ARDMS SPI (Sonography Principles & Instrumentation) Exam — Questions and Answers

Question 1: Which effect describes the heating of tissue caused by the absorption of ultrasound energy?

Thermal bioeffect (Correct answer)
Cavitation
Piezoelectric effect
Doppler shift

Correct answer: Thermal bioeffect

Thermal bioeffects occur when absorbed ultrasound energy is converted to heat within tissue.

Question 2: Which statement best describes lateral resolution in ultrasound?

It is determined by beam width perpendicular to the beam axis (Correct answer)
It is determined by pulse length along the beam axis
It is independent of depth
It improves with lower frequency transducers

Correct answer: It is determined by beam width perpendicular to the beam axis

Lateral resolution depends on beam width; the narrower the beam at a given depth, the better the lateral resolution.

Question 3: In the Doppler equation, doubling the transmitted frequency while keeping all other variables constant will have what effect on the detected Doppler shift?

The Doppler shift will be halved
The Doppler shift will remain unchanged
The Doppler shift will double (Correct answer)
The Doppler shift will quadruple

Correct answer: The Doppler shift will double

Since Δf = 2f₀v cosθ / c, the Doppler shift is directly proportional to the transmitted frequency f₀; doubling f₀ doubles Δf when velocity, angle, and speed of sound remain constant.

Question 4: Which parameter directly determines the number of pixels used to represent a digital ultrasound image?

Frame rate
Bit depth
Matrix size (Correct answer)
Dynamic range

Correct answer: Matrix size

Matrix size (e.g., 512×512 or 1024×1024) defines the total number of pixels in the digital image grid.

Question 5: A sound wave with frequency of 5 MHz traveling through soft tissue (c = 1540 m/s) has a wavelength of approximately:

31 mm
0.031 mm
0.31 mm (Correct answer)
3.1 mm

Correct answer: 0.31 mm

λ = c / f = 1540 m/s ÷ 5,000,000 Hz = 0.000308 m ≈ 0.31 mm.

Question 6: If the propagation speed of sound increases while frequency remains constant, what happens to wavelength?

Wavelength stays the same
Wavelength becomes zero
Wavelength increases (Correct answer)
Wavelength decreases

Correct answer: Wavelength increases

Wavelength = propagation speed / frequency, so an increase in speed with constant frequency results in a longer wavelength.

Question 7: To optimize lateral resolution at a specific depth of interest, the sonographer should:

Increase the PRF
Increase the dynamic range
Decrease the transducer frequency
Adjust the focal zone to the depth of interest (Correct answer)

Correct answer: Adjust the focal zone to the depth of interest

Lateral resolution is best where the ultrasound beam is narrowest. The focal zone is the region of the beam with the minimum diameter. By adjusting the electronic focus to coincide with the anatomical structure of interest, the sonographer ensures the narrowest possible beam width at that location, thereby maximizing lateral resolution.

Question 8: At the near field (Fresnel zone) boundary, the beam diameter is approximately:

Equal to the wavelength
Half the transducer diameter (Correct answer)
Equal to the transducer radius
Twice the transducer diameter

Correct answer: Half the transducer diameter

At the last axial maximum (near-field/far-field boundary), the beam width is approximately half the transducer diameter.

Question 9: A sonographer tilts the transducer away from perpendicular when scanning a tendon. What effect does this have on the echogenicity of the tendon?

The tendon shows posterior shadowing
The tendon appears hyperechoic due to increased reflection
The tendon appears the same regardless of angle
The tendon appears hypoechoic due to anisotropy (Correct answer)

Correct answer: The tendon appears hypoechoic due to anisotropy

Tendons exhibit anisotropy; off-axis imaging reduces specular reflection from their parallel fibers, making them appear hypoechoic.

Question 10: A sonographer performing a color Doppler study of the carotid artery observes a mosaic pattern of colors in the center of the vessel where flow velocity is highest. This artifact is most likely:

Color bleed, which should be corrected by decreasing the color gain.
Clutter, which should be corrected by increasing the wall filter.
Aliasing, which should be corrected by increasing the PRF/Scale. (Correct answer)
Mirror image, which should be corrected by changing the Doppler angle.

Correct answer: Aliasing, which should be corrected by increasing the PRF/Scale.

The mosaic pattern in the area of highest velocity is the classic appearance of aliasing. This artifact occurs when the Doppler shift frequency exceeds the Nyquist limit (PRF/2). [12] The most direct way to correct this is to increase the Pulse Repetition Frequency (PRF), also known as the velocity scale, which raises the Nyquist limit and allows the system to display higher velocities correctly. [4]

Question 11: Which of the following best explains why QA phantoms must be stored at a controlled temperature?

Speed of sound in the phantom changes with temperature, affecting distance accuracy (Correct answer)
Color dyes in the phantom degrade above 25°C
Temperature changes alter the phantom's electrical impedance
Phantom radioactivity increases at higher temperatures

Correct answer: Speed of sound in the phantom changes with temperature, affecting distance accuracy

The speed of sound in phantom material is temperature-dependent; significant deviation from calibration temperature changes the apparent distances of internal targets.

Question 12: When evaluating a small vessel for low-velocity flow, which transducer choice optimizes color Doppler sensitivity?

Mechanical sector probe with maximum depth
High-frequency linear array with low PRF (Correct answer)
Phased array with wide color box
Low-frequency curved array with high PRF

Correct answer: High-frequency linear array with low PRF

A high-frequency linear array provides better spatial resolution for small vessels, and low PRF lowers the Nyquist limit to detect slow flow.

Question 13: How does increasing ultrasound frequency affect attenuation in soft tissue?

Attenuation first decreases then increases
Attenuation increases (Correct answer)
Attenuation is unaffected
Attenuation decreases

Correct answer: Attenuation increases

Attenuation increases with frequency because higher-frequency sound waves are more readily absorbed and scattered by tissue.

Question 14: What is the primary purpose of recording baseline QA images when a new ultrasound system is installed?

To satisfy Medicare billing requirements
To calibrate the DICOM network settings
To document the phantom's serial number
To establish reference measurements for future performance comparisons (Correct answer)

Correct answer: To establish reference measurements for future performance comparisons

Baseline images provide documented reference values so that subsequent QA tests can detect degradation in system performance over time.

Question 15: Which of the following best describes the concept of the Nyquist limit in pulsed-wave Doppler?

