densities of the two media are different. Which is correct? A. reflection will definitely occur B. reflection will definitely not occur C. refraction may occur D. none of the above

D. The facts presented indicate that the propagation speeds and the densities of the two media are different, but this information is insufficient to determine whether reflection will take place. The important fact is whether the impedances of the media are different. If the impedances of the media are different, then reflection will occur. If the impedances are the same, then reflection will not occur. In this case, since we are unsure as to whether the impedances of the media are the same, we are unsure whether choices A or B are correct. Choice C is incorrect because refraction will never occur when a sound wave strikes a boundary at a 90° angle. The only appropriate answer is D.

308. All of the following are true of the focus except: A. it is at the end of the near zone B. it is at the beginning of the Fraunhofer zone C. it has the highest spatial peak intensity D. it is at the start of the Fresnel zone

D. The focus is located at the end of the near or Fresnel zone. The Fresnel zone starts at the transducer.

6 MHz, and the PRF is 5 kHz. What is the 521. The frequency of a pulsed Doppler wave is maximum Doppler shift that can be recorded without aliasing? A. 6 MHz B. 5 kHz C. 3 MHz D. 2.5 kHz

D. The frequency at which aliasing occurs is called the Nyquist limit and is one-half the pulse repetition frequency. In this example, the pulse repetition frequency is 5 kHz or 5,000 pulses/sec. Thus, the Nyquist limit is 2.5 kHz. Aliasing will occur when Doppler frequencies exceed this value.

296. Which properties of the piezoelectric crystal of a continuous wave transducer result in the highest emitted acoustic wave frequency? A. thin, high propagation speed B. thick, slow propagation speed C. thin, slow propagation speed D. none of the above

D. The frequency of sound emitted by a continuous wave transducer is determined only by the frequency of the electrical signal that excites the piezoelectric crystal. The crystal's thickness and propagation speed do not affect the frequency of sound from a continuous wave transducer.

218. Which value is closest to the impedance of soft tissue? A. 1.5 kiloRayls B. 2.5 deciRayls C. 19 megaRayls D. 2,000,000 Rayls

D. The impedance of soft tissue is in the range of 1.5 to 2.5 million Rayls. Choices A and B are far too low, and choice C is too high.

91. When the power in an acoustic beam is doubled and the cross-sectional area of the beam is halved, then the intensity of the beam is: A. doubled B. halved C. quartered D. four times larger

D. The intensity rises to four times its original value. Intensity is equal to power divided by beam area. In this case, the power is doubled and the area is halved. For example, if the original power was 4 watts and the initial beam area was 4 cm?, then the starting intensity was 4 watts divided by 4 cm?, or 1 watt/cm2. Now, the power is doubled from 4 to 8 watts and the beam area is halved, from 4 to 2 cm2. The new intensity is 8 watts divided by 2 cm2, or 4 watts/cm2. Since the initial intensity was intensity has increased fourfold. 1 and the final intensity is 4 watts/cm2, the

440. What was the original purpose for the ultrasound system's analog scan converter? A. to increase the dynamic range of ultrasound systems B. to make real-time imaging possible C. to increase the sensitivity of ultrasound systems D. to allow for gray scale imaging

D. The introduction of scan converter technology in ultrasound allowed for the presentation of gray scale images. That is, the images were not limited to black and white (bistable), but had various shades of gray within them. Additionally, the scan converter changed the format of the system's data from penetrations to a format suitable for display.

261. Two System A has with 12 bits. Which system has the best 4 bits. System B has 750,000 pixels, each 1,000,000 pixels, each with systems are undergoing evaluation. longitudinal resolution? A. System A B. System B C. both are the same D. cannot be determined

D. The longitudinal resolution of an ultrasound duration or the spatial pulse length. Since system is determined primarily by the pulse the pulse, it is impossible to determine no information is provided on the length of which of the systems will have superior longitudinal resolution. Hint: Longitudinal resolution is also called axial resolution.

302. You are asked to fabricate a pulsed ultrasound transducer with the highest possible frequency. Which piezoelectric crystal would you select? A. 6mm thick, 4 cm diameter, 4.0 mm/us propagation speed B. 8 mm thick, 2 cm diameter, 6.0 mm/us propagation speed C. 4 mm thick, 9 cm diameter, 5.0 mm/us propagation speed D. 2 mm thick, 6 cm diameter, 6.0 mm/us propagation speed

D. The main frequency (also called resonant, natural, or center frequency) emitted by a piezoelectric crystal operating in the pulsed mode is principally determined by the thickness and propagation speed of the crystal. The frequency is greater when the crystal is thin and its propagation speed is high, so the active element listed in D is the proper choice. The diameter of the active element does not affect the frequency of the pulse.

284. What is the thickness of the matching layer of a 2 MHz pulsed wave transducer? A. 1.54 mm B. 0.77 mm C. half the wavelength of the sound wave in the PZT D. one-quarter the wavelength of sound in the matching layer

D. The matching layer is one-quarter wavelength thick. That is, the thickness is equal to one-quarter the wavelength of sound in the matching layer.

233. What is the minimum permissible value for both the intensity reflection coefficient and the intensity transmission coefficient? A. different from each other В. -1 C. 100% D. 0

D. The minimum value for the intensity transmission and the intensity reflection coefficients is zero. At one extreme, it is possible to have total transmission and no reflection (intensity reflection coefficient = 0). At the other extreme, it is possible for total reflection to occur. No transmission would exist and the intensity transmission coefficient = 0.

103. Which pulse has the lowest power? A. the 10 MHz pulse B. the 2 MHz pulse C. neither pulse D. cannot be determined

D. The power of a wave is not related to its frequency. The power relates to the strength of the wave, and in this case, no information is provided about the power. Therefore, we cannot answer this question based on the information provided.

