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

Question 1: When PRF is increased to correct aliasing, which undesirable consequence may occur?

Improved sensitivity to low-velocity flow near the baseline
Increased wall thump artifact at the baseline
Range ambiguity — inability to unambiguously sample deep vessels (Correct answer)
Decreased temporal resolution of the waveform

Correct answer: Range ambiguity — inability to unambiguously sample deep vessels

High PRF sends pulses before previous echoes return from deep structures, so the system cannot determine which echo came from which pulse depth, creating range ambiguity artifact.

Question 2: The Doppler equation states that the Doppler shift is directly proportional to which of the following?

The cosine of the Doppler angle only
The pulse repetition period
The sample volume depth
The transmitted frequency, flow velocity, and cosine of the Doppler angle (Correct answer)

Correct answer: The transmitted frequency, flow velocity, and cosine of the Doppler angle

The Doppler shift (Δf) = 2 × f₀ × v × cos θ / c, meaning it is directly proportional to the transmitted frequency, flow velocity, and the cosine of the angle between the beam and flow direction.

Question 3: Increasing the wall filter setting on a spectral Doppler display will:

Decrease the pulse repetition frequency
Remove low-frequency signals from the spectral display (Correct answer)
Remove high-frequency signals from the spectral display
Increase the Nyquist limit

Correct answer: Remove low-frequency signals from the spectral display

The wall filter (high-pass filter) eliminates low-frequency Doppler signals produced by slow-moving vessel walls and surrounding tissue, reducing clutter near the baseline.

Question 4: In the context of obstetric ultrasound, TIS (Soft Tissue Thermal Index) is preferred over TIB (Bone Thermal Index) during which trimester?

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

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

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

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 6: Non-specular (diffuse) reflectors differ from specular reflectors in that they:

Only reflect when struck perpendicularly
Scatter sound in many directions regardless of beam angle (Correct answer)
Require higher frequency to produce echoes
Produce echoes proportional to acoustic impedance alone

Correct answer: Scatter sound in many directions regardless of beam angle

Non-specular (diffuse) reflectors have irregular or small surfaces that scatter sound in all directions, making them angle-independent.

Question 7: An artifact that results from excessive color gain is known as:

Color bleed
Color funfetti
Color confetti (Correct answer)
Crosstalk

Correct answer: Color confetti

Color confetti is an artifact that occurs when the color gain in Doppler ultrasound is set excessively high. It manifests as random, spurious color pixels appearing throughout the image, often outside of vessels or in areas of no flow. This happens because the system amplifies even very weak noise signals to the point where they are incorrectly interpreted and displayed as blood flow.

Question 8: Using electrical steering technology, spatial compounding can:

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

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 9: Which material property of a tissue-mimicking phantom most directly simulates the acoustic attenuation of soft tissue?

Impedance mismatch between gelatin layers
Attenuation coefficient of approximately 0.5 dB/cm/MHz (Correct answer)
Speed of sound set to 1540 m/s
Density equal to water at 37°C

Correct answer: Attenuation coefficient of approximately 0.5 dB/cm/MHz

Soft tissue has an attenuation coefficient of ~0.5 dB/cm/MHz, and QA phantoms are formulated to match this value for realistic signal depth behavior.

Question 10: Which of the following is NOT a mechanism of ultrasound attenuation in tissue?

Reflection
Absorption
Refraction (Correct answer)
Scattering

Correct answer: Refraction

Refraction redirects the beam but does not remove energy from it, so it is not an attenuation mechanism; absorption, reflection, and scattering all reduce beam intensity.

Question 11: Which ultrasound mode typically produces the highest time-averaged acoustic intensity and greatest potential for thermal bioeffects?

B-mode imaging
M-mode
Harmonic imaging
Pulsed-wave Doppler (Correct answer)

Correct answer: Pulsed-wave Doppler

Pulsed-wave Doppler has a high duty factor and focuses the beam on a small sample volume, resulting in the highest time-averaged intensity and greatest heating potential.

Question 12: Compared to pulsed-wave (PW) Doppler, which statement about continuous-wave (CW) Doppler is TRUE?

CW uses a range gate to precisely localize the sample volume
CW cannot measure high velocities without aliasing
CW provides superior depth resolution compared to PW
CW has no Nyquist limit and can measure very high velocities without aliasing (Correct answer)

Correct answer: CW has no Nyquist limit and can measure very high velocities without aliasing

CW Doppler continuously transmits and receives simultaneously; because it does not use pulsed sampling, it has no PRF and therefore no Nyquist limit, allowing measurement of very high velocities — at the cost of range discrimination.