The maximum wall filter setting
The maximum Doppler shift frequency that can be unambiguously detected, equal to one-half the PRF (Correct answer)
The maximum depth from which a signal can be returned
The minimum detectable velocity

Correct answer: The maximum Doppler shift frequency that can be unambiguously detected, equal to one-half the PRF

The Nyquist limit is PRF/2; Doppler shifts exceeding this value cannot be correctly displayed and appear aliased (wrapped around the baseline).

Question 16: What hemodynamic effect does a vessel with increased compliance (elasticity) have on the Doppler waveform?

Higher peak systolic velocity
Increased resistivity index
Sharper systolic upstroke
Dampened pulsatility and smoother waveform (Correct answer)

Correct answer: Dampened pulsatility and smoother waveform

A compliant vessel absorbs systolic pressure energy by expanding, then recoils in diastole, dampening pulsatility and producing a smoother, less pulsatile waveform.

Question 17: A sample volume placed just distal to a significant arterial stenosis would be expected to show which spectral Doppler finding?

A normal monophasic low-resistance pattern
A turbulent, broadened waveform with elevated peak velocity and possible aliasing (Correct answer)
A high-resistance triphasic waveform with sharp systolic upstroke
Absent systolic peak with preserved diastolic flow

Correct answer: A turbulent, broadened waveform with elevated peak velocity and possible aliasing

Immediately distal to a stenosis, the high-velocity jet and turbulent post-stenotic flow cause spectral broadening, elevated velocities, and often aliasing on the PW Doppler tracing.

Question 18: The Mechanical Index (MI) is an on-screen indicator of the potential for which ultrasound bioeffect?

Tissue heating
Radiation force
Cavitation (Correct answer)
Microstreaming

Correct answer: Cavitation

The Mechanical Index (MI) is a value calculated to estimate the likelihood of non-thermal bioeffects, with the most significant being cavitation. Cavitation is the formation, growth, and collapse of gas bubbles in response to the pressure fluctuations of the ultrasound wave. The MI is directly related to the peak negative pressure and inversely related to the square root of the frequency.

Question 19: The Pulsatility Index (PI) is calculated as:

PSV / EDV
(PSV + EDV) / 2
(PSV - EDV) / TAMV (Correct answer)
(PSV - EDV) / PSV

Correct answer: (PSV - EDV) / TAMV

PI = (PSV - EDV) / TAMV (time-averaged mean velocity); unlike RI, PI can exceed 1.0 and can be calculated even when end-diastolic flow is zero or reversed.

Question 20: Which clinical scenario represents the LOWEST bioeffect risk from diagnostic ultrasound?

Continuous wave Doppler across the fetal aorta
Color Doppler evaluation of a renal transplant in an adult (Correct answer)
Pulsed Doppler of the fetal heart at 10 weeks gestation
Transcranial Doppler of fetal middle cerebral artery

Correct answer: Color Doppler evaluation of a renal transplant in an adult

Adult renal transplant evaluation has no embryonic sensitivity concern and involves tissue with normal repair capacity, making it the lowest-risk scenario listed.

Question 21: Which Doppler mode provides the best sensitivity for detecting slow-flow states such as organ perfusion?

Power Doppler (Correct answer)
Pulsed wave Doppler
Color flow Doppler
Continuous wave Doppler

Correct answer: Power Doppler

Power Doppler displays the amplitude (power) of the Doppler signal and is more sensitive to slow flow than color or pulsed wave Doppler.

Question 22: Which color Doppler parameter directly controls the number of pulses used to estimate each color pixel?

Color priority
Wall filter
Color gain
Ensemble length (packet size) (Correct answer)

Correct answer: Ensemble length (packet size)

Ensemble length (packet size) is the number of pulses per scan line used for color velocity estimation; more pulses improve sensitivity but reduce frame rate.

Question 23: A 'tardus-parvus' waveform pattern on spectral Doppler is characterized by:

A high-amplitude, sharp systolic peak with absent diastolic flow
A dampened waveform with slow systolic rise (tardus) and reduced peak amplitude (parvus), seen distal to a significant proximal stenosis (Correct answer)
Bidirectional flow above and below the baseline
A triphasic high-resistance waveform with reverse flow

Correct answer: A dampened waveform with slow systolic rise (tardus) and reduced peak amplitude (parvus), seen distal to a significant proximal stenosis

Tardus-parvus describes the delayed systolic upstroke (tardus = slow) and reduced amplitude (parvus = small) seen in vessels distal to a significant upstream stenosis due to energy loss across the obstruction.

Question 24: Increasing the dynamic range setting on the ultrasound unit will:

Increase the transmit power to deeper structures
Display more gray shades, producing a softer-appearing image (Correct answer)
Produce a higher contrast image with fewer gray shades
Narrow the range of displayed gray levels

Correct answer: Display more gray shades, producing a softer-appearing image

A wider displayed dynamic range maps more levels of echo amplitude into the gray scale, resulting in more subtle gray-scale gradations and a lower-contrast appearance.

Question 25: Increasing the depth setting on an ultrasound system will have what effect on frame rate?

Frame rate is unaffected
Frame rate decreases (Correct answer)
Frame rate increases
Frame rate doubles

Correct answer: Frame rate decreases

Increasing depth requires longer pulse travel time, reducing the number of frames that can be acquired per second.

Question 26: The far field (Fraunhofer zone) of an unfocused transducer is characterized by:

Beam divergence and degrading lateral resolution (Correct answer)
Beam convergence and improving lateral resolution
Constant beam width
Improved axial resolution

Correct answer: Beam divergence and degrading lateral resolution

In the far field the beam diverges, widening the beam and worsening lateral resolution.

Question 27: Frame rate in real-time ultrasound is most directly limited by:

Focal zone placement
Transducer frequency
The speed of sound and imaging depth (Correct answer)
Dynamic range setting

Correct answer: The speed of sound and imaging depth

Because the system must wait for echoes to return from maximum depth before firing the next pulse, imaging depth and the speed of sound directly limit frame rate.

Question 28: During a quality assurance check, a sonographer notes that small reflectors located in the first centimeter of the image, immediately below the transducer face, are not visible. This finding suggests a problem with which performance parameter?

Sensitivity
Dead zone (Correct answer)
Axial resolution
Lateral resolution

Correct answer: Dead zone

The dead zone is the region near the transducer face where imaging is inaccurate due to the time required for the system to switch from transmitting a pulse to receiving echoes. Reflectors within this zone may not be properly displayed. It is measured by finding the shallowest depth from which a uniform echo is displayed.