147. What is the pulse duration equal to? A. frequency multiplied by period B. period multiplied by wavelength C. the number of cycles in the pulse divided by the wavelength D. period multiplied by the number of cycles in the pulse

D. The pulse duration is the total time that the transducer is producing a pulse. The pulse duration is equal to the time to make a single cycle (the period) multiplied by the number of cycles that make up the pulse. For example, if there are 6 cycles in a pulse, each with a period of 0.2 usec, then the pulse duration is 6 x 0.2 = 1.2 usec.

99. Which of the following terms best describes the relationship between frequency and wavelength for sound traveling in soft tissue? A. reciprocal B. direct C. related D. inverse

D. The relationship between frequency and wavelength is inverse. Higher frequency waves are related to shorter wavelengths. Lower frequency waves are related to longer wavelengths.

412. What is the typical voltage of the signal that is the input to the receiver of an ultrasound system? A. 0.1 volts B. 500 mvolts C. 250 volts D. 10 uvolts

D. The signal produced by the transducer upon reception and sent to the receiver of the ultrasound system is extremely small and is in the micro- to millivolt range.

104. Which pulse has a longer spatial pulse length? A. the 10 MHz wave B. the 2 MHz wave C. neither wave D. cannot be determined

D. The spatial pulse length is equal to the wavelength multiplied by the number of cycles in the pulse. We know that 2 MHz sound has a longer wavelength than 10 MHz ultrasound. However, the number of cycles that comprise each pulse is unknown. The information provided is insufficient to answer the question.

129. What is the propagation speed of a 5 megahertz sound wave in soft tissue? A. 1,450 meters per sec B. 1,540 km/sec C. 1.54 m/s D. 1.54 mm/us

D. The speed of any sound wave moving through soft tissue, regardless of frequency, is 1.54 mm/usec, 1,540 m/sec, or 1.54 km/sec.

230. What results when the intensity transmission coefficient and the intensity reflection coefficient are added together? A. incident intensity coefficient B. acoustic impedance C. total intensity D. 1.0

D. The sum of the intensity reflection coefficient (IRC) and the intensity transmission coefficient (ITC) equals one or 100%. The ITC is the percentage of a sound wave's intensity that is transmitted of a wave's intensity that is reflected at a at a boundary. The IRC is the percentage boundary. Since there is conservation of energy at the boundary, these percentages added together equal 100% (or 1.0).

426. All of the following are used to describe compensation except: A. swept gain B. depth gain C. time gain D. amplitude gain

D. The terms swept gain, depth gain, and time gain are used interchangeably when describing compensation. The term amplitude gain is not synonymous with the other three terms.

299. An ultrasonic pulse is traveling in soft tissue. Which of the following is most important in the determination of the frequency of the sound? A. the propagation speed of the ultrasound transducer's matching layer B. the thickness of the transducer's backing material C. the impedance of the transducer's matching layer D. the propagation speed of the transducer's active element

D. The two characteristics that determine the frequency of sound in a pulse are: 1. the thickness of the ultrasound crystal and 2. the propagation speed of the crystal. The speed and impedance of the matching layer and the thickness of the backing material are unrelated to the frequency of an ultrasound pulse.

134. What two properties establish sound's propagation speed in a given medium? A. elasticity and stiffness B. stiffness and impedance C. conductance and density D. density and stiffness

D. The two properties of the medium that affect sound's propagation speed are density and stiffness.

325. All of the following terms describe the shape of a sound wave created by a tiny fragment of PZT except: A. spherical B. Huygens' wavelet C. V-shaped D. hourglass shaped

D. The waves are not hourglass in shape. Small pieces of PZT create V-shaped waves. Choices A and B have the same meaning as V-shaped.

625. The upper limit for the SPTA intensity of a focused ultrasound wave where there have been no observed bioeffects is A. 1 mW/cm2 B. 10 mW/cm2 C. 100 mW/cm2 D. 1 W/cm2

D. There have been no independently confirmed significant bioeffects in mammalian tissue exposed to focused ultrasound with intensities below 1 W/cm2.

347. Two ultrasound systems have near zone lengths of 8 cm. At the focus, System S's lateral resolution is 3.0 mm, whereas System C's is 5.0 mm. Which system is most likely to appropriately display two small body structures that lie, one in front of the other, at depths of 8.6 and 9.0 mm? A. System C B. System S C. both have comparable quality D. cannot be determined

D. There is insufficient information to answer the question. The information provided gives insight into the lateral resolution of the systems. However, the question asks about the ability to distinguish two structures that lie one in front of the other, or parallel to the sound beam's main axis. This depends upon axial resolution, and no information is provided about this.

213. Which of these lists indicates media with increasing attenuation of ultrasound? A. water, lung, soft tissue, bone, air B. lung, air, soft tissue, bone C. lung, fat, muscle D. water, blood, fat, muscle, bone, air

D. This list orders tissues with increasing attenuation rates of ultrasound.

479. All of the following decrease the flow energy of a fluid except: A. frictional loss B. viscous loss C. inertial loss D. velocity loss

D. Three energy losses associated with flow throu the circulation are frictional, viscous, and inertial loss.

257. One reflector is 5 times deeper than another. The time of flight of sound to the deeper structure is _____ the time of flight of the shallower reflector. A. one fifth as much as B. equal to C. less than D. five times more than

D. Time of flight and reflector depth are directly related. When a reflector is five times deeper than another, the pulse's time of flight is five times greater.

338. What will lower the value of an ultrasound system's lateral resolution? A. decrease the # of cycles in the pulse B. increase the effective damping material C. increase the pulse repetition period D. use an acoustic lens

D. To lower the numerical value of lateral resolution of an ultrasound system, the diameter of the beam must be reduced, A commonly used technique to decrease the diameter of the beam is to focus the beam with an acoustic lens.

283. Which of the following lists orders the impedance from highest to lowest? A. skin, gel, matching layer, PZT B. PZT, gel, matching layer, skin C. gel, PZT, matching layer, skin D. PZT, matching layer, gel, skin

D. To maximize the transmission of sound energy between the transducer and the body, the impedances of the active element, matching layer, gel, and skin must be in decreasing order. The impedance of the piezoelectric crystal is the highest, the matching layer's impedance is a bit lower, the gel's impedance is lower yet, and the impedance of the skin is the lowest of all.

