Ultrasound physics 2
What is line density?
# of scan lines per frame
What determines the PRF?
#of lines per frame and the frame rate
Major principles of medical ethics....
* autonomy * non maleficence * beneficence * justice
Tissue Harmonics......
*created during transmission in tissue * occurs as sound propagates in tissue * results from nonlinear behavior of transmitted sound beam *weaker harmonic signal
What can you do in preprocessing?
-compensation - compression - edge enhancement - fill- in interpolation - spatial compounding - Temporal Compounding (persistence) - write magnification
What does the pulser's voltage range from?
0-100volts
One limitation of the linear arrays is the inability to dynamically create thin slices. What newer types of transducers have improved slice thickness?
1 1/2-D array has not only side by side PZT but Up and down PZT. The array has 700 total elements (100 wide by 7 high)
how many lines for every degree
1 line per every degree
PW 7 characteristics
1. accurately identifies the location of flow 2. range resolution 3. moderately sensitive 4. very good temporal res 5. subject to aliasing 6. limited max velocity 7. sample volume
5 techniques that can be used to avoid aliasing artifact
1. adjust the scale to its maximum 2. select a new ultrasonic view with a shallower sample volume 3. select a lower freq xdcr 4. use baseline shift 5. use CW Doppler
deeper imaging has
1. long go-return time 2. longer t frame 3. lower frame rate 4. inferior temporal resolution.
What are the two study techniques used to study bioeffects are:
1. mechanistic approach 2. empirical approach
Shallow imaging has
1. short go-return time 2. shorter T frame 3. higher frame rate 4. superior temporal resolution
The 2 most important bioeffects mechanisms are
1. thermal 2. cavitation (non thermal)
PD 6 characteristics
1. used with low velocity or small volume blood flow 2. range res 3. greater sensitivity than color flow 4. lowest temp res 5. subect to flash artifact, not to aliasing 6. no velocity meas.
Low line density, narrow sector and single focus has
1. widely spaced lines (line density) 2. one pulse per scan line (focus) 3. fewer pulses per frame 4. shorter tframe 5. higher frame rate 6. high temporal resolution 7. Low spatial resolution
The acoustic footprint of a curvilinear array transducer may be as long as...
10cm
What is the Dynamic range of the original uncompressed signal if the system has a Dynamic Range of 70 dB however, the original signal was compressed by 40 dB? 70 dB 40 dB 110 dB 90 dB 30 dB
110dB
An uncompressed signal within the receiver of an US system has a dynamic range of 110dB. The signal undergoes 40dB of compression. What is the dynamic range of the compressed signal?
110dB - 40dB = 70dB
What transducer frequencies are used to perform clinical Doppler exams?
2-10MHz
Sound with a frequency of 4MHz is created by a xdcr. What is the fundamental frequency?
4MHz The fundamental frequency is that which is produced by the xdcr.
After compression, a signal within the US system has a dynamic range of 70dB. The original signal was compressed by 40dB. What is the dynamic range of the original, uncompressed signal?
70dB + 40dB = 110dB
An uncompressed signal has a dynamic range of 85dB. The signal undergoes 30dB of compression. What is the dynamic range of the compressed signal?
85dbn - 30dB = 55dB
Which of the following terms also describes sequential? A. switched B. phased C. array D. steered
A
Which of the following is associated with the highest mechanical index? A. low frequency, extreme peak rarefactional pressure B. High frequency, extreme peak rarefactional pressure. C. low frequency, extreme peak compression pressure. D. high frequency, extreme peak compression pressure.
A MI is directly related to peak rarefactional pressure and inversely related to frequency.
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 B. 120 dB C. 3 dB D. 80 dB
A. 160 dB 120 + 40 = 160
How is Doppler shift related to velocity and transducer frequency?
Both are directly related
What transducers have a electronic focusing technique?
All but mechanical. Linear sequential, phased array, annular phased, convex, and vector
This transducer has a fan or sector shaped image and when the transducer malfunctions, only a portion of the image is lost in a horizontal band "side-to-side" band of dropout. A. linear phased B. vector array C. annular phased array D. convex array
C
What is A mode and what is its x axis and y axis?
Amplitude mode. x axis is amplitude and y axis is depth.
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
When can a patient revoke consent?
At any time, even during the procedure
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. estimated in a computer simulation
C An in vitro is performed out of the body and in an artificial environment. The observations may be described as "in a test tube"
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 xdcr freq. when the freq is 1/2 the Doppler shift is 1/2.
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 xdcr, the Doppler shift is negative.
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 use of a continuous wave system
C if the US tech slects an imaging view with a greater PRP, the PRF will decrease and the likelihood of aliasing will increase.
AN 8MHz xdcr with a PRF of 5000Hz is imaging to a depth of 7cm. what is the Nyquist freq? A. 4MHz B. 3.5 Hz C. 2.5 kHz D. 2.5 dB E. 5kHz
C the nyquist limit is 1/2 of the PRF2.5kHz or 2500Hz.
WHat is the typical pulser output voltage that excites a piezoelectric crystal? a. 0.1 volts b. 500 millivolts c. 40 volts d. 10 microvolts
C.
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.
What is the attenuation in dB using a 2.5 MHz transducer and imageing to a depth of 16 cm? A) 35.2 dB B) 16 dB C) 10 dB D) 20 dB
D Atten Coeff: MHz/2 Attenuation= Atten coeff X distance
When the frame rate is 30 Hz, how long does it take to create a frame? a. 30 sec b. 3 sec c. 0.3 sec d. 1/30 sec e. 1/3 sec
D Frame rate and tframe are reciprocals
All of the following reduce temporal resolution by increasing the number of pulses per image except: a. increasing the number of focci 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 the depth of view decreases temp res by changing the PRP while leaving the # of pulses in each image unchanged.
Epidemiology studies of in utero exposure to US have included all of the following findings except _____. a. birth weight b. cancer c. structural abnormalities d. none of above
D Many epidemiologic studies on the effects of US have been reported. End points of birth weight, cancer, and structural abnormalities have all been studied. There is no correlation between US exposure and these events.
Which of the following creates harmonics? A. reflection B. transmission C. linear behavior D. nonlinear behavior
D Nonlinear behavior creates harmonics
Blood moving at a velocity of 2m/s creates a Doppler frequency of 3,000Hz. What will the Doppler shift be if the velocity increases to 4m/s? A. 3,000 Hz B. 2 Hz C. 1,500 Hz D. 6,000 Hz
D. whenvelocity doubles, the Doppler shift doubles
Doppler shift is also called
Doppler frequency
T or F: the number of lines per frame and the frame rate determine the frequency.
F the number of lines per frame and the frame rate determine the PRF
T or F: A machine that displays A mode and 2D images is called a duplex scanner
F. A machine that displays doppler and 2D is called a duplex scanner
True or False: In vitro studies are performed exclusively on living animals.
F. in vitro literally means in glass.
What is fundamental vs harmonic frequency/imaging?
Fundamental: Frequency of sound created by the transducer and transmitted into the body. Harmonic: the creation of an image from sound reflections at twice the frequency of the transmitted sound.
What are the types of Array transducers?
Linear, Annular, and Convex
What xdcr steer the beam with a motor and focus the beam with an acoustic lens or a curved PZT element?
Mechanical xdcr
Guidelines to minimize the risk of health care workers to contract blood borne infection have been developed. What are these guidelines called? OSHA guidelines standard precautions beneficence best practices
Standard precautions
Empirical strengths and weaknesses
Strength: no need to understand mechanism Weaknesses: no need to understand mechanism (+/-) biological significance is obvious species differences may alter results.
T or F: spatial resolution improves with higher line density
T
T or F: temporal res may be improved if the bottom of the ROI is shallower than the original image's depth of view
T
T or F: the maximum imaging depth determines frame rate.
T
T or F: the process of calculating velocities from measured Doppler shifts is not obvious to the sonographer because the calculated velocities will be identical, regardless of the transducer frequency
T
T or F: the temp rises in soft tissues near bone is significally higher than in other locations
T
T or F: the use of harmonics increases the signal to noise ratio.
T
T or F: when line density is low, few pulses create each image and the frame rate is high and temporal resolution is high.
T
T or F: when the pulser is set to a low voltage the PZT vibrates gently.
T
T or F: with high line density, each image contains more detail, known as improved spatial detail resolution.
T
T or F: with pulse inversion and power modulation, a positive and negative pulse is transmitted down each scan line.
T
T or F:The relationship between the shell and the internally trapped gas determines the contast agent's stability and its longevity while circulating in blood.
T
T or F:When using contrast harmonics, the mechanical index will increase with lower frequencies and higher pressure.
T
T or F? A digital representation of a number can achieve only specific fixed values.
T
T or F? The duty cycle of the continuous wave is 100%.
T
T/F: Proper QA programs require the assessment of every transducer used in the clinical laboratory.
T
True or False: It is generally believed that the US bioeffects are minimal at intensity levels typical of those produced by diagnostic imaging equipment.
T
What is viscous vs frictional vs inertial loss?
Viscous: thickness of the blood. Low hematocrit is anemia and it is thin. Frictional: occurs when flow energy is converted to heat as one object rubs against another. Inertial: It relates to the tendency of a fluid to resist changes in its velocity regardless of whether the fluid speeds up or slows down.
What is epidemiology
a branch of medicine associated with population studies. It is empirical.
Packet size should be selected to balance 2 competing interests of CD
accurate velocity and adequate temporal res
What does the hydrophone measure?
acoustic pressure, period, PRP, PRF, and pulse duration.
Which of the following may be present in pulsed Doppler but NOT in continuous wave Doppler? A) aliasing B) wall filter control C) directional detection capabilities D) spectral analysis of the Doppler
aliasing
What are the requirements for a quality assurance program?
assessment of system components repairs preventative maintenance record keeping
What is an energy gradient?
blood moving from regions of higher energy to regions of lower energy.
All of the following will result in a decrease in Frame Rate except: body habitus imaging deeper increasing sector size increasing line density
body habitus
How are contrast agents entered into the body?
by IV or oral.
Dynamic range is a synonym for which of the following terms? compression compensation demodulation reject amplification
compression
What is rectification?
converts all negative voltages into positive voltages.
Research performed within the living body is known as: A) in vivo B) in vitro C) empirical
in vivo
What is the disadvantage of a PW Doppler?
inaccurate measurement of high velocity signals.
Electrical resistance is reported in units of
ohms
Spatial compounding is only used with what type of transducers?
phased array.
What is the only cavitation bioeffect?
tissues with a well defined population of stabilized gas bodies such as the lung.
Flow is also called
volume flow rate
When a sonographer zooms on a particular region of interest (ROI) and the region is rescanned and new information is acquired, this is called? post processing read magnification write magnification none of the above
write magnification
Does the sonographer control pre-processing and post processing?
yes
Is the pulser output adjustable?
yes
Can the sonographer adjust the magnitude of the pulser's electrical voltage spike?
yes by adjusting power output or brightness
What does the beam former do?
•Coordinates electrical signals sent to each active element •Does apodization •Established correct time delays for dynamic receive focusing •Controls dynamic aperture •Transmit-receive switch
AIUM Statement on in vitro bioeffects......
* In vitro bioeffects research is important * In vitro bioeffects are real even though they may not apply to the clinical setting. * In vitro bioeffect research that claims direct clinical significance (w/o in vivo validation) should be viewed with caution.
The conclusions of the AIUM training and research include:
* No confirmed bioeffects on pt's or sonographers have been found with the use of diagnostic US. * Experience with diagnostic US may differ from research and training, due in part to longer research exams and greater exposure * When used w/o direct medical benefit to the pt, the subject should be informed how the research study differs from standard diagnostic procedures.
The conclusions of AIUM include for clinical safety and prudent use:
* No confirmed harmful bioeffects from exposure to diagnostic US have ever been reported. * It is possible that bioeffects may be identified in the future. * The benefits to the pt outweighs the risk. * It is appropriate to use diagnostic US prudently to provide benefit to the pt * It is inappropriate (NEVER appropriate) to use diagnostic US in a non medical setting for entertainment.
Overall safety considerations in US
* Only perform studies with valid medical justification * Do not prolong studies without valid medical justification. Minimize exposure time while performing a complete diagnostic exam. Exam time is the primary determinant of pt exposure. * Minimize pt exposure. Use the minimum output power and maximum amplification to optimize image quality. ALARA. In summary, be prudent, careful, and judicious.
Many epidemiologic studies deal with in utero fetal exposures to ultrasound because:
* a large percentage of pregnant women in the US are scanned * US is routinely used during normal pregnancies. Even a small risk creates concern when a procedure is performed on individuals without disease. * harmful effects, if present, have the potential to affect the fetus for life.
What are the 3 limitations of epidemiologic studies?
* studies have retrospective meaning the information is obtained from old medical records. * Ambiguities may exist in the data, such as justification for the exam, gestational age, number of scans, technique, and exposure time. * Risk factors other than exposure to US may precipitate a bad outcome in the fetus. THese include environmental factors, poor nutrition, smoking, or alcohol and drug abuse.
Theoretical models appear to correlate with experimental data even though:
* the US beam is quite complex * diagnostic equipment is diverse * tissue characteristics are different.
Complete informed consent includes the following:
* the nature of the procedure * reasonable alternatives * the risks, benefits, and uncertainties related to each alternative * assessment of the pts understanding * the pts acceptance
What is Transient cavitation?
*Bubble bursting *also called normal or interial * shock waves (enormous pressure) and very high temperatures * Higher MI
What are the 5 goals of quality assurance?
*Gaurantee proper operation of the system *detect gradual changes *minimize downtime *reduce the number of non-diagnostic exams *reduce the number of repeat scans
Contrast harmonics are...