Question 13: During QA of a color Doppler system using a flow phantom, the color signal disappears below a certain depth. What does this finding most likely indicate?

The wall filter setting is too low
Doppler sensitivity has degraded at depth, possibly due to element dropout (Correct answer)
The PRF is set too high for the depth
The color map is inverted

Correct answer: Doppler sensitivity has degraded at depth, possibly due to element dropout

Loss of color Doppler signal at depth despite adequate flow in the phantom suggests reduced sensitivity, often from failing transducer elements that cannot detect low-amplitude Doppler shifts at distance.

Question 14: 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
Increase the PRF/Scale
Decrease the wall filter

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 15: Which imaging scenario is MOST likely to produce a refraction artifact causing a false double image of a structure?

Scanning through the rectus abdominis muscle edge into deeper tissue (Correct answer)
Imaging a gallstone with acoustic shadowing
Scanning a cyst in a homogeneous liver
Using a linear transducer on a flat superficial tendon

Correct answer: Scanning through the rectus abdominis muscle edge into deeper tissue

The curved edge of the rectus abdominis acts as a refracting lens, splitting the beam and creating a duplicated image of deeper structures.

Question 16: A 5 MHz transducer in soft tissue (c = 1540 m/s) produces a wavelength of approximately:

0.03 mm
3.1 mm
0.62 mm
0.31 mm (Correct answer)

Correct answer: 0.31 mm

λ = c/f = 1540/5,000,000 ≈ 0.308 mm ≈ 0.31 mm.

Question 17: Which artifact can make a non-vascular structure such as a simple cyst appear to contain color Doppler signal?

Acoustic shadowing
Twinkling artifact
Bayesian noise
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 18: The effective radiating area (ERA) of a transducer is always:

Determined solely by the frequency of operation
Greater than its geometric face area due to fringing effects
Less than its geometric face area (Correct answer)
Equal to its geometric face area

Correct answer: Less than its geometric face area

The ERA is the area that actually produces ultrasound energy and is always somewhat less than the total geometric area of the transducer face because edge regions vibrate less effectively.

Question 19: The phrase that best expresses this is "amplifying image contrast directly at structure boundaries"

Frequency compounding
Edge enhancement (Correct answer)
Spatial compounding
Fill-in interpolation

Correct answer: Edge enhancement

Edge enhancement is a post-processing technique designed to improve the visual clarity of anatomical structures. It works by selectively amplifying the contrast at the boundaries between different tissues or structures, making the edges appear sharper and more defined. This process enhances the perception of detail without altering the raw data.

Question 20: During a renal artery duplex examination, the acceleration time (AT) from a waveform sampled in the intrarenal arteries is measured at 0.12 seconds. This finding is:

Normal because AT should always exceed 0.10 s
Abnormal; AT >0.07 s (some labs use >0.10 s) suggests hemodynamically significant proximal renal artery stenosis (Correct answer)
Normal; AT <0.07 s is the threshold for significant stenosis
Irrelevant; only PSV is used for renal artery evaluation

Correct answer: Abnormal; AT >0.07 s (some labs use >0.10 s) suggests hemodynamically significant proximal renal artery stenosis

Acceleration time >0.07–0.10 seconds in intrarenal waveforms is associated with proximal renal artery stenosis; the prolonged upstroke reflects dampening of the waveform distal to the obstruction.

Question 21: 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 attenuation of the ultrasound beam (Correct answer)
Decreased image resolution
Decreased propagation speed
Increased penetration depth

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 22: What is the primary disadvantage of continuous-wave (CW) Doppler compared to pulsed-wave (PW) Doppler?

It requires a higher PRF setting
It produces more noise artifacts
It cannot detect high-velocity flow
It has no range resolution and cannot localize the depth of flow (Correct answer)

Correct answer: It has no range resolution and cannot localize the depth of flow

CW Doppler uses two separate crystals (one transmitting, one receiving continuously), so it cannot determine the depth of origin of Doppler signals — it samples all velocities along the entire beam path.

Question 23: How does the presence of a gas bubble affect ultrasound beam propagation?

It selectively absorbs low frequencies
It increases refraction but not reflection
It enhances transmission due to low density
It causes near-total reflection and distal shadowing (Correct answer)

Correct answer: It causes near-total reflection and distal shadowing

Gas has very low acoustic impedance, creating an extreme mismatch with tissue that reflects almost all incident energy and shadows structures behind it.

