Davies Ultrasound Physics Review

You are scanning an interface w a high acoustic impedance mismatch. How will this be displayed on B mode image?

A bright dot B mode stands for brightness mode. Echo signals are assigned a gray scale level according to the amplitude of the reflected signal. Higher amplitude signals are assigned brighter gray scale dots. An interface w a high acoustic impedance mis match will produce a large, high emplitude reflection

Pre processing functions may be defines as:

A function that is performed before the echo data are stored in memory Any function that occurs after this point is referred to as post processing. The easiest way to distinguish pre and post processing functions is this: If it can't be performed on a frozen image, its preprocessing

Which statement about the two pulses trans displayed below is true? Each represents a signal vs time

A has a lower freq than B PERIOD is the time it takes on complete cycle to occur. A's period is longer than B's. The pulse train w the shortest wavelength will have the highest freq, which again is B. The shortest pulse (B) will produce the better axial resolution. The longer pulse (A) produces the greatest spatial pulse length

Which display mode may be used to calculate distance measurements?

A mode B mode M mode

You are examining a patient w retrograde flow demonstrated in this image. What causes the flow to reverse its normal flow direction (arrow)?

A pressure drop due to a stenosis in the prox artery Flow is reversed in systole and integrate in diastole resulting from a pressure drop caused by a high grade pros stenosis. The pressure decrease is greater during systole bc of the higher velocities during that part of the cardiac cycle. Flow reverses toward the area of low pressure. During diastole, the proximal velocity is lower and the pressure drop is not great enough to change flow direction; therefore, integrate flow is maintained

You want to use 3D imaging to display an anatomic structures because 3D has the following advantage over 2D imaging?

Ability to display image planes impossible to obtain w 2D imaging Ability to display orthogonal planes simultaneously

***What is an advantage of using high PRF doppler?

Ability to measure high velocities High PRF doppler, is a method used to allow measurement of high velocities w pulsed doppler while reducing aliasing. Bc the PRF sets the Nyquist limit (1/2 PRF), higher velocities can be measured w out aliasing by increasing the PRF

During a diagnostic ultrasound exam, you encounter all of the interactions of ultrasound and tissue listed below. Which one will NOT cause a redirection of part of the ultrasound energy?

Absorption Absorption is the conversion of sound into heat. It does contribute to attenuation but does not redirect the sound beam.

Attenuation of the sound beam is affected by:

Absorption Scattering Reflection propagation speed does not affect attenuation of the sound beam

What term describes the hyper echoic region (arrow) seen beneath this complex structure?

Acoustic enhancement Enhancement is caused by a lower attenuation within the structure than in the surrounding tissue.

The intensity of the transmitted pulse can be adjusted most directly by the following control:

Acoustic output (transmit) power

17*The operator control most directly adjusts the intensity of the transmitted pulse?

Acoustic output (transmit) power Pulse repetition freq can also affect the intensity, specifically the I(SPTA) because it affects the duty factor

Interference patterns of reflected waves cause:

Acoustic speckle

The salt and pepper appearance you observe in this ultrasound image is a result of?

Acoustic speckle

You are observing a sonographic artifact based on the interference patterns or scattered echoes. What artifact are you seeing?

Acoustic speckle

The motion of particles in a fluid is sometimes observed in an intense ultrasound beam. This is termed:

Acoustic streaming Acoustic streaming is defined as an acoustically generated transport of fluid within the body of the insinuated fluid or tissue (AIUM nomenclature, 09). This is a mechanical instruction of tissue and sound, where the beam literally pushes the media. If the medium is a fluid and fluid is free to move or it particles in the medium are free, they can move in directions determined by the beam and any obstacles that are present, such as interfaces

The purpose of the SMPTE test pattern is to:

Aid in the setup and quality assurance of displays and cameras The SMPTE test pattern is a standard patten for evaluation of monitors and cameras. "SMPTE" stands for Society of Motion Picture and Television Engineers

What artifact will you see in the color doppler image. If you cannot increase the PRF to a level greater than two times that of the doppler req shift?

Aliasing

The doppler waveform can be most accurately described as exhibiting:

Aliasing W an aliased signal, the peak of the waveform is clipped off and appears on the opposite side of the baseline. It starts from the bottom of the image and points up toward the baseline. It does not start from the baseline and point down. That would indicate retrograde flow

You are imaging a structure containing two media having the same acoustic impedance. What will occur a the boundary of the two structures?

All of the sound will be transmitted For sound to be reflected, there must be a difference in acoustic impedance at the interface. If no difference is present, all of the sound will be transmitted at the boundary. (Normal incidence indicates a 90° angle of incidence; i.e. the sound beam is perpendicular to the surface it strikes).

Which of the following interactions of sound and tissue decreases the intensity of the trnsmtted beam?

All of these interactions will result in decreased intensity of the transmitted beam

The maximum cyclical change in a quantity is known as:

Amplitude

The z-axis (brightness) on the doppler spectrum provides the following information:

Amplitude

What information does the z-axis (brightness) on the doppler spectrum provide?

Amplitude The z-axis on the doppler spectrum is represented by the brightness of the dot. The brighter the dot, the greater the amplitude of the reflected signal. The factor affecting the amplitude is the relative number of RBC's reflecting that particular freq shift. So by noting the brightness of a specific point on the spectral waveform we an get an idea about how much of the flow is moving at any given velocity at a particular point in time

Terms used to describe the strength of he sound beam include?

Amplitude and intensity

W an A mode display, the internal contents of a simple cyst will appear as:

An area w no spikes On the A most display, the height of the spike is directly related to the amplitude of the reflector. Bc no signals are reflected from the internal contents of a simple cyst, the depth corresponding to the inside of the cyst will be absent of spikes. The walls of the cyst, however, are highly reflective and will be represented by a tall spike

***The velocity scaled on this color map is 17 cm/s. If the flow direction is at zero degrees to the sound beam axis, the colors on either end of the bar would represent?

An average velocity of 17 cm/ s Color doppler displays average values-not peak values. If the angle to the flow is at zero degrees, the velocity for the colors at either end of the bar

What type of txd has the same measurement for elevational and lateral resolution?

Annular array An Annular array txd produces a beam that is symmetric about the beam axis. Therefore, its lateral resolution is equal to its elevational (slice thickness) resolution

What type of txd could you choose to produce a beam that is symmetric about the beam axis?

Annular array An annular array is a round txd in which the elements are arranged concentrically. This txd creates a cone shaped beam that is symmetric in all dimensions. Linear, phased and curved arrays produce beams that are asymmetric. They can have multiple focal zones in the plane along the length of the txd by electronically focusing the beam but can have only one area of focus in the plane along the width of the txd. This is accomplished w a mechanical focus.

126* You are imaging w a 5 MHz linear array txd. What sound parameter stays consistent as the beam propagates thru the tissue?

As sound propagates thru tissue, high freq are attenuated ore rapidly than low freq. This results in a shifting toward the lower freq in the transmitted bandwidth w increasing depth. The intensity and amplitude of the beam decrease as a result of attenuation. The wavelength is altered w the downshifting of the overall freq bandwidth

What term is used to describe the reduction in the intensity of sound as it propagates thru tissue?

Attenuation

The rapid technique used in most color doppler systems to obtain the mean doppler freq shift is:

Autocorrolation

Which represents the best measure of resolution for modern day ultrasound scanners?

Axial Axial resolution is the best measure of resolution for today's instruments. The worst measure of resolution is usually elevational. Lateral and elevational resolutions vary considerably w depth. Axial resolution does not

You are scanning a large mass that is composed primarily of fat. Which of the following are you most likely to encounter?

Axial misregistration of objects distal to the mass on the screen due to the slower propagation speed thru fat. Because sound travels slower in fat than in soft tissue, a large mass composeed primarily of fat may cause axial misregistration of the objects distal to the mass on the ultrasound image. This occurs bc the system must assume a constant sound propagation speed of 1540 m/s. If sound travels more slowly thru a medium, the round trip travel time will be longer and the system will place the structure deeper on the image. Conversely, if sound travels thru a medium w a propagation speed faster than that of soft tissue, the round trip travel time will be shorter and the structure will be placed shallower on the image.

Resolution of two structures at different depths along the path of the sound beam is termed?

Axial resolution

Which type of resolution is most affected by pulse duration?

Axial resolution

What type of resolution is affected most by pulse duration?

Axial resolution We usually think of axial resolution as being determined by spatial pulse length. Spatial pulse length and pulse duration are directly related. Pulse duration (also called temporal pulse length) is the length of time required to complete one pulse. The shorter the pulse duration, the better the axial resolution

What letter represents the strain relief portion of the txd?

B The strain relief is the portion of the txd that protects the insertion of the cable info the txd housing. This is an area that is prone to wear and tear w repeated use and bending of the cable. The strain relief area should be regularly inspected for cracks and exposed wiring.

What txd component is designed to control ringing of the piezoelectric element?

Backing material The backing material is used to dampen the ultrasound pulse and to reduce the spatial pulse length, thereby improving axial resolution. It also reduces sensitivity by decreasing the overall intensity of the sound beam. But this is a small price to pay for the improvement in axial resolution

What component of a pulsed wave txd helps to reduce the spatial pulse length and improve axial resolution?

Backing material The backing material reduces the length of time the crystal rings. This, in turn, shortens the spatial pulse length and improves axial resolution

The spectrum of freq emitted by a pulsed wave txd is known as the:

Bandwidth

What technique would be most likely to produce grating loves in your image?

Beam Steering

What part of the sonographic instrument is responsible for apodization, beam steering, focusing and aperture control?

Beam former

What system component is most responsible for transmit focusing?

Beam former Specifically, the transmit beam former, which introduces time delays into the excitation pulse sequence applied to the elements

Which factor LEAST influences axial resolution?

Beam width -Damping -Freq -Pulse duration -Pulse freq Beam width affects lateral resolution rather than axial resolution. All others are factors that influence axial resolution

While imaging a cyst, you notice shadowing posterior to each lateral border of the cyst. What is the source of the shadows?

Bending of the sound beam due to different media propagation speeds. This is refraction of the sound beam and occurs wherever there is both oblique incidence and a difference in media propagation speeds

Digital to analog conversion of the ultrasound signal must occur at what part of the imaging process?

Between the scan converter and the display

***What color represents flow at 90°

Black

You are performing a sonographic examined notice that the thermal index (TI) is > 1. Any increase in temperature would be greatest in:

Bone

What is the source of the bright echoes indicated by the arrow in this doppler waveform?

Bruit A bruit may be seen on the spectral waveform int he area of post stenotic turbulence. It appears as bight echoes near the zero baseline located under neath the systolic peak

What is a disadvantage of a water path scanner?

Bubbles in the fluid can inhibit sound transmission into the body Although water path scanners reduce the reverberation from sallow structures, they require vigorous maintenance to keep the fluid path completely filled at all times. If the fluid path is only partially filled, air within bubbles can become trapped between the txd and the probe surface, reflecting the sound before it can enter the body

Complete destructive interference echo reflections will affect the display in the following way?

By creating black pixels

A group of 8 bits is called:

Byte

An M mode display is most commonly used for what type of ultrasound imaging?

Cardiac

Which of the following ultrasound exams would require the highest frame rate?

Cardiac Since the heart is a rapidly moving structure, high frame rates are required to assess it accurately

***What should be done to improve the doppler waveform in the previous question?

Change the doppler angle

***Which of the following would be most helpful to enhance the contrast difference between tissues having subtle variations in echogenicity?

Changing the gray scale map assignment The gray-scale map assignment determines the shadows of gray that are assigned to incoming signal amplitudes. Bc the maximum number of gray shades is predetermined, the distribution of brightness levels over the range of signal amplitudes must be sent by some assignment. This is accomplished by various assignment curves in which different signal amplitudes are given their gray assignments Common curves are a linear or S-curve assignment. The contrast resolution in a certain range may be diminished or emphasized , depending on the map selection

You are performing an exam on a patient w highly attenuating tissue. Which of the following solutions would be most likely to improve penetration thru the tissue?

Choose a lower freq txd

Txd should not be cleaned w:

Cidex

What control allows the user to freeze and then scroll back thru the most recently acquired image frames?

Cineloop

In an ultrasound phantom, the targets typically used for measuring axial resoltuion are:

Closely spaced targets of varying distances

You have obtained a color doppler image of the common carotid artery. If the received ultrasound freq is greater than the transmitted ultrasound freq, which of the following would be correct?

Color encoding red, positive doppler shift When the doppler ultrasound beam intersects a vessel in which the blood is flowing toward the doppler beam, the freq of the reflected signal is higher than that of the transmitted signal. This is termed a positive freq shift. All doppler systems are set up so that positive doppler shifts are color encoded red and negative doppler shifts are colored encoded blue. The specific color map is use determines the shading of red and blue and the colors in between An invert function is available on most systems that allow the user to reverse the color designation

Which of the following artifacts is the result of reverberation?

Comet tail This artifact is commonly seen w metallic objects. Multiple reverberations w in a highly reflective object cause the artifact. A reverberation occurs when the sound bounces back and forth multiple times between two interfaces

***What control should you adjust to modify the image if the attenuation coefficient of the tissue is very high?

Compensation Compensation is generally referred to as time gain compensation (TGC) or depth gain compensation (DGC). It is used to increase amplification to account for the effects of attenuation.

1. What action would be most in keeping w the ALARA principle while performing a diagnostic ultrasound exam?

Complete the diagnostic scan in a timely fashion at the lowest output power that achieves a quality image Advocating use of the ALARA principle (as low as reasonably achievable) prudently minimizes the risk of bio effects (even tho epidemiological studies have revealed no known risk associated with the use of diagnostic ultrasound).

You may observe sound attenuation by all of the following EXCEPT:

Compression -Reflection -Scattering -Conversion of sound to heat -absorption Attenuation includes all sound interactions that result in a weakening of the beam. These include reflection, scattering, absorption and to a lesser extent, refraction. Absorption is the conversion of sound to heat in tissue. Refraction results in a bending of the beam.

In sound wave propagation, a region of elevated pressure is termed:

Compression Sound propagates thru tissue as a series of compressions and rarefactions (regions of lower pressure).

***Which control would you adjust to alter the dynamic range of the displayed echoes?

Compression The compression control reduces the difference between the largest and smallest reflected signal amplitudes, decreasing the dynamic range of the incoming signal to a level that the display can handle

***What receiver function is responsible for decreasing the difference between the smallest and largest received signal amplitudes?

Compression The range of echo strengths reflected from the tissue is too great for the display to handle. For this reason, the difference between the smallest and largest amplitudes of the received signals must be reduced. This accomplished by a logarithmic compression, which amplifies weak signals more than strong signals

An interaction of echoes that leads to reinforcement rather than to partial or total cancellation is known as:

Constructive interference

Which term refers to the fact that the volumetric flow rate must be the same pros, at and dust to a stenosis?

Continuity rule

Which of the following describes an analog signal?

Continuous variation of the signal is possible An analog signal does not have discrete steps. Its value may vary continuously between a minimum and maximum point, Digital devices have discrete values that have fixed steps between values. Bits determine the levels in a digital system

What type of doppler device uses two elements, one to receive and one to transmit?

Continuous wave doppler

What doppler technique does NOT provide range resolution?

Continuous wave doppler Range resolution is the ability to determine the depth from which an echo has arrived. For range resolution, the sound must be pulsed so that the echo arrival time from each pulse can be measured. Once the arrival time of the echo is known, the distance to the reflector can be determined. This works bc we know the speed of sound in tissue and assume it to be constant

***What can you improve by changing the gray scale map?

Contrast resolution

The ability to differentiate between two regions at different depths having similar echogenicity, such as in this liver image w focal fatty infiltration, is termed?

Contrast resolution

This image shows a clear distinction between the gray scales of various structures in the fetal brain. The ability to distinguish similar structures w varying gray scales is termed:

Contrast resolution

The ability to distinguish between adjacent structures that produce echoes of similar amplitude is termed:

Contrast resolution W good contrast resolution, objects having similar but different reflective properties can be assigned different shades of gray and will be visually distinguishable. W poor contrast resolution, such objects will be not be differentiated.

You obtained a 3D sweep in an axial plane and are viewing it in a multi planar display. What orthogonal planes will be displayed?

Coronal and sagittal

What maintenance issue is demonstrated in this image?

Damage to the txd crystals

What factor LEAST influences lateral resolution?

Damping

Which best describes the effect of damaged txd elements in the B mode image?