*created during reflection off of microbubbles * occurs only when contrast agents are present and with MIs greater than 0.1 *results from nonlinear behavior of microbubble * stronger harmonic signal
The numerical value of the mechanical index, and therefore, harmonic production, increases with
*lower frequency sound *stronger sound waves (substantial pressure variation)
Low mechanical index less than 0.1...
*no harmonics *backscatter *linear behavior *higher frequency sound *low beam strength *bubble expands very little
What conditions create aliasing?
*occurs with PW, not CW. *occurs when the Doppler sampling rate is too low in comparison to the measured blood velocities.
Higher MI 0.1-1.0....
*some harmonics *resonance *nonlinear behavior *lower frequency sound *higher beam strength *bubble expands moderately
Highest MI greater than 1
*strongest harmonics *bubble disruption *extreme nonlinear behavior *lowest frequency sound *highest beam strength *bubble expands greatly
Two characteristics of contrast agents are important:
*the nature of the outer shell and *the gas that fills the microbubble
The cosine of 180 is which of the following? A) 1 B) 0 C) -1 D) none of the above
-1
What is the hydrostatic pressure for supine?
0 mmHg at all parts of the body.
At what angle between the sound beam and the direction of motion will the Doppler shift be the highest?
0 or 180 degrees (the sound beam and the direction of motion should be parallel)
How many pulses is in 1 degree?
1 pulse per 1 degree
What are the US system's majore components?
1. Transducer 2. pulser and beam former 3. receiver 4. display 5. storage 6. master synchronizer
What is the rationale for studying thermal effects?
1. as sound propagates through the body, energy is converted into heat. 2. Core temp is regulated at 37 celcius. Life processes may not function normally at other temperatures.
What are the 3 devices that measure the output of US xdcrs by absorption, the conversion of sound energy into heat.....
1. calorimeter 2. thermocouple 3. liquid crystal
CW 7 characteristics
1. identifies highest velocity jets anywhere along the length of the US beam 2. range ambiguity 3. most sensitive 4. very good temporal res 5. no aliasing 6. peak velocity meas. 7. region of overlap
CD 6 characteristics:
1. provides 2D flow info directly on anatomic image 2. range res 3. moderately sensitive/size of color jet is most affected by CD gain settings 4. reduced temporal res due to multiple packets 5. based on pulsed US, subject to aliasing 6. mean velocity meas
High line density, wider sector, and multiple focus has
1. tightly packed lines (line density) 2. many pulses per scan line (focus) 3. more pulses per frame 4. longer tframe 5. lower frame rate 6. low temporal resolution 7. High spatial resolution
When an ultrasound system creates an image in 1/10 of a second, the frame rate is...
10 Hz and vice versa
Continuous wave Doppler requires how many crystals?
2 crystals. One crystal constantly transmits ultrasonic energy while the other crystal receives reflection from blood cells.
compression is performed how many times?
2 times
Doppler shift formula
2 x velocity x xdcr freq x cos/prop speed
How many possible shades of gray with 5 bits of memory?
2^5 bits =32
How to determine the number of gray shades?
2^number of bits
What would be the harmonic frequency of a 2 MHz transducer? 2 MHz 3 MHz 4 MHz 6 MHz
4 MHz
How many bits are required to store 9 shades of gray? A) 1 bit B) 2 bits C) 3 bits D) 4 bits
4 bits
How many bits are required to store 25 shades of gray? 2 bits 3 bits 4 bits 5 bits
5 bits
A signal with a system's receiver has a dynamic range of 60dB after compression. The original signal was compressed by 50dB. What is the dynamic range of the original, uncompressed signal?
60dB + 50db = 110dB
The current FDA regulatory limit for SPTA is
720mW/cm^2
What percentage of sonographer are thought to experience musculoskeletal pain related to work? 20% 40% 60% 80%
80%
Sound with a frequency of 4MHz is created by a transducer. What is the harmonic frequency?
8MHz The harmonic frequency is a multiple of the fundamental frequency.
At what angle between the sound beam and the direction of motion will the Doppler shift be the lowest?
90 degrees. No Doppler freq exists because the cosine of 90 degrees is 0.
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
All of the following are related to a dedicated continuous wave Doppler transducers EXCEPT: A. wide bandwidth B. high quality factor C. higher sensitivity D. range ambiguity
A
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
No confirmed bioeffects on patients or sonographers have been found with the use of diagnostic ultradsound. A) True B) False
A
Some ultrasonic bioeffects studies are performed in vivo. What is the meaning of the term in vivo? a. observable in human body b. observations based on an experiment c. discernible in a test tube d. estimated in a computer simulation
A
The arterial blood pressure of a supine individual is 120 mmHg. WHat is the hydrostatic pressure at the subject's ankle? A. 0mmHg B. 40mmHg C. 120mmHg D. -120mmHg E. 100mmHg
A
The info that is processed by a standard duplex US system includes all of the following except: A. attenuation B. amplitude C. freq D. time of arrival
A
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 of displaying very small details in an image? A. system A b. system b c. both are the same d. cannot be determined
A
What form of resolution is evaluated by measuring the width of reflectors arising from small, point targets? A. lateral resolution B. axial resolution C. temporal resolution D. elevational resolution
A
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
What happens to the diaphragm when an individual breaths out? A. increases B. decreases C. remains the same
A
What happens to venous flow in the legs when an individual exhales? A. increases B. decreases C. remains the same
A
What happens to venous return to the heart when an individual inhales? A. increases B. decreases C. remains the same
A
What information should be provided to a patient when undergoing a study for the purpose of research or training? a. the anticipated exposure conditions & how these compare to normal diagnostic procedures b. the duration of exam c. the research study's goal d. bioeffects associated w/ the technique
A
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
What is the smallest amount of digital storage called? a. bit b. byte c. pixel d. fractel
A
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
What nonlinear behavior creates contrast harmonics? A. microbubbles expand to a greater extent than they compress. B. sound reflects off of boundaries with different impedances C. sound travels faster in compressions and slower in rarefactions D. microbubbles compress to a greater extent than they expand
A
Which US modality is associated w/ the highest tissue temperature elevation? a. pulsed doppler b. color flow doppler c. gray scale imaging
A
Which of the following components typically has the lowest dynamic range? A. display B. pulser C. amplifier D. demodulator
A
Which of the following describes the system's ability to display similar reflectors in the phantom with echoes of equal brightness. A) uniformity B) focal zone C) range accuracy D) horizontal calibration
A
Which of the following determines the grayscale in a Doppler spectrum? A. number of reflectors B. velocity C. frequency shift D. laminar flow
A
Which of the following is best described as mechanically steered and multifocus? A. annular phased array B. annular sequential array C. mechanical D. linear phased
A
Which of the following is the best choice when the image on your US system displays only reflectors in a region close to the transducer but no reflectors that are deep? a. adjust the system's compensation b. use a higher frequency transducer c. increase the output power d. adjust the reject level
A
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
Which of the following transducers create multiple transmit focal zones through the use of its unique phased technology? A. annular phased array B. curvilinear sequential array C. linear sequential array D. vector array
A
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
Which one of the following is a requirement for any lab? A) record keeping B) new ultrasound systems C) horizontal registration D) range accuracy
A
Which technique is used to perform spectral analysis on CD data? A. AUTOCORRELATION B. DEMODULATION C. FFT D. PULSE INVERSION
A
Why is it necessary for the receiver to perform compression on the electrical signals that it processes? A. dynamic range of the system's electronics is less than the dynamic range of the received sound reflection B. the displays dynamic range exceeds the transducers dynamic range C. dynamic range of the receiver is less than the dynamic range of the image processor D. dynamic range of the display exceeds the dynamic range of all other components of the US system
A
With frequency compounding, how many pulses are transmitted down each scan line? A. 1 B. 2 C. 4 D. cannot be determined
A
which of the following technologies uses long sound pulses to create an image? A. coded excitation B. Harmonics C. pulse inversion D. rendering
A
A sonographer reduces the sector angle from 90 degrees to 30 degrees. At the same time, the ultrasound system automatically increases the line density from 1 line per degree to 2 lines per degree. No other changes are made. What will happen to the frame rate? A. increases B. decreases C. Remains unchanged
A from 90 degrees to 30 degrees, the number of pulses is reduced by 30. if it increased to 2 lines per degree. It increased 60 lines per degree which means the frame rate increased by a total of 30.
Which two of the following devices convert US energy into heat? a. calorimeter b. thermocouple c. hydrophone d. schlieren
A and B The calorimeter and the thermocouple are 2 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. Aschlieren uses the interaction of sound and light to evaluate a sound beam profile.
The process of demodulation incorporates which of the following tasks (may be more than one): a. smoothing b. amplification c. rectification d. decompression
A and C
What is dynamic range?
A method of reporting the extent to which a signal can vary and still be accurately measured.
While using linear array transducers, why is it necessary to fire a group of crystals to produce a sound beam? Why can't a single crystal be used?
A sound wave fired from a single element of a linear sequential array would have a hyugens wavelet.
Converting information from the real world (patient's body) to the ultrasound system during reception is called? digitizing A to D converter D to A converter post processing
A to D converter
When high velocities appear negative on the spectral tracing it is termed? A) aliasing B) crosstalk C) spectral broadening D) overgain
A) aliasing
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 nu,ber of tires on a car
A. the weight is analog because it is continuous.
Which of these statements regarding a bit of computer memory is false? A. it is the smallest element of an image B. it is bistable C. 8 bits combine to make a byte D. It is a component of a digital scan converter
A. A bit is not a part of an image. A bit is the smallest element of computer memory.
The next step following the identification of an in vitro bioeffect is: a. propose in vitro research to evaluate the clinical significance of the bioeffect b. cease performing clinical studies that may include bioeffects in vitro c. ignore the results; its only an in vitro observation d. continue with in vitro research e. obtain an informed consent regarding this report from all patients
A. Further in vivo research should be performed to understand the impact of in vitro identified bioeffects on living subjects
Are the following procedures pre or post processing? A. modifying a frozen image B. read zoom C. write zoom D. adjusting the brightness on the monitor E. increasing the receiver gain
A. POST B. POST C. PRE D. POST E. PRE
This type of pulser generates numerous electrical spikes, which ultimately create a single sound pulse. A. PW, Phased array B. CW C. PW, single crystal
A. PW, Phased array With phased array tech, the pulser emits numerous electrical spikes that excite numerous crystals while one single acoustic pulse is created.
What is color confetti?
AKA bleeding. Gain is set too high
What is resolution?
Accuracy in imaging.
What is the arrangement of a convex array transducer?
Active elements are arranged in a bowed or arched line. The transducer may also be called a curved or curvilinear array.
What is the arrangement of a linear array transducer?
Active elements are arranged in a straight line.
What are the advantages and disadvantages of using a baseline shift when there is aliasing?
Advantage: The baseline shift slides down so the the entire velocity scale is devoted to one direction. Disadvantage: *little else is accomplished. *Sound will be heard in the incorrect speaker. *Baseline shift will be ineffective when the Doppler shift is so high that the signal completely wraps around itself.
What are the advantages and disadvantages of using continuous wave Doppler after aliasing?
Advantage: aliasing never appears with CW Doppler. Disadvantage: Range ambiguity
What are the advantages and disadvantages of selecting a lower frequency transducer when there is aliasing?
Advantages: Decreases doppler shift. Disadvantages: None except the image will be affected and be lower quality.
What are the advantages and disadvantages of adjusting the scale to its maximum when there is aliasing?
Advantages: Maximizes PRF, raises the nyquist limit. Disadvantages: higher PRF reduces sensitivity to low velocities. Aliasing can still persist when the scale is to its max
What are the advantages and disadvantages of selecting a new ultrasonic view with a shallower sample volume when there is aliasing?
Advantages: PRF is increased and the nyquist limit is increased Disadvantages: None
Which of these functions are performed by the receiver of an ultrasound system? (more than one may be correct) A. amplification B. threshold C. compensation D. demodulation
All of them
What is the process of amplification?
Amplification upon the return of the signals
What receiver functions are adjustable?
Amplification, compensation, compression, and reject.
Synonyms for receiver functions:
Amplification: receiver gain Compensation: TGCs, DGCs, swept gain Compression: log compression, Dynamic range Demodulation: None Reject: Suppression, Threshhold
Objective vs. subjective standards?
An objective statement is completely unbiased. A subjective statement is one that is influenced by an individual's experience or beliefs. Quality assurance programs should be based on objective standards.
Analog numbers vs digital numbers?
Analog numbers have real world numbers unlimited number of choices continuous values digital numbers have computer world numbers limited choices discrete values
What is Apodization vs Subdicing.
Apodization reduces side lobes by altering the electrical spike voltages making the inner crystals stronger in vibration and the outer crystals weaker in vibration. Subdicing reduces array grating lobes by getting a group of smaller crystals and electronically join them and act as if they are one crystal.
Following the revocation of consent, when should a sonographer terminate the exam?