Question 24: What is the main advantage of power Doppler over conventional color flow Doppler?

It measures velocity more accurately
It eliminates the need for the wall filter
It has greater sensitivity for detecting slow or low-volume flow and is less angle-dependent (Correct answer)
It shows the direction of flow

Correct answer: It has greater sensitivity for detecting slow or low-volume flow and is less angle-dependent

Power Doppler displays the amplitude (power) of the Doppler signal rather than the mean frequency shift, making it more sensitive to slow flow and virtually angle-independent, though it sacrifices directional and velocity information.

Question 25: The ALARA principle in diagnostic ultrasound instructs operators to:

Avoid Doppler modes in all obstetric exams
Always use maximum power for best image quality
Keep acoustic output as low as reasonably achievable while obtaining diagnostic information (Correct answer)
Limit scanning time to no more than 5 minutes per session

Correct answer: Keep acoustic output as low as reasonably achievable while obtaining diagnostic information

ALARA (As Low As Reasonably Achievable) requires using the minimum acoustic output necessary to obtain clinically useful images.

Question 26: A sonographer is scanning a patient with a known lung consolidation. They should be particularly mindful of the Mechanical Index (MI) because:

The MI is always highest in the far field of the image.
Thermal effects are amplified in air-filled structures.
Consolidated lung tissue is more susceptible to overheating.
Gas bubbles present in the lung are nuclei for cavitation. (Correct answer)

Correct answer: Gas bubbles present in the lung are nuclei for cavitation.

The Mechanical Index (MI) indicates the risk of cavitation, which is the interaction of sound waves with gas bubbles. Tissues that contain gas, such as the lungs and intestines, are more susceptible to cavitation bioeffects because the pre-existing gas bubbles can act as nuclei for this phenomenon. Therefore, sonographers should be extra cautious and monitor the MI when imaging near or within such structures.

Question 27: A phased array transducer steers and focuses the beam primarily by adjusting:

The size of the active aperture only
Time delays applied to individual element firings (Correct answer)
The physical curvature of the array
The frequency of each element independently

Correct answer: Time delays applied to individual element firings

Phased arrays use programmable electronic time delays across all elements to steer and dynamically focus the beam in real time.

Question 28: The systolic-to-diastolic (S/D) ratio used in obstetric Doppler is calculated as:

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

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

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

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 30: Scattering of ultrasound is most likely to occur when the reflecting structure is:

Much larger than the wavelength
A perfect flat surface
Similar in size or smaller than the wavelength (Correct answer)
Located at the transducer face

Correct answer: Similar in size or smaller than the wavelength

Non-specular (diffuse) scattering occurs when reflectors are small relative to wavelength, producing omnidirectional echoes used in gray-scale imaging.

Question 31: A spectral Doppler waveform displaying a mirror image of the true waveform simultaneously on both sides of the baseline is most likely caused by:

Aliasing due to velocity exceeding the Nyquist limit
Insonation angle of 90 degrees creating a bidirectional artifact
Doppler gain set too high, causing cross-talk (ghosting) artifact (Correct answer)
Wall filter set too low, allowing vessel wall signals through

Correct answer: Doppler gain set too high, causing cross-talk (ghosting) artifact

Cross-talk (ghosting or mirror image artifact) in spectral Doppler occurs when the Doppler gain is set too high, causing the waveform signal to bleed through to the opposite side of the baseline.

Question 32: The continuity equation in hemodynamics states that flow rate is conserved, meaning:

Resistance is equal in all vessel segments
Viscosity determines velocity distribution
Pressure is constant throughout the circulation
Cross-sectional area × velocity is constant at any point along a vessel (Correct answer)

Correct answer: Cross-sectional area × velocity is constant at any point along a vessel

The continuity equation (Q = A × V) states that volumetric flow rate equals cross-sectional area times velocity and is conserved, so a smaller area requires higher velocity.

Question 33: Which transducer array configuration uses a convex curved surface to produce a fan-shaped image wider than the footprint?

Phased array
Linear sequenced array
Curvilinear array (Correct answer)
Annular array

Correct answer: Curvilinear array

A curvilinear (convex) array has elements arranged along a curved surface, producing a trapezoidal or sector image that widens beyond the transducer footprint.

Question 34: A sonographer is tasked with measuring the peak velocity of a severe aortic stenosis jet, which is expected to be approximately 4 m/s. Which Doppler modality is most appropriate for this measurement and why?