Dark vertical bands beginning at the top of the image

Relative measurement of intensity based on a logarithmic scale is expressed in:

Decibels The unit of sound intensity is the decibel. Decibel actually means one-tenth of a bel and is named for Alexander Graham ell (the inventor of the telephone). A decibel does not specify a specific level of sound intensity. Rather it is a way to express the ratio or comparison between two sound intensity levels. A decibel scale is logarithmic. The Richter scale used to measure earthquakes is another example of a logarithmic scale. A common value to remember w decibels is that a 3dB decrease represents 50% and a 6 dB decrease represents 75%.

***You have increased the packet size while using color doppler to evaluate flow. What negative result will occur from this action?

Decrease frame rate Increasing the packet size increases the number of pulses per scan line for the color image. As the number of pulses required to create each line of sight increases , the time to create one frame increases. This results in a slower frame rate

***You obtained this color doppler image while performing hepatic sonography. There is no color signal detected w in the portal vein. What can yo do to improve sensitivity to slow flow?

Decrease pulse repetition freq When slow flow is present, the color doppler system must be sensitized to detect low freq shifts (slow flow produces low freq shifts). Setting PRF lower increases sensitivity to low freq shifts. At low PFR's there is more time between the pulses, which allows time for the slow moving blood flow to move and be detected by the system. Other methods of improving sensitivity y to slow flow include decreasing the wall filter and increasing the doppler freq

***What can you do to improve the temporal resolution while scanning?

Decrease the acoustic scan line density Decreasing the number of acoustic scan lines that make up an image decreases the time required to create the image. This results in increased frame rate

While performing a color doppler exam in the abdomen you have adjusted several system controls and notice that the fame rate has decreased. What adjustments can you make to improve the color frame rate?

Decrease the color box width The wider the color box, the more lines of sight that must be fired to increase one frame So the width of the box will improve the frame rate. Increasing the packet size will increase the frame rate. Decreasing the pulse repetition freq may or may not affect the frame rate but is more likely to decrease it rather than increase it. Increasing the scan line density will decrease the frame rate. Adjusting the wall filter will not affect the frame rate

***You have expanded the image sector width to improve visualization of a large mass. What can you do to maintain the same temporal resolution you had before your adjustment?

Decrease the number of focal zones On each line of sight, a pulse echo sequence is required for each focal zone selected. Therefore, as the number of focal zones increases, the frame rate decreases

***What can you do to achieve a higher frame rate?

Decrease the number of focal zones Decrease the line density Decrease the sector width

***While performing an obstetric exam, you wish to increase the frame rate to evaluate the fetal heart. What should you do?

Decrease the sector width As the width of the sector decreases, the number of scan lines in the image decreases. This results in a narrower field of view and a higher frame rate. All other answer choices would result in a decreased frame rate

***While evaluating the liver vasculature w color doppler, you are unable to obtain signals from the deeper vessels. What should you do to enhance your ability to demonstrate deep flow?

Decrease the ultrasound freq Lower freq have increased penetration compared to higher freq. No other answer choice would improve penetration of the color doppler

Increasing the threshold controls will have the following effect on the image:

Decreased appearance of weak echo signals

***What effect will you detect in the image if you increase the threshold?

Decreased appearance of weak echo signals "Threshold" is another name for the reject control. It is used to reduce the display of weak echo signals that most likely arise from electronic noise. Increasing the threshold reduces the display of weak signals

The hyper echoic region in the preveious illustration results from:

Decreased attenuation thru a fluid filled structure Acoustic enhancement results from decreased attenuation thru a fluid filled structure compared to the adjacent tissue. Changes in propagation speed do not produce acoustic enhancement. The sound absorption in the region distal to the fluid filled structure is not affected. A high acoustic impedance mismatch at the cyst tissue interface would result in greater reflection of sound w possible shadowing instead of enhancement. She shadowing posterior to the lateral border of the cyst is refraction due to bending the sound beam w oblique incidence.

***What effect will you see on the image if you increase the reject level?

Decreased low level echoes The reject control is used to eliminate weak echo signals from the display. As signal rejection increases, display of the weaker signals decreases. This results in fewer low level gray echoes

If you choose a lower freq txd to image a highly attenuating structure, what tradeoff are you making?

Decreased spatial resolution for improved penetration This is the classic tradeoff in ultrasound. High freq have better spatial resolution but greater attenuation than low freq. So in order to gain penetration, one must sacrifice some spatial resolution by using a lower freq. If improved spatial resolution is desired, then one must sacrifice penetration by using a higher freq

What is the disadvantage of using multiple transmit focal zones?

Decreased temporal resolution Each transmit focal position requires a separate pulse echo sequence (txd firing). Multiple focal zones improve lateral resolution but degrade temporal resolution

The doppler waveform you have obtained from a collateral channel shows high resistance compared to he contra lateral normal artery. The increased resistance may be attributed to:

Decreased tube diameter Increased vessel length Collateral vessels have a longer length and a small diameter, both resulting in increased resistance to flow

What is the main advantage you will have by choosing a txd that produces a thin slice over the image plane?

Decreased volume averaging The slice thickness is controlled by the out of plane focusing. The out of plane focusing is usually accomplished by an acoustic lens, which provides focusing at one depth along the beam. Slice thickness is the worst measure of resolution in sonography (compared to lateral and axial resolution). Matrix or 2D array txd are capable of focusing the sound beam electronically at multiple points in and out of plane dimension. This produces a thinner beam compared to traditional 1D array txd. The thinner the beam, the more accurately a structure can be imaged w out interference from surrounding tissue. When the beam is wider than the structure being interrogated, tissue on both sides of the structure sends back reflections at the same time. The sonographic system cannot distinguish between these reflections (since they arrive simultaneously,) and so the echoes are combined on the display. The result is termed volume averaging, partial volume effect, or slice thickness artifact. An example would be to image a fluid filled structure w a wide beam and see artifactual echoes w in it from the tissue on each side that is w in the beam at the same instant

98* What would you do if the image does not show adequate penetration and the far field displays noise instead of tissue?

Decreases transmit freq When penetration thru the tissue is inadequate and the far field demonstrates noise, lower the transmit freq is a good option and may provide adequate penetration. Increasing the TGC will not help if the far field is already demonstrating noise. Increasing the acoustic output may also be helpful if it is not already set to the maximum level. Another option maybe to move the focal zone position to a deeper position.

How will increasing the dynamic range setting affect the ultrasound image?

Decreasing image contrast

If you wish to acquire a sonogram w the largest possible field of view both in the near field and at depth, what type of txd would be most preferable?

Curved array

What type of txd was used to obtain this image?

Curved array

Which txd would have a lower line density in the far field compared to the near field?

Curved array Tightly curved array Phased array Only the linear array txd has the same line density for both the near and far fields. All txd's producing a curved or sector image format have more spreading of the lines in the far field. This results in lower lateral resolution in the far field

During the performance of a sonographic exam you would be most likely to encounter refraction in the view:

Curved interfact Refraction of the sound beam requires sound reflection from a curved interface. Therefore, this is the best answer. The curved interface may also be a specular reflector, but specular reflection is NOT required for refraction to occur.

***Increasing the dynamic range setting affects the ultrasound image by?

Decreasing image contrast As the dynamic range is increased, small changes in echo amplitude result in assignment to different shades of gray. The echo amplitudes are reassigned to a larger dynamic range. some of the amplitudes may have been assigned to zero when the dynamic range was set to a lower value. When you increase the dynamic range, these echo amplitudes are now assigned a low level of gray. This results in display of more information but reduces the overall contrast of the image, it is post processing

***What receiver function listed is NOT operator adjustable?

Demodulation -Amplification -Compensation -Rejection The operator can control amplification, compensation and rejection but now demodulation

***What function of the receiver converts electric signals from radio freq to video form?

Demodulation Demodulation is accomplished by rectification and smoothing (filtering). Demodulation may also be called amplitude detection or envelope detection

For soft tissue, one of the factors responsible for determining acoustic impedance is:

Density The equation for acoustic impedence is z=pc where z is the rayl (unit for acoustic impedance), p is density, and c is the speed of sound. Because the speed of sound in tissue is relatively constant (1540 m/s), the main factor determining acoustic impedance is changes in tissue density

Ultrasound propagation velocity depends on:

Density and compressibility

What determines acoustic impedance?

Density and propagation speed of the medium Acoustic impedance is determined by the density and propagation speed of the medium as expressed in this equation: z=pc where z represents acoustic impedance, p represents density and c represents propagation sp

Spectral analysis is used to:

Determine the distribution and magnitude of freq shifts in the reflected doppler signal

When you image a structure that is a specular reflector, the strength of the received signal depends on the following two facotrs:

Difference in acoustic impedance and angle of incidence The amplitude os the reflected signal depends on the difference in acoustic impedance between the two tissues. The greater the difference, the greater the reflection. As mentioned previously, specular reflection is highly angle dependent. If the beam strikes the interface at a right angle (90°), the reflected energy will be directed back to the txd. But if the beam strikes the interface at another angle, the reflected energy will be directed at the same angle AWAY from the txd.

While scanning a curved structure, you notice shadowing at the lateral edges of the structure. What is required for this artifact to occur?

Different media propagation speeds

Which phenomenon is associated w a pattern produced by a sound beam after passing thru a small aperture?

Diffraction Diffraction is te general term for various phenomena in which waves from different parts of a source add or subtract (AIUM recommended nomenclature 09)

***What system control converts the numbers stored in memory to proportional voltage that control the brightness on a CRT (cathode ray tube) monitor?

Digital to analog converter For display, the numbers stored in memory must be converted to proportional voltages to drive the brightness of the monitor. Monitors are digital in modern ultrasound equipment

What is meant by the "dead zone" in performance testing?

Distance from the txd to the trash first identifiable echo

String test objects are used to evaluate:

Doppler accuracy

***During doppler interrogation of the carotid artery, you detect spectral mirroring. Which of the following is common cause of this artifact?

Doppler angle of interrogation near 90° At 90° doppler angle, flow direction cannot be determined and the waveform will be seen on both sides of the baseline

If you increased the doppler angle during the exam, what wold be the expected result?

Doppler freq shift would decrease Increasing the doppler angle reduces the doppler freq shift for any given velocity. If aliasing were present, increasing the doppler angle would reduce it. Neither flow velocity nor sound velocity is affected by doppler angle

If you increased the transmit freq during a doppler exam, wha would be the expected result?

Doppler freq shift would increase Penetration is decreased w increasing freq. Aliasing would be more likely to occur w increasing doppler freq bc the freq shift would be greater for any given flow velocity. The flow velocity is not affected by the transmit doppler freq

What info is colorized in an image using power doppler?

Doppler signal amplitude Power doppler colorizes the amplitude of the reflected doppler signal. This brightness of the colors is related to the number of red blood cells

As you perform a sonographic exam, you switch from a 3.5 MHz txd to a 7 MHz txd to image a superficial structure. Compared to the 3.5 MHz txd, what will the 7 MHz attenuation rate and wavelength be?

Double the attenuation rate, one half the wavelength If freq is doubled, the rate of attenuation is doubled but the wavelength is haled. Remember: as freq increase wavelength decreases, improving resolution but decreasing penetration because of increased sound absorption

In the scan converter, interpolation is performed to:

Fill in the empty pixels that occur between acoustic scan lines Interpolation is necessary bc there is not data available for all pixels in the scan converter matrix. As the line density i the ultrasound image is decreased, more interpolation becomes necessary to fill in the image is decreased, more interpolation becomes necessary to fill in the empty spaces. Although there are alot of different interpolation schemes used by different manufacturers, in general the empty pixels are filled in w a value that is averaged between adjacent pixels.

You are scanning a phantom containing multiple rows of identical 5 mm spherical fluid filled structures embedded in a tissue mimicking material. What type of resolution is best eval w this phantom?

Elevational This type of phantom is used to evaluate the slice thickness of the ultrasound beam. The slice thickness denotes elevational resolution. At the depths in which the cystic structures are resolved, ths slice thickness is very thin. At the depths where the cystic structures are not visible, the slice thickness is wide. In this case, the beam thickness is so great that the tissue mimicking material on each side of the cyst is also included in the beam. Bc this tissue will send back echoes at the same depth as the cyst, the cyst will not be seen.

What type of resolution is most affected by the mechanical focus on a linear array txd?

Elevational resolution Elevational resolution is determined by the slice thickness. (slice thickness is also known as the z-axis, or elevational plane.) Elevational resolution is a measure of the beam width perpendicular to the imaging plane. On linear, curved, linear and phased array probes, elevational resolution is determined by the mechanical focus that is placed along the width of the array. The mechanical focus narrows the beam at one fixed point in the z-axis

Which statement is most accurate regarding resolution w a standard one dimensional linear array txd?

Elevational resolution is the worst measure of resolution w this type of txd Currently, elevational resolution is the poorest measure of resolution for array probes (excluding annular or matrix arrays). This is bc the elevational slice thickness is controlled by a mechanical focus that is fixed at only one depth. Although lateral resolution varies w depth, it can be enhanced at multiple depths by using a combination of multi zone transmit, dynamic receive, and dynamic aperture focusing. Axial resolution is more constant w depth and is determined by the pulse duration and freq of the txd. Neither contrast nor temporal resolution is a measure of spatial resolution and therefore cannot be determined by measuring the beam.

What is another name for the hyperechoic artifact seen in this image distal to a fluid filled structure?

Enhancement

What artifact is related to the sound beam traveling thru a structure w low attenuation?

Enhancement Occurs distal to a structure that has less attenuation of the sound beam compared to the surrounding tissue. Hence, there is more signal beyond it and the reflections have greater amplitude, resulting in a brighter image

A study designed to determine if there is an association between an adverse effect in a population and exposure to a particular agent is an:

Epidemiological study

When sound strikes a specular reflector at an oblique angle, the angle of reflection is:

Equal to the angle of incidence

Acoustic impedance:

Equals density times the propagation speed Z=pc

The most numerous cells in the blood are the:

Erythrocytes

The thermal index indicates:

Estimated temperature increase in tissue Temperature increase is calculated assuming certain values for the absorption and thermal properties of tissues and taking into account factors such as beam geometry, freq and power. Technically, it is the ratio of the power being produced to the power needed for a 1° C temperature increase if tissues have the assumed properties

Which echo amplitude in the following illustration would produce the brightest dot on a B mode display?

E The brightness of the dot on B mode image is directly related to the amplitude of the reflected signal

Which txd would NOT detect a doppler freq shift?

E The txd labeled E is firing its beam at a 90° angle to flow. The doppler equation tells us that we cannot detect a freq shift at an incident angle of 90°

According to Poiseuille's equation, what will happen to flow if pressure difference increases?

Flow rate will increase Pressure differences drive flow. The greater the pressure difference between two points, the greater the flow rate

Which of the following best describes the f-number?

Focal length divided by aperture The f-number is the ratio of the focal length to the size of the aperture

Where is the point of maximum intensity in a sound beam?

Focal point At the focal point, the beam width is narrowest, resulting in more of the energy being confined to a small area. Sound energy is therefore more intense at the focal point compared to other points in the ultrasound beam. This is analogous to using a magnifying glass to start a fire. If the magnifying glass is placed between the sun and some shredded paper or leaves, it focuses the solar energy so intensely that the paper bursts into flame

The location where the sound beam reaches its narrowest diameter is known as the:

Focal zone

You are using a linear array txd w four transmit focal zones, How many pulses are required on each scan line to create the image?

Four

What method is most commonly used to perform spectral analysis for pulsed doppler?

Fourier analysis

What control could you adjust to improve the signal to noise ratio on the image?

Frame averaging (persistence)

The number of images displayed per second in real time imaging is termed the:

Frame rate

***You have decreased the image sector width. Which of the following will most likely change as a result of this adjustment?

Frame rate In general, when the sector angle is decreased, the number of scan lines is reduced. This increases frame rate. An alternative approach is to keep the same number of scan lines but move them closer together. In this approach, frame rate is not affected but lateral is improved. The first scenario is the most common approach

***If you increase the pulse repetition freq and leave all other controls unchanged, what will happen?

Frame rate will increase The pulse repetition freq (PRF) is the number of pulses emitted by the txd in one second. If the PRF is increased and all other factors remain the same, the frame rate will increase bc it will take less time to fire all the necessary pulses to create one frame

14*What should you limit when the thermal index exceeds 1?

Exposure time

***What two controls affect the spatial resolution of the color image?

Freq and line density

What aspect of the doppler spectrum is color encoded w color doppler?

Freq shift Color doppler (also called color flow imaging) is a method of displaying the average doppler freq

Which of the following best describes the doppler freq shift when you encounter high velocities w in a vessel?

Freq shift is increased When the doppler beam encounters high flow velocities, a large freq difference occurs between the transmitted and received freq. This freq difference is known as the doppler freq shift

Increasing which of the following will result in improved axial resolution?

Frequency Axial resolution is improved by reducing pulse length or pulse duration. This can be accomplished by reducing the number of cycles in a pulse (damping) or by reducing the size of the wavelength (increased freq)

Which of teh following factors does NOT affect impedance?