368. How are the piezoelectric crystals of a linear phased array transducer fired? A. in a single specific pattern B. in order, from top to bottom C. at exactly the same time D. at almost exactly the same time

D. To steer and focus the ultrasound beam that a linear phased array transducer produces, the PZT crystals are excited by electronic pulses at almost the same time. Only billionths of seconds separate the electronic pulses that strike the PZT crystals in the transducer.

61. Ultrasound is defined as a sound with a frequency of ______ A. greater than 20,000 kHz B. less than 1 kHz C. greater than 10 MHz D. greater than 0.02 MHz

D. Ultrasound is defined as an acoustic wave with a frequency so high that it is not audible to humans. Ultrasound is an inaudible wave with a frequency of at least 20,000 Hz, 20 kHz or 0.02 MHz.

64. What is characteristic of acoustic waves with frequencies exceeding 20,000 Hz when compared with waves having frequencies of less than 20,000 Hz? A. they travel more effectively in soft tissue B. they travel more rapidly C. they attenuate less when traveling in soft tissue D. humans can't hear them

D. Waves with frequencies exceeding 20 kHz are inaudible to humans and are called ultrasonic. They travel at the same speed as waves with lower frequencies and attenuate at a faster rate than waves with lower frequencies.

65. What is characteristic of acoustic waves with frequencies of less than 20 Hz when compared with waves having frequencies of more than 20 Hz? A. they travel less effectively in soft tissue B. they travel more rapidly C. they attenuate more when traveling in soft tissue D. humans can't hear them

D. Waves with frequencies of less than 20 Hz are inaudible to humans and are called infrasonic. They travel at the same speed as waves with higher frequencies and attenuate at a lesser rate than waves at higher frequencies.

469. A signal with a 120 dB dynamic range is compressed by 40 dB. What is the dynamic range of the compressed signal? A. 40 dB B. 120 dB С. 3 dB D. 80 dB

D. When a signal's dynamic range is compressed, the decibels of compression are simply subtracted. In this case, 120 - 40 = 80 dB.

237. A sound pulse strikes a boundary between speed of sound in the two media are very two media with normal incidence. The media are identical. What will happen? different; however, the impedances of the A. a big echo will be produced D. there will be no echo at all C. a small echo will result B. a medium echo will result

D. When a sound wave is normally incident at Under these circumstances, no reflection but the media have identical impedances. this example, the wave is normally incident the media have dissimilar impedances. In will occur and 100% of the sound will be transmitted.

558. While imaging a test object, an ultrasound system displays one image 1.8 cm deeper than another. Upon measuring the test object, it is found that it is actually 2.0 cm deeper. What conclusion can be drawn from this? A. speed of sound in the test object is the same as soft tissue B. speed in the test object is less than that in soft tissue C. attenuation of sound in the test object is less than that in soft tissue D. speed in soft tissue is less than that of the test object

D. When vertical misregistration occurs, it is likely that the speed of sound in the medium differs from 1,540 m/sec. If the measurements on the image are less than the true distances, then the speed of sound in the medium is greater than that of soft tissue.

238. Two acoustic waves strike a boundary between two media. The waves are traveling in a direction 90° to the boundary. Reflection of these waves depends on differences in the ______ A. frequencies of the two waves B. propagation speeds of the two media C. amplitudes of the two waves D. impedances of the two media

D. With normal incidence, reflection will occur side of the boundary have different acoustic impedances. Reflection is not dependent on the waves' characteristics such as amplitude and frequency. With normal impedance, only one condition must be met for reflection to take place: the impedances of the media on either side of the boundary must be different.

595. Which modes of Doppler may be assessed with a Doppler phantom? A. color flow Doppler B. pulsed Doppler C. power mode Doppler D. continuous wave Doppler E. all of the above

E. A Doppler phantom is a versatile device that evaluates all Doppler modes including pulsed, continuous wave, color flow, and power mode.

476. Which of the following is not associated with laminar flow? A. layered B. normal C. aligned D. smooth E. chaotic

E. Chaotic does not describe laminar flow. Chaotic flow is associated with turbulent flow.

484. The arterial blood pressure of a standing individual is 120 mmHg at the level of the heart. What is the measured blood pressure at the subject's ankle? A. 100 mmHg B. 0 mmHg C. 40 mmHg D. -100 mmHg E. 220 mmHg

E. Measured blood pressure is equal to the sum of actual blood pressure at heart level and hydrostatic pressure. In this example, 120 mmHg + 100 mmHg 220 mmHg.

272. A sonographer is performing a study on a patient and desires superior depth resolution. Which of the following changes would create such a system? A. higher frequency B. shorter wavelengthS C. fewer cycles per pulse D. less ringing E. all of the above

E. Systems that produce shorter pulses create better pictures and have lower numerical values for depth resolution. Higher frequency, shorter wavelength, and fewer cycles per pulse all shorten the spatial pulse length, decrease the numerical depth resolution, and create more accurate images.

146. The pulse duration cannot be changed under any circumstances or by any action of the sonographer. T/F

False. A sonographer can alter the pulse duration by using a different imaging transducer or ultrasound system.

247. True or False? Refraction always occurs at the interface between two media when the propagation speeds of the media are unequal.

False. A sound wave refracts at the boundary between two media when two conditions are satisfied: 1. the sound beam must be obliquely incident, and 2. the propagation speeds of the two media must be different from each other.

363. Foci exist at multiple depths as an ultrasound beam propagates through the body.

False. A standard mechanical transducer cannot focus at multiple depths or provide for variable or user-selectable focal depths. Mechanical transducers support only a single, unalterable focal depth.

111. The frequency of the wave increases as it travels through the mass. T/F

False. A wave's frequency is determined by the sound source only, and is unaffected by the tissues through which it travels.

604. True or False? The AIUM suggests that in vitro research confirming bioeffects is valuable and valid. Their results are significant and should be directly applied to the clinical arena.