At the first opportunity when it is safe (NOT Immediately)
Which of the following provides the basis for informard consent? Notice A contract Autonomy Beneficence
Autonomy
Axial resolution vs lateral resolution vs slice thickness resolution
Axial res - length of beam lat res - width of beam elev res - height of beam
A linear sequential array xdcr has 128 crystals. How many of these crystals are fired to create a single sound beam? A. 1 B. a small group C. a large group D. 128
B
A video display that is limited to only black and white, with no other shades of gray, is called___. A. binary B. bistable C. monochrome D. inchworm
B
All of the following are goals of quality assurance EXCEPT: A) detect gradual changes B) increase repeat scans C) minimize downtime D) reduce non-diagnostic exams E) insure proper operation of the equipment
B
Normally, what happens to venous flow in the legs during inspiration? A. increases B. decreases C. No change
B
The two most common color maps used in color flow imaging are: A. variance and direct B. variance and velocity C. turbulent and variance D. power and velocity
B
This transducer has a small footprint "small square" where the beam is steered and focused electronically. A. annular phased B. linear phased C. convex array D. linear sequential
B
Two digital scan converters are undergoing evaluation. System A has 100,000 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
WHat happens to venous return to the heart when an individual exhales? A. increases B. decreases C. remains the same
B
What form of resolution is evaluated by visualizing closely spaced pins that are parallel to the sound beam's main axis? A. lateral resolution B. axial resolution C. temporal resolution D. elevational resolution
B
What happens to the diahragm when an individual breaths in? A. it ascends tot he thorax B. It descends into the abd
B
What happens to venous flow in the legs when an individual inhales? A. increases B. decreases C. remains the same
B
What is the fundamental limitation of temporal resolution? a. imaging depth b. speed of sound in the medium c. line density d. sector size
B
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/cm2
B
What is the period of a 10MHz transducer? A) 1 microsecends B) 0.1 microseconds C) 10 seconds D) 10 microseconds
B
What is the process of adjusting for path length related attenuation called? A. compression B. compensation C. TGCs D. reconfirmation
B
Which component of an US system is most likely to expose a patient to danger? a. monitor b. transducer c. scan converter d. pulser
B
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
Which of the following epidemiologic studies is considered most likely to produce meaningful results? a. retrospective & prospective b. prospective & randomized c. retrospective & empirical d. prospective & mechanistic
B
Which of the following evaluates mock cysts and solid masses? A) AIUM 100 mm test object B) tissue equivalent phantom C) Doppler phantom D) slice thickness phantom
B
Which of the following is the processor used to analyze spectral Doppler? A) autocorrelation B) fast fourier transform C) zero crossing dector D) bidirectional Doppler E) Histogram
B
Which of the following is the unit for impedance? A) pascals B) rayls C) Kg/cm3 D) W/cm2
B
Which of the following statements regarding cavitation is true? a. it has never been observed in any biological media b. stable cavitation relates to oscillating 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
Which of these terms best describes the empirical investigation of bioeffects? a. cause-effect b. exposure-response c. cause-response d. exposure-cure
B
You are using spectral Doppler to evaluate the heart pressure and need to know exactly where the velocities are coming from. In this case you would use which of the following? A) CW Doppler B) PW Doppler C) color Doppler D) power Doppler
B
A byte is composed of ____ bits. A word is composed of ____bytes. a. 2,2 B. 8,2 c. 16,16 D. 8,16
B A string of 8 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.
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.
Which of the following transducers creates a shape like the spokes of a wheel radiating from a single point? (more than one may apply) A. linear sequential B. linear phased C. curvilinear sequential D. annular phased
B and D
Which of the following is not a potential mechanism for production of bioeffects from US exposure to the body? a. temperature elevation b. fractionation c. cavitation d. vibration
B fractionalization means "to separate a mixture into its ingredients" and has nothing to do with bioeffects.
Two US transducers are used to perform Doppler exams on the same pt. 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 higher freq = greater Doppler shifts ans vice versa.
What is the approximate number of frames that must be presented each second for the human eye to perceive the display without flickering? A. 2 B. 30 C. 100 D. 500
B. 30
This type of pulser generates a constant electrical signal in the form of a sine wave: A. PW, Array B. CW C. PW, single crystal
B. CW The pulser from a CW US system creates a continuous electrical signal.
In standard Doppler, what is true about the reflected frequency produced by blood cells traveling in a direction 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. it is ultrasonic
Why would a vessel appear without color?
Because the direction of the beam is at 90 degrees. cosine of 90 is 0.
What is the typical range of Doppler shift found in diagnostic imaging examinations?
Between 20 Hz and 20 kHz (in the audible range)
What is the difference between Bistable and grayscale?
Bistable means black and white while gray scales is all shades of brightness.
What is B mode and what is its x axis and Z axis?
Brightness mode. x axis is depth and z axis is amplitude.
A comprehensive & scholarly review of bioeffects is performed by the American Institute of US in Medicine for all of the following reasons except: a. US is a versatile technique b. US has proven widespread clinical utility c. US is considered highly toxic d. applications of US are growing considerably
C
A duplex ultrasound system displays _________ information. A. M mode, 2D image, and A mode B. A mode and B mode C. 2D image and doppler D. 2D and M mode
C
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
A region between the transducer to a depth of meaningful reflections is called which of the following A) focal zone B) focus C) dead zone D) minimum sensitivity
C
A sonographer adjusts an ultrasound system to change the sector size from 90 to 45 degrees. The frame rate was unchanged. What else must have happened? a. temporal resolution was doubled b. sector size was halved c. line density was doubled d, imaging depth was halved
C
A sonographer reduced the sector size from 90 degrees to 30 degrees. The frame rate did not change. What else happened? a. imaging depth increased b. PD increased c. multifocus was turned on d. PRF was increased
C
Adding more focal zones will do which of the following? A) increase frame rate B) increase sweep speed C) decrease temporal resolution D) decrease imaging depth
C
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
All of the following are consistent with an image containing only black and white and no other shades of gray EXCEPT: A. bistable B. high contrast C. wide dynamic range
C
All of the following occur during expiration except: A. venous return to the heart decreases B. venous flow in the legs increases C. abdominal pressure increases D. the diaphragm rises into the thoracic cavity
C
At what interval should QA evaluations be performed? A. weekly B. daily C. routinely D. periodically
C
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
Of the following, which imaging modality has the poorest temporal resolution? a. 2D, real time b. a mode c. color flow imaging d. m mode
C
The acoustic power of a sound beam emitted from a transducer is determined by the ________ of the pulser's signal. a. PRF b. frequency c. voltage d. rectification
C
The primary investigative technique of epidemiology is: a. computer modeling b. library research c. reviewing data from patients d. performing animal experiments
C
The relationship between the largest and smallest signal amplitudes processed by a component of an US system is called the ___________ and has units of ______________________ A. decibels, watts B. intensity, W/cm^2 C. dynamic range, dB D. proportionality, dB
C
What is the smallest part of a digital picture called? a. bit b. byte c. pixel d. fractel
C
What nonlinear behavior creates tissue harmonics? A. microbubbles expand to a greater extent than they compress. B. sound reflects off of boundaries with different impedances C. sound travels faster in compressions and slower in rarefactions D. microbubbles compress to a greater extent than they expand
C
What standard is best used in a quality assurance program? A. SUBJECTIVE B. EXPERT C. OBJECTIVE D. LEGISTLATIVE
C
What was the original purpose for the ultrasound system's analog scan converter? a. to increase the dynamic range of the ultrasound system b. to make real-time imaging possible c. to allow for grayscale imaging
C
Where are harmonics created? A. in the pulser B. in the transducer C. in the tissues D. in the receiver
C
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
Which display is limited to a single pair of brightness or display levels? A. CRT B. binary C. bistable D. grayscale
C
Which measure of intensity is related most closely to tissue heating? a. SATA b. SPPA c. SPTA d. SPTP e. Im
C
Which modality is associated w/ the lowest tissue temperature elevation? a. pulsed doppler b. color flow doppler c. gray scale imaging
C
Which of the following US beams has a characteristic that is most likely to cause temperature elevation in soft tissue? a. strongly focused b. medium focused c. unfocused
C
Which of the following forms of resolution improve when frame rate increases? A. lateral B. longitudinal C. temporal D. spatial res
C
Which of the following is a typical value for the amplification of a signal by the receiver? a. 50-100 watts b. -50 - -100 dB c. 50-100 dB d. 5 - 25 2/cm2
C
Which of the following is the unit for pressure? A) Kg/cm3 B) W/cm2 C) Pa D) Rayls E) dB
C
Which of the following techniques is used to create image data where none really exists? A. edge enhancement B. temporal compounding C. fill in interpolation D. spatial compounding
C
Which of the following terms does not belong with the others? A. phasic B. spontaneous C. pulsatile D. venous
C
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
Which of these components typically has the greatest dynamic range? A. display B. pulser C. amplifier D. demodulator
C
Which of these factors are relevant w/ regard to the thermal mechanism of bioeffects? a. rarefactional pressure & frequency b. compression pressure & frequency c. temperature & exposure time d. SPTA intensity & spatial pulse length
C
Which technique is used to perform spectral analysis on pulsed Doppler data? A. AUTOCORRELATION B. DEMODULATION C. FFT D. PULSE INVERSION
C
Why are dedicated CW xdcrs so sensitive? A. absence of the matching layer B. increased electrical conductance C. absence of backing material D. inclusion of demodulator
C
what is the true Doppler shift when the sound beam is normally incident to the velocity? A. it is maximum B. it is half of minimum C. it is absent D. it is at minimum
C
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 MI indicate low likelihood of cavitation. Derived mathematically from a sound wave's frequency and pressure, MI is lowest with high freq and low pressure.
An ultrasound system with a 4.0MHz transducer is used to image structures as deep as 15 cm. Twenty images are produced each second, each requiring 100 acoustic images pulses. What is the PRF of the system? a. 1500 Hz b. 300Hz c. 2000 Hz d. 4Hz
C PRF is defined as the number of pulses produced by an ultrasound system in one second. 100 pulses are required to construct a single image and 20 images are displayed each second. Thus you would multiply them both to get 2000 Hz
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 MI is derived mathematically from the pressure in a sound beam and the sound's frequency. MI is the highest with a high pressure and low freq.
Which of the following is the half value layer thickness of a 7 MHz transducer? A) 1 cm B) 0.65 cm C) 0.85 cm D) 1.1 cm
C atten coeff = MHz/2 Half layer thickness = 3/atten coeff
Research has indicated that cavitation _____. a. never occurs b. cannot occur w/ long pulses c. can be lethal to living things d. effects are purely theoretical
C cavitation resulting from US exposure is lethal to the fruit fly. Cavitation has the potential for significant and harmful bioeffects under specific circumstances.
In modern elastography, how are the tissues deformed? A. by pressing on the xdcr into the skin B. with the use of a second probe C. automatically D. as a result of respiration
C current elastography techniques collect info from tissues that are deformed by the sound beam itself.
Under certain conditions, an ultrasound system creates each image in 0.01 seconds. what is the frame rate? a. 1Hz b. 10 sec c. 100Hz d. 200Hz e. 0.02 Hz
C frame rate and tframe are reciprocals
Which of the following sector imaging systems will have the best image detail if all other parameters are identical? a. a 90 degree sector with 100 pulses/image b. an 80 degree sector with 40 pulses/image c. a 70 degree sector with 84 pulses/image d. a 60 degree sector with 60 pulses/image
C the best image detail is provided by the system with the highest line density. To determin which has the best image detail, divide pulses per image by degree sector. 100/90 = 1.11 40/80 = 0.5 84/70 = 1.2 60/60 = 1 The highest image quality is C because the answer is higher.
Of the following choices, which is considered the most important for the sonographer w/ regard to bioeffects? a. pulse repetition frequency b. frequency c. duration of the study d. imaging mode
C the exam duration is the most significant because the sonographer directly controls it.
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.
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 2m/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 max velocities are meas at a 0 degree angle. Only 1/2 of the true velocity is meas when the angle is 60 degrees.
Two US transducers are used to perform Doppler exams on the same pt. 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 B. the 5 MHz C. neither D. cannot be determined
C the velocities measured by the Doppler exams are the same, regardless of freq of the xdcr. although the Doppler shifts associated with the velocities may vary with different transmitted freq, the meas velocities are identical
If red blood cells are traveling toward a transducer, the frequency emitted by the transducer is ___ the frequency reflected from the red blood cells. A. greater than B. equal to C. less than
C when blood cells approach a xdcr, a positive Doppler freq shift results. The emitted freq is less than the reflected freq.
Where does the coded excitation take place? A. in the transducer B. in the receiver C. in the pulser D. in the PACS system
C.
The Doppler effect is observed as a change in ________ and has units of ________. A. amplitude, watts B. power, watts C. freq, sec D. wavelength, mm
C. 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. Freq may be expressed as hertz, Hz, cycles/sec, or per sec
Which of the following is not associated with the mechanistic approach? A. Identifying cause-effect relationship B. Proposing a specific means that could produce a bioeffect C. Studying charts of patients who have been exposed to US D. Analyzing the mechanism using theoretical methods. E. Reaching valid scientific conclusions.
C. Evaluating charts is an element of the empirical study of bioeffects.
This type of pulser generates a single electrical spike, which ultimately creates a single sound pulse. A. PW, Phased array B. CW C. PW, single crystal
C. PW, single crystal The pulser of a single crystal pulsed wave system creates a single electrical signal that excites the xdcr to create a single acoustic pulse.
Which statement allows us to conclude that diagnostic US doest not injure tissues from temperature elevation? a. death resulting from an US exam has never been reported b. mechanistic data indicate that diagnostic US is safe c. conclusions from empirical data & mechanistic data are consistent; that is, diagnostic US is unlikely to cause thermally induced bioeffects d. patients do not complain of burning during US exams
C. Scientific conclusions are strongly justified when empirical and mechanistic investigations reach conclusions that are consistent.
CD vs SD
CD measures mean velocity SD (PW and CW) measures peak velocity.
What user controls on video can alter the characteristics of displayed images?
Contrast and brightness
How do the strengths of tissue and contrast harmonics compare?
Contrast harmonics created by microbubbles are much stronger than tissue harmonics.