Frequency Impedance increases if density or propagation speed increases. Impedance is also affected by stiffness. It is not affected by freq. Z = pc, where p is the density and c is the speed of sound. C depends on density and tissue stiffness.

Wavelength depends on what two factors?

Frequency and propagation speed Wavelength is determined by the following equation: Y=c/f Where y represents wavelength , c represents propagation speed and f represents freq

***What control should you adjust to increase the amplification applied to the color doppler signal?

Gain

The amount of amplification that occurs in the receiver is determined by this system control:

Gain

This image was obtained w a linear array txd. The trapezoidal field of view increases the field of view. How is the trapezoidal shape created?

Electronic beam steering A trapezoidal image can be obtained w a linear array txd by electronically steering the beam

What best describes the method used to create the triangular shaped image format in the image above?

Electronic steering w most elements fired for each pulse echo Phased array txd's (sometimes called linear phased array or sector txd's) from the beam by firing most, if not all, elements at once w small time differences. The time delays are changed w each subsequent firing so that the beam direction is varied. the result is that the beam is electronically steered to create the sector image format

What method is used to steer the color beam w a linear array txd?

Electronic time delays A linear array txd steers the beam for color doppler in the same way a phased array txd steers its beam--electronically. the active elements are fired w very slight time delays, causing the beam to veer off at an angle from the txd face

Which of the following describes a phased array txd?

Electronically focused along the length of the array, mechanically focused along the elevational dimension (width) and electronically steered W phased array txd, all of the elements are fired as one group but w very small time delays to steer the beam. Along the length of the array, time delays are also introduced to focus the beam. In the elevational dimension, however, a lens (mechanical focus) is applied. This allows only one point of focus in the z-axis.

In this illustration, Letter A is demonstrating what type of resolution?

Elevational

In this phantom image, two fluid filled tubes are present. What type of resolution is being evaluated?

Elevational

The mechanical focus on a linear array txd most affects this type of resolution?

Elevational

The propagation speed for sound is lowest in which of the following biologic tissues?

Fat Propagation speeds of commonly encountered human tissue:

What advantage is related to the txd type in question 256?

Field of view is improved

Which of the following s a commonly recommended ingredient in cleansers for intra cavitary probes?

Glutaraldehyde In general, an intra cavitary probe may be cleaned w a glutaraldehyde based cleaner. It is necessary to check w the manufacturer of the txd to obtain a list of acceptable cleansers for their txd. All of the other choices are not recommended cleaners

What artifact might you see w an array txd due to energy that propagates from the txd in a direction different from that of the primary beam?

Grating lobe Are the same as side lobes but occur w array txd. These lobes are the result of sound energy traveling from the txd array in a direction different from that of the main beam. They generally are much weaker than the main beam and do not produce tissue reflections w enough strength to be displayed. But in some cases they may strike a strong reflector or be strong enough to cause artifactual echoes in the image. They are most easily seen when imaging fluid bc of the decreased attenuation and increased visibility of artifacts

Choose two benefits of tissue harmonic imaging

Grating lobe artifacts are reduced and lateral resolution is improved Grating lobe beams are not strong enough to generate harmonics and are therefore greatly reduced in harmonic imaging. Lateral resolution is improved bc the harmonic beam width is narrower since harmonics are generated only from the portion of the beam w the highest intensity signal

This image was obtained w a linear array txd that employs phasing to steer the beam. What artifact do the arrows point to?

Grating lobes Grating lobes are a summation of side lobes generated by array txd. Grating lobes cause a smearing of the ultrasound beam and degrade lateral resolution. The smeared echoes on the edge of this image are related to grating lobes

While performing a sonographic examination, you have performed both pre-processing and post-processing functions. Which of the following functions is post-processing?

Gray scale map assignment The easiest way to determine if a function is pre- or post- processing is this: If it cannot be performed on a frozen image, it is pre processing; if it can be performed on a frozen image it is post processing

4. What potential bioeffect occurs through absorption of sound energy by tissue?

Heating Sound attenuation in tissue is primarily due to absorption (conversion of ultrasound to heat).

***What doppler control removes freq below a given threshold, resulting in a clean zero baseline?

High pass filter The high pass filter is also called the wall filter

What is the relationship of freq to absorption?

If frequency is doubled, absorption is also doubled There is a direct relation between absorption and freq. As freq doubles, the rate of absorption doubles. That is why there is less penetration w higher freq --absorption is increased

These B mode images of the common carotid artery show a graphic overlay indicating the number of lines of sight used to acquire each frame of information. No other system parameter was adjusted. Which statement below is true comparing image A to image B?

Image A has better lateral resolution than image B

Increasing the transmit power during a pelvic ultrasound exam increases:

Image brightness Penetration Acoustic power Voltage applied to the txd elements

A digital scan converter is another name for what system component?

Image memory

Propagation speed error results in which sonographic appearance?

Improper axial position of an echo If the propagation speed thru a mass differs significantly from that of surrounding tissue, improper axial position of the mass will occur. Why? The ultrasound system is set up to assume that the speed of sound is constant at 1540 m/s. If it is much slower than this, it will take longer for the ultrasound to travel round trip to and from a reflector, and the reflections will be placed deeper in the image. Conversely, if the propagation speed thru amass is significantly faster than that of surrounding tissue, the round trip travel time will be reduced, and the reflections will be placed more shallowly in the image.

You are performing a sonographic exam w a wide bandwidth txd. The advantage you obtain w this txd compared to a narrow band txd is:

Improved axial resolution Axial resolution is improved w wide bandwidth txd

The Frank-Starling mechanism helps to explain that when an arrhythmia is present, the peak systolic velocity following a heart cycle w a longer time interval ____________________________one w a shorter time interval.

Will be higher than This is bc there is more time for filling of the ventricle and the systolic contraction will therefore be greater and produce a higher velocity. This is important when measuring velocity in patients w arrhythmias

A DICOM feature that allows you to select a patient name and automatically populate the patient information on the ultrasound system is:

Work list

What is the advantage of using write soon instead of read zoom?

Write zoom provides better spatial resolution than read zoom This is bc the entire image memory can be used for storing data for the image

You are using a txd w poor elevational resolution. What problem will most likely to be encountered as a result?

You will not be able to clear an anechoic tube oriented w its axis in the scan plane

When you perform a doppler exam, the freq of the transmitted signal is determined by:

The freq of the electric signal applied to the txd Broad bandwidth txd can be driven at different freq. In doppler sono, longer duration pulses generally are used. The freq is determined by the pulse transmitter (s). The sonographer can change the ultrasound freq for doppler studies, similar to the way she/he can change the freq in B mode imaging.

Diagnostic ultrasound is limited in its diagnostic application to the adult brain because:

The great acoustic 23 mismatch between the cranium and soft tissue causes most of the sound to be reflected at that interface. This acoustic impedance mismatch causes nearly all of the sound to be reflected at the bone soft tissue interface and leaves very little energy for transmission into the brain, Since attenuation is greatest with hi-freq transducers, imaging of the adult brain must be limited to very low freq to enhance penetration. This results in poor spatial resolution

100* You have decreased the acoustic power by -3dB. Which of the following post accurately describes this adjustment?

The intensity has been halved An intensity change of 3 dB corresponds to a doubling of the intensity. If the intensity is changed by -3dB, then the intensity is halved.

Atherosclerosis begins w in:

The intima Atherosclerotic dz begins as fatty streak w in the intimal layer of the vessel wall

***You are performing a sonographic examination and select the tissue harmonics operating mode. Wha advantage will you obtain over conventional imaging?

Improved contrast resolution Tissue harmonics is a method of ultrasound imaging in which the harmonic of the transmitted freq is used to create the image Typically, the second harmonic is used, which is 2x the transmitted freq. Since the harmonic freq of the transmitted pulse is generated within the body, it has numerous advantages over conventional imaging. Improved contrast resolution is one of the main advantages. There are several reasons for the improvement. First, contrast resolution is always improved by the increasing freq, and harmonics always results in use of a higher freq. Secondly, harmonics reduces clutter and side lobe artifacts The absence of theses extraneous echoes improves contrast resolution compared to conventional scanning methods, Additionally, effects of reverberations are reduced bc the harmonic component is weak at shallow depths, where reverberations often occur

What advantage is obtained by steering a linear array txd to create a trapezoidal shape to the display as demonstrated in this image?

Improved field of view The steered beams allow for increased field of view along both edges of the displayed image. Lateral resolution is slightly decreased in the far field bc the scan lines are now farther apart, but axial, contrast and elevational resolution are not affected

***What would be the most likely result from increasing the transmit freq of the color doppler?

Improved sensitivity to slow flow Increasing the color doppler transmit freq will result in larger freq shifts from slow flow and thus improved visibility. It will decrease penetration to flow in vessels deep within the tissues. Changing the ultrasound freq has a negligible effect on frame rate, flash artifact or visualization of complex flow hemodynamics. although one could argue that the increased freq shifts from slow moving tissue would be more visible w higher freq and may result in increased flash artifact, increased visibility or slow flow is still the best answer to this question

***What positive result will occur from the action taken in the previous question?

Improved signal to noise ratio W more pulses on each line, there is more data to compare when determining the freq shift. Comparison of more data allows better separation of the weak doppler signal compared to the surrounding noise floor

Parabolic flow is most likely to occur:

In laminar flow states W laminar flow, a parabolic flow profile maybe seen. This is bc the flow speed varies across the width of the vessel, w the fastest flow in the center and flow becoming progressively slower toward the vessel wall

If you are using a txd w poor elevational resolution, which of the following problems are you most likely to encounter?

Inability to clearly demonstrate small cystic structures Elevational resolution is determined by beam slice thickness. If the slice is thick, small cystic structures may not appear cystic. They will be displayed w the internal echoes reflected from the surrounding tissue. This occurs bc the beam is wider than the cystic structure, and tissue on either side reflects the sound beam from the same depth as the cyst. Since the echoes arrive back at the txd at a round trip time that is consistent w both the tissue and the cyst, they are assigned the same depth location on the image. If the beam slice is narrower, it will not cover the cystic structure and the surrounding tissue at the same time. Since the fluid portion of the cyst will not send back reflections, it will then appear anechoic

What does the mechanical index indicate on an ultrasound system?

The likelihood of cavitation during an ultrasound exam Mechanical index is derived from the peak rarefaction pressure and the ultrasound freq, parameters shown to be associated w onset of cavitation

A waveform from the internal carotid artery obtained at a doppler angle of 45° shows aliasing. What will help you unwrap this waveform?

Increase the PRF Decreasing the angle of incidence would cause a larger freq shift for any given velocity and increase the odds of aliasing. The high pass filter has no effect on aliasing. To reduce aliasing, the zero baseline should be lowered instead of raised. Increasing the PRF raises the Nyqyist limit and will help reduce aliasing (unwrap the waveform). Increasing the doppler freq will result i a larger freq shift for any given velocity and increase the chances of aliasing

***During the course of a sonographic exam, you notice lateral splaying of the echoes in the far field. What can you do to improve the image?

Increase the number of transmit focal zones and optimize their location Lateral resolution is dependent on beam width, The primary method of improving lateral resolution os focusing. Bc increasing freq increases the near zone length, beam width is also reduced w higher freq. Acoustic power or receiver gain does not affect lateral resolution. Lateral resolution varies w scanning depth and is best at the point of focusing. Using the minimum scanning depth does not ensure the best lateral resolution unless that is the point of focus.

***You notice a loss of detail in the lateral dimension of the ultrasound image. What can you do to improve this?

Increase the scan line density A loss of detail in the lateral dimension is related to poor lateral resolution. This can be improved by increasing the scan line density, increasing the number of focal zones or increasing the txd freq. The frame averaging (persistence) and dynamic range will not affect lateral resolution

Color flash artifact is obscuring the anatomy of interest in an exam of the abd aorta. What can you do to reduce impact of the flash?

Increase the wall filter Flash artifact is typically a high amplitude but low freq shift signal. It can be reduced on the display by increasing the wall filter. Of course, this comes at a price. Increasing the wall filter also reduces the sensitivity to the low req shifts associated w slow flow

2. During performance of an obstetric ultrasound exam, you adjust the system parameters to improve the image. Which of the following parameters would increase acoustic exposure?

Increase transmit power. The transmit power is the only control listed that will affect the exposure of the patient to acoustic power. Gain, TGC, and frame averaging (persistence) do not affect sound transmission and therefore do not affect exposure. Increasing frequency will not increase exposure.

***Which of the following helps to improve the lateral resolution in a B mode image?

Increased aperture

Edema involving the right lower extremity maybe caused by:

Increased intravenous pressure

Your patient has edema involving the right lower extremity. This maybe caused by:

Increased intravenous pressure

What is the advantage of using multiple transmit focal zones?

Increased lateral resolution

The image on the left demonstrated poor lateral resolution compared to the image on the right. Ho were the system controls adjusted to optimize the image on the right?

Increased line density The image on the left shows lateral smearing of the echoes. This is the result of poor lateral resolution, W the increase in line density, lateral resolution is improved in the image on the right

139* Which of the following would increase the spatial pulse length?

Increased number of cycles per pulse

112* Which of the following properties would result in increased propagation speed of sound thru a medium?

Increased stiffness Propagation speed decreases w increased density. Freq does not affect propagation speed. Increasing distance will increase the round trip time but will not affect the rate of travel (propagation speed). Increasing amplitude will increase the sound intensity but have no effect on propagation speed

137* Acoustic impedance increases w which of the following:

Increased tissue density Increased propagation speed

138* When you adjust the pulse repetition freq, you are changing: freq, you are changing:

The number of pulses per second

Adjusting the pulse repetition freq changes:

The number of pulses per second

***Which action would decrease frame rate?

Increasing acoustic scan line density Temporal resolution is determined by the frame rate. Several factors affect the frame rate. As the density of the acoustic scan lines increases, lateral resolution increases, but frame rate decreases bc it takes additional time to perform the pulse listen sequences for each new line of sight. All of the other answer choices would result in increased temporal resolution (increased frame rate)

108* Which of the following is most likely also to decrease beam intensity?

Increasing beam area For a given output power (mW) the intensity (mW/cm2) is expected to fall if the beam area (cm2) is increased o

***Which of the following actions would decrease color doppler frame rate?

Increasing line density Increasing the density of the scan lines w in the color box requires more firings to crease each image frame. This results in a decrease overall frame rate

***You made changes to the following controls during an exam. Which adjustment increased the duty factor?

Increasing pulse repetition frequency The PRF is the number of pulses emitted in one second. The duty factor is the percentage of time that the ultrasound is being transmitted. As the PRF increases, the percentage of time the ultrasound is "on" increases. None of the other choices will increase the amount of time the sound is actually "on"

According to the doppler equation, which of the following is NOT true?

Increasing the doppler interrogation angle will increase the freq shift -Increasing doppler freq will increase the freq shift -Decreasing the reflector speed will decrease the freq shift -Velocity information can be obtained from the freq shift if the angle of incidence is known The doppler equation is ∆f = 2fV (cos 0) ÷ C where ∆f represents the freq shift, cos 0) represents the doppler angle of incidence, F represents doppler freq, an C represents sound propagation speed. From this equation we an see that the value for the freq shift will increase if the velocity of the reflector (the red blood cell) increases. Also, if the doppler freq increases, the freq shift will increase. The cosine value of the doppler angle of incidence (represented by ), the Greek letter theta) is used in the equation. This tells us that the smaller the angle, the larger the freq shift obtained for any given velocity

***Which of the following adjustments would NOT decrease frame rate?

Increasing the receiver gain Increasing the receiver gain does not affect frame rate. All of the other answer choices would decrease the frame rate

The following advantage is associated w use of the MI and TI indices:

Information is available on the screen to help the sonographer implement the ALARA principles

Power divided by the beam area is equal to the:

Intensity The unit for intensity is watts/m2, which is "power per unit area"

The algebraic summation of waves leading to patterns of minima and maxima is called?

Interference As waves from multiple interfaces come in contact w each other, they can interact either positively or negatively, If they are of the same phase, constructive interference occurs and the resultant wave has increased amplitude. If they are not of the same phase, the resultant wave has a weaker amplitude. If they are completely out of phase and of equal amplitude, they will completely cancel each other out.`

In the images in the previous question what technique is used to fill in the empty data between the scan lines?

Interpolation

You have decreased the scan line density. What technique will be employed to fill in the empty data between the scan lines?

Interpolation Interpolation is used to fill in the missing data between scan lines in both gray scale and color doppler. This missing data are estimated from the data present in nearby pixels on adjacent scan lines

The layer of the vessel wall that is a single layer of cells backed by a thin layer of elastin and collagen fibers is the:

Intima

Which of the following statements about turbulent flow is NOT true?