False. Although in vitro experiments results are extremely important, it is difficult to assess their direct clinical significance. Further studies should be performed before applying these conclusions clinically.

531. True or False? Absence of color on a color Doppler image always indicates a region of no blood flow.

False. Although this statement may be true, it is not always true. Even with blood flow, if the direction of the sound beam is 90° to the direction of blood flow, no Doppler shift will be created. The region will remain colorless even when flow is present.

530. True or False? On a color Doppler image, red always represents flow toward the transducer, whereas blue indicates flow away from the transducer.

False. Although this statement may be true, it is not always true. The color associated with flow toward the transducer appears in the upper half of the color map. The color associated with flow away from the transducer appears in the lower portion of the color map.

263. True or False? One way that a sonographer can alter the axial resolution achieved during an exam is to adjust the maximum imaging depth.

False. Depth of view and axial resolution are unrelated. A sonographer cannot adjust imaging depth to change a system's axial resolution.

443. True or False? Digital scan converters do not use computer technology to process electronic data into images.

False. Digital scan converters use computer technology to process data.

371. True or False? The "curved pattern" of delays in the electrical spikes used in a linear phase array transducer focuses the beam during reception.

False. Focusing using time delays of the electrical spikes is a form of transmit, not receive, focusing.

105. True or False? Lower frequency sound creates higher quality images with greater detail.

False. Frequency plays a very important role in image quality. Higher frequency sound usually produces higher quality images with greater detail.

262. True or False? The lower the numerical value of the longitudinal resolution, the worse the picture.

False. Higher quality images are associated with lower values of longitudinal resolution. The numerical value indicates how close two structures can be and still produce two distinct images on the ultrasound display. Lower numbers identify ultrasound systems that display images with fine detail.

242. True or False? When reflection occurs with oblique incidence, the angle of reflection equals the angle of incidence. This is known as Snell's Law.

False. It is indeed true that the angle of reflection is equal to the angle of incidence when reflection occurs at an oblique incident angle. The falsehood in this statement is that this is not Snell's Law.

515. True or False? The appearance of negative velocities in a pulsed Doppler display always indicates that red blood cells are moving away from the transducer.

False. Negative velocities on the spectral display of a pulse Doppler exam may indeed indicate that red blood cells are traveling away from the transducer. However, aliasing may also cause negative velocities in the spectrum. Aliasing occurs when very high Doppler shifts are processed incorrectly as flow in the opposite direction.

421. True or False? The sonographer can make an image of uniform brightness by adjusting both output power and receiver gain.

False. Neither output power nor receiver gain can create images of uniform brightness because they do not correct for attenuation. The function that corrects for attenuation is called time-gain compensation, or TGC.

460. True or False? Preprocessing of image data occurs after the data has been stored in the scan converter.

False. Preprocessing of image data is achieved before image storage in the scan converter. TGC and write magnification are examples of preprocessing.

590. True or False? Quality assurance evaluations of ultrasound systems should be performed weekly.

False. Quality assurance evaluations must be performed routinely. The actual time between evaluations is determined by the pattern of use of the system.

591. True or False? Quality assurance evaluations of ultrasound systems can only be performed by biomedical engineers or physical scientists.

False. Quality assurance evaluations should be performed by the sonographers who use the system. Although other individuals may be capable of evaluating system performance, the sonographer plays an essential role in the quality assurance program.

250. True or False? The period of a sound wave determines whether refraction will occur.

False. Refraction does not depend upon the characteristics of a wave. Refraction only depends upon the incidence of the sound beam and the speeds of the media.

393. True or False? An ultrasound system with a longer pulse duration will generally have better temporal resolution.

False. Temporal resolution of a system is unaffected by the pulse duration.

280. True or False? The characteristic impedance of acoustic gel is greater than. the matching layer's impedance but less than the piezoelectric element's impedance.

False. The acoustic impedance of gel is lower than the impedances of both the active element and the matching layer. The gel increases the efficiency of sound transmission at the transducer/skin boundary. Consequently, the gel must have an impedance that is between those of the matching layer and the skin.

285. True or False? The acoustic impedance of the skin is greater than the acoustic impedances of both the matching layer and the piezoelectric element.

False. The acoustic impedance of the skin is lower than the impedances of both the matching layer and the piezoelectric crystal.

288. The pulse duration is increased as a result of the presence of backing material. T/F

False. The backing material inhibits the crystal's oscillations and shortens the pulse duration. When a ferroelectric crystal does not have backing material, it can vibrate freely and ring for a long time.

598. True or False? The biological effects of ultrasound are thought to be negligible and thus, few investigations have been performed on the subject.

False. The biological effects of ultrasound are studied extensively by scientists throughout the world. Under specific circumstances, bioeffects have been confirmed and are the subject of many discussions, investigations, and publications.

314. If the narrowest diameter of a sound beam is at a depth of 8 cm, then the PZT crystal's diameter is 16 cm.

False. The depth of the focus is not determined solely by the diameter of the piezoelectric crystal producing it.

115. The waves travel through all three media at the same speed since they have identical frequencies. T/F

False. The determinant of the propagation speed in a medium is the medium only. The fact that these three waves have the same frequency is irrelevant. The waves are traveling in media with vastly different densities and stiffnesses and as a result will travel at different speeds through the wood, brick, and fat.

178. True or False? The duty factor is a characteristic of an ultrasound and transducer system and does not change as long as the system components remain unchanged.

False. The duty cycle changes when the sonographer adjusts the maximum imaging depth during an exam.

528. True or False? Color flow Doppler relies on pulsed Doppler principles and is immune to aliasing artifact.

False. The first portion of the statement is true: color flow does indeed rely on pulsed Doppler principles. However, the second part of the statement is false. It is continuous wave Doppler, not pulsed Doppler, that is immune to aliasing.

315. The higher the frequency of the acoustic wave, the shorter the length of the near zone.

False. The focus gets deeper as the frequency of the wave increases. With low frequency sound, the focus is shallower.