Question 29: A sonographer observes a strong, bright reflection from the diaphragm-lung interface, with a complete loss of signal (acoustic shadow) posterior to it. This is primarily due to:

High absorption in the lung tissue.
The critical angle being exceeded.
Significant refraction at the curved diaphragmatic surface.
A large mismatch in acoustic impedance. (Correct answer)

Correct answer: A large mismatch in acoustic impedance.

The interface between soft tissue (diaphragm) and air (lung) represents a very large acoustic impedance mismatch. Because of this significant difference, nearly all (over 99%) of the sound is reflected at this boundary. This strong reflection creates a bright echo, and the lack of transmitted sound results in an acoustic shadow posterior to the interface.

Question 30: A resistive index (RI) value close to 1.0 in a renal artery waveform suggests:

Absent or reversed diastolic flow (Correct answer)
Normal low-resistance flow
Elevated systolic velocity only
High diastolic flow

Correct answer: Absent or reversed diastolic flow

An RI near 1.0 indicates minimal or absent end-diastolic flow, suggesting markedly elevated distal resistance.

Question 31: The decibel (dB) scale is used in ultrasound because:

It directly measures wavelength
It simplifies multiplication of intensities into addition (Correct answer)
It makes calculations linear
It eliminates the need for gain adjustment

Correct answer: It simplifies multiplication of intensities into addition

The logarithmic dB scale converts large multiplicative intensity ratios into manageable additive numbers, matching human perception of loudness.

Question 32: Color Doppler 'color bruit' (perivascular color artifact) around an AV fistula is caused by:

Color bleed from high gain settings
Mirror image of the vessel
High-velocity turbulent flow causing tissue vibration that is detected as Doppler shifts (Correct answer)
Flash artifact from patient breathing

Correct answer: High-velocity turbulent flow causing tissue vibration that is detected as Doppler shifts

Tissue vibration from high-velocity turbulent flow in an AV fistula generates low-frequency Doppler shifts in surrounding soft tissue, producing a color bruit.

Question 33: Which control is adjusted to change the size of the color Doppler sample box?

Color box size/region of interest (Correct answer)
PRF
Color gain
Ensemble length

Correct answer: Color box size/region of interest

The color box size or region of interest control determines the area over which color Doppler information is displayed, directly affecting frame rate.

Question 34: When a tissue-mimicking phantom is scanned with a transducer at a frequency significantly higher than the phantom's design frequency, how does this typically affect the penetration depth result?

Penetration depth increases because resolution improves
Penetration depth decreases because higher-frequency sound attenuates faster (Correct answer)
Penetration depth is unchanged because the phantom speed of sound is fixed
Penetration depth doubles due to improved axial resolution

Correct answer: Penetration depth decreases because higher-frequency sound attenuates faster

Acoustic attenuation increases with frequency, so scanning at a higher frequency than the phantom's design frequency results in greater signal loss per centimeter and shallower penetration.

Question 35: A color Doppler image shows a mosaic pattern within a vessel lumen. This most likely indicates:

Incorrect wall filter setting
Laminar flow at high velocity
Turbulent or disturbed flow with aliasing (Correct answer)
Color bleed from adjacent tissue

Correct answer: Turbulent or disturbed flow with aliasing

A mosaic pattern of mixed colors represents turbulent flow combined with aliasing, commonly seen distal to a stenosis.

Question 36: Apodization in ultrasound beamforming refers to:

Varying element excitation amplitude across the aperture to reduce side lobes (Correct answer)
Setting the pulse repetition frequency
Adjusting time gain compensation at each depth
Increasing transmit power to all elements equally

Correct answer: Varying element excitation amplitude across the aperture to reduce side lobes

Apodization applies a weighting window (e.g., Hanning) to element amplitudes to suppress side lobes at a slight cost to main-lobe width.

Question 37: Which statement correctly describes the relationship between ultrasound frequency and cavitation threshold?

Cavitation only occurs at frequencies above 10 MHz
Higher frequency lowers the cavitation threshold, making it easier to induce
Lower frequency lowers the cavitation threshold, making cavitation more likely (Correct answer)
Frequency has no effect on cavitation threshold

Correct answer: Lower frequency lowers the cavitation threshold, making cavitation more likely

Lower frequencies produce longer rarefaction half-cycles that allow bubbles more time to grow, thereby lowering the pressure threshold required to initiate cavitation.

Question 38: Which of the following phantom measurements is most useful for evaluating the effectiveness of harmonic imaging compared to fundamental imaging?

Doppler velocity accuracy
Depth of penetration test
Caliper distance measurement
Contrast-detail analysis comparing anechoic cyst visibility (Correct answer)

Correct answer: Contrast-detail analysis comparing anechoic cyst visibility

Comparing anechoic cyst detectability between fundamental and harmonic modes reveals harmonic imaging's improvement in contrast resolution by reducing reverberation and clutter.

Question 39: A quality assurance program requires testing the system's ability to place echoes in their correct positions on the display, ensuring that a pin target appears in the same location whether imaged from the top or side of the phantom. Which parameter does this test evaluate?

Axial resolution
Dynamic range
Registration accuracy (Correct answer)
Uniformity

Correct answer: Registration accuracy

Registration accuracy is the ability of the system to display echoes in their proper anatomical positions on the screen. This test ensures that the system's internal coordinate system is correctly calibrated, so structures are mapped accurately in A-mode, B-mode, and M-mode.

Question 40: Which Doppler insonation angle range provides the most accurate velocity measurement?

60 degrees or less (Correct answer)
Angle does not affect velocity accuracy
75–90 degrees
61–74 degrees

Correct answer: 60 degrees or less

Angles of 60 degrees or less are recommended because the cosine function changes gradually in this range, minimizing the amplification of small angle errors in velocity calculations.

Question 41: A transducer with a low Q-factor is characterized by:

A narrow bandwidth and a short spatial pulse length.
A narrow bandwidth and a long spatial pulse length.
A wide bandwidth and a short spatial pulse length. (Correct answer)
A wide bandwidth and a long spatial pulse length.

Correct answer: A wide bandwidth and a short spatial pulse length.

The Quality factor (Q-factor) is the ratio of the center frequency to the bandwidth. A low Q-factor indicates a wide (or broad) bandwidth. Transducers with a wide bandwidth are heavily damped, which results in a short spatial pulse length (SPL). This combination is ideal for diagnostic imaging because a short SPL provides good axial resolution.

Question 42: Axial resolution is most correctly defined as the minimum distance between two reflectors that can be distinguished along:

The width of the beam
The direction of beam propagation (Correct answer)
The elevation plane
The Doppler axis

Correct answer: The direction of beam propagation

Axial resolution separates targets along the direction of sound travel, determined by spatial pulse length.