A linear phased array xdcr has 128 crystals. How many of these crystals are fired to create a single sound beam? A. 1 B. a small group C. a large group D. 128
D
All of the following are characteristics of a tissue equivalent phantom except: A. speed of sound similar to that in soft tissue B. attenuation properties similar to that of soft tissue C. scattering characteristics similar to that of soft tissue D. density similar to that of soft tissue
D
All of the following are functions of the receiver except: a. demodulation b. suppression c. amplification d. attenuation
D
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
In clinical imaging, which reflectors produce most relevant Doppler shifts? A. blood vessels B. blood plasma C. platelets D. red blood cells
D
Linear switched array transducers are steered and focused by which of the following methods? A. electronic B. mechanical C. lenses and mirrors D. no steering
D
Multiple disc shaped elements similar to rings of a "bulls eye" target is which one of the following transducers? A. linear phased B. array C. vector array D. annular array E. linear sequential
D
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 upper limit for the SPTA intensity of a focused US 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
Under which condition is it permissible to perform a diagnostic US exam? a. when patient will benefit b. when patient has insurance c. then exam is perfectly safe d. when benefits outweigh the risks
D
What does the black area in the center of both vessels represent? A. no flow B. a clot C. zero Doppler shift D. all of the above
D
What is the typical voltage of the signal that is the input to the receiver of an US system? a. 0.1 volts b. 500 mvolts c. 250 volts d. 10 microvolts
D
When studying bioeffects, which research approach is more important? a. empirical b. mechanistic c. neither is important d. both are equally important
D
Which component of an US system exposes a patient to greatest risk? a. the CRT b. the electric cord c. the pulser d. the transducer
D
Which electronic component is required for gray scale imaging? A. VCR B. non interlaced display C. computer memory D. scan converter
D
Which of the following best describes the demodulation process? a. changing the grayscale of an image b. changing the frequency of the signal c. changing the form of a sound pulse d. changing an electrical signal's form
D
Which of the following is an advantage of a large packet size? A. less aliasing B. increased frame rate C. improved lat res D. increased Doppler accuracy
D
Which of the following is an appropriate use of US in obstetrics? a. determine fetal gender b. viewing the fetus c. obtaining a picture of fetus d. to provide medical benefit to the patient
D
Which of the following is not true about spatial compounding? A. data is collected from different viewing angles B. frame rates are reduced C. shadowing artifact can be eliminated D. can be performed with a mechanical transducer
D
Which of the following tasks is not performed by the receiver of an ultrasound system? (more than one may be correct) A. rectification B. compression C. smoothing D. degaussing
D
Which of the following types of resolution displays the smallest distance at which two pins parallel to the sound beam and are displayed as two distinct echoes? A) lateral B) azimuthal C) angular D) axial
D
Which one of the following will give the most accurate spectral Doppler information? A) 60 degrees B) 90 degrees C) 45 degrees D) 180 degrees
D
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
What happens to an image when the # 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 as the number of bits assigned to each pixel increases, the number of different shades of gray in the image increases.
According to the AIUM, at what in situ tissue temperature is there danger to a fetus? a. 100 degrees C b. 98.6 degrees F c. 1 degrees F over normal temperature d. 41 degrees C
D elevation of fetal tissue in excess of 41 degrees Celsius is considered potentially harmful.
Two imaging systems produce acoustic pulses; one pulse is 0.4 millisec long and the other is 0.2 milli sec long. which is most likely to provide the best temporal resolution? a. 0.4 millisec system b. 0.2 millisec system c. they are not the smae d. cannot be determined
D temporal resolution is unrelated to pulse duration. temp res is determined by the number of frames, or images that are produced each second. There is insufficient information to answer the question.
Which ultrasound imaging modality has the best temporal resolution? a. b-scanning b. duplex imaging c. color flow imaging d. m mode
D M mode is the only mode that uses one dimension instead of 2.
The frequency of a pulsed Doppler wave is 6 MHz, and the PRF is 5 kHz. What is the maximum Doppler shift that can be recorded without aliasing? A. 6 MHz B. 5 kHz C. 3 MHz D. 2.5 kHz
D nyquist limit is 1/2 the PRF
When the signal is converted from the ultrasound system to the display it uses which of the following? A - D converter digitizing D - A converter post processing
D to A converter
When the signal is converted from the ultrasound system to the display it uses which of the following? A) A - D converter B) digitizing C) D - A converter D) post processing
D to A converter
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 C. 3 dB D. 80 dB
D. 80 dB 120 - 40 = 80
Dynamic aperture vs dynamic frequency tuning vs coded excitation
DA: desined to keep the sound beam narrow over a substancial depth range. DFT: improves image quality in the superficial region is improved. CE: improves image quality by using long sound pulses with a wide range of frequencies. The pulse is strong but it is used to reduce bioeffects since the FDA has a limit on peak intensity.
What does DICOM stand for?
Digital imaging and computers in medicine.
What is the relationship between the velocity of blood and Doppler shift?
Doppler shift is directly related to the velocity of the blood cells.
What is the Doppler shift formula?
Doppler shift(Hz) = reflected frequency - transmitted frequency
What is the significance of the gradual development of a harmonic signal?
During fundamental imaging, significant amounts of artifact arise within the first few cm of tissue. These artifacts appear for two reasons: the beam is very strong the many different superficial anatomic layers distort the sound beam
A bio effects report claims that obstetrical scanning may be harmful to a particular group of patients. What should be the response of the medical community? scanning may be harmful to a particular group of patients. What should be the response of the medical community? A. perform the exams on all pts when the benefits are outweighed by the risks. B. Stop all diagnostic exams C. Ignore the report D. Halt all exams on this pt group E. Perform exams on all pts when the benefits outweight the risks.
E
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
Which of the following might a Doppler phantom may assess? A) color Doppler B) pulsed wave Doppler C) continuous wave Doppler D) power Doppler E) all of the above
E
Which statement/s are true of tissue equivalent phantom? A. it has the same propagation speed as soft tissue B. it attenuates US 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 E. all of the above
E
AN 8MHz xdcr with a PRF of 5000Hz measures a Doppler shift of 7kHz. The study is repeated with a 4MHz xdcr. What Doppler shift will be measured. A. 4MHz B. 3.5 Hz C. 4 kHz D. 3.5 dB E. 3500Hz
E the measured Doppler shift is directly related to the xdcr freq. In this example, the xdcr freq is halved. The Doppler shift will be halved as well.
All of the following can reduce the workplace injuries except......... A. pt scheduling B. proper use of equipment C. educational programming D. pt positioning E. none of the above
E.
Which of the following is not a limitation of epidemiological studies? a. medical charts are sometimes incomplete or inaccurate b. other factors, unrelated to the study's ultimate goal, must be accounted for c. when the bioeffect is identified, the investigator is still unsure of the specific reason for its occurrence d. even when a bioeffect is identified, the investigator is still unsure of the specific reason for its occurance e. it does not provide greater understanding of the biologic significance of bioeffects
E. The greatest strength of epidemiological research is its dependence on clinical significance.
Veterans of a military operation suspect that they have been exposed to chemical warfare agents. The Veteran's Administration Hospital surveyed these soldiers to identify the presence of symptoms & their prevalence. What form of medical investigation is this?
Empirical Approach. Bioeffects are being investigated in an "exposure-response" context.
A patient only communicates in a foreign language. It is acceptable to speak to a bilingual family member and obtain consent from the relative...... TRUE OR FALSE
F
A sonographer with advanced practitioner status can provide her impression of a study to the patient....... TRUE OR FALSE
F
Power Doppler can determine the direction of flow but not the speed of blood flow. A) true B) false
F
Quality assurance can only be performed by engineers or physical scientists. A) True B) False
F
T or F: eliminating aliasing does not improve the ability to measure the maximum velocity with Doppler.
F
T or F: shallower sample volume result in more aliasing.
F
T or F: side lobes degrade axial res
F
T or F: the pulser of a mechanical sdcr is typically more complex than the pulser of a phased array xdcer.
F
T or F:If a weak sound beam is transmitted into the body, strong signals are received.
F
T or F? Absence of Color on a color Doppler image always indicates a region of no blood flow.
F
T or F? Color flow Doppler relies on pulsed Doppler principles and is immune to aliasing artifact.
F
T or F? On a color Doppler image, red always represents flow toward the transducer, whereas blue indicates flow away from the transducer.
F
T or F? Problems with aliasing significantly limit CW Doppler's clinical utility.
F
T or F? The appearance of negative velocities in a pulsed Doppler display always indicated that red blood cells are moving away from the transducer.
F
T or F? The higher the pulse repetition frequency of a Doppler exam, the more likely aliasing is to occur.
F
T or F? Velocity mode color Doppler and variance mode color Doppler will produce identical images when blood flow patters are turbulent.
F
T/F: QA evaluations of US systems can only be performed by biomedical engineers or physical scientists.
F
The AIUM 100 mm test object can evaluate grayscale. A) true B) false
F
The diaphragm movement during respiration causes variations in arterial flow away from the heart. A) True B) False
F
True or False. There are no bioeffects associated with ultrasound having characteristics typical of those in diagnostic medicine.
F
T or F: Many active elements fire at almost the same time in a mechanical scanner.
F Mechanical xdcr only has one crystal
T or F: If 100 scan lines make up an image and the frame rate is 30 per second, then the transducer's frequency is 3000 Hz.
F That is the transducer's PRF
T or F: The critical factor in determing frame rate, line density, and imaging depth is the transducer style.
F The critical factor in determining frame rate, line density, and imaging depth is time.
T or F? The greater the number of bits assigned to each pixel of a digital image, the greater the spatial resolution of the image is.
F The number of bits assigned to each pixel of a digital image does not directly affect the spatiel res of the image
T or F: The sonographer can make an image of uniform brightness by adjusting both output power and receiver gain?
F because they do not correct attenuation
T or F: lower pulser voltages maximize the likelihood of bioeffects
F they minimize the likelihood of bioeffects
T or F: compensation processes all reflected signals in a similar manner.
F those reflections arising from shallow structures are barely compensated. Those arising from deep structures are substantially compensated.
T or F: An ultrasound system with a longer pulse duration will generally have a better temporal resolution
F Temporal resolution of a system is unaffected by the pulse duration.
True or False: The AIUM suggests that in vitro research confirming bioeffects is valuable and valid. Their results are significant & should be directly applied to the clinical arena.
F. Although in vitro results are extremely important, it is difficult to asses their direct clinical significance. Further studies should be performed before applying these conclusions clinically.
True or False: Exposing an individual to US from a diagnostic imaging system is never appropriate when there is absolutely no clinical benefit to that individual.
F. It is appropriate to perform US studies for the sake of research and training even when no direct medical benefit is anticipated. Informed consent should be obtained from the subject.
Informed consent must always be obtained from the patient..... TRUE OR FALSE
F. Pts must have the capacity to provide consent.
True or False: Bioeffects identified through in vitro research are not considered real.
F. The AIUM conclusively states that in vitro bioeffects must be considered real; however, their clinical importance is unknown.
True or False: It is generally believed that the effects of US on biologic media are minimal.
F. US bioeffects are substantial under certain conditions, including, bot not limited to, therapeutic US and lithotripsy.
T or F: A successful Doppler exam cannot be performed on a severely anemic pt.
F. Within the physiologic range, variations in RBC concentration will not affect the ability to successfully perform a Doppler exam.
T or F: the lumen of a horizontal vessel evaluated with a CD sector shaped image contains a single color.
F. the vessel will have both the toward and away colors. the center of the lumen will be black.
T or F: There are large time delays in the firing pattern of a linear phased array xdcr.
F. there are tiny time delays
True or False: The biological effects of US are thought to be negligible & thus, few investigations have been performed on the subject.
F. they are studied extensively
What is the current method of processing Doppler signals?
FFT method of spectral analysis for pulsed and CW. Autocorrelation is the method of spectral for CD.
True or False. There are two forms of cavitation: inertial and normal.
False. Stable and normal.
What are the 2 methods of spectral analysis?
Fast Fourier Transform Autocorrelation
What types of tissues are less tolerant to heat.
Fetal and neonatal
Fewer bits per pixel vs more bits per pixel
Fewer bits per pixel: fewer shades of gray degraded contrast resolution More Bits per pixel: more shades of gray improved contrast resolution
The Doppler effect is presented as a __________ when the source and the receiver are ___________.
Frequency shift, in motion relative to each other
What is the unit for temporal resolution?
Hz just like frame rate
What is the units for frame rate?
Hz (images per second)
What is the rule of ALARA?
If the image is too dark, first increase the receiver gain. If the image is too bright, first decrease the output power.
What are the limitations of an analog scan converter?
Image fades, images flicker, instability, and deterioration.
Imaging Vs Doppler Needs
Imaging: normal incidence to 90 degrees higher freq improves res PW is the only one that can do images minimum of 1 crystal Doppler: 0 to 180 degrees lower freq avoids aliasing can be done with both PW and CW min. of 1 (pulsed) or 2(CW) crystals
Where is pressure lowest in a stenosis? Pre stenosis post stenosis in narrowing
In narrowing
When is persistance the most useful?
In still images and not in moving structures such as the heart.
Bioeffects research may be conducted in two broad areas......
In vivo and in vitro.
What is the first action of sonographer upon entering a patient's room? Introduce themselves to the patient plug in the US system check the pts wristband wash their hands
Introduce themselves to the patient
What is randomized epidemiologic studies?
It creates 2 groups of patients. One group is exposed to US and the other is not.
What is contrast?
It determines the rance of brilliances within the displayed image. Bistable images, in which only white and black appear are high contrast.
What is a beam former switch and what does it do?
It helps change from transmit to receive and vice versa. During pulse creation the volatages are high while during reception, the voltages are low. It protects the sensitive electrical components in the receiver from the high voltages created during transmission.
You are using a 4 MHz transducer and have adjusted the TGC perfectly, as represented by the red TGC line. You are given a new transducer with an unknown frequency. The TGC is then adjusted to create the same image as that obtained using the 4 MHz transducer - this new TGC setting is the purple dotted line. Is the frequency of the new transducer greater than or less than 4MHz and why?