It causes an increase in pressure downstream Pressure is reduced distal to a stenosis in turbulent flow

What happens when pressure is applied to a piezoelectric crystal?

It emits an electric signal

Which of the following statements most correctly describes the occurrence of diastolic flow reversal in the arterial system?

It is seen in and prox to high resistance vessels

What is the purpose of the radio freq shield that is placed around the crystal and backing material of the ultrasound probe?

It reduces electromagnetic interference Electromagnetic interference contributes to the noise level and reduces the detection of weak echoes The use of a radio freq shield around the crystal and backing material reduces this noise and enhances sensitivity to weak signals

***Which of the following is associated w improper adjustment of the brightness and contrast on the video monitor?

The operator will likely over gain or under gain the image The amount of gain the operator applies is subjectively determined by the appearance of the image brightness, if the monitor is set too dark, the operator may over gain the image to compensate for the dark monitor, If the monitor is too bright, the operator may under gain the image to compensate

What statement is NOT true regarding lateral resolution?

It remains constant thru out scanning depth -It is equal to beam width -It is improved by focusing -It is defined as the minimum separation required to resolve two structures perpendicular to the beam axis -It is also known as azimuthal resolution Lateral resolution varies w depth, It is best at the focal point and degrades on either side

What effect will increasing the wall filter during doppler sampling have?

It will reduce display of low freq shifts

The flow condition i which parallel streamlines of flow are present w in a tube is termed?

Laminar flow

This waveform was obtained from the center flow channel w in the common carotid artery. What term best describes this flow states?

Laminar flow A small sample volume was used to sample the flow in the center of the vessel. Since the spectral window is clean (absent of echoes), it can be assumed that most of the red blood cells passing thru the sample volume location are traveling at a similar speed. This is consistent w laminar flow

In this illustration, the letter A is demonstrating?

Lateral

***You have been requested to image a superficial mass and to adjust your equipment to optimize spatial resolution. Spatial resolution consists of:

Lateral and axial resolution

You have obtained an ultrasound image that demonstrates refraction of the sound beam This artifact might be manifested as:

Lateral displacement of the displayed position or a reflector Refraction is a bending of the sound beam. Bc the system must assume that the ultrasound is coursing straight from the txd face, refraction results in a misplacement of the reflectors laterally

When the sound beam is refracted during a sonographic exam, which of the following might you detect on the ultrasound image?

Lateral misregistration Refraction is a bending of the sound beam that results in lateral misregistration of structures posterior to the refracted beam. Refraction depends on both oblique incidence and different media propagation speeds

Measuring the lateral width of a target on an ultrasound phantom is most closely related to:

Lateral resolution

***Increasing the number of acoustic scan lines in one frame improves which of the following?

Lateral resolution As the number of lines in one frame increase, the distance between lines decreases. Bc structures that are smaller in the lateral dimension than the distance between he lines of sight cannot be detected, reducing this distance improves lateral resolution. Increasing the number of lines of sight decreases temporal resolution. The other types of resolution are not affected

When you increase the scan line density in the B mode image, you improve:

Lateral resolution Lateral resolution decreases when the distance between vectors (lines of sight) is greater than the beam width

W a standard one dimensional linear array transducer, what type of resolution is affected most by electronic focusing and dynamic aperture?

Lateral resolution Lateral resolution is improved at depth by increasing txd width or aperture size in an array. Essentially, the larger the aperture (the active portion of the array), the smaller the beam width at the focal point

What is being measured on the three rods in the center of this image?

Lateral resolution This image clearly demonstrated that lateral resolution varies w depth. As the sound beam widens in the far field, lateral resolution visibly suffers. This is shown by the increasing width of the deepest rod. All of the rods are actually the same size but measure differently due to the degradation oil lateral resolution w depth

What disadvantage is related to the txd type in the previous question?

Lateral resolution degrades w depth Lateral resolution degrades w depth bc the scan lines become spaced farther apart in the far field compared to the near field

What conclusion can be reached by comparing the rods labeled A and B in this phantom image?

Lateral resolution has deteriorated w depth There is no focal zone positioned at the level of the rods labeled B, and the lateral resolution has deteriorated. This width of the rods denotes the lateral resolution. The wider the rid appears on the image, the poorer the lateral resolution.

***Increasing the number of transmit focal zones to improve spatial resolution involves the following tradeoff:

Lateral resolution vs temporal resolution Each transmit focus required a pulse/listen cycle. As more focal zones are added, the frame rate is decreased. Temporal resolution is related to frank rate

A common used material in modern txd elements is:

Lead zirconate titanate

The term for a txd that has an array of rectangular elements arranged in a straight line is:

Linear array

What type of txd produced this image?

Linear array

Which of the following txd creates a rectangular image shape?

Linear array

Which txd type is best suited to vascular imagine?

Linear array

Which of the following is NOT associated w a low Q txd

Long pulse length Txd's used for diagnostic ultrasound are low Q txd's. Low Q txd's have a wide band width, which allows multifreq selection. They have short pulses for good axial resolution. Bc the pulse is short, most of the energy w in it is lost after the first few vibrations

You are using an ultrasound exam mode that is useful for measuring dimensions of structures. This mode produces a display more similar to a tracing than an actual anatomic picture. Which of the following most closely matches this description?

M mode

Which of the following can NOT focus the sound beam?

Matching layer

***The sound beam can be focused by all of the following EXCEPT:

Matching layer The matching layer does not focus the beam. It is used to reduce the acoustic impedance mismatch between the crystal and tissue -Acoustic mirror -Acoustic lens -Curved crystal -Electronic phasing

***When measuring penetration on a tissue mimicking phantom, how should yo adjust the receiver gain and acoustic output?

Maximum gain, maximum acoustic output

Volume flow is determined by multiplying the cross sectional area of the vessel w:

Mean velocity

What is an advantage of using a 3D/4D txd w an automated sweep compared to a traditional txd w a freehand sweep?

Measurement accuracy A volume data set may be obtained by a freehand sweep of the probe over the anatomy or by an automated sweep of the txd within the probe, Automated 3D sweeps can be obtained w specially designed mechanical or electronic txd. One advantage of the automated method is that measurements can be accurately obtained because the distance of the sweep is known

For a linear array txd consisting of a single row of elements, what method is most used to focus the beam in the elevational direction?

Mechanical focusing the z-axis is also known as the out of plane dimension It is the axis that runs across the width of the txd. It is the axis that runs across the width of the txd. Transmit, dynamic receive, and aperture focusing require the use of multiple elements. Since there are not multiple elements along the width of the txd, these types of focusing cannot be accomplished in this dimension. Focusing in the z-axis is accomplished b mechanical means--either a lens or curvature of the element

Which of the following best characterizes an ultrasound wave in human tissue?

Mechanical longitudinal wave

Which of the following txd produces side lobes or grating lobes?

Mechanical sector Linear sequential array Phased array Convex array Side lobes are secondary beams of energy that are displaced from the main beam and produced by all probes. Side lobes can be made as much as 60 to 100 dB less intense than the main beam thru broad band width excitation of the txd and thru apodization or array txd's. At higher intensities, they produce noise and artifacts in the image

Which most correctly describes sound propagation in a medium?

Molecules oscillate back and forth to propagate wound waves but do not move from one end of the medium to another In sound propagation, molecules oscillate back and forth, creating a series of compressions and rarefactions

***Which answer provides the best explanation for the reason that the frame rate decreases when color doppler is activated?

More pulses are fired on each line of sight Color doppler required from 4 to 32 pulses for each scan line or line of sight. B mode requires only 1 pulse for each focal zone on each scan line. So even if three focal zones are being used in B mode, there are still only 3 pulses per scan line The number of pulses per scan line is called the packet size or ensemble length

The "M" in M mode stands for?

Motion

Which of the following is NOT a limitation of M mode scanning?

Motion axial to the txd is not displayed

All of the following are limitations of M mode scanning EXCEPT?

Motion axial to the txd is not displayed -Information is obtained along one one line of sight -Motion lateral to the txd is not displayed -The two dimensional shape of a structure is not shown W M-mode, motion axial to the txd is not displayed thru time, so tis answer choice is correct, bc it does NOT represent a limitation of M mode scanning

Which of the following artifact may result in both axial and lateral displacement of a reflector on the ultrasound image?

Multi path reflectors A multi path artifact is created when the sound beam bounces off of one more reflectors before it encounters a reflector that redirects it back to the txd. The increased round trip time of the echo leads to its incorrect axial and lateral placement in the image. Bc the artifact is caused by reflections that take multiple paths to reach the txd, it is called multi path

What type of focusing decreases the frame rate?

Multiple transmit focusing When multiple focal zones are employed, the beam must be fired once for each zone on each line of sight, This reduces the frame rate. The other types of focusing do not affect frame rate.

What is the main advantage of using a 1.5D or multi-row array txd?

Narrow slice thickness over a large part of the scanned volume

What is an advantage of a water path scanner?

Near field reverberations are reduced

For a non focused txd, the region between the txd element and point at which the sound beam is narrowest is called the:

Near zone length The near zone length is also called the Fresnel zone or near field. This Fraunhofer zone is the term used to describe the far field

Which of the following conditions will result in aliasing of the doppler freq shift using continuous wave doppler?

None Aliasing does not occur w CW doppler. Aliasing of the doppler spectrum is an artifact that occurs w pulsed wave (PW) doppler when the freq shift is greater than half the doppler PRF

23* Which of the following occurs when you use the maximum system gain? Increased tissue heating Increased risk of cavitation Fluid particle streaming Increased sound absorption None of the above

None of the above

The following conditions will result in aliasing of the doppler freq shift using continuous wave doppler:

None of the above

What is the maximum velocity limit for a 3 MHz CW doppler unit operating at a depth of 4 cm? 40 cm/s 200 cm/s 2.5 m/s 4 m/s

None of these CW doppler does not have an imposed max velocity limit like PW doppler. In face doppler maybe used in instances where accurate velocities cannot be obtained w PW doppler They key to this answer is the term CW rather than PW. PW systems are subject to aliasing, which limits the maximum velocity that can be accurately measures. CW systems do not share this limitation

35* When you change the transmit freq, which of the following is altered?

Number of cycles per second

The spatial resolution of the scan converter is determined by:

Number of pixels in the scan converter matrix A matrix of 512 x 512 pixels is capable of must better spatial resolution than a similarly size matrix containing only 64 x 64 pixels. In the latter example, the image would appear blocky w discrete square-shaped segments. Image resolution would be degraded. The more pixels in the scan converter matrix, the greater the spatial resolution

You are performing 3D sonography and notice the volume rate 8 Hz. What does this represent?

Number of volumes displayed per second

When you select one focal zone, how many pulse/listen cycles are required for each acoustic scan line in one image frame?

One

Which txd freq would have the thinnest crystal?

One w a 15 MHz center freq The crystal (or element) must be thinner for higher freq

What is the optimal thickness for the matching layer?

One-fourth of a wavelength

You will see aliasing of the doppler spectrum whenever the freq shift exceeds:

One-half the pulse repetition freq Aliasing of the doppler spectrum is an artifact that occurs w PW doppler, when the freq shift is greater than half the doppler PRF

The ultrasound application w the lowest FDA approved SPTA values is:

Ophthalmic

What sonographic application has the lowest FDA approved SPTA values?

Ophthalmic

A most display is out commonly used for what type of ultrasound imaging?

Ophthalmologic

While performing a sonographic exam, you encounter the following interfaces. Which will produce the weakest reflected signal?

Organ parenchyma/organ parenchyma Reflected signal strength depends on acoustic impedance mismatch, A small reflected signal occurs when the acoustic impedance mismatch is negligible, as it is at small interfaces within a parenchymal organ such as the liver or kidney, A large reflected signal occurs when the acoustic impedance mismatch is large, as it is between organ parenchyma (soft tissue) and fluid, air, bone or ligament.

***You have the ability to adjust the following controls during an abd ultrasound study, Which control most closely affects patient exposure?

Output power Gain and TGC (time gain compensation) amplify the reflected signal. They do not increase patient exposure

***Which control would you adjust to increase the tensity of the transmitted pulse?

Output power The output power control is used by the operator to adjust the magnitude of the voltage pulse applied to the crystal. As it increases, the intensity of the transmitted pulse increases

A system commonly used to handle the archiving and electronic distribution of sonographic images using a DICOM format is?

PACS stands for picture archive and communications system

This image show flow w in the sac of a pseudo-aneurysm. Image A shows more color fill than image B. What color control was changed to make image A look like image B?

PRF The PRF (scale) was increased in image B compared to image A. This results in less sensitivity to slow flow, hence the reduction of color fill within the pseudoaneurysmal sac. The flow w in the larger arteries in image A exhibits aliasing. This is consistent w a lower PRF setting compared to image B. Another hint in this image is the velocity scale on the color bar. The velocity scale numbers are low in image A, indicating a low PRF setting and a high in image B, indicating a higher PRF setting

Which of the following would most likely have the highest SPTA value?

PW doppler

The terms ensemble length and dwell time are synonymous w:

Packet size

What term describes the number of pulses that are used to determine the velocity along a color line of sight?

Packet size Is also known as ensemble length or shots per line

What flow characteristic is depicted in this illustration?

Parabolic flow profile

A method for improving frame rates w multi zone electronic focusing is:

Parallel processing With parallel processing (also called co-processing), frame rate can be improved by simultaneously acquiring data for multiple acoustic scan lines. This is accomplished by firing one set of elements and forming more than one acoustic scan line signal w the signals by the active elements

Which of the following artifacts commonly results in echoes filling in the lumina of small vessels?

Partial volume

You are using a txd that reduces a beam w a very wide slice thickness. Which of the following problems are you most likely to encounter as a result?

Partial volume artifact Is also known as slice thickness artifact. It occurs when the slice thickness is wider than the structure being imaged. In other words, if you are imaging a small vessel in a sagittal plane, it may appear to contain echoes. Yet when you turn transverse to the vessel, you see that it is completely free of echoes. Yet when you turn transverse to the vessel, you see that it completely free of echoes. The source of the echoes in the sagittal plane is the slice thickness artifact. The beam is wider than the vessel, Tissue on both sides of the vessel reflects signals from that depth to the txd. These echoes are placed at that depth on the image, artifactual filling in the vessel

A longitudinal wave is characterized by:

Particle motion occurring in the same direction as propagation Particle motion that is perpendicular to the direction of propagation characterizes a transverse wave

91* Attenuation of the sound beam increases w increasing:

Path length Absorption Frequency Scattering and reflection The attenuation coefficient is the degree of attenuation for each centimeter of sound propagation. Anything that increases attenuation will increase the attenuation coefficient

96* You have increased the transmit power while performing a pelvic ultrasound exam. This action increases which of the following?

Penetration Acoustic power Image brightness Voltage applied to the txd elements

An example of a specular reflector is:

Pericardium A specular reflector is a large, smooth interface such as the renal capsule, diaphragm or pericardium. Specular reflection is primarily responsible for the bright interfaces seen at organ boundaries

Which of the following terms denotes the time it takes for one cycle to occur?

Period Period is the inverse of the freq, so doubling the freq halves the period

A commonly used process for determining direction in a doppler instrument is:

Phase quadrature detection

You are reviewing an ultrasound image that has a sector display format that narrows to a point at the txd surface. What kind of txd was most likely used to acquire this image?

Phased array

The optimal txd technology for cardiac scanning is?

Phased array A phased array txd has a small surface area w a flat face. This allows for the best contact between the rubs. In addition, high frame rates can be achieved by electronically steering the beam

What array txd fires all of the elements for each acoustic scan line, using small time delays to steer the beam?

Phased array The phased array txd fires all of its elements to create each acoustic scan line. Small time delays are employed to focus the beam and beam steering

The conversion of an incident pressure wave to an electric signal is the:

Piezoelectric effect A sound wave is a pressure wave. Conversion of a sound wave to an electric signal occurs when the sound wave strikes the txd surface. This is the piezoelectric effect

The picture elements in a scan converter matrix are termed?

Pixels

A mirror image artifact maybe observed w the following imaging mode:

Power mode B- mode Color Doppler Spectral doppler

You have chosen to enlarge an ultrasound image w a read magnification. Which of the following is NOT related to read magnification?

Preprocessing Read magnification is a post processing method of enlarging a portion of the ultrasound image. A pre-processing method of enlarging the image is termed write magnification. Read magnification increases pixel size and results in some resolution loss in the enlarged image

Using a hydrophone, you can measure:

Pressure amplitude and duty factor

What does hydrophone measure?

Pressure amplitude and duty factor

***The control that sets the gray scale brightness at which color will be displayed instead of gray scale at a pixel location is termed:

Priority

What sound parameter is determined only by the medium?