Pulsed-Wave Doppler, because its specific sample volume can be placed precisely in the jet.
Power Doppler, because it is most sensitive to the presence of flow.
Color Flow Doppler, because it can visualize the turbulent flow pattern.
Continuous-Wave Doppler, because it is not subject to aliasing and can measure very high velocities. (Correct answer)

Correct answer: Continuous-Wave Doppler, because it is not subject to aliasing and can measure very high velocities.

A velocity of 4 m/s will create a Doppler shift that far exceeds the Nyquist limit of Pulsed-Wave Doppler, resulting in severe aliasing. Continuous-Wave (CW) Doppler is the correct choice because it does not alias and is designed to accurately measure such high velocities. While PW Doppler is precise in location, it cannot handle the speed. Color and Power Doppler are for qualitative assessment, not peak velocity quantification.

Question 35: Which Doppler mode provides the best sensitivity for detecting slow-flow states such as organ perfusion?

Pulsed wave Doppler
Continuous wave Doppler
Power Doppler (Correct answer)
Color flow 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 36: Which statement best describes lateral resolution in ultrasound?

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

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 37: Many PZT crystals are placed in an arched line with ______ transducers.

Linear array
Annular array
Mechanical
Convex array (Correct answer)

Correct answer: Convex array

Convex array transducers, also known as curvilinear arrays, are characterized by their PZT crystals being arranged in an arched or curved line. This curved configuration allows for a wider field of view in the far field, producing a sector-shaped image. This design is commonly used for abdominal and obstetric imaging.

Question 38: Color priority threshold in color Doppler determines:

How many pulses form one color line
The color hue assigned to arterial flow
Which pixels display color versus grayscale based on echo amplitude (Correct answer)
The maximum velocity displayed

Correct answer: Which pixels display color versus grayscale based on echo amplitude

Color priority sets the brightness level above which grayscale tissue signal overrides color, preventing color from painting solid structures.

Question 39: 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 40: Which clinical finding is associated with markedly increased peak systolic velocity (PSV) at a focal arterial segment?

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

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 41: Which of the following is a primary component of attenuation?

Increased propagation speed
Refraction
Conversion of sound to heat (Correct answer)
Amplification

Correct answer: Conversion of sound to heat

Attenuation is the overall weakening of the sound beam and is composed of three main factors: absorption, reflection, and scattering. Absorption, which is the conversion of acoustic energy into heat, is the dominant component of attenuation in soft tissues.

Question 42: Compared to soft tissue, fat has a propagation speed that is:

Higher (~1700 m/s)
Lower (~1450 m/s) (Correct answer)
Highly variable with temperature
Identical (~1540 m/s)

Correct answer: Lower (~1450 m/s)

Fat propagates sound at approximately 1450 m/s, slower than the 1540 m/s assumed by scanners, which can cause focal-zone registration errors.

Question 43: A sonographer is performing a cardiac echo on a patient with tachycardia and needs to optimize the imaging of the rapidly moving mitral valve leaflets. Which of the following actions will improve temporal resolution?

Increasing the line density
Decreasing the imaging sector width (Correct answer)
Activating spatial compounding
Increasing the number of focal zones

Correct answer: Decreasing the imaging sector width

Temporal resolution refers to the ability to accurately display moving structures in real-time and is determined by the frame rate. To increase the frame rate, the ultrasound system needs to acquire the data for each frame more quickly. Decreasing the sector width reduces the number of scan lines needed to create an image, thus reducing the time per frame and increasing the frame rate.

Question 44: The ability of an ultrasound system to distinguish between two adjacent tissues based on their different echogenicities is known as:

Temporal resolution
Contrast resolution (Correct answer)
Spatial resolution
Axial 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 45: Elevated end-diastolic velocity (EDV) in an arterial waveform typically indicates:

High downstream vascular resistance
Proximal arterial occlusion
Low downstream vascular resistance (high diastolic demand) (Correct answer)
Arterial vasospasm

Correct answer: Low downstream vascular resistance (high diastolic demand)

High EDV indicates continued forward flow throughout diastole, reflecting low downstream resistance from vasodilation, as seen in low-resistance organs like the kidney or brain.

Question 46: The Mechanical Index (MI) is an on-screen indicator of the potential for which ultrasound bioeffect?