453. True or False? The greater the number of bits assigned to each pixel of a digital image, the greater the spatial resolution of the image is.

False. The number of bits assigned to each pixel of a digital image does not directly affect the spatial resolution of the image.

112. The period of the sound wave decreases as it travels through the mass. T/F

False. The period of a wave is determined by the sound source only, and is unaffected by the tissues through which it travels. Recall that period and frequency are reciprocals. Since the frequency remained unchanged, so too must the period.

535. True or False? Velocity mode color Doppler and variance mode color Doppler will produce identical images when blood flow patterns are turbulent.

False. The principal difference between velocity and variance modes is that variance mode maps are able to identify turbulent flow. Turbulent flow appears on the image as a third color, such as green, that is located on the right side of the color map. When turbulent flow exists, the variance color will appear. Since there is no variance color with velocity mode, the variance and velocity mode images will differ.

286. The damping material helps to decrease the pulse repetition period achieved at a given imaging depth. T/F

False. The pulse repetition period (PRP) is the time from the start of one pulse to the start of the subsequent pulse. The pulse repetition period is determined by the maximum imaging depth established by the sonographer. PRP is unrelated to the presence of backing material.

54. True or False? The sonographer has the ability to alter the period of an ultrasound wave that is produced by a basic transducer.

False. The sonographer cannot adjust the period (or frequency) of a wave produced by a basic transducer. Think of striking a key on a piano. The frequency of sound created by striking a single key is constant. If the sound beam's frequency and period are not suited for the particular type of imaging, the sonographer must select a new transducer with a different frequency.

309. The near zone is the only region where the diameter of the sound beam is smaller than the transducer's.

False. The sound beam created by a disc- shaped continuous wave crystal is smaller than the crystal in the near zone and the initial part of the far zone.

Which of the following 8 selections are acoustic variables? (True or False) 30. Frequency 31. Pressure 32. Propagation speed 33. Wavelength 34. Voltage 35. Intensity 36. Motion of particles in the wave 37. Density

False. True. False. False. False. False. True. True. Acoustic variables identify certain wave as sound waves. These quantities are pressure, density and particle motion.

114. The power in the wave increases as it travels through the mass. T/F

False. Typically, the power of a beam diminishes as it travels. This is a result of attenuation. If anything, the wave's power diminishes as it propagates through the mass.

599. True or False? It is generally believed that the effects of ultrasound on biologic media are minimal.

False. Ultrasonic bioeffects are substantial under certain conditions, including, but not limited to, therapeutic ultrasound and lithotripsy.

122. True or False? The wavelength of an acoustic wave is shorter when it is pulsed rather than continuous.

False. Wavelength reports the length of one cycle in a wave. The wavelength does not change based on whether the cycle is part of a pulsed or continuous wave.

311. If the diameter of a sound beam is 8 mm at a depth equal to twice the near zone length, then the PZT crystal has a diameter of 16 mm.

False. When a continuous wave is produced by a disc-shaped crystal, the beam's diameter equals the crystal's diameter at a depth of twice the near zone length.

108. The wavelength of the 5 MHz wave is greater than the wavelength of the 5 kHz wave. T/F

False. When two sound waves travel through the same medium, the higher frequency wave has a shorter wavelength. The wave with the lower frequency has a longer wavelength. In this question, the 5 MHz wave has a higher frequency and therefore has a shorter wavelength. Specifically, the wavelength of the 5 kHz wave is 1,000 times that of the 5 MHz wave.

430. True or False? The lower the frequency of the ultrasound beam, the shallower is the delay of the TGC curve.

False. With lower sound frequencies, the delay of the TGC curve is deeper. There is less attenuation with low frequency sound, and this allows for a deeper TGC delay.

435. True or False? Typically, the sonographer can control the demodulation process performed by a receiver.

False. With the majority of ultrasound systems, the process of demodulation is not under the sonographer's control. The parameters of demodulation are set within the ultrasound system and cannot be adjusted.

116. The sound waves travel through all three media at different speeds because the waves have different powers. T/F

False., The fact that the waves have dissimilar powers is not the reason they travel at different speeds. The waves travel at different speeds because of the dissimilarities in the densities and stiffnesses of the media through which they travel.

442. True or False? A digital representation of a number can achieve only specific fixed values.

True. A digital representation of a number is limited to discrete values and cannot take on unlimited values. Because of this, digital scan converters can store only a fixed number of gray shades.

78. True or False? A sonographer can routinely change the power of a wave emitted by a transducer used in diagnostic ultrasonic imaging.

True. A sonographer can alter the power of an ultrasound wave by adjusting a control on the ultrasound system. Power and amplitude are related; if the amplitude is increased, then so is the power. When the amplitude decreases, the power also decreases.

608. True or False? The AIUM considers an ultrasound-induced biologic tissue temperature rise of less than 2° Centigrade above normal body temperature as safe for clinical studies.

True. AIUM guidelines state that an exam is considered free of the potential for thermally induced bioeffects if the tissue temperature is within 2° C of normal.

420. True or False? The signal-to-noise ratio remains unchanged when a sonographer adjusts receiver gain.

True. Adjustments to receiver gain alter both the meaningful signal and the destructive noise to the same extent. Therefore, the signal-to-noise ratio is unaltered.

506. True or False? The appearance of negative velocities on the spectral display of a continuous wave Doppler exam always indicates that red blood cells are moving away from the transducer.

True. Aliasing does not occur with continuous wave Doppler. Negative velocities appear on the spectral display only when red blood cells travel away from the transducer.

461. True or False? Postprocessing of image data occurs after the data has been stored in the scan converter.

True. All processing that occurs after the image is stored in the scan converter is called postprocessing. Examples of postprocessing are read magnification and the various forms of gray scale assignment. Any manipulation of a frozen image is postprocessing.

110. Both the 5 MHz and the 5 kHz waves travel at similar speeds through the medium. T/F

True. All sound waves travel at exactly the same speed while moving though a particular medium.