Question 43: The FDA regulatory limit for spatial-peak temporal-average intensity (ISPTA.3) for fetal/obstetric ultrasound is:

1000 mW/cm²
72 mW/cm² (Correct answer)
720 mW/cm²
430 mW/cm²

Correct answer: 72 mW/cm²

The FDA limits ISPTA.3 to 72 mW/cm² for fetal and neonatal cephalic applications to protect the developing fetus.

Question 44: While evaluating blood flow, a sonographer notices low-frequency, high-amplitude color signals originating from the vessel walls that obscure the true flow within the lumen. Which control should be adjusted to mitigate this specific artifact?

Doppler Angle
Wall Filter (Correct answer)
Color Gain
PRF/Scale

Correct answer: Wall Filter

The artifact described is clutter, or ghosting, which is caused by strong, low-frequency Doppler shifts from moving anatomy like vessel walls. [15] The Wall Filter is a high-pass filter specifically designed to eliminate these low-frequency signals, allowing the weaker, higher-frequency signals from blood flow to be displayed more clearly. [16]

Question 45: What is the primary purpose of the matching layer in a transducer?

Increase the transducer's center frequency
Reduce acoustic impedance mismatch between crystal and tissue (Correct answer)
Protect the piezoelectric element from mechanical damage
Absorb backward-propagating sound waves

Correct answer: Reduce acoustic impedance mismatch between crystal and tissue

The matching layer minimizes reflection at the crystal-tissue interface by presenting an intermediate acoustic impedance, maximizing energy transmission.

Question 46: In the context of obstetric ultrasound, TIS (Soft Tissue Thermal Index) is preferred over TIB (Bone Thermal Index) during which trimester?

Third trimester only
First trimester, before ossification is significant (Correct answer)
TIS and TIB are interchangeable throughout pregnancy
Second trimester, after limb bones are fully ossified

Correct answer: First trimester, before ossification is significant

TIS is used in the first trimester when fetal ossification is minimal; TIB becomes more relevant later when bone absorbs more ultrasound energy and heats significantly.

Question 47: Which artifact can make a non-vascular structure such as a simple cyst appear to contain color Doppler signal?

Acoustic shadowing
Bayesian noise
Twinkling artifact
Color bleed (blooming) (Correct answer)

Correct answer: Color bleed (blooming)

Excessive color gain (blooming) can cause color signal to spill into adjacent avascular structures such as simple cysts.

Question 48: Increasing the sample volume (gate) size in spectral Doppler will most likely:

Improve angle correction accuracy
Decrease wall filter artifact near the baseline
Reduce aliasing by increasing the Nyquist limit
Include more of the vessel lumen and potentially increase spectral broadening (Correct answer)

Correct answer: Include more of the vessel lumen and potentially increase spectral broadening

A larger sample volume captures flow across more of the vessel cross-section, including slower cells near the vessel walls, which introduces a wider range of velocities and increases spectral broadening.

Question 49: In harmonic imaging, the transducer transmits at frequency f₀ and receives at:

f₀
4f₀
f₀ / 2
2f₀ (Correct answer)

Correct answer: 2f₀

Tissue harmonic imaging transmits at the fundamental frequency f₀ and selectively receives the second harmonic at 2f₀, which is generated nonlinearly in tissue.

Question 50: A high-resistance spectral Doppler waveform is characterized by:

Absent systolic peak with preserved diastolic flow
Continuous forward flow throughout the entire cardiac cycle
High end-diastolic velocity with low peak systolic velocity
Low or absent end-diastolic velocity with a sharp systolic peak (Correct answer)

Correct answer: Low or absent end-diastolic velocity with a sharp systolic peak

High-resistance vessels (such as resting peripheral arteries) display a sharp systolic peak with little or no diastolic flow and may demonstrate brief flow reversal in early diastole.

Question 51: While performing a routine QA scan on a phantom with pins spaced exactly 30 mm apart vertically, a sonographer measures the distance between two pins as 32.5 mm. This indicates a potential issue with which system parameter?

Vertical distance accuracy (Correct answer)
Lateral resolution
Contrast resolution
System sensitivity

Correct answer: Vertical distance accuracy

Vertical distance accuracy assesses the system's ability to correctly measure distances parallel to the ultrasound beam's axis. A discrepancy between the known distance in the phantom and the measured distance on the system indicates a calibration error in depth measurement.

Question 52: Acoustic shadowing posterior to a gallstone is caused by:

Increased transmission through the stone's interface
Total reflection and high attenuation by the stone preventing sound transmission (Correct answer)
Constructive interference of side lobes behind the stone
Refraction of the beam around the calcification

Correct answer: Total reflection and high attenuation by the stone preventing sound transmission

Calcifications strongly reflect and absorb sound, so little energy passes through to deeper tissues, producing a dark shadow posteriorly.

Question 53: Dynamic receive focusing (dynamic aperture) in ultrasound systems:

Widens the beam on receive to improve elevational resolution
Increases the number of transmit pulses to improve lateral resolution
Changes transmit focus depth during a single pulse cycle
Continuously adjusts receive delays to focus at the depth from which echoes are returning (Correct answer)

Correct answer: Continuously adjusts receive delays to focus at the depth from which echoes are returning

As echoes return from progressively greater depths, the system continuously updates the receive time delays so the beam is always focused at the current echo depth, improving lateral resolution throughout the image.

Question 54: While scanning a patient's liver, you switch from a 3 MHz transducer to a 6 MHz transducer. Which of the following is the most likely consequence of this change?

Increased penetration depth
Decreased propagation speed
Increased attenuation of the ultrasound beam (Correct answer)
Decreased image resolution

Correct answer: Increased attenuation of the ultrasound beam

Attenuation, the weakening of the sound beam as it travels through tissue, is directly related to frequency. Higher frequency waves are attenuated more than lower frequency waves. Therefore, switching from a 3 MHz to a 6 MHz transducer will increase the attenuation rate. This leads to decreased penetration but improved axial resolution. Propagation speed is a property of the medium (liver tissue) and is not affected by the transducer frequency. [4, 5, 17]

Question 55: Rayleigh scattering is characterized by scatterers that are:

Equal in size to the wavelength
Much larger than the wavelength
Made of bone or calcified tissue only
Much smaller than the wavelength (Correct answer)

Correct answer: Much smaller than the wavelength

Rayleigh scattering occurs when scatterers (e.g., red blood cells) are much smaller than the ultrasound wavelength, scattering energy in all directions.