Propagation speed

In medicine, what do the initials PHI indicate?

Protected health information

The time it takes for one pulse to occur is known as the:

Pulse duration

Axial resolution is determined chiefly by:

Pulse duration The shorter the pulse duration, the better the axial resolution

A type of sonographic imaging that transmits two pulses of opposite phase in rapid succession so they can be canceled out upon reception is termed:

Pulse inversion harmonics Is an effective method to filter out the fundamental fro (transmitted freq) and leave only the harmonic freq for display. It uses two pulses of opposite polarity transmitted into the tissue in rapid succession. The received echoes from the pulses are added together and will cancel out the transmitted freq, leaving the harmonics that were generated w in the tissue

***What system control should be adjusted to optimize this waveform?

Pulse repetition freq Bc aliasing occurs when the freq shift exceeds half the PRF, the freq at which aliasing occurs increases as the PRF increases. Depending on the ultrasound system, the PRF control may be called velocity scale, velocity range, flow rate or other terms. What ever it is called it controls PRF

Pulse repetition period is the inverse of:

Pulse repetition freq Pulse repetition period is the time between the pulses, whereas pulse repetition freq is the number of pulses that occur in one second

What term below describes the rate at which the transmitter apples electronic voltage pulses to the txd?

Pulse repetition freq The PRF is the number of pulses emitted by the txd per second. The number of pulses is determined by the rate (per second) at which the crystal is stimulated by electronic voltage rom the transmitter

107* If the number of cycles in a pulse in increased but the wavelength remains the same, which of the following is true?

The pulse duration is increased PULSE DURATION is the time it takes to complete one pulse. If the number of cycles in the pulse in increased, it will take more time for one pulse to occur. FREQUENCY is how many cycles occur in one second--not how many cycles are contained in one pulse. PROPAGATION SPEEED (the speed at which sound travels thru a particular medium) is not affected by the umber of cycles in a pulse; it is determined by the medium. PERIOD is the inverse of freq. It describes the time it takes for one cycle to occur--not the time it takes for one pulse to occur. When freq increased, period decreases, and vise versa. BULK MODULUS is related to media stiffness and helps to determine propagation speed.

Which of the following describes diffuse reflection?

The reflected beam is scattered in various directions With diffuse reflection, the beam is weakened bc of incoherence. Diffuse reflection occurs when the sound beam strikes a large, rough surface. The beam is reflected at many different angles bc it strikes the rough surface at varying angles of incidence This has the result of causing the reflected waves to be incoherent (out of phase) w each other, weakening and defocusing the beam

Why do blood vessels usually appear anechoic on B mode imaging?

The reflection from the red blood cells is too weak to be displayed

The ter signal to noise ratio denotes:

The relative amplitude of the signal compared to the amplitude of the noise Noise is inherent in all electronic circuits and cannot be totally eliminated. Since noise occurs randomly, it is very difficult to isolate. One method of reducing the display of system noise is frame averaging (persistence). The system electronics, power line voltage variations, and radio freq interference induce noise. System shielding is a method employed to reduce the presence of noise in the system, The greater the signal to noise ratio (SNR) of the imaging instrument, the weaker the signal that can be reliably differentiated from noise. System sensitivity is often defined as its SNR

According to Snell's law, the angle of transmission is related to the incident beam angle and:

The relative speeds of sound in the two media Snell's law dictates the angle of transmission that will occur at an interface w refraction of the sound beam. Refraction (bending) of the sound beam occurs whenever there is oblique incidence and different propagation speeds between two media

You are using a conventional linear array txd to image the phantom. Why does the tube labeled B contain echoes, whereas the tube labeled A does not?

The slice thickness resolution at the level of tube B is worse than that at the level of tube A Elevational resolution is determined by slice thickness. The point of mechanical focus determines the slice thickness in linear array. In this case, the point of mechanical focus (to of plane focus) must be closer to the level of tube A than tube B. Since the beam is wider i the elevational tube send back reflections for that depth. These reflections cause till in of the tube lumen

You will NOT see refraction in the sonographic image if:

The sound beam is perpendicular to the interface Refraction is a bending of the sound beam and occurs whenever the beam strikes an interface where the propagation speed is different between the two media and the angle of incidence is not perpendicular (oblique incidence)

The interpreting physician has asked you to use a standoff pad to evaluate a superficial mass. What is the main advantage the standoff pad provides to improve the image?

The standoff pad increases the distance between the txd and the mass, making it more likely that the mass will be located close to the elevational focus of the sound beam

***What error will occur if the angle correct cursor is NOT adjusted parallel to the vessel wall?

The velocity estimation will be inaccurate Angle correct is needed to provide accurate velocity information

While performing a doppler study, you underestimate the measurement of the doppler angle of incidence. What error will result from this mistake?

The velocity estimation will be inaccurate The velocity estimation in doppler ultrasound is based on measurement of the doppler angle of incidence--the angle at which the doppler beam intersects the blood flow. Bc the blood flow is not directly visualized, the doppler angle correction cursor is aligned parallel to the walls of the vessel at the point of sampling. If this measurement is under estimated, the velocity of flow will be overestimated. Any time the angle correction cursor is not adjusted parallel to the wall, the velocity estimation is in error

Spatial pulse length is equal to:

The wavelength minus the number of cycles in the pulse

Spatial pulse length is equal to:

The wavelength times the number of cycles in the pulse It is more common for engineers to specify the pulse duration. Then spatial pulse length is equal to the pulse duration times the speed of sound

You are manipulating a volume data set that was previously obtained o your patient. What is the maximum number of imaging planes that can be obtained from this data set?

There is no limit An advantage of obtaining a volume data set is that it can be manipulated to show an infinite number of imaging planes with many different images

***These two images show a pseudoaneurysmal sac. In image A the gray scaled echoes within the flow are visible and the color does not fill the sac. What control was optimized in image B to allow the color to write over the gray scaled echoes?

Threshold priority The threshold or Priority control adjusts the brightness of the shade of gray that the color doppler is allowed to write over. In image A, the threshold is set low and the color does not overwrite any pixels containing the low level echoes of the blood flow

What type of txd was used to create this image of the uterus?

Tightly curved array A tightly curved array has elements arranged in a linear fashion on a tightly curved radius. The tight curvature increases the field of view while keeping the probe size small.

Dynamic receive focusing uses:

Time delays before echo signals from array elements are combined As the reflected echoes are received back to the txd elements, their curved wave front will cause them to be received at slightly varying times at the different elements. W dynamic receive focusing, the echoes that are received first are held in delay circuitry until all of the echoes from the same depth have been received. This results in constructive interference of the waves and produces a higher amplitude and more focused signal

Electronic focusing in the transmit mode is accomplished using:

Time delays to excite crystal elements

***What control should you adjust to better compensate for the attenuation of sound as it propagates thru tissue:

Time gain compensation

What information is present in the M mode display

Time, motion pattern and amplitude

Selective reception of echoes generated within the body by nonlinear propagation describes:

Tissue harmonic imaging

What technique would be most helpful in reducing grating lobes in your image?

Tissue harmonic imaging

Which of the following would improve visualization of distal acoustic shadowing from calcification?

Tissue harmonic imaging

Which imaging technique may increase visualization of the reflections from blood flow on the real time ultrasound image?

Tissue harmonic imaging Moving blood flow is more likely to be see on the realtime ultrasound image w tissue harmonic imaging bc of the reduced clutter, improved contrast resolution, and higher freq (which results in greater scattering from the RBC's since they are Rayleigh scatters).

What type of imaging results in selective reception of freq that are two times that of the transmitted freq?

Tissue harmonic imaging The receiver selectively "listens" to the harmonic freq that are generated as the sound travels thru the tissue. The second harmonic is the strongest harmonic produced. This is twice the transmitted freq

What can you do to improve visualization of distal acoustic shadowing from calcification?

Tissue harmonic imaging Tissue harmonic imaging produces a thinner beam and improved contrast resolution. Demonstration of acoustic shadowing from small calcifications is improved by reducing slice thickness w a thinner beam. Compound imaging actually reduces the appearance of shadowing in the image

What is the purpose of the pre amplification of the incoming signal that occurs in the txd assembly?

To increase echo voltages before noise is induced thru the cable Amplification of electronic noise is reduced by amplifying the signal before it passes thru the txd cable. This improves the signal to noise ratio and the sensitivity of the receiver

What is the purpose of the gel coupling between the txd and the skin?

To provide a medium for sound transmission, since ultrasound does not propagate thru air Any air between the txd and skin would cause total reflection and hence poor coupling

What is the purpose of curving the txd elements or applying a lens over the elements?

To provide focusing in the out of plane (elevational) direction

What is the purpose of sub dicing?

To reduce grating lobes Grating loves are secondary lobes off the main sound beam that occur with linear arrays. They can produce significant artifacts in ultrasound images. Grating lobes are related to the spacing of the elements in the array. If the spacing can be reduced to less than one wavelength, grating lobes are eliminated. Unfortunately, the elements are always spaced greater than one wavelength. Sub-dicing the elements into many smaller subelements decreases the effective distance between elements. The sub diced portions of the element are individually wired but fired as one unit. The end result is greatly reduced grating lobes

What component of the ultrasound system converts the electric energy provided by the pulser into acoustic pulses transmitted into the patient?

Transducer The function of the transducer is to convert electric energy into mechanical vibrations (sound energy) for transmission into the patient. Conversely, when the reflected sound energy is received by the transducer, it converts it into electric energy

Which of the following does NOT affect the time required to create one image frame?

Transducer aperture The time required to create one image is determined by all of the answer choices EXCEPT txd aperture. The aperture in an array is the number of active elements

Which scanning mode does NOT rely on the principle of echo ranging to determine interface location?

Transmission

***According to the doppler equation, for any given velocity, the freq shift will increase by increasing the:

Transmit freq This is important to know bc the freq shift obtained from very slow flow will be very small. To increase the freq shift and improve detection of slow flow, the transmit freq can be increased

For pulsed ultrasound, which of the following factors determines the freq of the sound wave?

Transmitter freq Txd can be operated over a range of freq; the transmitter generally dictates the actual freq. The number of electric pulses delivered to the active element per second is the pulse repetition frequency (PRF) but does not affect the imaging freq. The freq is determined by the propagation speed and the thickness of the piezoelectric material in the txd, and by the center freq of the drive signal applied to the txd.

You have encountered spectral broadening of the internal carotid artery waveform. This most likely indicates:

Turbulent Distal to a stenosis, flow becomes turbulent, demonstrating many different speeds and directions (although net flow is still in the forward direction). This range of speeds and directions results in the reflection of a wide range of freq shifts that is termed spectral broadening. As the term implies, it is simply a broadening of the spectrum of freq reflected back to the txd

You are most likely to see a color bruit in which of the following cases?

Turbulent flow distal to a high grade stenosis

How many levels of information can a single bit represent?

Two A single bit can represent only 2 values, on and off. The earliest ultrasound systems showed only 1 bit of info.

These two phantom images were obtained w maximum gain and acoustic power using two different txd. What information can be obtained by this comparison?

Txd A has less penetration than txd B Both lateral and axial resolutions are superior w txd A

The txd you are using is an array assembly. What is an advantage of this type of txd?

Txd arrays enable electronic focusing and steering Txd arrays use multiple elements rather than a single element to form the beam. W delayed transmit firing times to the elements, both focusing and beam steering can be accomplished electronically. This allows a sector shape to be present w out the necessity of moving parts (as in a mechanically steered txd). Also multiple points of focus can be achieved electronically, whereas w single element txd's only one point of focus is possible. Single element txd focus the beam mechanically by curving the element, applying a lens or using a curved mirror.

What is the order in which the signal travels in the ultrasound system?

Txd, receiver, scan converter, display

You are imaging a 3D data set that has anisotropic resolution. What does this mean?

Unequal resolution is present between imaging planes Isotropic resolution means that the spatial resolution is equal in all dimensions or imaging planes. Anisotropic resolution is the opposite of this

3. To minimize the risk of biologic effects of ultrasound to the fetus, which imaging mode tradeoff would be most applicable?

Use M-mode instead of pulsed-wave Doppler to measure the fetal heart rate. Pulsed wave Doppler increases the time average intensity compared to M-mode.

What can you do to improve contrast resolution in the ultrasound image?

Use a 2D or matrix array txd A 2D or matrix array txd has both rows and columns of elements. This allows electronic focusing in the out of plane dimension w the result that the slice thickness of the sound beam is thinner compared to traditional 1D txd's. Contrast resolution is improved w thin slices due to decreased volume averaging

15*To practice the ALARA principle, which of the following techniques should you employ?

Use the lowest transmit power that allows adequate tissue visualization Use a high gain and low transmit power

In this image the color green represents?

Variance Variance (or variance map) adds a color, usually green, to the color doppler display. It signifies disturbed, turbulent blood flow. the greater the increase in variance in velocity, the brighter the green

What display method will help you to demonstrate flow turbulence w color doppler?

Variance Variance maps have a green shade that is used to indicate turbulence. Although they may be used anywhere in the body, variance maps are used primarily for cardiac scanning. Variance maps should not be confused w rainbow maps, which contain some green adjacent to the blue color. These maps are commonly used in vascular scanning. W rainbow maps, the green down not indicate turbulence but merely helps to differentiate levels of freq shifts in the negative direction

What term is used to describe a three dimensional pixel element in 3D sonography?

Voxel The term voxel is used to describe the smallest element of a three dimensional volume. Its is analogous to the term pixel in 2D imaging

5. When practicing universal precautions, you should do all the following EXCEPT:

Wash gloves between exams for reuse from one patient to another. (It is recommended that gloves be worn during every ultrasound examination. They should be discarded after use). -wear gloves when there is a potential for contract with patient body fluid -change gloves when moving from one patient to another -Wash hands immediately after gloves are removed - Wear face masks or eye protection whenever there is a possibility of blood splashing in your face

The rate of sound attenuation in lowest in:

Water

What statement is correct regarding the comparison of these two waveforms?

Waveform A indicates a low resistance state compared to waveform B The amount of diastolic flow in the two waveforms differs, and resistance is best described thru the amount of flow during diastole. When there is continuous forward flow thru out diastole, a low resistance state is indicated. If the flow is coursing to an area of high resistance, the diastolic flow maybe reversed or absent. Waveform A is a low resistance waveform B is a high resistance waveform w flow reversal during early diastole and low flow in end diastole

The following illustration depicts acoustic pressure v distance in a medium in which a sound wave is present What wound parameter is measured by the length of the bar labeled A in the following illustration?

Wavelength

The length of space over which one cycle occurs is known as the:

Wavelength

What is the maximum velocity limit for a 3 MHz CW doppler unit operating at ad depth of 4 cm? 40 cm/s 200 cm/s 2.5 m/s 4 m/s

none of the above CW doppler does not have an imposed max velocity limit like PW doppler. In face doppler maybe used in instances where accurate velocities cannot be obtained w PW doppler

What system function is limited by the speed of sound in tissue?

Pulse repetition freq The maximum useable PRF is limited by the speed of sound in tissue bc there must be enough time between the pulses for the ultrasound to travel to and back from the reflector. As the PRF is increased, there is less "listening" time between the pulses and hence less travel time for the echoes. If echoes from deeper structures are received from the first pulse after a second pulse has been transmitted, range ambiguity results. In other words, the system cannot accurately detect the depth of the returning echo and will assume it arrived from the most recently transmitted pulse. This will cause the reflector to be misplaced axially on the image in a position relating to a more superficial structure. If sound traveled faster in tissue, the max PRF could be increased. Unfortunately, the speed of sound in tissue is determined by the medium thu which it travels and cannot be adjusted by the operator or the system

When scanning w pulsed wave doppler, you would affect the acoustic exposure by changing which of the following?

Pulse repetition freq The pulse repetition freq is the number of pulses per second transmitted by the transducer, which varies w the velocity setting on the spectral display. Increasing pulse repetition freq has the potential to increase the acoustic exposure

When you increase the scanning depth, which of the following is automatically decreased by the system to avoid range ambiguity?

Pulse repetition freq The system automatically adjusts the PRF downward when the scanning depth is increased to avoid range ambiguity

***When you adjust the output power control, you affect the following system component?

Pulser

What system component determines the pulse repetition freq?

Pulser The pulser produces the electric voltages that drive the txd. The rate at which the voltages are applied determines the pulse repetition freq

To generate a sonographic image, what is the order in which the following system components are activated?

Pulser, beam former, receiver memory, display The action begins w the pulser (which contains the clock). The pulser produces the electric voltage pulses to the beam former and on to the transducer. The returning echoes are sent to the receiver. The resultant image is stored in the memory and then displayed on the video monitor

In color doppler, "packet size" denotes the number of:

Pulses per acoustic scan line

What feature would you use if you wis to recall a previous exam from the PACS system to your ultrasound machine?