85. True or False? With diagnostic ultrasonic imaging instruments, the operator can alter the intensity of an ultrasound beam produced by a transducer.

True. Although operators cannot change all th characteristics of an ultrasound beam produced by an individual transducer, they can change the initial power. As the operator increases the output power of a transducer, the initial intensity increases.

398. True or False? An ultrasound system with a shorter pulse repetition period (PRP) will have better temporal resolution than a system with a longer PRP.

True. An ultrasound system with a shorter PRP has the ability to produce more pulses each second. With more pulses per second, the system creates many images per second. Increased frame rate improves temporal resolution.

582. True or False? Artifacts are likely to appear when the dimensions of the sound beam area are larger than the dimensions of the reflectors in the body.

True. Artifacts are created for many reasons. Some artifacts, such as slice thickness and axial resolution, result from the sound beam being larger than the reflectors.

236. True or False? The proportion of the incident intensity that is reflected at a border between two media will increase as the impedances of the media become increasingly dissimilar.

True. As sound waves strike the border between two media, reflection occurs if their impedances are different. Greater differences between the two impedances create stronger reflections. If the impedances are only slightly different, then a weak reflection will be produced.

63. True or False? Waves in the ultrasound range behave in the same general manner as sound waves that are audible.

True. As stated above, the primary difference between audible and ultrasonic waves is that humans can hear audible waves. A wave's behavior or adherence to physical laws and principles is generally the same, regardless of whether it can be heard by humans.

214. True or False? Attenuation and propagation speed are unrelated.

True. Attenuation and propagation speed are entirely unrelated. Attenuation is the weakening of a beam as it travels and has nothing to do with how fast it travels.

264. True or False? With a specific ultrasound system and transducer, the system's axial resolution is invariant, and the sonographer can do nothing to improve it.

True. Axial resolution is determined only by the components of the system. When you are using a particular ultrasound system, axial resolution remains constant.

310. The far zone is the only region where the beam diameter exceeds the transducer diameter.

True. Beam diameter exceeds transducer diameter only in the far zone, never in the near zone.

464. True or False? The to the digital numbers. assignment of different shades of gray stored in the scan converter acts to improve the diagnostic value of an ultrasound exam.

True. By using will be distinguished sonographer selects what tissue different gray scale maps, the textures from each other on the important when thereby enhancing tissues appear differently on the screen. gray scale map, these reflections that are different tissues display. This is very in the body produce quite similar. By using an appropriate an exams's diagnostic value.

523. True or False? TGC cannot be used with continuous wave Doppler.

True. CW Doppler is not associated with TGC. Unlike pulsed ultrasound, attenuation effects cannot be remedied with continuous wave Doppler.

277. True or False? The purpose of the backing material of an ultrasound transducer is to shorten the pulses, thereby creating images with better image quality.

True. Diagnostic imaging transducers are especially effective in creating excellent images when their pulses are short. The backing material reduces the ringing of the active element and shortens the pulse duration.

292. True or False? In general, ultrasound imaging transducers have a lower quality factor and a wider bandwidth than therapeutic ultrasound transducers.

True. Diagnostic imaging transducers have a lower quality factor than therapeutic ultrasound transducers. The backing material acts to shorten the pulse, but concurrently increases the bandwidth and decreases the Q-factor.

346. True or False? In comparison to other locations along the length of an ultrasound beam, focusing is generally ineffective in the far zone.

True. Focusing is a technique that narrows the width of a sound beam to improve image quality. When a beam undergoes focusing, it narrows in the region in the focal zone but not in the deep far zone.

370. True or False? The "curved pattern" of delays in the electrical spikes used in a linear phase array transducer focuses the beam during transmission.

True. Focusing using time delays of the electrical spikes is a form of transmit focusing.

68. True or False? If the periods of two waves are the same, then the frequencies of the waves must also be the same.

True. Frequency and period are reciprocals. When the periods of two waves are identical, the frequencies of the waves must also be identical.

331. True or False? The pulse duration does not profoundly influence the lateral resolution.

True. Generally, the primary determinant of lateral resolution is the sound beam's diameter. The pulse length, or duration, does not dramatically alter the lateral resolution.

568. True or False? Grating lobes are attributed only to array transducers.

True. Grating lobes are associated with array transducers.

337. True or False? When using an instrument typical of today's diagnostic imaging devices, a higher frequency transducer is likely to improve the axial resolution.

True. Higher frequency ultrasound pulses typically have shorter pulse lengths. Short pulse lengths correspond to images with good range resolution.

316. The greater the diameter of a transducer's piezoelectric crystal, the longer the near zone length is.

True. Large diameter crystals tend to produce continuous wave sound beams with a deeper focus. The beam's near zone is longer.

581. True or False? Side lobe, grating lobe, and refraction artifacts all reduce lateral resolution.

True. Lateral resolution is related to structures that lie in a plane perpendicular to the sound beam's main axis. These three artifacts all degrade lateral resolution.

333. True or False? When using ultrasonic imaging instrumentation, the standard lateral resolution has a higher numerical value than the axial resolution.

True. Most imaging systems have better axial resolution than lateral resolution. The lateral resolution will have a higher numerical value than the axial resolution because a sound pulse is typically wider than half its length.

527. True or False? Color flow Doppler imaging incorporates pulsed Doppler principles and provides range resolution.

True. One of the greatest advantages of color flow Doppler is its ability to superimpose two-dimensional color velocities upon a two-dimensional gray scale image of anatomy. Color flow Doppler provides range resolution and is based on pulsed Doppler principles.

171. True or False? The pulse repetition frequency and the frequency are unrelated.

True. PRF and frequency are unrelated. The PRF is determined only by the depth of view. The frequency is determined by the characteristics of the transducer.

431. True or False? Typically, the sonographer can adjust the compression function of a receiver.

True. Part of the compression function involves the assignment of gray scale levels on the display. This is adjusted by the operator.

245. True or False? Refraction occurs at the border between two media if and only if there is oblique incidence of the wave at the boundary.