Question 56: The Doppler angle cursor should be aligned parallel to which structure during angle correction?

The beam axis
The transducer face
The vessel wall perpendicular to flow
The direction of blood flow (Correct answer)

Correct answer: The direction of blood flow

The angle correction cursor must be aligned parallel to the direction of blood flow so that the cosine of the angle can accurately correct the measured velocity.

Question 57: In B-mode imaging, increasing the time gain compensation (TGC) at depth primarily compensates for:

Grating lobe formation
Refraction artifact
Attenuation of the ultrasound beam (Correct answer)
Aliasing in Doppler

Correct answer: Attenuation of the ultrasound beam

TGC amplifies returning echoes from deeper structures to compensate for the progressive attenuation of the beam as it travels through tissue.

Question 58: Using electrical steering technology, spatial compounding can:

Enhance shadowing artifact
Increase frame rate
Improve temporal resolution
Decrease speckle artifact (Correct answer)

Correct answer: Decrease speckle artifact

Spatial compounding acquires multiple scan lines from different angles using electrical steering and then averages them to create a single composite image. By viewing structures from various perspectives, random noise and speckle artifacts, which are angle-dependent, are significantly reduced. This leads to a smoother image with improved contrast resolution and better visualization of tissue textures.

Question 59: The Nyquist limit for color Doppler is defined as:

Half the pulse repetition frequency (Correct answer)
The maximum detectable depth
The minimum detectable velocity
The maximum ensemble length

Correct answer: Half the pulse repetition frequency

The Nyquist limit equals PRF/2; velocities producing Doppler shifts above this threshold will alias and wrap to the opposite color.

Question 60: When depth is raised, which of the following happens?

Tframe shortens
Temporal resolution increases
Frame rate decreases (Correct answer)
Time of flight decreases

Correct answer: Frame rate decreases

When imaging depth is increased, the ultrasound pulse must travel a greater distance to and from the deepest reflector. This increases the 'time of flight' for each pulse, which in turn lengthens the pulse repetition period (PRP) and decreases the pulse repetition frequency (PRF). Since frame rate is directly proportional to PRF, an increase in depth ultimately leads to a decrease in the frame rate.

Question 61: A phased array transducer achieves electronic steering and focusing of the ultrasound beam by:

Mechanically moving the crystal elements.
Applying a curved acoustic lens to the transducer face.
Changing the thickness of the piezoelectric elements.
Introducing precise time delays to the excitation of individual elements. (Correct answer)

Correct answer: Introducing precise time delays to the excitation of individual elements.

Phased array transducers consist of multiple small piezoelectric elements that are activated in complex patterns. By introducing minute time delays (phasing) in the electrical pulses sent to each element, the resulting ultrasound wavefront can be steered in different directions and focused electronically without physically moving the transducer.

Question 62: When the Doppler angle correction cursor is positioned at 90 degrees, the calculated velocity will be:

Infinite or mathematically undefined (Correct answer)
Halved compared to the true velocity
Equal to the true velocity
Doubled compared to the true velocity

Correct answer: Infinite or mathematically undefined

At 90 degrees, cos(90°) = 0, making the denominator of the Doppler equation zero, which produces a mathematically undefined (infinite) velocity value.

Question 63: When a sound beam travels from muscle into fat, which phenomenon occurs because fat has a lower propagation speed?

Specular reflection
Absorption
Refraction (Correct answer)
Scattering

Correct answer: Refraction

Refraction occurs when sound crosses an interface at an oblique angle between media with different propagation speeds, causing the beam to bend.

Question 64: What artifact is produced when refraction causes the beam to miss its intended target?

Enhancement
Shadowing
Reverberation
Lateral displacement artifact (Correct answer)

Correct answer: Lateral displacement artifact

Refraction can displace the apparent position of a structure laterally, creating a lateral displacement artifact.

Question 65: What distinguishes grating lobes from side lobes in array transducers?

Grating lobes improve frame rate
Side lobes are more intense than grating lobes
Grating lobes arise from the periodic spacing of array elements, not from the element aperture (Correct answer)
Grating lobes only occur in phased arrays

Correct answer: Grating lobes arise from the periodic spacing of array elements, not from the element aperture

Grating lobes result from constructive interference due to the regular inter-element spacing of array transducers, while side lobes are inherent to any finite aperture.

Question 66: A heavily damped transducer will produce:

Higher amplitude and better penetration
Longer pulses and better axial resolution
Shorter pulses and better axial resolution (Correct answer)
Narrower beams and better lateral resolution

Correct answer: Shorter pulses and better axial resolution

Heavy damping reduces ringing, shortening the pulse and thus improving axial resolution.

Question 67: In M-mode echocardiography, what does the vertical axis represent?

Velocity
Time
Depth (distance from transducer) (Correct answer)
Frequency shift

Correct answer: Depth (distance from transducer)

In M-mode, the vertical axis shows depth from the transducer while the horizontal axis represents time.

Question 68: A sonographer performing an extended neonatal brain exam should be MOST concerned about which type of Thermal Index?

TIS — because soft tissue heating dominates in neonates
TI is irrelevant for neonatal imaging
TIB — because fetal bone is the target near the fontanelle
TIC — because the cranial bone is in the near field of the beam (Correct answer)

Correct answer: TIC — because the cranial bone is in the near field of the beam

TIC (Cranial Bone Thermal Index) applies when the beam passes through the skull in the near field, as the bone absorbs energy and heats the adjacent brain tissue.

Question 69: Poiseuille's Law states that blood flow through a vessel is most sensitive to changes in which parameter?

Pressure gradient
Blood viscosity
Vessel length
Vessel radius (Correct answer)

Correct answer: Vessel radius

Flow is proportional to the fourth power of radius; halving the radius reduces flow 16-fold, making radius by far the most powerful determinant of vascular resistance.

Question 70: What is the primary purpose of adjusting the focal zone position on an ultrasound system?

To increase overall image brightness
To maximize lateral resolution at a specific depth (Correct answer)
To reduce frame rate
To minimize shadowing artifact

Correct answer: To maximize lateral resolution at a specific depth

The focal zone is positioned at the depth of interest to minimize beam width and maximize lateral resolution at that location.

Question 71: Increasing the number of focal zones in a linear array will:

Increase temporal resolution
Reduce slice thickness
Improve lateral resolution throughout the image at the cost of frame rate (Correct answer)
Improve axial resolution

Correct answer: Improve lateral resolution throughout the image at the cost of frame rate

Multiple transmit focal zones improve lateral resolution over more depths but require multiple firings, reducing frame rate.