It is less than 4 MHz because the delay is deeper with the new transducer.
How is slice thickness meaured?
It is measured in a direction perpendicular to the imaging plane. or above to below the imaging plane.
You are using a 4 MHz transducer and have adjusted the TGC perfectly, as represented by the red TGC line. You are given a new transducer with an unknown frequency. The TGC is then adjusted to create the same image as that obtained using the 4 MHz transducer - this new TGC setting is the green dotted line. Is the frequency of the new transducer greater than or less than 4MHz and why?
It is more than 4 MHz because the delay is shallower with the new transducer.
How does the slice thickness phantom measure the beam?
It measures the beam geometry perpendicular to the imaging plane.
What would justice mean in respect to ethics?
Justice in healthcare is usually defined as fairness. Equal treatment.
What are the forms of energy associated with blood?
Kinetic pressure gravitational
What is the cheat to learn variance mode map?
L:L L for left and L for laminar.
WHat is the typical resistance of veins?
Low resistance just like some arteries
Maximum sensitivity
Max sensitivity is evaluated with the output power and amplification of the system set to the maximum practical levels. With these settings, a tissue equivalent phantom is images, and the depth of tissue like texture on the display is measured. Maximum visualization depth is used to asses sensitivity and should not differ from one routine eval to the next.
What transducers use a fixed focusing technique?
Mechanical
What transducers have a mechanical steering technique?
Mechanical and annular phased
the amount of contrast harmonics produced may be estimated by a number called
Mechanical index
What is M mode and what is its x axis and y axis?
Motion mode. x axis is time and y axis is depth.
Do tissue signals exist at extremely superficial depths?
NO, they develop deeper in the tissue.
What do these terms mean in a TGC curve? slope, knee, far gain, near gain, delay
Near gain: at superficial depths, reflections undergo a small amount of compensation. Delay: the depth where variable compensation begins. Slope: compensation for increasing attenuation knee: where reflections start maximally compensating. Far gain: maximum amount of compensation area.
Can harmonic signals distort?
No because since tissue harmonic signals do not occur at superficial depths and harmonics does, they are distortion free.
Does amplification improve signal to noise ratio?
No because this is receiver gain and not output gain and both signal and noise are amplified equally.
Do continuous waves create anatomic images?
No they do not
What 2 forms of sensitivity are there?
Normal and maximum
Normal Sensitivity
Normal sensitivity settings are those at which all the pins, solid masses, and cystic structures in the test phantom are accurately displayed. Output power, TGC, and amplification are adjusted to establish normal sensitivity. All quality assurance performance meas are made at the normal sensitivity.
Output power vs receiver gain
Output power - alters signal to noise ration - alters pt exposure - bioeffect conserns - decrease this forst if image is too bright receiver gain - does not effect signal to noise ratio - does not change pt exposure - no bioeffect concerns - increase this first if image is too bright
What is PACS VS DICOM?
PACS is the physical computer network DICOM is the set of rules that allows the components of the network to communicate.
What are the disadvantages of certain media?
PM: Hard to store difficult to make copies cannot display dynamic images MM: can be erased by magnetic fields CM: Hard to store Requires chemical processing Artifacts can arise from dirt or contamination OM: Requires a display system No standardized format for image and storage
What are the advantages of certain medias?
PM: Portability and does not require a device to read MM: Stores large amounts of info can store and play dynamic images can record color CM: High Resolution Accepted in the medical community can produce color images OM: Store large amounts of info Inexpensive
PW xdcr vs CW xdcr has
PW: at least one crystal dampened PZT low q factor wide bandwidth lower sensitivity CW: at least 2 crystals undampened PZT high q factor narrow bandwidth higher sensitivity
What is an example of a medias?
Paper Media: paper Magnetic media: computer discs/memory magnetic tape video tape Chemical Photographs: Photos/Films Optical Media: Laser Discs Compact Discs
What is temporal resolution?
Pertains to accuracy in time, describes the ability to precisely position moving structures from instant to instant.
What is commonly used for bidirectional Doppler?
Phase quadrature or quadrature detection.
What does PACS stand for?
Picture, Archiving and Communications System
Viscosity is measured in units of
Poise
What is a positive vs negative Doppler shift?
Positive: The reflected frequency is higher than the transmitted frequency. Negative: the reflected frequency is lower than the transmitted frequency.
Where is the pressure highest in a stenosis? Pre stenosis post stenosis in narrowing
Pre stenosis
preprocessing vs postprocessing in regards to reversing...
Preprocessing cannot be reversed postprocessing can be reversed
Inertial energy loss occurs during 3 events
Pulsatile flow Phasic flow Velocity changes at a stenosis
What is pulse inversion harmonics vs Power Modulation?
Pulse Inversion: an imaging technique that specifically designed to uitilize harmonic reflections, which are distortion free, while eliminating distorted fundamental reflections Power Modulation: It achieves the same goals as pulse inversion harmonic but uses a different engineering approach.
What is pulsatile vs phasic vs steady flow?
Pulstatile occurs when blood accelerates and decelerates as a result of cardiac contraction. Therefore, flow commonly appears in arterial circulation. Phasic occurs when blood accelerates and decelerates as a result of respiration. Therefore, phasic flow often appears in the venous circulation. Steady occurs when fluid moves at a constant speed or velocity. It is present in the venous circulation when individuals stop breathing for a brief moment.
What is range resolution vs range ambiguity?
RR: being able to select the exact location where velocities are measured. PW RA: not being able to select the exact location where velocities are measured. CW
The selected part of the image is known as the
Region of interest or ROI
Which of the following is least likely to make a patient experience a loss of dignity? advanced age sickness lack of privacy sedation
Sedation
What are the 5 characteristics in a annular phased xdcr?
Shape and # - Disc, multi ringed elements (bullseye) Steering - Mechanical steering Focus - electronic focus Image shape - sector Damaged PZT - horizontal curved black band
What are the 5 characteristics in a mechanical transducer?
Shape and # - circular, 1 element/small footprint Steering - mechanical steering Focus - fixed focal depth (curved PZT, lens, mirrors) Image shape - Sector Damaged PZT - entrire image is gone.
What are the 5 characteristics in a linear phased xdcr?
Shape and # - rectangular and narrow 100-300 elements/small footprint Steering - electronic steering (phasing and angles out like wheel spokes) Focus - electronic focus Image shape - sector Damaged PZT - erratic steering and focusing
What are the 5 characteristics in a linear sequential array xdcr?
Shape and # - rectangular, 120-250 elements/ large footprint Steering - No steering Focus - fixed focusing Image shape - rectangular Damaged PZT - vertical straight line black under damaged PZT
What are the 5 characteristics in a curvilinear sequential array xdcr?
Shape and # - rectangular, 120-250 elements/ large footprint Steering - electronic steering Focus - electronic focus Image shape - blunted curved sector Damaged PZT - top to bottom black line under damaged PZT
What are the 5 characteristics in a vector array xdcr?
Shape and # - rectangular, 120-250 elements/ small footprint Steering - electronic steering Focus - electronic focus Image shape - trapezoid Damaged PZT - erratic steering and focusing
what are the 5 characteristics of each xdcr style?
Shape and number steering of sound beams focusing of sound beams image shape Effects of damage to PZT
What is spatial vs frequency vs temporal compounding?
Spatial: uses different imaging angles to produce a better image. Frequency: separates one wave into different waves to produce a better image. Temporal: displays information from older images and are superimposed on the most current frame.
A patient only communicates in a foreign language. It is acceptable to have a bilingual family member serve as an interpreter, speak to the patient, and obtain consent from he patient...... TRUE OR FALSE
T
Adding too much filter or decreasing the filter too much will lead to a loss of information on the spectral Doppler waveform. A) true B) false
T
T or F: A combination of temperature and exposure time determine the likelihood of harmful effects. With higher temps, harmful effects can occur with shorter exposure times.
T
T or F: Any alterations to a frozen image must be post processing.
T
T or F: Autocorrelation is somewhat less accurate but substantially faster to perform than FFT
T
T or F: Beams that are most likely to create harmonics are least likely to create artifacts.
T
T or F: Bones absorbs more acoustic energy than soft tissue.
T
T or F: Bubbles expand to a greater extent than they shrink.
T
T or F: Contrast harmonics are created during reflection, created by non-linear behavior, related to the MI, and determined by the contrast agent.
T
T or F: Higher freq xdcrs have a thinner dead zone than lower freq xdcrs.
T
T or F: Images with many shades of gray have better contrast resolution
T
T or F: In PD the amplitude of the reflection is directly related to the number of moving blood cells.
T
T or F: In addition to axial and lateral resolution, slice thickness contributes to image quality.
T
T or F: Maximum velocity exists where the vessel is narrowest.
T
T or F: No confirmed bioeffects have been reported for temp elevations of up to 2 degrees Celsius above normalfor exposures of less than 50 hours
T
T or F: Numerous fetal defects resulting from temp elevation have been documented. None have been observed at temps less than 39 degrees celsius
T
T or F: Phased array always means adjustable or multi-focus.
T
T or F: Slice thickness is likely to degrade the image quality because the imaging plane is thicker than either the beam width (which determines lateral res) or pulse length (which determines axial res).
T
T or F: Strength of the tissue harmonic signal builds up as the wave travels deeper into the tissues and then dies down?
T
T or F: Temporal resolution is excellent when a system produces many frames persecond and substandard when it producesfew frames per second.
T
T or F: The beam former adjust electrical spike voltages to reduce lobe artifacts in a process called apodization.
T
T or F: The beam former controls dynamic aperture by varying the number of PZT crystals using both reception and transmission.
T
T or F: The elevational resolution is identical to the lateral resolution with disc shaped active elements?
T
T or F: The higher the emitted freq, the more likely a PW signal is to alias.
T
T or F: The number of lines per frame and the frame rate determine the PRF
T
T or F: There are no known cases of diagnostic imaging at standard intensities in the absence of contrast agents resulting in biological effects and tissue injury.
T
T or F: Velocity decreases as blood flows out of stenosis into a vessel segment of normal diameter
T
T or F: When a person is supine, the hydrostatic pressure is 0 everywhere.
T
T or F: dedicated CW xdcrs have increased sensitivity. They detect low amplitude reflections and small Doppler shifts
T
T or F: epidemiologic data indicate that US exposure is not associated with adverse fetal outcome.
T
T or F: gaseous nuclei are found in tissues and are different than gas bubbles introduced into the body as contrast agents
T
T or F: higher frame rates are possible when each individual image is made with fewer pulses and vice versa.
T
T or F: improved contrast resolution is associated with additional bits.
T
T or F: in a standing individual, the hydrostatic pressure changes
T
T or F: lateral resolution improves with multi focusing.
T
T or F: low intensity ultrasound has no known bioeffects while extremely high ultrasound intensities damage biologic tissues.
T
T or F: output power alone cannot make an image of uniform brightness from top to bottom.
T
T or F: side lobes degrade lateral res
T
T or F: spatial resolution improves with high pixel density
T
T or F? Color flow Doppler exams tend to have lower temporal resolution than traditional two-dimensional, real-time imaging.
T
T or F? Color flow Doppler imaging incorporates pulsed Doppler principles and provides range resolution.
T
T or F? Color flow Doppler systems display anatomical data in grayscale while simultaneously displaying flow info in color.
T
T or F? For digital image information to be displayed on a conventional television screen, the data must be processed by a digital-to-analog converter.
T
T or F? Frequencies measured at the transducer are produced from many different locations along the ultrasonic beam for a CW Doppler.
T
T or F? In a pulsed Doppler exam, the use of a higher transducer frequency increases the likelihood that aliasing will appear.
T
T or F? TGC cannot be used with continuous wave Doppler.
T
T or F? 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.
T
T or F? The greater the number of bits assigned to each pixel or digital image, the greater the number of shades of gray in the image is.
T
T or F? 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.
T
T or F? Velocity mode color Doppler and variance mode color Doppler will produce identical images when blood flow pattern are laminar.
T
Tor F: only PW exams have a sample volume
T
True or False. Cavitation describes the interaction between sound waves and small gas bubbles that exist in tissues.
T
True or False. Normal, transient, or inertial cavitation describes the bursting of microbubbles.
T
True or False: Focused sound beams are considered less likely to create bioeffects b/c the beams will strike fewer gas bubbles that could potentially cavitate.
T
True or False: One reason focused US beams w/ 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.
T
True or False: The AIUM considers an US-induced biological tissue temperature rise of less than 2 degrees Centigrade above normal body temperature as safe for clinical studies.
T
True or False: A bioeffect identified through the mechanistic approach rather than the empirical approach is more likely to have clinical significance.
T An empirical study is one where investigators look for a relationship between two events without necessarily uncerstanding the fundamental cause and effect that relates the 2 factors. An example of 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. Empirical approach is considered "exposure-response"
T or F? The assignment of different shades of gray to the digital numbers stored in the scan converter acts to improve the diagnostic value of an ultrasound exam.
T By using an appropriate grayscale map, the tissues appear differently on the screen thereby enhancing an exam's diagnostic value.
T or F: Although with a 10cm footprint may produce an 8cm wide image, it cannot create and image wider than 10 cm. With linear sequential transducer.
T Linear sequential arrays are 10cm long and cannot go wider than what it is.
T or F: If 100 scan lines make up an image and the frame rate is 30 per second, then the system's PRF is 3,000 Hz.
T PRF is the # of pulses created per second. In this example, it is lines per image multiplied by frame rate
T or F: The length of a pulse does not directly influence the temporal resolution.
T The factors that do influence the temporal resolution are maximum imaging depth, sector angle, line density, and the number of focci per scan line.
T or F: with the sector scanning, images with greater detail (spatial res) are created when the number of acoustic pulses per degree of sector is increased.
T spatial res is improved with more pulses per degree of sector.