True. Refraction cannot occur if a wave is normally incident to the boundary between two media. It can occur only if the incident wave is oblique to the boundary.

627. True or False? Focused sound beams are considered less likely to create bioeffects because the beams will strike fewer gas bubbles that could potentially cavitate.

True. Small gas bubbles, or gaseous nuclei in tissues, serve as sites of cavitation, When a beam is focused, its diameter is smaller and is less likely to strike cavitation nuclei,

128. True or False? Soft tissue is an imaginary construct that actually does not exist.

True. Soft tissue is an imaginary structure with characteristics that represent an "average" of body tissues, including muscle, blood, kidney, and spleen. It is used as an approximation.

402. True or False? With sector scanning, images with greater detail (spatial resolution) are created when the number of acoustic pulses per degree of sector is increased.

True. Spatial resolution is improved with more density is low, gaps may exist between pulses per degree of sector. When the line adjacent pulses. Reflectors within the gaps will not accurately appear on the image.

394. True or False? The length of a pulse does not directly influence the temporal resolution.

True. Temporal resolution is not affected by the length of the pulses produced by the system. The factors that influence the temporal resolution are maximum imaging depth, sector angle, line density, and the number of foci per scan line.

287. The backing material helps to decrease the duty cycle at a particular PRF. T/F

True. The backing material of an imaging transducer tends to shorten the pulse duration. This decreases the percentage of time that the system is "talking" and therefore decreases the duty factor.

290. The spatial pulse length is decreased with the application of backing material. T/F

True. The backing material tends to diminish element after it is excited by the electrical signal from the pulser. This shortens the pulse length. The action of the damping material is similar to the action of a cymbal player in a band. If a short tone is desired. the musician pinches the cymbals between his arms and ribs. This stops the cymbals from vibrating and shortens the spatial pulse length. The terms backing material and damping material are synonymous.

177. True or False? The sonographer alters the duty cycle when adjusting the maximum imaging depth of a scan.

True. The duty cycle is the percentage of time that an ultrasound system is creating an acoustic wave. Duty factor is inversely related to depth of view. Duty factor decreases when depth of view increases.

282. True or False? The piezoelectric crystal of a transducer typically has an impedance higher than the impedance of skin.

True. The impedance of piezoelectric crystals typically exceeds the impedance of skin. To calculate impedance, multiply the density of a material by the propagation speed of the material. The density of lead zirconate titanate (a common piezoelectric material) is greater than the density of skin. The propagation speeds of piezoelectric crystals are usually three to four times greater than skin.

605. True or False? The mechanistic approach to the study of bioeffects and safety includes the identification of a theoretical construct that could produce an effect.

True. The mechanistic approach is based on developing a theory as to how something happens. If the theoretical mechanism is proven correct, it provides great insight into the system and its component factors. The development of a computer simulation of tissue temperature and its relation to exposure is such an example. The mechanistic approach is considered "cause and effect."

448. True or False? The greater the number of bits assigned to each pixel of a digital image, the greater the number of shades of gray the image has.

True. The number of gray shades in an image increases when the number of bits assigned to each pixel increases.

415. True or False? The sonographer can alter the pulser power.

True. The output voltage of the pulser and the strength of the acoustic pulse produced by the transducer are in the sonographer's control. The output power has different names depending on the manufacturer, but the sonographer can always alter its level.

154. True or False? While imaging soft tissue, the spatial pulse length does not change as long as the components of the ultrasound system are the same.

True. The overall length of a pulse is equal to the wavelength multiplied by the number of cycles in the pulse. Using a particular ultrasound system and transducer, the pulse length cannot change.

107. The period of the 5 MHz wave is less than the period of the audible wave. T/F

True. The period and frequency of any wave are inversely proportional. That is, the higher the frequency of wave, the shorter the period. In this case, the 5 MHz wave has a higher frequency than the 5 kHz wave and, thus, will have a shorter period.

67. True or False? The period of an ultrasound wave is related to the frequency and is the same, regardless of whether the wave is pulsed or continuous.

True. The period of a wave is a characteristic of each individual cycle in the wave. The period of a wave (as well as frequency and wavelength) remains unchanged, whether the wave is continuous or pulsed.

159. The period of the 3 MHz sound is greater than the period of the 6 MHz sound. T/F

True. The period of a wave is the time that is required to complete one single cycle. A sound signal's period and frequency are reciprocals; therefore, the lower the frequency, the higher the period. In this case, the 3 MHz wave has a period twice as long as the 6 MHz wave.

434. True or False? The primary purpose of demodulation is the preparation of the electrical signal for display on a television monitor.

True. The primary purpose for demodulating a signal within an ultrasound system is to prepare it for ultimate display on a television monitor.

534. True or False? Velocity mode color Doppler and variance mode color Doppler will produce identical images when blood flow patterns are laminar.

True. The principal difference between velocity and variance modes is that variance mode maps identify turbulent flow. Turbulent flow. appears on the image as a third color, such as green, that is located on the right side of the color map. If turbulent flow is not present, then the third color will not appear on the image and the velocity and variance mode images will look identical.

145. The sonographer cannot change the duration of a sound pulse unless the transducers are switched. T/F

True. The pulse duration depends upon the interaction of the pulser electronics of the machine and the transducer. The pulse duration may change when the sonographer changes transducers.

141. True or False? The pulse duration of an ultrasound and transducer system does not change significantly as long as the system components remain unchanged.

True. The pulse duration is the timespan that a pulse exists. It is determined by the ultrasound system and the transducer. Generally, it remains constant for a particular transducer.

459. True or False? For digital image information to be displayed on a conventional television screen, the data must be processed by a digital-to-analog converter,

True. The representation of an image in digital format is not suitable for display on a standard television because a TV is an analog device. After all the signal processing is completed, the image data is passed through a digital-to-analog converter. It is then suitable for TV display.

72. True or False? With standard diagnostic imaging instrumentation, the sonographer has the ability to vary the amplitude of a sound wave produced by the transducer.