Question 72: The color Doppler 'ghosting' artifact differs from flash artifact in that ghosting:

Is caused by high gain rather than motion
Fills the entire color box
Appears as persistent color in a specific location after the source has moved (Correct answer)
Only occurs with power Doppler

Correct answer: Appears as persistent color in a specific location after the source has moved

Ghosting is a residual color signal that lingers at a location after a moving structure has passed, due to slow color frame updates.

Question 73: Epidemiological studies of diagnostic ultrasound in pregnancy have consistently shown:

No confirmed adverse outcomes at diagnostic exposure levels (Correct answer)
Elevated rates of fetal cardiac arrhythmia
Decreased birth weight in exposed fetuses
Increased incidence of childhood leukemia

Correct answer: No confirmed adverse outcomes at diagnostic exposure levels

Large epidemiological studies have not identified adverse pregnancy outcomes attributable to diagnostic ultrasound exposure at clinical levels.

Question 74: Which of the following best describes a low-resistance Doppler waveform?

Continuous forward flow throughout diastole with elevated end-diastolic velocity (Correct answer)
Triphasic flow pattern with reversal in early diastole
Sharp systolic peak with absent end-diastolic flow
Monophasic waveform with uniformly very low velocities

Correct answer: Continuous forward flow throughout diastole with elevated end-diastolic velocity

Low-resistance organs (kidney, brain, liver) require constant blood supply and maintain continuous forward flow throughout diastole, producing waveforms with elevated end-diastolic velocities.

Question 75: Which artifact is caused by the assumption that all echoes return along the central beam axis when they actually originate from a side lobe?

Shadowing
Enhancement
Side lobe artifact (Correct answer)
Comet tail artifact

Correct answer: Side lobe artifact

Side lobe artifacts are misregistered echoes from off-axis reflectors that the system incorrectly places along the main beam axis.

Question 76: Which clinical finding is associated with markedly increased peak systolic velocity (PSV) at a focal arterial segment?

Normal vessel anatomy
Focal arterial stenosis with hemodynamic significance (Correct answer)
Arteriovenous fistula distal to the site
Complete vessel occlusion

Correct answer: Focal arterial stenosis with hemodynamic significance

Flow accelerates as it passes through a stenotic segment due to reduced cross-sectional area, causing a focal jet with markedly elevated PSV.

Question 77: In digital ultrasound imaging, bit depth refers to:

The lateral width of the scan plane
The number of image frames stored per second
The maximum imaging depth in centimeters
The number of bits used to encode the gray-scale value of each pixel (Correct answer)

Correct answer: The number of bits used to encode the gray-scale value of each pixel

Bit depth determines how many distinct gray levels can be represented; 8-bit depth yields 256 gray levels.

Question 78: Increasing the amplitude of an ultrasound wave will directly increase its:

Acoustic power and intensity (Correct answer)
Propagation speed
Frequency
Wavelength

Correct answer: Acoustic power and intensity

Amplitude is proportional to pressure variation; acoustic intensity is proportional to amplitude squared, so larger amplitude means greater power and intensity.

Question 79: When the color Doppler gate is positioned at 90° to flow direction, the resulting color display will show:

No color signal (Correct answer)
Aliasing
Maximum color saturation
Reversed color assignment

Correct answer: No color signal

At 90° insonation angle the Doppler frequency shift is zero, so no color signal is generated.

Question 80: A sonographer observes that the spectral waveform on a Pulsed-Wave Doppler display appears to "wrap around" from the top of the scale to the bottom. This artifact is known as:

Aliasing (Correct answer)
Range ambiguity
Spectral broadening
Crosstalk

Correct answer: Aliasing

Aliasing occurs in PW Doppler when the measured Doppler shift exceeds the Nyquist limit (half the PRF). The system cannot sample the signal fast enough, causing the highest velocities to be incorrectly displayed on the opposite side of the baseline.

Question 81: A sonographer is optimizing a color Doppler image and notices that the color extends beyond the vessel walls into the surrounding stationary tissue. Which of the following adjustments should be made FIRST to correct this?

Decrease the color gain (Correct answer)
Change the Doppler angle
Decrease the wall filter
Increase the PRF/Scale

Correct answer: Decrease the color gain

When color appears in stationary tissue outside the vessel lumen, it is known as color bleed, blooming, or flash artifact. [13, 16] This is caused by the color gain being set too high, which over-amplifies the signal and noise. [7] The first and most appropriate action is to incrementally decrease the color gain until the color is confined within the vessel walls. [7, 13]

Question 82: The mechanical index (MI) is used to estimate the risk of:

Non-thermal (cavitation) bioeffects (Correct answer)
Image aliasing
Thermal damage to tissue
Grating lobe formation

Correct answer: Non-thermal (cavitation) bioeffects

The Mechanical Index estimates the likelihood of cavitation and other non-thermal mechanical bioeffects from ultrasound exposure.

Question 83: In a linear array transducer, electronic focusing in the elevation plane is achieved by:

Changing the PRF
Time-delay steering of individual elements
A fixed acoustic lens (Correct answer)
Variable aperture selection

Correct answer: A fixed acoustic lens

Elevation-plane focusing in a linear array is fixed and accomplished by a curved acoustic lens bonded to the transducer face.

Question 84: Active elements in 3D transducers are arranged in a particular pattern, or _________.

Straight
Arched
Backgammon
Checkerboard (Correct answer)

Correct answer: Checkerboard

Active elements in 3D transducers, also known as matrix arrays, are arranged in a two-dimensional pattern, commonly described as a checkerboard or grid. This arrangement allows for electronic steering and focusing in multiple planes (azimuth and elevation), enabling the acquisition of volumetric data necessary for three-dimensional imaging.

Question 85: The resistivity index (RI) is calculated as:

PSV / EDV
(PSV − EDV) / PSV (Correct answer)
(PSV − EDV) / EDV
(PSV + EDV) / 2

Correct answer: (PSV − EDV) / PSV

The Resistivity Index = (Peak Systolic Velocity − End Diastolic Velocity) / Peak Systolic Velocity, reflecting downstream vascular resistance.

Question 86: According to the U.S. Food and Drug Administration (FDA) guidelines, which principle should sonographers always follow to minimize patient exposure to ultrasound energy?