T or F: pulser voltage is related to brightness.
T the higher the voltage, the brighter the image is and the stronger the reflected ehoes are.
T or F: If the imaging depth of a scan is 15cm and there are 100 lines in the image, then the number of pulses making up the scan is 1500.
T 1 line = 1 pulse 100*15 cm = 1500
True or False. There are no harmful bioeffects associated with ultrasound having characteristics typical of those in diagnostic medicine.
T bioeffects are not typically observed with diagnostic ultrasound.
True or False: The intensity limit established for diagnostic US is higher for focused sound beams than for broad, unfocused sound beams.
T. Broad, unfocused sound beams cause greater tissue heating. The maximum intensity limit for these beams is therefore lower than that for focused beams.
Which of the following is the thermal index of soft tissue? A) TIB B) TIS C) TIC
TIS
Thermal index is reported in 3 forms:
TIS, or soft tissue thermal index, assumes that sound is traveling in soft tissue. TIB, or bone thermal index, assumes that bone is at or near the focus of the sound beam TIC, or cranial bone thermal index, assumes that cranial bone is in the sound beam's near field. These thermal indices are the best measurements or estimates of in vivo tissue temperature elevation.
What is the difference between the analog beam former and the digital beam former?
The Digital Beam Former applies the time delays on the echo signals AFTER they are digitized.
Starting form the same point, the sound source is moving toward the east at 12 MPH and the receiver is moving toward the west at 10 MPH. The Doppler shift is pos + or Neg-?
The Doppler shift is negative.
What is edge enhancement?
The computer identifies and emphasizes sharp edge boundaries in the image which makes things look more defined.
When do the 2 shifts occur?
The first shift is when the sound wave from the xdcr strikes moving blood cells. The second shift is the reflections return to the xdcr.
How does a phased array system create images with multiple focus?
The machine would emit different patterns down each scan line to create different focuses.
If the sound beam and flow direction are not parallel, what determines how much of the velocity is measured?
The percentage of the true velocity that is measured depends on the cosine of the angle between the sound beam and the direction of motion.
What is dynamic frequency tuning?
The receiver processes sound at higher frequencies from superficial reflectors, mid frequency and then low frequency for deeper reflectors. Thus, the image quality in the superficial region is improved.
What is the significance of displaying all component frequencies with FFT?
The spectral display of an FFT distinguishes laminar flow from turbulent flow.
What is Frame rate
The system's ability to create numerous frames each second and making an ultrasound movie.
What are phase delays?
The time difference at which the electronic signal hits each PZT.
What 2 measurements are used to measure output?
Thermal index and mechanical index.
Grating Lobes Vs Side Lobes and how do you eliminate them
They are the same thing. They are additional areas of sound energy extend outside of the main beam in the far zone. Grating lobes are for single element xdcrs. Eliminated with subdicing. Side Lobes are for array xdcrs. Eliminated with apodization
Thicker slice thickness results in
Thicker slices diminish spatial res (image detail) and reduce the ability to visualize small, low contrast reflectors. When the US beam is overly thick, cystic structures may appear filled in.
What is static scanning?
This is how they used to scan back in the day where images were displayed one frame at a time.
What are tissue equivalent, doppler, and slice thickness phantoms?
Tissue equivalent: have ultrasonic features similar to soft tissue. They are used to evaluate characteristics such as grayscale and tissue texture, and multi focus and adjustable focus phased array xdcrs. Doppler: It evaluates Doppler systems for quality assurance. The includes PW, CW, CD, and PD Slice thickness: assesses the slice thickness/elevational res.
How many shades of gray can be represented by a group of: 4 bits and 2 bits
To determine the number of gray shades multiply 2 by the exponent of bits 2^4 = 16 shades 2^2 - 4 shades
Dynamic range of components...
Transducer - 120dB Receiver - 100 - 120 dB Scan Converter - 40-50dB Display - 20-30dB Archive - 10-30dB
True or False: Stable cavitation describes the rhythmic swelling & shrinking of gaseous nuclei.
True. With stable cavitation, the microbubbles do not burst.
When it is appropriate to question a pts ability to participate in decision making?
Underage pt incapacitated or incapable of providing consent If the pt does not speak English
How do you eliminate clutter or ghosting artifact?
Wall filter
How does sample volume affect the presence of aliasing?
When the sample volume is deep, the PRF is low and the nyquist limit is low. Velocity is sampled fewer times and the system is unable to accurately measure high velocities. Deeper sample volumes create aliasing.
How can you distinguish bidirectional flow from aliasing with CD?
With aliasing, colors touch while bidirectional has a bit of black in between.
Does focusing occur in both horizontal and vertical planes because of the hourglass shape of the sound beam in a mechanical transducer?
Yes
Can phase delays be used to focus a sound beam during reception?
Yes.
Does increasing the scale have any other effect on CD?
Yes. It decreases the sensitivity of slower flows.
What is signal to noise ratio?
a comparison of the meaningful information (signal) in an image compared to the amount of contamination (noise).
What is Fast Fourier Transform FFT?
a digital technique, used to process both pulsed and CW doppler signals.
What is an array?
a group or arrangement of elements (multiple not single).
What is coded excitation?
a method of improving image quality that uses long sound pulses with a wide range of frequencies. The pulse is strong but it is used to reduce bioeffects since the FDA has a limit on peak intensity.
Temporal resolution has to do with ______________ and image quality has to do with _______________.
a movie, an actual photograph.
What is stenosis?
a narrowing in the lumen of a vessel
Which of the following would demonstrate the highest resistance waveform? A) a large artery B) a small artery C) a large vein D) a small vein
a small artery
What is crosstalk?
a special form of mirror image artifact that arises only with spectral doppler. bidirectional.
What is spectral analysis?
a tool that breaks the complex signal into its basic building blocks and identifies the individual velocities that make up the reflected doppler signal.
What is the thermal index?
a useful predictor of maximum temp increase under most clinically relevant conditions.
What part of the xdcr helps with elevational resolution in phased array, linear array, and convex array transducers?
acoustic lens
what does write magnification do?
acquires new data preprocessing identical pixel size more pixeld than in the original ROI improved spatial res may improve temp res
The mathematics of compression using dB is just
add and subtract.
What is a hydrophone?
aka microprobe, is similar to a small hypodermic needle with a tiny piece of PZT attached to its end. A wire connects the PZT crystal to an oscilloscope. The hydrophone is placed in the sound beam created by the US xdcr. A voltage from the hydrophone relates to the sound beam's pressure and is displayed on the oscilloscope. Since the hydroscope is small, the acoustic pressure is measured at specific locations within the sound beam.
What is range accuracy?
aka vertical depth calibration, describes the system's accuracy in placing reflectors at correct depths located parallel to the sound beam.
When there are several colors in a vessel it is called
aliasing
All of the following are components of the ultrasound system EXCEPT? pulser alternator transducer synchronizer receiver display
alternator
what is the effect on the image with compression?
alters the gray scale mapping of an ultrasound image.
What receiver functions process signals identically?
amplification
Which of the folowing is the correct order of receiver operations? reject, compression, compensation amplification, demodulation compression amplification, compensation, reject, demodulation amplification, compensation, compression, demodulation, reject amplification compression, compensation demodulation, reject
amplification, compensation, compression, demodulation, reject
Gray shades on a Doppler spectrum are related to
amplitude of the reflected signal or number or blood cells creating reflection.
What is elastography
an emerging technology that produces images relating to stiffness. Helps to detect cancer.
What is the analog and digital image 5 step process?
analog to digital conversion sent to digital memory preprocessing post processing digital to analog conversion now in analog
What can you do in post processing?
any change after freeze frame - black/white inversion - read magnification - contrast variation - 3D rendering
In the circulatory system, the resistance vessels are called
arterioles
What is the current method for analyzing color Doppler information? A) chirp z transform B) autocorrelation C) zero crossing detector D) fast fourier transform E) time interval histogram
autocorrelation
What is acousto-optics?
based on the interaction of sound and light. A shadowing system, called a Schlieren, allows us to view the shape of a sound beam in a medium.
Why is converting from analog to digital image advantageous?
because digital information is far susceptible to contamination by electrical noise.
Why is autocorrelation used with CD?
because of the enormous amount of data that is processed.
WHat is the advantage for a PW Doppler?
being able to select the exact location where velocities are measured. AKA Range resolution.
Which of the following terms describes the value that the actions of health care providers should benefit the patient? nonmaleficence beneficence justice autonomy
beneficence
A series of 0's and 1's is called a... decimal number binary number bit byte
binary number
Velocity refers to: A) speed of red blood cells B) direction of flow of red blood cells C) both speed and direction of red blood cells D) neither speed nor direction of red blood cells
both speed and direction of red blood cells
What is stable cavitation?
bubbles that expand but do not burst. *oscillating bubble * microstreaming and shear stress * lower MI
Stenosis may have what effects on blood flow?
changes in direction of flow increased velocity as vessel narrows Post stenotic turbulence pressure gradient across stenosis loss of pulsatility.
What is turbulent flow?
chaotic flow patterns in many different directions and speeds. The streamlines are often obliterated. This is not normal flow.
On spectral displays, low freq doppler shift artifacts are called
clutter
What do the colors in variance mode map mean?
colors change up and down and side to side. same as variance on up and down except colors on the left side mean laminar while colors on the right side mean turbulent.
What is a channel?
combination of the active element, wire, and system electronics.
Signals in compensation, compression, and reject are treated differently based on what?
compensation: reflector depth compression: depending on strength reject: only weak signals are treated differently
What does compression do ?
compression keeps the electrical signal levels within the accuracy range of the system's electronics and keeps an image's grayscale content within the range of detection by the human eye.
What is the effect of compression, demodulation, and reject on images?
compression: changes gray scale mapping demodulation: none reject: weak echoes appear or disappear.
How is information and images stored in a PACS?
computer hard drives.
Bits have to do with
computer memory gray shades contrast resolution
What are nonthermal or mechanical mechanisms?
consists of cavitation and radiation force.
PW characteristics
contain backing material low quality factor lower sensitivity wide bandwidth pulses
Auto correlation is also called
correlation function
An increasingly deeper dead zone may indicate a.....
cracked signal, detached backing material, or a longer pulse duration.
Contrast agents are designed to...
create strong reflections that actually "light up" blood chambers, vessels, or other anatomic regions.
What does the pulser and beam former do and determine?
creates and controls the electrical signals that excite PZT and create sound beams. it determines the amplitude, PRP, and PRF Beam former is the array version of the pulser.
Methods of focusing
curved element lens electronic mirrors (all are curved to create focusing)
What will the beam spike pattern look like if you want a steared and focused beam?
curved for focus but not evenly curved to create an angle.
What pattern of electrical spikes do you need to have focus?
curved pattern where the outer crystals are excited earlier than the inner crystals.
What are the other names of a curvilinear array transducer?
curved, convex, and curvilinear array.
What is the unit for dynamic range?
dB
What is the units of amplification, compensation, and compression?
dB
Using your critical thinking skills, how might adding color Doppler affect frame rate? increases frame rate decreases frame rate frame rate is unaffected
decreases frame rate
During Inspiration, pressure in the thoracic cavity________while abdominal pressure _____________? A) increases, increases B) increases, decreases C) decreases, decreases D) decreases, increases
decreases, increases
A receiver function that converts negative voltages into positive voltages is called: demodulation reject compression amplification
demodulation
In regard to Doppler ultrasound, the extracting of lower Doppler frequencies from higher transducer frequencies is called? A) compression B) demodulation C) rectification D) thresholding
demodulation
What receiver functions are not adjustable?
demodulation
formula for # of pulses
depth X lines in the image
What are the sonographer controlled settings of an ultrasound frame rate?
depth and number of pulses per frame
The accuracy of reflector depth positioning in A mode, M mode, B mode, and 2D imaging is called
depth calibration
What is Bernoulli's Principle?
describes the relationship between velocity and pressure in a moving fluid. The sum of kinetic energy and pressure energy remains constant.
What is uniformity or compensation operation?
describes the system's ability to display similar reflectors in the phantom with echoes of equal brightness. With proper TGC, identical reflectors should have the same appearance on the monitor, regardless of their depth.
What is the muscle responsible for breathing?
diaphragm
What happens during inspiration?
diaphragm moves downward toward the abdomen thoracic pressure decreases (chest cavity expands creating negative pressure) abdominal pressure increases venous return to the heart, neck, arms and vena cava increases venous flow in the leg decreases
What happens during expiration?
diaphragm moves upward into the thorax thoracic pressure increases abdominal pressure decreases venous return to the heart, neck, arms, vena cava decreases venous flow in legs increases
What is the relationship between the transmitted frequency and the Doppler shift?
directly related
What is the relationship between the cosine 0 and the Doppler shift?
directly related.
What is the relationship between line density and #of pulses per image, frame rate, and temporal res.
directly, inversely, inversely.
What shape of PZT creates the best elevational resolution?
disc shaped PZT
The purpose of the FFT, fast fourier transform program is to? A) eliminate aliasing B) automatically limit system gain C) display the Doppler frequency spectrum D) filter out low frequency Doppler
display the Doppler frequency spectrum
What are the units for velocity?
distance/time such as cm/s
What is noise?
disturbance that obscures or reduces signal clarity.
Crosstalk results from....
doppler gain set too high (electronic crosstalk) or incident angle is near 90 degrees between the sound beam and the flow direction, when flow is at the beam's focus.
The science of identifying and measuring the characteristics of an ultrasound beam that are relevant to its potential for producing bioeffects is which of the following? A) dosimetry B) risk-benefit ratio C) radiation force D) epidemiology
dosimetry
How to predict flow in an angle steered, one color image?
draw an imaginary line downward from the corner of the steered box that does not run into color. that is the starting point for ex from left to right or right to left.