Query/retrieve This is a DICOM feature that allows yo to recall a previous DICOM study (CT/MRI/Sono) onto your ultrasound system for viewing

The waveform you obtained fro an arterial stenosis demonstrates aliasing. If you increase the pulse repetition freq to eliminate the aliasing., what artifact could be introduced?

Range ambiguity If pulses are transmitted very rapidly (high PRF) it becomes increasingly likely that an echo from w in the doppler r sample volume will arrive at at the txd after another pulse has been transmitted along the doppler beam line. Bc the system assumes that all reflections are related to the most recently transmitted pulse, the echo will be misplaced closer to the txd face than its actual location. This is bc the system will think it took much less time to arrive than it actually did. This phenomenon is called range ambiguity

***If you increase pulse repetition freq to a level too great for the depth of field, the result will be

Range ambiguity If the PRF is too high for the imaging depth, range ambiguity will result. If the PRF is set so that a pulse can be received from the bottom of the field of view before the next pulse is transmitted, If another pulse is transmitted before all echoes from the first pulse are received, then the echoes would be misplaced axially on the image. Why? bc the system must assume that all received echoes have arrived from the most recently transmitted pulse.

Bandwidth refers to:

Range of freq in a pulse

What does "bandwidth" denote?

Range of freq in a pulse

Another name for axial resolution is:

Range resolution

What term refers to regions of decreased particle density in a sound beam?

Rarefaction Sound propagates thru tissue as a series of compressions and rarefactions. Particles in the medium are pushed together during Compression and pulled apart during rarefaction. The analogous to a slinky being pulled apart and pushed together. The density of particles is decreased during rarefaction.

The regions of low pressure and density that are formed during sound propagation are termed?

Rarefactions High pressure regions are compressions, while low pressure regions are rarefactions

Which physics concept best explains why doppler signal strength would be greater w a 6.3 MHz txd than w a 5.0 MHz txd?

Rayleigh scattering Red blood cells are considered Rayleigh scatterers bc they are smaller than the wavelength of the sound beam. The reflected signal from Rayleigh scatterers increases to the 4th power of the freq. Therefore, increasing freq will increase the signal strength unless the tissue path is too deep and the sound beam is attenuated

Dynamic apodization is a method employed to:

Reduce side lobes Side lobes are part of the beam pattern from any txd. They are transmitted into the tissue at various angles w respect to the main beam and can result i significant artifacts in the ultrasound image. Use of broad bandwidth pulses reduces their strength. W array txd, maximizing the excitation voltage for elements hear the center of the beam and reducing it toward the periphery can reduce side lobes. This variation in excitation strength to the array elements is termed apodization.

The matching layer between the piezoelectric element and the tissue is designed to:

Reduce the acoustic impedance mismatch between the element and tissue There is a large acoustic impedance mismatch between the crystal and the tissue. This would result in a large reflection w very little energy transfer into the body. This matching layer impedance is intermediate between the crystal and tissue, which enhances the transmission of the sound into aand out of the body by reducing the amount of reflection that occurs at that interface.

***While performing a sonographic exam, you increase both imaging depth and scan line density. These adjustments produce the following result:

Reduced temporal resolution Increasing the imaging depth reduces the frame rate because the system must allow more time between pulses for the arrival of echoes from deeper structures. Increasing the scan line density reduces the frame rate by requiring more pulse listen sequences to create each image. Decreasing the frame rate reduces temporal resolution. Contrast resolution and axial resolution are not affected by these changes. Increasing the scan line density will improve lateral resolution

The shadow depicted in this image of a renal stone is primarily a result of the following sound tissue interaction:

Reflection Because of the large acoustic impedance mismatch between soft tissue and calcium, most of the sound is reflected at the stone tissue interface. Very little sound is transmitted thru the stone to provide reflections from tissue distal to the stone. This results in shadowing distal to the calcification

If sound waves of 3 MHz, 5 MHz and 10 MHz are transmitted thru the same section of anatomy, reflections from which freq would reach the txd first?

Reflections from all three freq would have nearly identical transit times. The speed of sound does not vary appreciably w freq. Freq describes the number of cycles that occur in one second. The speed of sound is determined by the medium, not the sound source. Freq is determined by the sound source (the txd), not by the medium

Which of the following sound interactions produced the shadows indicated by the arrows on the image?

Refraction The edge shadowing seen w the curved interfaces is caused by refraction of the sound beam. This is the same physical principle that can be observed by placing a pencil in a partially filled glass of water. When viewed from the side, the pencil appears bent

You are imaging a rounded mass w irregular borders. The mass has a much slower propagation speed than surrounding tissue. What sound tissue interaction will be encountered as the ultrasound propagates thru this interface?

Refraction Reflection Absorption Scattering Refraction occurs bc of the oblique incidence (round surfaces) and different propagation speeds of the insonated media. Reflection occurs bc the acoustic impedance is different (different densities and propagation speeds). Absorption occurs as sound propagates thru tissue, and so it will be present. Scattering occurs as a result of the irregular margins of the mass.

Electronic noise is reduced in the ultrasound system by this method:

Rejection

WHa does the doppler signal spectral display depict?

Relative signal power at each freq in the doppler signal The doppler signal spectral display depicts the freq bandwidth and range of amplitudes in the reflected signal. The amplitude or signal power depends on the relative number of red blood cells comprising each component of the freq shift spectrum

What term describes the ability of an imaging device to separate closely spaced objects?

Resolution

The ultrasound system in your lab has a txd w a small footprint. This kind of txd has the following disadvantage:

Resolution is degraded at large distances With small footprint txd, the beam diverges very rapidly in the far field, resulting in poor lateral resolution

The arrow in this image points to flow below the zero baseline. These echoes represent?

Retrograde flow due to post stenotic turbulence

What is the source of the echoes depicted by the arrows in this image of the kidney?

Reverberation

You are imaging a fluid filled structure that has equidistant horizontal bands appearing in the near field. The bands have decreasing brightness w depth. What artifact are you seeing?

Reverberation

Which of the following actions is NOT compliant w HIPPA?

Reviewing your neighbors medical studies on your hospital PACS system so you can give her your opinion of her condition The Health Insurance Portability and Accountability Act (HIPPA) includes rules to protect the privacy of the individuals health information. This answer would violate HIPPA

In this image of an arterial stenosis, the waveform indicates post stenotic turbulence. What term describes the point at which flow becomes turbulent?

Reynolds number This describes the point at which flow becomes turbulent

The range equation describes the relationship between:

Round trip pulse travel time and distance to the reflector

8. Which intensity descriptor has the lowest numeric value for the characterization of a pulsed-wave ultrasonic field?

SATA SATA, a term that is infrequently used, means spatial average, time average. Note: I(SPTA) is the spatial peak, time average intensity; I(SPTP) is the spatial peak, temporal peak.

Which intensity parameter is not applicable for continuous wave ultrasound?

SPPA and SAPA refer to pulse average intensities, which do not apply to continuous wave ultrasound.

Which of the following would show the highest intensity value?

SPTP Note that Im is the intensity over the half wave period within the transmit pulse where it is the greatest! This term is seldom specified

The Nyquist limit describes which of the following?

Sampling freq needed for detecing the doppler signal

What component is necessary for a real time B mode scanner but is not present in an A mode scanner?

Scan Converter

Where are the images stored in the ultrasound system?

Scan converter

Where is the echo information stored when an image is "frozen"?

Scan converter

When you "freeze" the ultrasound image, where is the echo information stored?

Scan converter The scan converter is the digital memory of the system

***During a sonographic exam, you adjusted the following controls. Which one was most likely to have affected the frame rate?

Scan depth As the scanning depth (field of view) is increased, the system must decrease the PRF to avoid range ambiguity. In other words, it must increase the time between pulses to account for the additional time it takes the ultrasound pulse to travel to and from a reflector at the bottom of the field of view. As the PRF decreases, frame rate decreases. It takes longer to fire the required number of pulses to create the image bc the time interval between pulses is greater.

86* What can you do to enhance the visibility of a specular reflector?

Scan w perpendicular incidence With specular reflectors, the angle of reflection is equal to the angle of transmission, so the greatest reflection will be received back by the txd whenever perpendicular incidence i used Increasing the amount of received energy enhances the visibility of the reflector

What interaction of ultrasound and tissue is primarily responsible for imaging the internal structure or organs?

Scattering

In the following illustration, if the propagation speed is unchanged at the interface, whih most correctly describes the sound tissue interaction taht will take place when the ultrasound

Scattering Occurs when the sound strikes an irregular or rough surface that is small compared to the wavelength. Specular reflection occurs when the surface is smooth and large compared to the wavelength. Diffraction requires the speed to pass thru a small aperture. Refraction occurs w oblique incidence and a change in propagation speeds at the interface.

Another term for nonspecular reflection is:

Scattering Specular reflection occurs when the interface is large and smooth. Non specular reflection or scattering occurs when the interface is small, less than several wavelengths across

Which of the following statements regarding the effect of freq on Rayleigh scattering is TRUE?

Scattering intensity is proportional to freq raised to the 4th power

Imaging frame rate decreases when:

Sector width increases

You are imaging a structure that is highly attenuating. Which imaging effect do you expect to encounter?

Shadowing With increased attenuation, there will be loss of sound energy thru reflection, scattering and absorption. This loss will result in less penetration and shadowing distal to the highly attenuating region.

What phantom is used to detect:

Slice thickness

The following sag images of an artery were obtained w different txd's emitting the same freq. What type of resolution is limiting visualization of the arterial lumen in the image on the top?

Slice thickness The artery on the top is not well demonstrated bc the slice thickness of the beam is too great at that scanning depth. If the beam is wider than the vessel, tissue on either side will send back reflections, resulting in filling of the fluid filled structure. The top image shows the radial artery w an anechoic lumen. This can be seen bc the slice thickness is no wider than the vessel w this txd. The txd used to obtain this image is a matrix array in which there are multiple rows to obtain this image is a matrix array in which there are multiple rows of elements along both the width and length of the txd. This arrangement allows for the electronic focusing in both dimensions, resulting in a thinner beam slice

You notice that the image in the far field is less bright compared to the near field. This is due to:

Sound attenuation As sound propagates thru tissue, the beam strength is weakened thru absorption, reflection and other interactions w the medium. This weakening of beam strength is termed attenuation and accounts for decreased brightness of the image in the far field compared to the near field

What is a side lobe?

Sound beam emitted from the txd that travels in a different direction from the main beam

Which of the following describes sound propagation thru a vacuum?

Sound cannot travel thru a vacuum Sound requires a material medium for propagation. The physical movement of particles within a medium transports the sound. Since there are no particles to vibrate in a vacuum, sound cannot propagate.

Which describes constructive interference:

Sound waves are in phase and resulting amplitude is increased

What type of resolution is determine by the number of pixels in the scan converter?

Spatial As the number of pixels increases, the spatial resolution of the image improves. The spatial resolution can be no better than that obtained from the beam forming, but it can be worse

In this image the doppler freq shifts exhibits:

Spectral broadening

Which of the following is present in this doppler spectral waveform?

Spectral broadening The waveform shows fill i of the spectral window. This loss of the window is indicative of spectral broadening. Spectral broadening is associated w turbulent flow

What term would describe a doppler waveform obtained at location "C" in this depiction of an arterial stenosis?

Spectral broadening flow profile

Which term most correctly describes this doppler waveform?

Spectral mirroring

***What system control on doppler adjusts the PRF?

Spectral velocity scale

***What control should you adjust to optimize the image if you are scanning a structure that produces very bright echoes on the display?

TGC

To compensate for sound attenuation as depth increases, you should adjust the following system control:

TGC

***If sound did not attenuate w increasing depth, what system control would you no longer need?

TGC TGC (time gain compensation) also called depth gain compensation) is used to amplify echoes from deeper structures so they appear as bright as similar structures located at shallower depths. TGC is necessary bc sound beam attenuation w depth results in reception of weaker signals from structures located deep in the image compared w those located more superficially. If the sound beam did not attenuate w depth located more superficially. If the sound beam did not attenuate w depth (ie, distance and travel time), TGC would not be needed. Master gain is used to adjust the amplification of all the reflected signals, not just those at a specific depth

***What system control should you adjust to compensate for sound attenuation w increasing depth?

TGC TGC (time gain compensation) and DGC (depth gain compensation) are two names for the same system control. TC is a method of increasing amplification applied to echo signals arising from deeper structures to account for the weakening (attenuation) of the sound beam w depth. If the TGC is adjusted appropriately, like structures will appear w the same brightness even if they are located at different depths. The overall receiver gain (master gain) amplifies signals from all depths equal and does not compensate for attenuation changes at specific depths.

52* What system control can you adjust to compensate for the effect of sound attenuation in the body?

TGC The TGC (time gain compensation) is used to amplify echo signals from deeper structures, which have undergone greater amounts of attenuation more than echo signals from shallow structures

Which of the following can NOT be evaluated w a tissue equivalent phantom?

Temporal resolution Temporal resolution is related to the amount of time it takes to complete a single frame of information. This cannot be assessed w a tissue phantom in which there are no moving structures

Decreased pressure occurs in areas of high flow speeds. This is known as:

The Bernoulli's law The Bernoulli' effect describes the decreased pressure that occurs at a stenotic site as a result of the increased blood velocity w in the stenosis. It is based on maintaining energy balance along the vessel

***Which of the following occurs when you lower the pulse repetition freq?

The Nyquist limits decreased The pulse repetition freq sets the Nyquist limit. If the doppler signal freq exceeds half the PRF, aliasing occurs

What occurs when you image a structure w oblique incidence?

The angle of reflection will be orientated away from the txd resulting in decreased visualization of the structure With specular reflectors, the angle of reflection is equal to the angle of incidence but will be orientated in the opposite direction. So if perpendicular indigence (also known as normal incidence) is used, most of the sound will be reflected back at the transducer But if oblique incidence is used, most of the sound will be reflected away from the transducer at an angle equal to that of the transmitted angle.

Snell's law describes:

The angle of sound transmission at an interface between media having different propagation speed Snell's law related the angle of transmission of the sound beam to the relative velocities of sound in the two media. Refraction of sound at an interface obeys Snell's law.

Using the modality wordlist has the advantage of:

-Avoiding the need to type patient information -Reducing patient information error -Speeding up patient prep time -Easily confirming patient information

***Which of the following could be used to increase the color frame rate for a cardiac image?

-Decrease image width -Decrease the packet size -Decrease the line density Frame rate increases when the image width is narrowed bc fewer scan lines are required to create one image frame. Decreasing packet size increases frame rate bc fewer pulse are generated for each scan line. Decreasing line density increases frame rate bc fewer lines are fired for each image frame

The end result of the issue from the question above is?

-Degradation of image quality -Underestimation of maximum flow velocity

The Reynolds number increases w increasing:

-Flow speed - Vessel diameter -Blood density -Blood flow viscosity

Which of the following should be regularly checked as a component of a quality control program?

-System penetration -Image uniformity -Assurance of electric safety -Distance measurement accuracy

***Which of the following will decrease the presence of the artifact you are seeing i the previous question

-Using frame averaging (persistence) -Using compound imaging

What type of txd should you select to produce the narrowest slice thickness thru out the image plane?

1.5 D multirow array The txd producing the thinnest beam is the annular array. All of the types of linear array probes cited in the answer choices produce asymmetric beams that are narrower along the length of the beam and wider along the width. This is bc electronic focusing can be accomplished only along the length of the array since it requires the use of multiple elements to focus the beam. A lens is applied along the width of the probe, which provides focusing in that dimension (z-axis) but only at one depth. If the linear array probe has multiple rows of elements in both dimensions (length and width), it can be electronically focused in both dimensions. This allows multiple depths of focus in the z-axis and results in a beam w a slice that is thinner than those that can be obtained w traditional linear array probes. A 2D linear array txd has a nearly equal number of elements i both axes. The 1.5D linear array txd has multiple rows of elements in the out of plane or short axis, but not an equal number of rows in the in plane or long axis. This allows for multiple focus positions in the out of plane dimension and reduces beam width, but the beam is still not symmetric in all dimensions

What type of txd will improve the artifact demonstrated i the previous question?

1.5 D or multi row array

10-3 equals

1/1000

You have been asked to perform an ultrasound study of a structure located about 3 cm below the skin surface. Which txd freq range would be most appropriate for this study?

10-12 MHz

What is a typical frame rate for B mode real time imaging?