The Doppler Shift Principle
The Inverse Square Law Principle
The Principle of Maximum Intensity
The As Low As Reasonably Achievable (ALARA) Principle (Correct answer)

Correct answer: The As Low As Reasonably Achievable (ALARA) Principle

The FDA, along with other regulatory and professional bodies like the AIUM, advocates for the prudent use of diagnostic ultrasound by following the As Low As Reasonably Achievable (ALARA) principle. This means using the lowest output power and shortest scan time that will yield diagnostic-quality images, thereby minimizing the patient's exposure to potential bioeffects.

Question 87: A sonographer compares current QA phantom images to baseline and notes reduced image brightness at depth despite unchanged gain settings. What is the most likely cause?

The phantom has been stored too cold
Transducer sensitivity has decreased due to element degradation (Correct answer)
The PRF was inadvertently lowered
The monitor brightness has increased

Correct answer: Transducer sensitivity has decreased due to element degradation

Decreased transducer sensitivity from element aging or damage reduces the amplitude of returning echoes, manifesting as reduced brightness at depth.

Question 88: In pulsed wave Doppler, aliasing occurs when the Doppler shift frequency exceeds:

One-half the pulse repetition frequency (Nyquist limit) (Correct answer)
The center frequency of the transducer
The wall filter setting
The frame rate

Correct answer: One-half the pulse repetition frequency (Nyquist limit)

Aliasing occurs when the detected Doppler shift exceeds the Nyquist limit, which is half the PRF.

Question 89: A mirror-image artifact occurs because of:

Side-lobe energy producing duplicate echoes
Attenuation differences creating ghost images
Refraction bending the beam to display two copies of a structure
Strong specular reflection at a curved or flat interface causing double registration (Correct answer)

Correct answer: Strong specular reflection at a curved or flat interface causing double registration

A strong specular reflector (e.g., diaphragm) re-reflects echoes back to a structure, causing its mirror image to appear on the other side.

Question 90: Which artifact occurs when a strong reflector redirects the ultrasound beam so that a structure appears to exist on the opposite side of the reflector?

Mirror-image artifact (Correct answer)
Grating-lobe artifact
Comet-tail artifact
Side-lobe artifact

Correct answer: Mirror-image artifact

A mirror-image artifact is produced when a specular reflector (e.g., the diaphragm) acts as an acoustic mirror, reflecting the beam toward a real structure whose duplicate appears on the far side of the reflector.

Question 91: Demodulation in ultrasound signal processing refers to:

Digitizing the analog echo signal
Steering the beam electronically to different angles
Applying time-gain compensation to raw RF data
Removing the radiofrequency carrier to extract the envelope of the echo signal (Correct answer)

Correct answer: Removing the radiofrequency carrier to extract the envelope of the echo signal

Demodulation (envelope detection) extracts the amplitude envelope from the high-frequency RF echo signal, which represents tissue reflectivity and is used to build the gray-scale image.

Question 92: Which of the following is a primary advantage of Continuous-Wave (CW) Doppler over Pulsed-Wave (PW) Doppler?

It offers better axial resolution in the image.
It uses a single crystal for both transmission and reception.
It is not limited by aliasing at high velocities. (Correct answer)
It provides superior range resolution.

Correct answer: It is not limited by aliasing at high velocities.

Continuous-Wave (CW) Doppler continuously transmits and receives ultrasound, so it does not have a sampling rate (PRF) that limits velocity measurement. This allows it to accurately measure very high velocities without the aliasing artifact that affects Pulsed-Wave (PW) Doppler.

Question 93: What is the primary acoustic effect that enables Doppler ultrasound to detect moving blood cells?

Increased attenuation of sound by erythrocytes
The Doppler effect: frequency shift in echoes from moving reflectors (Correct answer)
Impedance mismatch at the blood-vessel wall interface
Refraction of the sound beam by flowing blood

Correct answer: The Doppler effect: frequency shift in echoes from moving reflectors

Moving red blood cells shift the frequency of the returning echo relative to the transmitted frequency; this Doppler frequency shift is proportional to velocity.

Question 94: Which artifact causes a color Doppler signal to appear on the opposite side of a strong reflector at the same depth?

Range ambiguity
Mirror image artifact (Correct answer)
Aliasing
Acoustic enhancement

Correct answer: Mirror image artifact

Mirror image artifact duplicates the Doppler signal symmetrically on the opposite side of a specular reflector such as the pleura.

Question 95: Tissue harmonic imaging improves image quality primarily by:

Doubling the pulse repetition frequency
Applying a band-pass filter centered on the fundamental frequency
Increasing the transmit frequency beyond the transducer's rated bandwidth
Using the second harmonic frequency generated within tissue to form the image (Correct answer)

Correct answer: Using the second harmonic frequency generated within tissue to form the image

As sound propagates through tissue, nonlinear distortion generates harmonic frequencies; imaging at the second harmonic reduces near-field artifact and clutter because harmonics build up away from the transducer.

Question 96: The ability of an ultrasound system to distinguish between two adjacent tissues based on their different echogenicities is known as:

Spatial resolution
Axial resolution
Contrast resolution (Correct answer)
Temporal resolution

Correct answer: Contrast resolution

Contrast resolution is the ability to differentiate structures with slightly different amplitudes or brightness levels on the display. It allows the system to distinguish between tissues based on their echogenicity. This is distinct from spatial resolution (axial and lateral), which relates to distinguishing separate objects in space, and temporal resolution, which relates to motion.

Question 97: During an abdominal ultrasound, a sonographer decides to increase the line density to improve lateral resolution. Which of the following is an expected trade-off for this adjustment?

Decreased frame rate (Correct answer)
Improved axial resolution
Increased penetration depth
Decreased contrast resolution

Correct answer: Decreased frame rate

There is an inverse relationship between line density and frame rate. Increasing the number of scan lines (line density) in a single frame improves lateral resolution by sampling the tissue more finely. However, because each line requires a pulse-listen cycle, adding more lines increases the total time needed to build one frame. This increase in frame acquisition time results in a lower frame rate, thus degrading temporal resolution.

Question 98: The systolic-to-diastolic (S/D) ratio used in obstetric Doppler is calculated as:

PSV / EDV (Correct answer)
EDV / PSV
(PSV - EDV) / TAMV
(PSV - EDV) / PSV

Correct answer: PSV / EDV

The S/D ratio = PSV / EDV and is commonly used in umbilical artery Doppler to assess placental resistance; it cannot be calculated when EDV is absent.

Question 99: Which of the following best defines 'insonation angle' in Doppler ultrasound?