True. The sonographer can adjust the strength of the ultrasound signal that a transducer creates. When a sonographer increases the output power, the electrical voltage sent to the transducer is increased. This produces a more violent vibration of the piezoelectric crystal within the transducer and, in turn, a stronger ultrasound wave.

419. True or False? The sonographer can adjust the receiver gain.

True. The sonographer is in direct control of the receiver gain. The sonographer determines the degree to which the signal returning from the transducer is amplified. It is a primary control on the ultrasound system that helps determine the ultimate quality of images.

362. There is communication between the pulser of the ultrasound system and the piezoelectric crystal of the transducer.

True. The transducer's PZT must be directly connected to the pulser electronics of the ultrasound system. A wire provides a route for the electrical signal to travel from the pulser to the PZT. In addition, the crystal sends data back to the system regarding the reception of reflected echoes. This data goes to the receiver and creates an image.

117. The waves travel through all three media at different speeds because the media are different. T/F

True. This is correct! Finally, we have a statement that attributes variations in propagation speeds to the differences in the media. Again, the characteristics of the media alone determine the speed that sound can travel through it.

274. True or False? The shorter the pulse length, the better the picture.

True. This is the fundamental concept of longitudinal resolution. Shorter pulses produce better pictures. One of the most important design criteria for ultrasound systems and transducers is to minimize the pulse duration and spatial pulse length.

529. True or False? Color flow Doppler systems display anatomical data in gray scale while simultaneously displaying flow information in color.

True. This is the fundamental process by which color flow mapping works. A two- dimensional black and white image provides data on anatomical structures. A two-dimensional color image is displayed simultaneously on top of the black and white image. The color data deals with the Doppler frequencies produced by moving blood cells in the imaging plane.

265. True or False? The shorter the pulse duration, the better the picture.

True. This restates one of the fundamental principles of ultrasonic imaging. The shorter the pulse duration, the higher the quality the images.

367. True or False? All phased array transducer systems direct ultrasound pulses in many directions to create a two- dimensional image.

True. To create a two-dimensional image, the sound beams of annular, linear, and curvilinear phased array transducers must be steered through a path. The linear and curvilinear phased array systems steer the beam electronically, whereas the annular phased array steers the beam mechanically.

592. True or False? Proper quality assurance programs require the assessment of every transducer used in the clinical laboratory.

True. To establish a valid and rigorous quality assurance program, each component in clinical use must be evaluated. Thus, each transducer must be individually assessed.

628. True or False? It is generally believed that the ultrasound bioeffects are minimal at intensity levels typical of those produced by diagnostic imaging equipment.

True. Ultrasound is considered safe at levels typical of current diagnostic imaging equipment. The likelihood of significant, harmful bioeffects is extremely low.

437. True or False? Typically, the sonographer can adjust the threshold level.

True. Under normal circumstances, the operator adjusts the reject (suppression or threshold) level that is performed during signal processing.

533. True or False? Variance mode color maps may be identified by side-to-side changes in the color bar, whereas velocity mode color maps only change color vertically.

True. Variance mode maps change colors side to side as well as from top to bottom. Velocity mode maps only change color from top to bottom.

113. The wavelength increases while the wave travels through the mass. T/F

True. Wavelength is dependent on both the sound source and the medium. The speed of sound in soft tissue is 1,540 m/sec, and through the mass is 1,575 m/sec. As a wave travels in a faster medium, its wavelength increases.

160. The wavelength of the 3 MHz ultrasound is greater than the 6 MHz sound. T/F

True. Wavelength is the distance that a single cycle of a pulse occupies in space. When traveling through a particular medium, cycles from waves with lower frequencies have longer wavelengths. Thus, cycles from a 3 MHz wave have longer wavelengths than those from a 6 MHz wave.

121. True or False? Shorter wavelength sound creates higher quality images with greater detail.

True. Wavelength plays a very important role in image quality. Shorter wavelength (higher frequency sound) produces higher quality images with greater detail.

312. If the diameter of the acoustic beam produced by a crystal is 8 mm at a depth of twice the near zone length, then the PZT crystal has a diameter of 8 mm.

True. When a continuous wave is produced by a disc-shaped crystal, the beam's diameter equals the crystal's diameter at a depth that is twice the near zone length.

273. True or False? The higher the frequency of the cycles within a pulse, the lower the numerical value of the axial resolution.

True. When traveling through a particular medium, higher frequencies are associated with shorter wavelengths. Shorter wavelengths will shorten the spatial pulse length. Since the axial resolution is equal to one-half the spatial pulse length, the numerical value of the axial resolution will also be reduced.

360. The ultrasound beam is directed in many different directions to create an imaging plane.

True. With a mechanical transducer, the active element is aimed in several directions so that the pulses create a two-dimensional picture. Without this beam steering, the pulses would travel in the same direction and display only a single B-mode line.

336. True or False? When using an instrument typical of today's imaging devices, a higher frequency transducer is likely to mildly improve the system's lateral resolution.

True. With all other variables being equal, pulses made with higher frequency sound are somewhat narrower than low frequency pulses. Narrow beams improve the lateral resolution of the imaging system.

376. True or False? Annular phased array transducers focus sound beams in all planes and at all depths.

True. With annular arrays, the sound beam has the appearance of a straw. It is focused in all planes and at all depths.

626. True or False? One reason focused ultrasound beams with low intensities are less likely to cause bioeffects is that a focused beam is less efficient in heating a large mass of tissue to a critical temperature.

True. With focused beams, only a small mass of tissue is heated, and the heat flows rapidly to cooler neighboring tissues. There is limited accumulation of heat energy and the temperatures tend to stay below critical levels.

361. The ultrasound beam is not focused electronically.

True. With mechanical transducers, focusing is not achieved electronically. The beam is focused with an acoustic lens (external) or by a curved PZT crystal (internal).

372. True or False? Both linear and phased array technologies have the ability to variably focus an ultrasound beam to different depths.

True. With the phased delivery of electrical pulses to the crystals, the ultrasound beam may be focused at a variety of different depths.