Simultaneous imaging and Doppler is termed? A) bidirectional Doppler B) nondirectional Doppler C) Duplex imaging D) autocorrelation
duplex imaging
Pressure gradient increases when
either flow increases or resistance increases
What can happen when there is a cracked xdcr?
electrical shock to the pt.
What is Phasing
electronically steers and focuses the beam
Slice thickness is also called....
elevational resolution
The 1 1/2 D array transducers improve which of the following? (2 correct answers) temporal resolution elevational resolution create thinner beams steer the signal more rapidly
elevational resolution create thinner beams
What does wall filter do in SD?
eliminates low velocity flows near the baseline
PD is also called
energy mode or color angio
What is the study of the relationship between a worker and her environment called? pathology psychology ergonomics best practices
ergonomics
What is the advantage of FFT?
exceedingly accurate displays all individual velocity components that make up the complex reflected signal
A patient who has anemia should not have a Doppler exam performed because of the low concentration of red blood cells. A) True B) False
false
Absence of color on a color Doppler image always indicates no flow is present. A) True B) False
false
Color Doppler reports peak velocities. A) True B) False
false
It is appropriate to use diagnostic ultrasound in a non medical setting for entertainment. A) True B) False
false
On color Doppler image, red always indicates flow toward the transducer and blue always indicates flow away from the transducer. A) True B) False
false
Power Doppler can identify direction of flow but not velocities of flow. A) True B) False
false
What is the current method of processing spectral Doppler signals? A) chirp z transform B) autocorrelation C) zero crossing detector D) fast fourier transform E) time interval histograms
fast fourier transform
When are you more likely to get aliasing?
faster blood velocity higher freq xdcr deep gate (low PRF)
Low pixel density....
few pixels per inch larger pixels less detailed image lower spatial resolution
Narrow Dynamic Range means
fewer gray shades. few choices Black and white (Bistable) High contrast.
Sector size is also called
field of view
Temporal resolution is determined by
frame rate
How do you predict color flow when it changes in between?
from red to blue. This image is from right to left.
Read magnification is used on...
frozen imaging and post processing
Which of the following has the lowest mechanical index? fundamental imaging harmonic imaging
fundamental imaging
If angle is correct, why would there be no color flow?
gain is too low.
What are microbubbles?
gas bubbles encapsulated in a shell.
With color doppler, low frequency doppler shift artifacts are called
ghosting artifact
When the spike line is horizontal the beam...
goes downward
Temperature elevations become progressively greater from......
grayscale. to CD, to SG
Which of the following is generally true of diagnostic ultrasound? A) Only 3 D and intravascular ultrasound need to be evaluated for bioeffects B) harmful bioeffects are often seen but the benefit to the patient outweighs the risk C) harmful bioeffects do not occur but it would be irresponsible to ignore the possibility they may in the future D) harmful bioeffects do not occur so it is unnecessary to discuss them
harmful bioeffects do not occur but it would be irresponsible to ignore the possibility they may in the future
Harmonic imaging is the most useful in improving poor quality images because...
harmonic frequency waves undergo less distortion than fundamental sound waves.
An image created by reflectors at two times the transmitted frequency is called an ________. harmonic image fundamental image tissue Doppler contrast
harmonic image
Wall filters are also called
high pass filters
how does xdcr frequency affect aliasing?
higher frequency xdcrs create more aliasing.
What does coded excitation improve?
higher signal to noise ratio impoves axial res improves spatial res improves contrast res and has deeper penetration
When discussing "laminar flow" within a vessel, blood velocities are: A) turbulent or chaotic B) equal throughout the entire vessel cross-section C) highest in the center and decrease to zero at the walls D) at an angle to the vessel
highest in the center and decrease to zero at the walls
Spatial resolution means
image detail
Pixels have to do with
image element image detail spatial resolution
What is sequential?
in order, one after the other
You would expect to find less resistance to flow in which of the following ? A) in long narrow segments B) in short large segments C) at bifurcation D) in smaller vessels
in short large segments
During expiration, when the diaphragm moves upward, the venous flow in the lower extremities would? A) increase B) decrease
increase
How is aliasing reduced on a CD image?
increase the scale
Three advantages of power doppler
increased sensitivity to low flow or velocity, such as venous flow or flow in small vessels unaffected by Doppler angles unless the angle is exactly 90 degrees no aliasing since the velocity information is ignored
What adjustment did the US tech do to create image B?
increased the wall filter
What is the most common way to improve (increase) signal to noise ratio?
increasing output power
What is flow?
indicates the volume of blood moving during a particular time.
Which of the following correctly describes a typical television display? progressive scan bistable interlaced non-interlaced
interlaced
What are the 2 methods of fixed focusing?
internal focusing with the use of a curved element or external focusing with the use of a acoustic lens
How is blood flow related to resistance? A) directly proportional B) inversely proportional C) indirectly related D) unrelated
inversely proportional
Relationship between frame rate and time
inversely related
What is the relationship with temporal resolution and image quality
inversely related
What is the relationship of imaging depth and frame rate?
inversely related.
pulses per frame and frame rate are what relationship?
inversely related.
What is nonlinear behavior?
irregular or disproportionate. A system is nonlinear when it behaves unevenly.
color Doppler provides info on the location of flow and therefore:
is a pulsed ultrasound technique has range resolution (or range specificity) is subject to aliasing
When the spike line has a slope the beam...
is steered at an angle.
What is the mechanistic approach?
it begins as a proposal that a specific mechanism has the potentioal to produce bioeffects. The mechanistic approach searches for a relationship between cause and effect.
What is compensation?
it corrects attenuation by making the deeper depths brighter and an equally bright image as a whole.
What is aliasing?
it is a false identity. This is when there is wrap around in spectral doppler
What is the empirical approach?
it is based on the acquisition and review of information from patients or animals exposed to US. The empirical approach searches for a relationship between exposure and response.
A sonographer adjusts an ultrasound machine to change the sector size from 90 to 45 degrees. Nothing else changes. What happens to the frame rate? it is doubled it remains unchanged it is halved it is tripled none of the above
it is doubled
What is radiation force?
it is exerted by a sound beam on tissues. Sheer stress and streaming of fluids can distort or disturb biologic structures.
A sonographer adjusts an ultrasound scan to double the depth of view from 5 cm to 10 cm. What happens to the frame rate? it is halved it doubles in increases from 5 to 10 Hz it is unchanged all of the above
it is halved
What is the advantage of continuous wave Doppler?
its ability to accurately measure very high velocities.
Which one of these terms is not associated with informed consent? describing reasonable alternatives evaluation of the pts understanding the pts acceptance justice
justice
What is kinetic vs pressure vs gravitational energy?
kinetic: moving energy Pressure: potential energy. "The ability to do work". Pressure creates flow by overcoming resistance. Gravitational: potential energy associated with an elevated object.
Spectral window is associated with
laminar flow.
sequential xdcrs have...
large footprint width of element is equal to 1 wavelength 120-250 elements doesnt fit between ribs elements fired in sequence in small groups
Side lobes and grating lobes degrade what....
lateral resolution
Lower MI means
less cavitation less pressure higher frequency
What are the small footprint xdcrs?
linear phased annular phased vector
Which of the following transducers most likely created the image demonstrated above? (2 correct answers) linear sequential linear phased curvilinear sequential annular phased
linear phased annular phased
Which xdcrs have poor steering and focusing?
linear phased and vector
Which of the following transducers focus the beam electronically? (more than one may apply) linear phased array mechanical vector array curvilinear sequential array
linear phased array, vector array, curvilinear sequential array
what are the large footprint xdcrs?
linear sequenced curvilinear sequenced.
Which of the following transducers most likely created the image demonstrated above? linear phased annual phased vector array linear sequential
linear sequential
US systems using these xdcrs do not actually steer the ultrasound beams to create a 2D image.
linear sequential and curvilinear
Which of the following transducers creates an image by emitting parallel lines that when lined up are the same size as the transducer face? linear phased array linear sequential array annular phased array vector array
linear sequential array
Which xdcrs have a number of 120-250 crystals?
linear sequential, curvilinear, vector
What transducers have a electronic steering technique?
linear sequential, phased array, convex, and vector
What is read magnification?
magnification after storage
What is write magnification?
magnification before storage
What does a master synchronizer do?
maintains and organizes the proper timing and interaction of the system's components.
high pixel density...
many pixels per inch smaller pixels more detailed image higher spatial resolution.
Wide dynamic range means
many shades of gray (grayscale) wide dynamic range low contrast.
What 2 factors is kinetic energy determined by?
mass and speed
What is linear behavior?
means proportional or symmetrical. linear systems respond in an even manner.
What is the hydrostatic pressure formula?
measured pressure = circulatory pressure + hydrostatic pressure.
formula for measured velocity
measured velocity = true velocity X cos 0
Disc shaped PZT is found in what types of transducers?
mechanical and annular phased array.
Which of the following is related to the liklehood of harmful bioeffects from cavitation? A) thermal index B) thermocouple C) mechanical index D) radiation force
mechanical index
What does MI mean?
mechanical index. It is related to the likelihood of harmful bioeffects from cavitation.
Contrast agents are also known as? microbubbles shells reflections energy
microbubbles
Contrast agents are also called...
microbubbles.
What is the unit for hydrostatic pressure?
mmHg
Larger packets or large ensemble lengths have 2 advantages:
more accurate velocity measurement increased sensitivity to low flow
A high mechanical index will cause: A) less cavitation B) more cavitation
more cavitation
Higher MI means
more cavitation more pressure lower frequency
what disadvantages with packets with more pulses have?
more time needed to acquire data reduced frame rate decreased temporal resolution
What is a packet or ensemble?
multiple ultrasound pulses are used to accurately determine blood velocities.
Sounds associated with turbulence are
murmur bruit Tissue vibration is called a thrill or palpable murmur.
A sonographer adjusts an ultrasound scan to double the depth of view from 5 cm to 10cm. If the frame rate remains the same, which one of the following also occurs? increased line density wider sector multi-focus imaging turned on narrower sector
narrower sector
Starting from the same point, the receiver is moving toward the west at 12 MPH and the source is moving towaed the west at 10MPH. The Doppler shift is pos+ or neg-?
neg because the source and the receiver are moving farther apart.
A received frequency that is less than the transmitted frequency is which of the following. (multiple answers) A) positive Doppler shift B) negative Doppler shift C) flow away from the transducer D) flow toward the transducer E) antegrate flow F) retrograde flow
negative doppler shift flow away from the transducer retrograde flow
At locations above the heart hydrostatic pressure is
negative. pressure will be lower than the true circulatory pressure.
Three disadvantages of power doppler
no meas of velocity or direction lower frame rates than conventional CD susceptible to motion of the xdcr, patient, or soft tissues, which may result in a burst of color, or flash artifact.
PD is what type of doppler
non directional doppler
This form of Doppler is used in a clinical setting simply to identify the presence of flow when direction of flow is of no consequence. A) nondirectional Doppler B) bidirectional flow C) Duplex imaging D) Pulsed wave Doppler
nondirectional doppler
Harmonic frequency sound waves arise from
nonlinear behavior
Which of the following terms is defined by avoidance of unnecessary risk, harm, or needless injury? nonmaleficence beneficence justice autonomy
nonmaleficence
What factors determine the number of pulses per frame rate?
number of focal points (# of pulses per scan line) sector size line density (lines per angle of sector)
How does the audio work for a bidirectional Doppler?
one stereo has sound from towards the transducer and the other stereo has sound going away from the xdcr.
A bit has a value of....
only 0 or 1
How many crystals are necessary for a PW Doppler?
only one PZT. The crystal alternates from transmitting and receiving.
Pulser voltage is also called,
output gain, acoustic power, pulser power, energy output, transmitter ourput, power, or gain.
Increasing the strength of the signals from the transducer to the patient is performed by which of the following? receiver compensation output power overall gain compression
output power
Which of the following is not a force that opposes blood flow and is not a major source of resistance? A) friction B) vessel diameter C) vessel length D) blood viscosity E) oxygen content
oxygen content
Types of recording and archiving techniques?
paper media, magnetic media, chemically mediated photographs, and optical media.
The mechanical index is related to 2 sound wave characteristics:
peak rarefaction pressure, and lower frequency
What are the synonyms for temporal compounding?
persistence or temporal averaging
The smallest building block of a digital picture is called... byte converter bit ROI pixel
pixel
What are the 2 important elements of digital scanning (good imaging):
pixel and bit
Laminar flow has 2 forms of flow
plug flow parabolic flow
A locations below the heart level the hydrostatic pressure is
positive. It will be higher than the true circulatory pressure.
When changes are made to an image AFTER the image is frozen, then it is considered... pre-processing or read magnification post-processing or write magnification pre-processing or write magnification post-processing or read magnification
post-processing or read magnification
This function is designed to prevent electronic noise from contaminating tiny meaningful signals: amplification compression preamplification reject thresholding
preamplification
Comparison of fluid and electrical systems in Ohm's law...
pressure = voltage flow = current resistance = resistance
Which of the following is a form of potential energy that provides flow by overcoming resistance? A) Pressure energy B) Kinetic energy C) gravitational energy
pressure energy
What is Ohm's Law formula?
pressure gradient = flow x resistance or voltage = current x resistance
Which of the following is a correct statement reference a pressure gradient? A) pressure gradient increases when flow increases or resistance increases B) pressure gradient increases when flow increases or resistance decreases C) pressure gradient increases when flow decreases or resistance increases D) pressure gradient increases when flow decreases or resistance decreases
pressure gradient increases when flow increases or resistance increases
Flow increases when either
pressure increases or resistance decreases
What is hydrostatic pressure?
pressure related to the weight of blood pressing on a vessel measured at a height above or below heart level.