Tissue heating
Microstreaming
Radiation force
Cavitation (Correct answer)

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 47: Dynamic receive focusing in modern array transducers improves lateral resolution by:

Continuously adjusting the receive focus as echoes return from increasing depths (Correct answer)
Increasing the PRF during reception
Narrowing the bandwidth during receive processing
Continuously adjusting the transmit focal point during each scan line

Correct answer: Continuously adjusting the receive focus as echoes return from increasing depths

During reception, time delays are updated in real time to focus at the depth from which echoes are currently returning, providing optimum lateral resolution at all depths.

Question 48: Which transducer design characteristic MOST directly determines axial resolution?

Focal depth
Spatial pulse length (Correct answer)
Element diameter
Number of elements in the array

Correct answer: Spatial pulse length

Axial resolution equals half the spatial pulse length; shorter pulses (fewer cycles, higher frequency, greater damping) yield better axial resolution.

Question 49: Which of the following BEST describes the piezoelectric effect as used in diagnostic ultrasound transducers?

Conversion of magnetic energy to acoustic energy
Conversion of heat energy to mechanical vibration
Conversion of light energy to sound energy
Conversion of electrical energy to mechanical energy and vice versa (Correct answer)

Correct answer: Conversion of electrical energy to mechanical energy and vice versa

The piezoelectric effect allows certain crystals to convert electrical signals into mechanical (acoustic) vibrations and incoming pressure waves back into electrical signals.

Question 50: Increasing transducer frequency to improve resolution is limited primarily by:

Increased slice thickness
Greater acoustic attenuation reducing penetration depth (Correct answer)
Increased lateral resolution
Lower pulse repetition frequency

Correct answer: Greater acoustic attenuation reducing penetration depth

Higher frequencies are attenuated more rapidly in tissue, limiting the usable imaging depth.

Question 51: Acoustic impedance (Z) is calculated as the product of:

Density and propagation speed (Correct answer)
Frequency and wavelength
Pressure amplitude and particle velocity
Attenuation coefficient and path length

Correct answer: Density and propagation speed

Z = ρ × c, where ρ is the medium's density and c is the speed of sound in that medium.

Question 52: Non-thermal mechanical bioeffects of ultrasound include all of the following EXCEPT:

Protein denaturation from elevated tissue temperature (Correct answer)
Microstreaming near oscillating bubbles
Acoustic cavitation
Acoustic streaming

Correct answer: Protein denaturation from elevated tissue temperature

Protein denaturation is a thermal effect caused by temperature rise, not a non-thermal mechanical effect; cavitation, streaming, and microstreaming are all mechanical in nature.

Question 53: In a 1.5D array transducer compared to a standard 1D array, the key improvement is:

Higher center frequency output
Limited electronic control in the elevation dimension to improve slice-thickness resolution (Correct answer)
Faster frame rates due to reduced element count
Full 3D volumetric imaging capability

Correct answer: Limited electronic control in the elevation dimension to improve slice-thickness resolution

A 1.5D array adds a few rows of elements in the elevation direction, allowing limited electronic focusing to reduce slice-thickness artifacts compared to a fixed lens.

Question 54: A sonographer is trying to improve the temporal resolution while imaging the fetal heart. Which of the following adjustments would be most effective?

Decreasing the imaging depth (Correct answer)
Increasing the line density
Widening the sector size
Increasing the number of focal zones

Correct answer: Decreasing the imaging depth

Temporal resolution is determined by the frame rate. To increase the frame rate, the time it takes to acquire each frame must be reduced. Decreasing the imaging depth reduces the pulse-return time (go-return time), allowing the system to listen for a shorter period and thus acquire lines faster, which increases the frame rate. Increasing focal zones, widening the sector, or increasing line density would all require more time to build a frame, thereby decreasing temporal resolution.

Question 55: What is the primary purpose of a matching layer on a transducer face?

To increase transducer bandwidth by absorbing excess vibrations
To improve energy transfer by reducing acoustic impedance mismatch between crystal and tissue (Correct answer)
To prevent electrical interference from the patient
To cool the piezoelectric element during operation

Correct answer: To improve energy transfer by reducing acoustic impedance mismatch between crystal and tissue

The matching layer reduces the large acoustic impedance difference between the piezoelectric crystal and soft tissue, improving energy transmission.