10-50 Hz Frame rates are displayed in terms of hertz (Hz), a unit of freq equal to one cycle per second. Although frame rates vary typical real-time frame rates range from about 10 Hz to 50 Hz. If the frame rate is 30 Hz, that means 30 frames are produces in one second. Faster frame rates are found w cardiac imaging

Choose the probe that would provide the best axial resolution for measuring the thickness of a small structure:

10MHz has.linear array

While performing a doppler ultrasound exam, you adjust the pulse repetition freq to 12kHz. This can also be expressed as:

12,000 Hz Kilo is 1000 or 10+3

7. Thermally induced biologic effects should be preventable by avoiding a local tissue temperature increase exceeding:

1°C

You are performing a sonographic exam on a large patient. Which txd would provide the least amount of signal attenuation?

2.5 MHz Since attenuation is proportional to freq, lower freq are best to use for scanning a large patient's abd

What Reynolds number would indicate turbulent flow?

2000 and 3000 In general, laminar blood flow tends to become turbulent at Reyolds numbers exceeding 2000

What is the maximum number of shades of gray in an 8 bit digital scan converter?

256 An 8 bit system produces a maximum of 2 to the 8th power or 258 shades of gray. A 4 bit system is capable of a maximum of 16 shades of gray, 5 bits-32 shades, etc. The more bits, the greater the number of shades of gray.

What is the velocity of an ultrasound wave in bone?

4080 m/ s

***Regarding this image, the angle of the beam to the vessel is approx:

90°

The intensity transmission coefficient at the interface between two structures equals 1/100. What is the intensity reflection coefficient?

99/100 The intensity transmission coefficient described the fraction of sound transmitted at a boundary. The intensity reflection coefficient described the fraction of sound reflected at a boundary. The sum of these two coefficients must equal 1. Therefore, if only 1/100th of the energy is transmitted, then 99/100th of the energy has been reflected. These fractions can also be expressed a percentages for the sake of clarifying the principle. In this case, only 1% if the incident sound is transmitted from one medium to the adjacent medium. Therefore, 99% of the incident sound is reflected.

In order to display a structure on your sonographic image, the sound beam must be reflected at the interface. What is required for sound reflection at the interface of two structures?

A difference in the acoustic impedance of the media

Identify the parameters associated w tissue heating:

Absorptioh

Te transfer of acoustic energy into heat is termed:

Absorption

Which of the following parameters relates to tissue heating?

Absorption

A hydrophone measures:

Acoustic pressure output

The "A" in A most stands for?

Amplitude

What information is present in the A mode display?

Amplitude and reflector distance

Varying the excitation voltage to each element in the group used to form the ultrasound pulse is called:

Apodization

In this illustration, the Letter C demonstrates what type of resolution?

Axial

***If the number of cycles in the transmitted pulsed wave is increased:

Axial resolution is degraded Axial resolution is proportional to pulse length, Axial resolution is degraded as pulse length increases. Pulse length is increased b increasing the number of cycles in the pulse.

This image shows the color significantly over writing the vessel all. Which of the following provides the best explanation for this?

Axial resolution is lower w color doppler compared to B mode In general, color doppler uses a longer pulse length compared to B mode imaging to compensate for the lower reflectivity of red blood cells compared to tissue. This results in poorer axial resolution of color doppler wall. Reduction of color overwrite can be obtained by lowering the threshold or color write priority control

You may observe a mirror image artifact w which imaging mode?

B mode Spectral doppler Color doppler Power doppler

The txd lens, which may be easily damaged by mechanical shock, is represented by letter:

D The lens is a sensitive area of the txd and maybe damaged by any type of mechanical shock such as dropping or even hitting w the tip of a gel bottle

In this image, the red color indicated by the arrow represents:

Flow toward the ultrasound txd

***Which of the following helps to improve the elevational resolution in a B mode image?

Focusing w an acoustic lens

***What doppler control should be adjusted to optimize this doppler spectral waveform?

Gain The gain should be reduced. There is noise in the background behind the spectrum and w in the spectral window bc the gain is set too high. Changing the sample volume would not affect the back ground nose, or would changing the wall filter setting

***When you select harmonic imaging, which artifacts less likely to be observed?

Grating lobes

When you switch from a 2.5 MHz to a 5MHz txd, the sound wavelength?

Halves Wavelength is inversely proportional to freq. Doubling the freq halves the wavelength

With absorption, acoustic energy is converted to:

Heat

This image exhibits banding. This is a result of:

Incorrect TGC

***Imaging frame rate decreases when you:

Increase the sector width By increasing the sector width, the user forces the system to fire more lines of sight (scan lines) for each imaging frame. This increases the length of time it takes to create each frame and causes a decrease in frame rate

***You suspect that a bright spot on the B mode image is a calcification, but a posterior acoustic shadow is not preset. How can you best optimize your system to demonstrate a shadow distal to the calcification?

Increase the txd freq The demonstration of the acoustic shadow depends on beam width. If the sound beam is wider than the stone, a shadow may not occur bc tissue on either side of the stone will send back reflections for that depth and the results will be volume averaged To improve demonstration of the acoustic shadow, the beam width must be decreased by increasing freq and/or improving focusing.

9* Increased tissue heating could occur when you:

Increase transmit power

The dark area indicted by the arrow in the image is primarily due to:

Increased attenuation In this case, it appears to be caused by reflection at calcifications

Axial resolution is improved with:

Increased band width Shorter pulse length Shorter wavelength

***Which of the following helps to improve the axial resolution in a B mode image?

Increased bandwidth

You have increased the output power by 10 dB. The signal intensity has:

Increased by a factor of 10 Increasing a control by 3dB corresponds to a doubling of the setting. If it is increased by 10 dB, it has been increased by a factor of 10

***What would be the most likely result from lowering the color threshold?

Increased color writing on the vessel or cardiac wall The threshold controls the brightness of the shade of gray that the color is allowed to overwrite. If the threshold is lowered, if is more likely that the color will overwrite the vessel or cardiac wall. Axial resolution in color doppler almost always is poorer than in B mode

162* Which of the following will NOT improve axial resolution?

Increased focusing -Increased damping -Increased txd freq -Increased bandwidth -Decreased pulse length Focusing improves lateral resolution bc it decreases beam width. As the amount of focusing is increased, pulse length increases, resulting in slightly poorer axial resolution.

Loss of fluid energy thru inerta:

Is greatest in a tortuous vessel w multiple obstructions Inertial losses of fluid energy depend upon changes in flow direction and changes in velocity when blood is accelerated or decelerated as in pulsatile flow. Tortuous vessels w multiple obstructions would change the direction as well as the velocity of the blood flow, and this would create the greatest loss of fluid energy thru inertia

6. A nosocomial infection is defined as one that:

Is hospital-acquired

After a short waling exercise , the venous pressure at the ankle of a standing normal subject:

Is lower than the standing ankle pressure restL

Which txd has the same distance between the scan lines in both the near and far fields?

Linear array W convex (also called curvilinear or curved linear) arras, the txd face is curved. The acoustic scan lines fan out from the array, This results int he line density being somewhat greater in the near field than in the far field. Phased arrays also produce a sec tor shape in which the acoustic scan lines in the near field are ore closely spaced than in the far field, where they are spread out. W a mechanical sector probe, the same effect occurs.

If you wish to use an array txd that allows you to control transmit focal depth, what type would you select?

Linear array Convex array Phased array Annular array All array txd's types permit operator control of the transmit focal depth

The graphic overlay on this phantom image represents a gray scale assignment curve. What type of curve is being used?

Linear curve

Which condition is most likely to occur in patients having a normal arterial waveform shape but low velocites across all vessels?

Lower cardiac output

***In the following waveform, the end diastolic flow velocity cannot be measured. What control adjustment should be performed to obtain this measurement?

Lower the wall filter

***Which control optimization should you make to improve color doppler sensitivity to slow flow?

Lower the wall filter setting To improve sensitivity to slow flow, the wall filter should be lowered. Increasing packet size may slightly improve sensitivity since it affects the signal to noise ratio. Increasing the doppler freq will increase the freq shift and thus improves sensitivity to slow flow. Threshold controls the gray level that color is allowed to over write and does not affect low flow sensitivity

Which of the following human tissues has the highest rate of attenuation of an ultrasound wave?

Lung

The layer of the vessel wall that contains smooth muscle fibers is the:

Media

What determines the speed of sound?

Medium thru which sound waves passes

Which prefix equals 10-3?

Milli Micro is 10-6, mega is 10+6 and centi is 10-2

Wavelength is measured in?

Millimeters Wavelength is in units of length

What is the purpose of applying multiple matching layers to the txd face?

Multiple matching layers result in increased txd bandwidth The purpose of the matching layer is to reduce the impedance mismatch between the crystal and the tissue. This will improve sound transmission into the body and increase the txd band width. The optimal thickness for the matching layer is one-fourth of the wavelength of the center freq of the txd. Use of multiple matching layers will increase the txd band with w the result of improving axial resolution

During a sonographic exam of a large vessel, a 45° beam to vessel angle would be called?

Oblique incidence Normal incidence is also known as perpendicular incidence. It occurs when the sound beam strokes the interface at a 90° angle

What two conditions must be present to cause refraction of a sound wave?

Oblique incidence and different media propagation speeds Both must be present for refraction to occur. Reflector size does not affect refraction. Refraction does not occur w perpendicular incidence

Electronic steering is most commonly applied to which of the following realtime txd?

Phased array

What type of probe was used to take this image?

Phased array

Which of the following txd type is best suited to cardiac imaging?

Phased array

The doppler freq shift is the difference between the:

Received freq and the transmitted freq

***When you adjust the TGC, what component of the ultrasound system implements the changes?

Receiver

***What receiver function converts the negative portion of the radio freq (RF) signal to positive?

Rectification

Which of the following is an example of a Rayleigh scatter?

Red blood cells A Rayleigh scatterer is an object that is much smaller than the wavelength of the sound beam. A commonly encountered Rayleigh scatterer in diagnostic ultrasound is the red blood cell.

What 3 colors are used on a color monitor to produce the range of available colors?

Red, green and blue These three colors are commonly referred to as the RBG signal

***Increasing the wall filter during doppler sampling will:

Reduce display of low freq shifts The wall filter (also known as high pass filter) is used to eliminate freq shifts below a set threshold from the display. If the filter is set at 50 Hz, then any freq shift of 50 Hz or less will not be displayed. Increasing the wall filter helps to eliminate the high amplitude, low freq shift signals caused by movement of the vessel wall. Nevertheless, it must be kept in mind that low freq shifts may also be a result of slow flow. So any time the wall filter is increased, the system is less sensitive to slow flow

What can be done to reduct the presence of the artifact seen in the previous question?

Reduce or eliminate beam steering Grating lobes are usually relatively small compared to the main lobe when the sound beam is unstirred. But w beam steering (as in the trapezoidal display in this image), grating lobes become the more prominent in the image. one way to decrease grating lobes during the manufacturing process of ultrasound txd is to use a method calling sub-dicing, in which each major element is divided into smaller parts

***The technique of frame averaging (persistence) during real time acquisition is designed to:

Reduce random noise Frame averaging (also known as persistence) averages the data in pixels over successive frames. (The number of averaged frames it set by the user.) Slight movements of the txd or patient result in slight changes in the speckle pattern, so frame averaging has the effect of smoothing the image or reducing speckle. Additionally, electronic nose is smoothed

***If the frame rate is too slow for adequate temporal resolution, what action could you take to improve frame rate?

Reduce the number of transmit focal zones A pulse/listen cycle is required for each transmit focal zone, It follows, then, that as the number of zones are increased, the time required to create one frame is decreased.

Sonographic images are usually compressed before sending to PACS in order to

Reduce the time to transmit the image

***What is the result of increasing the wall filter during Doppler sampling?

Reduced display of low freq doppler signals The wall filter (also Known as high pass filter) is used to eliminate fro shifts below a set threshold from the display. If the filter is set at 50 Hz, then any freq shift of 50 Hz or less will not be displayed. Increasing the wall filter helps to elongate the high amplitude , low- freq shift signals caused by movement of the vessel wall. Nevertheless less, it must be kept i mind that low freq shifts may also be a result of slow flow. So any time the wall filter is increased, the system is less sensitive to slow flow

In this image of an artery there is a calcification w a dark vertical band extending beyond it (arrows). Which explanation best described the etiology of the dark band?

Reduction in signal amplitude in tissue distal to a highly attenuating or reflecting object

What sound tissue interaction is necessary to form an ultrasound image?

Reflection Reflection and scattering give rise to the echo signals that are displayed on the monitor

In ultrasound systems, the range equation is used to determine which of the following?

Reflector depth The range equation can be stated as: d = 1/2 ct Where d represents depth, c represents the speed of sound in tissue and t represents the round trip travel time. Bc the speed of sound in tissue is known (1540m/s) and the round trip travel time is calculated by counting the elapsed time between the transmit pulse and reception of the echo, the distance of the reflector can be determined. This is a basic principle of B mode imaging

At low velocities, the red blood cells adhere to one another forming multicellular clumps. This is termed:

Rouleau formation Is the stacking up of red blood cells that occurs at low velocities and low shear rates. This produces a larger echo and explains why the blood flow is sometimes visible in these cases. When the velocity increases, the rouleaux break up and the flow may no longer be visible

***If you wish to improve border definition, what imaging enhancement should you use?

Spatial compound imaging

Of the following, which is the best choice to help you demonstrate tissue boundaries that are not perpendicular to the sound beam?

Spatial compounding Spatial compounding is a method in which the sound beam is steered in multiple directions by employing time delays. The images from all of the steered frames are averaged together to produce one image for the display. The number of steered beams is usually chosen by the operator but varies from 3 to 9 or more The final composite image demonstrates tissue boundaries better than a single unsteered image bc more of the boundary is interrogated at angles approaching perpendicular

When you image sound reflected from a large smooth interface, you are observing results of:

Specular reflection

An echo from which one of the following sound reflectors is most dependent on the angle of incidence:

Specular reflector With specular reflection, the angle of reflection is equal to the angle of incidence. So in order to get most of the reflected sound to be angled back at the transducer, the transducer must be oriented so that the sound will strike the interface perpendicularly. That is why we get the best images of the kidney, aorta and similar structures when we have them positioned horizontally on the ultrasound image.

The speed of sound is defined as the:

Speed at which the sound wave propagates thru the medium

As a general observation about media in diagnostic sonography, sound propagates faster in material w greater:

Stiffness

Bulk modulus is closely related to which of the following qualities?

Stiffness

You are performing a sonographic exam and notice that the TI reading is 1. What does this indicate

The output level is high enough that temperature could increase as much as 1° C if the txd were held stationary

When you are educating your patient about the sonographic exam, sound travels thru air from your mouth to your patients ears. Which of the following is true regarding the speed of sound travel thru air?

The speed of sound in air is slower than the speed of sound in soft tissue Sound travels much more slowly in air than in soft tissue (approx 330 m/s vs 1540 m/s). The speed of sound in any medium does not approach the speed of light (approx 300,000 km/s in vacuum or air)

What imaging artifact is much worse on the left phantom image compared to the right phantom image?

Volume averaging

Which best describes the cardiac output?

Volume of blood pumped by the heart per minute

What is an advantage of single crystal or pure wave crystal txd?

Wide bandwidth

For a single txd to offer multiple freq selections for scanning, it must have:

Wide bandwidth W a wide bandwidth probe, a range of transmit freq is possible, This allows multiple freq to be selected w one probe

***Which color would represent an aliased doppler signal rom flow coursing away from the txd?

Yellow/orange

You are using a 5 MHz, 40 mm linear array txd to image a structure. What is the width of the image?

40 mm

Doppler pulses used for diagnostic purposes are typically ___ cycles long:

5-30

Which txd will detect the largest doppler freq shift?

A The txd labeled, A is firing its beam at a 0° angle to flow. For any given velocity of flow, the max freq shift will be obtained at 0°

Without interpolation, which of the following would best describe the resultant B mode image?

A series of scan lines w blank data between the lines Very early real time systems created images that looked like jail bars, in which the scan lines were displayed but the space between each pair of scan lines were displayed but the space between each pair of scan lines was left blank, Today, interpolation of the data is used to fill in the blank spaces to make the image appears smooth and continuous, even though it is still created by combining the values from surrounding scan lines

A linear array will produce which of the following image shapes?

A, C or E Shape A is the most typical of a linear array. Shape C occurs when the linear array is steered in both directions, resulting in a trapezoidal display. Shape E occurs when the linear array is steered in one direction

Use of a txd should be discontinued if a crack appears in the following area?

A,B,C,D Cracks in any areas of the txd will interfere w proper txd cleaning and maybe a source of electric shock

Which of the following describes sensitivity?

Ability of the system to detect weak echoes

Which txd would demonstrate a waveform above the zero baseline?