What is thermal mechanism?
proposes that bioeffects result from tissue temperature elevation.
The best epidemiologic studies are
prospective randomized
What does the variance mode map do?
provides more info than velocity mode. In addition to direction and speed, variance mode distinguishes laminar flow from turbulent flow.
What is a revocation of consent?
pt refusal of exam
What is pug flow vs parabolic flow?
pug flow occurs when all of the blood cells travel at the same velocity. parabolic flow is blood flow that has a bullet shaped profile. Velocity is highest at the center of the lumen and gradually decreases to its minimum at the vessel wall.
What are the 3 basic forms of flow?
pulsatile phasic steady
Which of the following types of flow would be seen due to cardiac contraction? A) phasic flow B) pulsatile flow C) steady flow
pulsatile flow
Which of the following controls the pulse repetition period? receiver pulser overall gain master synchronizer
pulser
What are the 2 ways to avoid aliasing?
raise the nyquist limit reduce the Doppler shift
Range resolution is also called
range specificity and freedom from range ambiguity artifact.
What are the 2 forms of magnification that exist?
read magnification and write magnification
The major reflector for Doppler ultrasound is which of the following? A) blood vessels B) fluid C) red blood cells D) tissue
red blood cells
What does compound imaging reduce?
reduces speckle and minimizes shadowing artifacts. Higher signal to noise ratio. reduces frame rates and temporal res
What is sensitivity relating to quality assurance?
refers to the ability of a system to display low level echoes.
Thresh-Holding or Suppression are other terms that mean... compression compensation demodulation reject
reject
What does wall filter do in CD?
removes the color from slowly removing reflectors such as blood cells and vibrating tissues.
Which of the following is the disadvantage of laser discs or compact discs as storage media? A) stores huge amounts of data B) inexpensive C) requires a display system D) not erased by exposure to magnetic fields
requires a display system
Which of the following is the disadvantage of laser discs or compact discs as storage media? stores huge amounts of data inexpensive requires a display system not erased by exposure to magnetic fields
requires a display system
What is in vitro?
research is performed outside the living body and in an artificial environment. In vitro means in glass. A computer model estimating the temp elevation of tissues during exposure to US is an example of in vitro research.
What nonlinear behavior of microbubbles creates contrast harmonics?
resonance/reflection
the area of interrogation in a Pulsed Doppler exam is called
sample volume
What is the sonographic equivalent to the size of a painter's canvas?
sector size
The dead zone is assessed with the
shallowest series of pins in a test object. The dead zone is the shallowest depth at which uniform tissue texture appears.
What is bidirectional Doppler?
shows direction toward and away from the transducer.
What is duplex imaging?
simultaneous anatomic imaging and Doppler.
What is the relationship between actual velocity and measured velocity when blood moves at a 60 degree angle to the beam?
since the cosine of 60 is 0.5, the measured velocity at 60 degrees is 1/2 the actual velocity. When blood travels at 2 m/s at a 60 angle to the sound beam, Doppler reports the velocity as 1 m/s.
When are you less likely to get aliasing?
slower blood velocity lower frequency xdcr shallow gate (high PRF)
Contrast agents must meet this requirement
small enough to pass through capillaries
Phased xdcrs have
small foot print width of element is 1/4 - 1/2 the wavelength fits between ribs elements fired at the same time in different directions
Higher pixel density is achieved with
smaller pixels
A function of the receiver that places an envelope around the electrical bumps to even them out is called: amplification demodulation smoothing compression
smoothing (enveloping)
Cycles distort because
sound crests travel faster than sound troughs.
What nonlinear behavior creates tissue harmonics?
sound travels at slightly uneven speeds through soft tissue, faster through compressions and rarefactions. This nonlinear variation in speed creates tissue harmonics in the biologic media.
advantages of an analog scan converter.
spatial resolution
What is the difference between speed and velicity?
speed has only magnitude while velocity has magnitude and direction.
Tissue equivalent phantoms are similar to soft tissue by:
speed of sound attenuation scattering characteristics echogenicity
Frame rate is determined by what 2 factors?
speed of sound in the medium and depth.
What are the 2 forms of cavitation?
stable transient
Mechanistic approach strengths and weaknesses
strength: broad exposure range can be evaluated. weaknesses: uncertainty about assumptions are other mechanisms involved is the bioeffect clinically significant?
If differences appear between the US scan and the actual pin locations in the test object, the error may be caused by: (regarding range accuracy)
system malfunction or the speed of sound in the phantom is different than 1540 m/s
A sonographer increases the line density from 1 line to 3 lines in a given sector. What is the most likely consequence of this action? frame rate increases temporal resolution decreases imaging quality decreases temporal resolution increases
temporal resolution decreases
A sonographer, using a phased array transducer, turns off the multi-focus feature. What is the most likely consequence of this action? frame rate decreases temporal resolution decreases imaging depth increases temporal resolution improves none of the above
temporal resolution improves
What is the formula for frame rate?
tframe = # of pulses X PRP
Why is there a 2 in the Doppler equation?
the 2 represents the fact that there are 2 Doppler shifts during a clinical ultrasound exam.
Aliasing in pulsed doppler occurs when:(May be more than one answer) A) the sample gate is too large. B) the signal doesn't reach the Nyquist limit. C) the Doppler frequency shift exceeds 1/2 the PRF. D) velocities are too low. E) the sampling rate is less than 2 times the frequency of the signal.
the Doppler frequency shift exceeds 1/2 the PRF. the sampling rate is less than 2 times the frequency of the signal.
What is registration accuracy?
the ability of the system to place reflections in the proper positions while imaging from different orientations.
What is a primary mandate regarding clinical ultrasound?
the benefits to the patient must outweigh the risks of the exam.
What is Doppler frequency/shift?
the change in frequency. It is a low frequency that rides on top of the much higher transducer frequency.
What event provides energy to the circulating blood?
the contraction of the heart during systole.
What is a Focal zone
the depth at which the intensity is the highest and the beam is the narrowest. Lateral res is excellent in the focal zone because the beam is narrow.
What are the primary disadvantages of continuous wave Doppler?
the exact location of the moving blood cells cannot be determined, cells located deeper will have lower amplitude than reflections from blood cells that are at shallower depths.
What will the beam spike pattern look line if you just want a shallower vs a deeper focus?
the higher the curvature, the shallower the focus. The lower the curvature, the deeper the focus.
What is cavitation?
the interaction of sound waves with microscopic, stabilized, gas bubbles in the tissues. These bubbles are known as gaseous nuclei.
What is post processing?
the manipulation of image data after storage in the scan converter.
What is preprocessing?
the manipulation of image data before storage in the scan converter.
What is the relationship between actual and measured velocities when blood moves perpendicular to the sound beam?
the measured velocity is 0 because the cosine of 90 is 0. Thus, Doppler shift and velocities cannot be measured with perpendicular incidence.
Lateral res in terms of phantom.
the minimum distance at which 2 side by side pins are displayed as 2 distinct images. Another method is to measure the width of reflections on the display that are created by point targets in the phantom. This approximates beam diameter at the depth.
What is pixel density?
the number of picture elements per inch.
The strength of the Doppler signal from flowing blood is most closely related to: A) the area of the ultrasound beam B) the shape of the red blood cells C) the speed at which the blood is moving D) the number of red blood cells in the beam
the number of red blood cells in the beam
What is informed consent?
the process by which pts are educated about the essentials of a medical procedure.
What does respect for autonomy mean?
the pt has the capacity to act intentionally, with understanding, and with free will. This principle is the basis of informed consent. In making voluntary, knowledgable decisions, the pt is assumed to be of sound mind.
What is quality assurance?
the routine, periodic evaluation of an ultrasound system to guarantee optimal image quality. quality assurance evaluations must be performed periodically and routinely.
What happens when the signal to noise ratio is high?
the signal is much stronger than the noise.
What happens when the signal to noise ratio is low?
the signal strength is weaker and closer to the strength of the noise which has less diagnostic value.
WHat is axial res?
the smallest distance at which two pins positioned parallel to the sound beam are displayed as 2 distinct echoes. It is evaluated by scanning sets of successively closer spaced pins within the phantom
Sensitivity is also assessed when....
the sonograpgher adjusts the system controls to change echo brightness from barely visible to full brightness (saturation).
The total energy at a specific location within the circulation is
the sum of all 3 energy forms
What is horizontal calibration?
the system's ability to place echoes in their correct position when the reflectors are perpendicular to the sound beam.
What is a look up table?
the table of color or dictionary to know what is towards or away in a CD
How do veins adapt to increase flow during periods of exercise?
the vein changes from hourglass to oval then round. This allows veins to accomodate large volume increase with a very small increase in pressure.
Name the two important mechanisms likely to induce bioeffects.
thermal & nonthermal (mechanical)
What advantages do digital beam formers have?
they are capable of using transducers with a wide range of frequencies.
What are prospective epidemiologic studies?
they are forward looking. The advantage is that a complete and accurate compilation of meaningful information is obtained. compares to retrospective data which is using past data.
What is the relationship between frame rate and time for one frame rate?
they are inversely related and are reciprocals. As the time needed to make each image decreases, the frame rate increases and vice versa.
what is the relationship between line density and temporal resolution?
they are inversely related. The higher the line density, the lower temporal resolution.
What are liquid crystals?
they change color based on their temperature. Regarding bioeffects.
What do the colors in a velocity mode map mean?
they provide flow direction and velocity black is no Doppler shift the color above black means towards the transducer while the color below the black indicated away from the transducer.
The Doppler shift is dependent on all of the following EXCEPT? A) frequency B) velocity of moving blood C) thickness of the vessel wall D) angle between sound beam and moving blood
thickness of the vessel wall
A signal that is too weak for the system to record is said to not meet the systems _________. saturation threshold accuracy range equation
threshold
The x axis of a Doppler spectrum represents_________ and the y represents___________
time, velocity
Name 3 devices that enable the sonographer to perform quality assurance?
tissue equivalent phantom Doppler phantom beam profile/slice thickness phantom.
As a sound wave travels in the body, a miniscule amount of energy is converted from the fundamental frequency to the harmonic frequency. This conversion creates....
tissue harmonics
why is log compression important in clinical ultrasound?
to see the differences in the weaker reflections.
Hydrostatic pressures while standing
top of head = -30 mmHg mid chest = 0 mmHg waist = 50 mmHg knee = 75 mmHg ankle = 100 mmHg
Which of the following is correct for dynamic range from widest to narrowest? archive, display, scan converter, receiver, transducer transducer, display, receiver, scan converter, archive receiver, scan converter, display, transducer, archive transducer, receiver, scan converter, display, archive transducer, receiver, display, scan converter, archive
transducer, receiver, scan converter, display, archive
What is a scan converter?
translates the information from the spoke format into the video format.
The pulser functions during transmission or receiving?
transmission
What are the ultrasound system's 2 major functions?
transmit and receive
Inaccurate angle correction may result in spurious velocity determinations which may lead to a misdiagnosis. A) True B) False
true
Spectral broadening is associated with
turbulent flow
What is the disadvantage of pulse inversion harmonics and power modulation?
two pulses are transmitted down each scan line and twice the number of pulses are required to create each image. The frame rate is halved and the temporal res is reduced.
dedicated CW transducers do not use backing material, which results in the following:
undampened transmitted signal narrow bandwidth high quality factor higher sensitivity
WHat does read magnification do?
uses old data post processing larger pixel size same # of pixels as in the ROI unchanged spatiel res unchanged temp res
A transducer with a combination of both linear sequential and linear phased is called? vector array annular array phased array curvilinear array
vector array
Which of the following transducers creates a shape that is trapezoidal? vector array curvilinear sequential annual phased linear phased
vector array
The Doppler shift produces information about which of the following? A) velocity B) speed C) direction D) distance
velocity
Which of the following information is recorded by spectral Doppler? A) speed of the reflector B) velocity of the reflector C) both speed and velocity of the reflector D) neither speed nor velocity of the reflector
velocity of the reflector
Doppler frequencies indicate velocity or speed?
velocity, not speed
Breathing effects 2 venous flows
venous flow in the legs venous return to the heart
In normal individuals, respiration effects venous flow for 2 reasons
venous system is low pressure muscles responsible for respiration alter pressures in the thorax and the abdomen.
Types of ways a Doppler phantom works to detect flow?
vibrating string moving belt flow with a circulation pump that propels fluid through "vessels"
As blood flows through the circulation, energy is lost in what 3 ways?
viscous loss frictional loss inertial loss
What is the units for flow?
volume/time such as L/min
What is the relationship between actual velocity and measured velocity when blood moves parallel to the sound beam?
when the angle between the direction of motion and sound is 0 to 180 degrees, flow is parallel to the sound beam, The measured and true velocities are equal. Cosine 0 is 1, indicating flow toward the xdcr, where as cosine 180 is -1, indicating flow away from the xdcr.
What is laminar flow?
when the flow is aligned and parallel and smooth. This flow is a normal blood flow.
Which of the following statements is/are correct? When the signal to noise ratio is high, the image quality decreases when the signal to noise ratio is low, the image quality increases when the signal to noise ratio is high, the image quality increases
when the signal to noise ratio is high, the image quality increases
When are Doppler shifts created?
when transmitted sound waves strike moving red blood cells.
WHat does the reynolds number predict? What is the Reynold's number for laminar and turbulent flow?
whether the flow is laminar or turbulent. The reynolds number for laminar flow is less than 1,500. The reynolds number for turbulent flow is greater than 2,000.
Which of the following statements is correct referencing Dynamic Range: narrow dynamic range, more shades of gray, high contrast wide dynamic range, more shades of gray, low contrast narrow dynamic range, fewer shades of gray, low contrast wide dynamic range, fewer shades of gray, high contrast
wide dynamic range, more shades of gray, low contrast