The angle of the spectral display baseline
The angle between two transducer crystals in a CW probe
The angle between the ultrasound beam axis and the direction of blood flow (Correct answer)
The angle of the sample volume gate relative to the vessel wall

Correct answer: The angle between the ultrasound beam axis and the direction of blood flow

The insonation angle (also called the Doppler angle or angle of incidence) is the angle between the ultrasound beam and the direction of blood flow, which must be known for accurate velocity calculation.

Question 100: Which index displayed on modern ultrasound systems specifically relates to the risk of acoustic cavitation?

Pulsatility Index
Thermal Index (TI)
Dynamic Range Index
Mechanical Index (MI) (Correct answer)

Correct answer: Mechanical Index (MI)

The Mechanical Index (MI) quantifies the likelihood of cavitation by comparing peak negative pressure to the square root of frequency.

Question 101: A sonographer performs a sensitivity test as part of a quality assurance protocol. This test is designed to assess the system's ability to:

distinguish between two closely spaced objects perpendicular to the beam.
detect and display weak echoes from deep structures. (Correct answer)
accurately measure the size of an anechoic structure.
maintain uniform brightness of echoes from similar structures at the same depth.

Correct answer: detect and display weak echoes from deep structures.

Sensitivity, also known as maximum depth of penetration, evaluates the ability of the ultrasound system to detect and display the weakest-amplitude echoes from reflectors located deep within a phantom. It is a measure of the system's overall performance in penetrating tissue and receiving faint signals.

Question 102: Dynamic range in ultrasound refers to:

The maximum frame rate achievable at a given depth
The ratio of the largest to smallest echo amplitudes the system can process and display (Correct answer)
The bandwidth of frequencies included in the transmit pulse
The range of depths over which the system can focus

Correct answer: The ratio of the largest to smallest echo amplitudes the system can process and display

Dynamic range (expressed in dB) describes the span between the strongest and weakest signals that can be meaningfully represented, influencing the number of displayed gray levels.

Question 103: A sonographer freezes an image and then activates the zoom function to enlarge a specific area of interest. This action results in larger pixels and does not improve spatial resolution. Which type of magnification was used?

Read magnification (Correct answer)
Acoustic magnification
Focal magnification
Write magnification

Correct answer: Read magnification

Read magnification is a postprocessing function that is applied to a frozen image. It takes the existing pixel data stored in the scan converter and simply enlarges it, making each pixel bigger. Because no new data is acquired, the spatial resolution is not improved and may even appear degraded. Write magnification, a preprocessing function, would rescan the area live to create a new image with more pixels, thereby improving spatial resolution.

Question 104: When assessing depth of penetration during QA, what endpoint is typically used to define maximum usable depth?

The point where the focal zone ends
The depth where frame rate drops below 15 Hz
The depth at which TGC compensation reaches maximum
The deepest depth at which a uniform speckle pattern is still visible (Correct answer)

Correct answer: The deepest depth at which a uniform speckle pattern is still visible

Penetration depth is defined as the greatest depth at which the speckle pattern from the tissue-mimicking material is still discernible above noise.

Question 105: Which of the following best describes the role of the physics QA physicist or qualified medical physicist in an ultrasound department?

Writing billing codes for ultrasound examinations
Calibrating DICOM network connections between scanners
Performing all clinical scans requiring QA phantom images
Overseeing and validating the QA program, interpreting results, and recommending corrective actions (Correct answer)

Correct answer: Overseeing and validating the QA program, interpreting results, and recommending corrective actions

The medical physicist oversees the QA program, interprets performance data, identifies equipment deficiencies, and recommends or validates corrective actions before systems return to clinical use.

Question 106: Specular reflection occurs when sound strikes a boundary that is:

Rough relative to the wavelength
Smaller than the wavelength
Angled at 90° to the beam
Large and smooth relative to the wavelength (Correct answer)

Correct answer: Large and smooth relative to the wavelength

Specular reflectors are large, flat, smooth surfaces that reflect sound at an angle equal to the incident angle, like a mirror.

Question 107: Which transducer type uses a rotating or wobbling mechanical element to sweep the beam?

Linear array
Mechanical transducer (Correct answer)
Phased array
Annular array

Correct answer: Mechanical transducer

Mechanical transducers use a physically moving element to sweep the ultrasound beam across the imaging plane.

Question 108: What happens to wavelength as ultrasound travels from soft tissue into bone?

Wavelength decreases because propagation speed is lower in bone
Wavelength decreases because frequency increases in bone
Wavelength increases because propagation speed is higher in bone (Correct answer)
Wavelength remains the same; only frequency changes

Correct answer: Wavelength increases because propagation speed is higher in bone

Bone has a higher propagation speed (~4080 m/s) than soft tissue; since frequency is constant, wavelength = c/f increases.

Question 109: Which statement about ultrasound bioeffects in diagnostic imaging is most accurate based on current evidence?

Thermal bioeffects are impossible below 1 MHz
No confirmed hazardous bioeffects exist at diagnostic levels, but prudent use is advised (Correct answer)
Cavitation is impossible with modern digital systems
Confirmed hazardous bioeffects have been documented at diagnostic exposure levels

Correct answer: No confirmed hazardous bioeffects exist at diagnostic levels, but prudent use is advised

No independently confirmed hazardous bioeffects have been established at diagnostic exposure levels, yet prudent minimization of exposure (ALARA) remains the standard of care.

Question 110: Which statement about annular array transducers is TRUE?

They focus symmetrically in all planes but require mechanical steering for scanning (Correct answer)
They provide electronic beam steering in all directions
They have lower near-field resolution than linear arrays
They are preferred for cardiac imaging due to their small footprint

Correct answer: They focus symmetrically in all planes but require mechanical steering for scanning

Annular arrays provide symmetric (round) electronic focusing in all planes but cannot steer electronically, requiring mechanical wobbling or rotation to sweep the beam.

Question 111: A sonographer is using a transducer with a heavy backing material. Which of the following is a primary consequence of this design feature?

Increased spatial pulse length
Narrower bandwidth
Improved axial resolution (Correct answer)
Increased sensitivity

Correct answer: Improved axial resolution

The backing (or damping) material absorbs the backward-directed ultrasound energy and dampens the crystal's ringing. This shortens the spatial pulse length (SPL), which is crucial for improving axial resolution, the ability to distinguish two structures that are close to each other along the beam's path. A shorter SPL results in better axial resolution. Heavy damping leads to a wider bandwidth and decreased sensitivity.

ARDMS SPI (Sonography Principles & Instrumentation) Exam

The ARDMS SPI (Sonography Principles & Instrumentation) Exam exam validates essential knowledge and skills required for certification or licensure in this field.

110

Questions

120 min

Time Limit

70%

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