All except E

The rods depicted by the arrows in this phantom are used to determine what feature of the machine?

Axial resolution

During production of a sonogram, you image the following structures, which is the MOST attenuating?

Calcification

The shape corresponding to the image created by a phased array txd most closely corresponds to which of the following?

D

A standard for handling and transferring images and medical information between computers is?

DICOM Stands for digital imaging and communications in medicine

Increasing the freq on a multi freq rxd from 3.5 to 5 MHz will?

Decrease the wavelength

Which of the following best describes M mode:

Depth of reflectors along a single line of sight vs time

You can reduce beam width to improve spatial resolution in the image by which of the following?

Focusing

***What system control determines the amount of amplification that occurs in the receiver?

Gain

In order to focus a sound beam relatively far away from the txd, it is advantageous to:

Increase the diameter of the element

What benefit would you obtain by choosing a txd having a large diameter compared to one having a small diameter?

It can focus at greater depths

When an electric signal is applied to a piezoelectric element, what happens to the element?

It expands and contacts This expansion and contraction of the element produces the mechanical vibrations we call sound waves

With a 1D linear array, where in the out of plane dimension is the dimension of the sound beam the narrowest?

It is at the point of mechanical focusing Slice thickness w linear array txd is determined by the point of mechanical focusing along the width of the array. The depth of mechanical focusing is included in the txd data provided by the equipment manufacturer. Remember, the out of plane dimension is perpendicular to the imaging plane. You can think of it as the "thickness" of the beam

What txd component reduces reflection at the txd/skin interface?

Matching layer

Axial resolution is determined chiefly by:

Pulse duration

The packet size in color doppler refers to the number of?

Pulse/listens cycles per acoustic scan line For color doppler, each line of sight must be pulsed multiple times. The number of pulses per line is termed ensemble length, packet size, or pulse repetition freq. The number of those pulses fired on each scan line is the ensemble length

The unit of impedance is the:

Rayl

What artifact is being described in the previous question?

Refraction

Which artifact is associated w resonance of a gas bubble?

Ring down

What is the main advantage of using an intra cavitary probe compared to a standard txd?

Since the intra cavitary probe is closer to the area of interest, a higher freq txd can be used, resulting in superior spatial resolution

What defines the best axial resolution that can be obtained w a given txd?

Spatial pulse length ÷2

The term duty factor is defined as:

The fraction of time the txd is actively transmitting sound This value is quite low in diagnostic ultrasound, typically less than 0.01 (1%)

What best describes the difference between the ultrasound freq used for doppler and B mode imaging w a given txd?

The freq for doppler is usually lower than for imaging In general, the transmitted freq for doppler studies is lower than the imaging freq for a given txd. This relates to the different types of reflectors being evaluated in doppler (red blood cells) and imaging (tissue). Since the scattered echoes from blood are much weaker than echoes from tissue, lower req help overcome attenuation losses

W A mode, the strength of the echo signal is represented by?

The height of the spike

***In this color map, what color represents the highest positive doppler shift?

Yellow/orange

What parameter describes the axial length of the sampling volume for a color pixel?

color sample gate

The elapsed time between the transmitted pulse and the detected echo is 20 microseconds. How far is the interface from the txd?

2 cm To determine reflector depth, the sound trip travel time must be considered. Bc the speed of sound in tissue is 1540m/s, we can deduce that it travels at a rate of 6.5 microseconds in 1 centimeter. So a pulse of ultrasound takes a total time of 13 microseconds to travel to a reflector that is

Which of the following increases as freq increases?

-Absorption -Scattering -Attenuation

Which of the following could be a source of color doppler signal

-Blood flow -Breathing motion -Cardiac motion -Transducer motion In color doppler, the freq shift is color encoded. Any motion that occurs w in the path of the sound beam can produce a freq shift that may be color encoded. Blood flow is just one type of motion that may be detected by doppler

An ultrasound system preventive maintenance program should include?

-Cleaning of air filters -Visual inspection of probes -Txd testing -External cleaning of the system

What must be known to convert the doppler shift freq spectrum into velocities:

-Doppler freq _Angle of incidence _Speed of sound in tissue -Ultrasound freq The doppler freq is determined by the txd, the speed of sound in tissue is programmed into the system, and the doppler angle of incidence is measured by the user

What should you do to avoid nosocomial and cross infection w sonographic probes?

-Probe cleaning should aways proceed high level disinfection -Disinfection using a germicide compatible w the txd is indicated when the probe is in contact w mucous membranes Alone, covering the prove w a condom is insufficient. Proper cleaning of the probe both before and after the procedure is required. Alcohol wipes are not recommended by manufacturers as they will degrade the txd surface over time

What can you test w a doppler flow pattern?

-Range-gate accuracy -Spectral doppler velocity accuracy -Color doppler penetration

***When you select spatial compound imaging, which artifact is less likely to be observed?

-Refraction -Shadowing -Enhancement -Acoustic speckle Since the beam is steered at the anatomy from multiple directions and formed into a composite image, some artifacts are less likely to be observed w compound imaging

***The presence of the systolic spectral window of the doppler waveform is affected by:

-Sample volume size -Turbulent flow -Doppler gain -Position of the doppler sample volume The spectral window is the area underneath the systolic peak on the doppler waveform that is absent of echoes. The echo free window is filled in or "lost" when the doppler sample volume is large compared to the size of the vessel, when turbulent flow is present, when the doppler gain is set too high, or when the doppler sample volume is not centered within the vessel

***What limitation is present when you use high PRF doppler?

-Sensitivity to slow flow -Range resolution High PRF mode increases the number of pulses per second to the point that following any single transmit pulse, one two or more additional transmit pulses have been sent out along the doppler beam line before echoes arrive from the sample volume of interest. This introduces range ambiguities in the doppler signal. Doppler instruments show multiple sample volumes on the image when high PRF mode is activated. This helps the user avoid vessels at those locations that might produce superimposed signals. Sensitivity to slow flow is reduced w high PRF bc there is less time between the rapidly fired pulses to detect slow moving blood flow

Requirements of magnetic field tracking for 3D reconstruction include which of the following?

-The electromagnetic interference must be minimized -The txd must be in close proximity to the receiver -Ferrous metals must not be within the electromagnetic field Magnetic field tracking is a successful method of obtaining a 3D data set and is based on a six degree of freedom magnetic field sensor. A transmitter produces a magnetic field and the sensor (on the txd) receives the signal, allowing the position and angulation of the txd to be tracked (w in the field).

When color doppler is activated, i order to maintain frame rate, what may be reduced in the underlying B mode image?

-The number of focal zones -The scan line density To maintain an adequate frame rate in color doppler, the B mode image is compromised by reducing the number of zones to 1 or 2 and by reducing the scan line density, which results in lower lateral resolution

A typical value for the duty factor in diagnostic sonographic imaging is:

0.1% - 1% The duty factor is the time that the sound beam is actually on. W pulsed wave imaging, the fraction of time the sound is on is quite low bc the txd is listening most of the time

How many lines of sight are sampled and displayed on the monitor in A mode?

1

How many pulses per scan line are typically used to create the underlying B mode image when color doppler is active?

1-2

When color doppler is active, how many pulses per scan line are typically used to create the underlying B mode image?

1-2 For most ultrasound systems, even if multiple focal zones were in use for B mode imaging, once color doppler is selected the system automatically turns off all but one or two focal zones. Remember, to create the B mode image, a firing sequence producing a focused beam for each selected focal zone must be performed. So if 3 focal zones are selected, 3 complete pulse listen cycles must be performed for each line of sight. Color doppler requires multiple pulses (usually 6 or more) on each line of sight. This reduces the frame rate. If the underlying B mode image also required multiple pulses, the frame rate in color doppler would be very slow. The number of focal zones in B mode is usually reduced when color doppler is activated and then added back when the color is deactivated

You are using a linear array td to evaluate the thyroid gland. For standard B mode imaging, this txd most likely produces pulses of how many cycles?

1-3 Txd's used for diagnostic ultrasound are damped to improve axial resolution. Damping reduces the pulse duration and spatial pulse length. These txd's typically have pulse lengths of one to three cycles. Longer pulse trains carry more energy and provide greater penetration but give very poor axial resolution

What represents the number 1234 in scientific notation?

1.234 x 10-3 From 1234, move the decimal point to the left until you have a number between 1 and 10. The number of places you move the decimal point equals the power of 10 in the scienfific notation representation--in this case 10+3. Scientific notation is a convenient way to write both large and small numbers while at the same time conveying a send=se of their magnitude. For negative number , the decimal point is moved to the right until you have a number between 1 and 10. see table

Which txd will exhibit the LEAST amount of volume averaging?

1.5D or multi row array It allows electronic focusing in the elevational (out of plane) direction

Which sound beam freq would exhibit the greatest intensity loss w increasing depth?

10 MHz

Which probe would provide the best axial resolution to measure the thickness of a small structure?

10 MHz linear array Axial resolution improves w increasing freq

Which txd would provide the longest near zone length?

10 MHz, 6 mm diameter aperture The near zone length increases w increasing aperture The aperture is the size of the source of the sound

When your patient asks you how much longer the ultrasound will take, his voice is in the audible freq range. Which of the following freq is in the audible freq range?

10 kHz

One MHz equals:

10+6 Hz Cycles per second (Hz)

Which technology would be most helpful to obtain accurate anatomic volume measurements?

3D imaging Is helpful for measuring anatomic volumes, especially those that are irregularly shaped

In sonography, the term 4D imaging means:

3D imaging w the addition of time

What is meant by the term 4D imaging in sonography?

3D imaging w the addition of time A 3D sonographic image that is real time is termed 4D. The fourth dimension is time

What 2D limitation is addressed by 3D ultrasound imaging?

3D provides visibility of the coronal plane The coronal plane is not routinely imaged in most sonographic applications w 2D imaging. W 3D imaging, multiplayer reformatting can be performed to demonstrate an infinite number of scan planes, including the coronal plane.

The sound propagation speed is used to calibrate range measuring circuits on diagnostic sonography instruments is:

1540 m/ s This is considered the average sound speed in soft tissue. (Note: some modern scanners allow the assumed speed to be varied, particularly when imaging thru significant amounts of adipose tissue)

In order for distance measurements to be accurate in an ultrasound tissue phantom, the phantom should propagation speed must be?

1540 m/s

Which of the following freq is considered to be ultrasound?

2MHz 20, 200, and 2000 Hz are in the audible range from 20 Hz to 20,000 Hz) while 2 Hz is infrasonic. Freq greater than 20,000 Hz are ultrasonic

In this image below, how many transmit focal zones are being used?

3 The number of transmit focal zones is shown by an indicator on the screen. The symbol used varies somewhat by manufacturers but is clearly visible w one symbol per focal zone

You have selected a wide bandwidth txd w multiple transmit freq to perform a sonographic exam. Which transmit freq should you select for maximum penetration?

3 MHz

You are performing a carotid duplex exam w the following parameters: 5 MHz doppler freq, 6 kHz PRF, 4 cm depth and a 1.5 mm sample volume length. What is the aliasing freq?

3 kHz The only factor that is useful in determining the point of aliasing (Nyqyist limit) is the PRF. Aliasing occurs when the freq shift exceeds half the PRF

The mass you are imaging has a diameter of 35 mm. This value can also be expressed as:

3.5 cm

You are imaging a mass w a diameter of 35 mm. How else can this value be expressed?

3.5 cm

What conditions are most likely to result in turbulent flow?

5 mm vessel w 300 cm/ s flow velocity Flow becomes turbulent at high Reynolds numbers. The Reynolds number increases w increasing flow speed and enlarging tube diameter. This is why turbulence tends to occur in the post stenotic area-the vessel diameter is increased and the flow velocity is still high. The equation for the Reynolds number is as follows: Reynolds number = average flow speed x tube diameter x density

If you make a mistake in the measurement of the doppler angle, the error in velocity estimation will be greatest at which doppler angle?

70° A small mistake in measurement of the doppler angle results in a large error in velocity estimation as the angle or incidence increases, This is bc the cosine changes rapidly at large angles, Angles of 60° or less are recommended to reduce this error

You measured an area reduction of 90% in the artery showing this image. This is equal to a diameter reduction is:

75% Area percent stenosis and diameter percent stenosis are not equal A 50% diameter stenosis is approx equal to a 75% area stenosis and a 75% diameter stenosis is approx equal to a (0% stenosis

Which of the following minimizes the degree to which beam width varies w depth?

Dynamic aperture By varying the active aperture w depth, the beam width variation is reduced

Which of the following is NOT a function of the receiver?

Dynamic aperture Dynamic aperture is a function of the beam former and pulser. It is performed during transmit and receive beam forming

All of the following are functions of the receiver EXCEPT:

Dynamic aperture RF to video conversion Amplification Demodulation Compression --these are

The ratio of the largest to the smallest signal that a system can handle is termed?

Dynamic range

***What system control do you adjust to equalize the differences in echo amplitudes received from similar structures situated at different depth?

Dynamic range or compression

What type of focusing is performed by delay circuitry upon reception?

Dynamic receive focusing

The repetitive pattern seen in the far field of this image is most likely a result of:

Electric interference pattern An electric interference pattern may be seen on the display due to interference from nearby electric fields. Diagnostic ultrasound equipment does contain shielding to minimize this effect. Damage to shielding may result in more req appearance of the interference pattern

How is reflector depth determined w pulse echo ultrasound?

Echo arrival time Reflector depth is determined by measuring the elapsed time between the transmitted pulse and the reception of the echo

What physical concept allows us to determine the location of an interface by measuring the elapsed time between the transmitted pulsed ultrasound wave and the detected echo from that interferance?

Echo ranging Echo ranging involves use of the range equation w pulsed wave imaging to determine reflector depth

***While performing an ultrasound exam, you decide to adjust the system settings to improve the image. Which of the following is NOT user-adjustable

Echo time arrival -Freq -Power -Gain -Compensation Echo arrival time is determined by the medium thru which the sound travels

Which is an assumption of sonographic imaging that determines how detected echoes are mapped in the image?

Echoes originate from the most recently transmitted pulse It is always assumed that received echoes originate from themes recently transmitted pulse. After a pulse is generated, time is counted for each received echo until generation of the next pulse, which starts the time count all over again The depth of the echoes on the display is determined by the elapsed time between the pulse transmission and reception of the echo. Range ambiguity occurs when an echo from one pulse arrives after the next pulse has been generated

The txd you are using transmits wide bandwidth pulses whose freq content is 2-5 MHz. Which of the following most correctly described the reflected echo signals after they have traversed the tissue?

The echo signals will be shifted down in freq due to the increased attenuation of higher freq

The doppler freq shift is defined as:

The difference between the transmitted and received freq The doppler effect causes the transmitted doppler freq to be altered when it encounters a moving reflector. The freq is increased if teh reflector is moving toward the beam ad decreased if the reflector is moving away from the beam. The difference that occurs between the transmitted freq and the altered freq that is reflected back is known as the freq shift

***This doppler waveform is displayed below the zero baseline. Given the settings displayed in this image, which of the following is true?

The direction of flow is toward the beam The color box and spectral doppler cursor are steered toward the patient head. The doppler has been inverted. Therefore, flow toward the beam is indicated by the color blue and displayed below the zero baseline

The incoming raw echo signals must be compressed into a smaller dynamic range bc:

The display cannot accommodate the wide dynamic range of the incoming signals Bc the dynamic range of the system electronics and display is less than that of the raw echo data, it must be compressed into a useable range

***If you increase the doppler transmit freq which of the following will result?

The doppler freq shift will increase Increasing the doppler freq results in a larger freq shift for any given velocity, It will not affect the flow velocity. Penetration will decrease rather than increase. The frame rate is usually unaffected by freq changes. The Nyquist limit will not be affected

Aliasing is a potential problem in PW doppler bc of?

The doppler signal being sampled rather than recorded continuously Aliasing occurs bc the freq shifted signal is not adequately sampled. The sampling rate is set by the system pulse repetition freq (PRF. If the freq shift exceeds half the PRF, aliasing of the signal will occur

Which of the following statements about formation of the color doppler image is TRUE?

The color image is superimposed on the existing B mode image The color and B mode images are formed from separate pulses. The color information is super imposed on top of the existing B mode image. The freq used for color doppler is generally lower than the one used for the B mode image. The spatial resolution of the color image is generally lower compared to the B mode image in both axial and lateral dimensions

Pulsing of the transmitted sound wave is necessary for real time imaging bc:

The depth of the interface from which the echo originated can be determined Pulse -wave (PW) ultrasound determines the depth of origin of reflected echoes by use of the range equation. Since the speed of sound in tissue is known, the system can count the elapsed time after pulse transmission to when the echo is received and determine the depth from which the reflection originated