Question 56: Critical angle refraction in ultrasound occurs when:

Attenuation equals the impedance mismatch
The refracted beam travels parallel to the interface (90° refraction) (Correct answer)
The incident beam strikes perpendicular to the interface
The frequency exceeds 10 MHz

Correct answer: The refracted beam travels parallel to the interface (90° refraction)

At the critical angle, refraction bends the transmitted beam to 90°, meaning it travels along the interface and no energy enters medium 2.

Question 57: During weekly QA, a sonographer notices the lateral resolution has worsened compared to baseline. What is the most likely cause?

Phantom temperature dropped below 20°C
One or more transducer elements have failed (Correct answer)
The speed-of-sound calibration changed
The TGC was adjusted incorrectly

Correct answer: One or more transducer elements have failed

Failed or weak transducer elements degrade the aperture and focusing ability of the array, directly worsening lateral resolution.

Question 58: Which of the following statements is true regarding the relationship between axial and lateral resolution?

Lateral resolution is primarily determined by the spatial pulse length.
Axial resolution is typically better than lateral resolution in the far field.
Axial resolution remains constant with depth, while lateral resolution varies. (Correct answer)
Both axial and lateral resolution are independent of imaging depth.

Correct answer: Axial resolution remains constant with depth, while lateral resolution varies.

Axial resolution is determined by the spatial pulse length, which does not change as the beam travels through tissue. Therefore, axial resolution is constant at all depths. Lateral resolution, however, is determined by the beam width. The beam width changes with depth, being narrowest at the focal zone and widening in the near and far fields. This means lateral resolution varies with depth.

Question 59: A sound wave with frequency of 5 MHz traveling through soft tissue (c = 1540 m/s) has a wavelength of approximately:

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

Correct answer: 0.31 mm

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

Question 60: Demodulation in ultrasound signal processing refers to:

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

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 61: Grating lobes in array transducers are caused by:

Excessive acoustic power causing nonlinear propagation
Constructive interference from equally spaced element spacing greater than half a wavelength (Correct answer)
Reflection of side lobes off the transducer housing
Refraction of the main beam at tissue interfaces

Correct answer: Constructive interference from equally spaced element spacing greater than half a wavelength

When element spacing exceeds half a wavelength, spatial aliasing causes grating lobes — additional beams fired at off-axis angles that can produce spurious echoes in the image.

Question 62: Total internal reflection of an ultrasound beam occurs when the angle of incidence exceeds:

The critical angle (Correct answer)
90 degrees
The Brewster angle
45 degrees

Correct answer: The critical angle

When the incident angle exceeds the critical angle at an interface where speed increases, refraction is impossible and all energy is reflected back.

Question 63: 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 provides superior range resolution.
It is not limited by aliasing at high velocities. (Correct answer)

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 64: A specular reflector produces a strong echo only when:

The medium has low acoustic impedance
The beam strikes the surface perpendicularly (Correct answer)
The surface is smaller than the wavelength
The frequency is below 1 MHz

Correct answer: The beam strikes the surface perpendicularly

Specular reflectors return maximum echo amplitude when the beam strikes perpendicular (90°) to the smooth, large surface.

Question 65: Grating lobes degrade image quality primarily by causing:

Improved lateral resolution at depth
Reduced frame rate
Artifactual echoes from off-axis structures appearing in the main image (Correct answer)
Increased axial resolution

Correct answer: Artifactual echoes from off-axis structures appearing in the main image

Grating lobes are secondary beams that return echoes from off-axis targets, producing artifacts in the image.

Question 66: Range ambiguity artifact in color Doppler occurs when:

Gain is set too high
The beam steers at too shallow an angle
A second pulse is transmitted before echoes from the first pulse are received (Correct answer)
The ensemble length is too short

Correct answer: A second pulse is transmitted before echoes from the first pulse are received

When PRF is too high for the imaging depth, returning echoes from deep structures arrive after the next pulse is sent, causing misregistration of color signals.

Question 67: A high-resistance Doppler waveform pattern is typically found in which vessel?

Hepatic vein
Femoral artery at rest (Correct answer)
Internal carotid artery (ICA) at rest
Renal artery

Correct answer: Femoral artery at rest

The femoral artery at rest supplies skeletal muscle which has high resting vascular resistance, producing a triphasic high-resistance waveform.

Question 68: The color Doppler 'ghosting' artifact differs from flash artifact in that ghosting:

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

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

Bidirectional flow above and below the baseline
A dampened waveform with slow systolic rise (tardus) and reduced peak amplitude (parvus), seen distal to a significant proximal stenosis (Correct answer)
A triphasic high-resistance waveform with reverse flow
A high-amplitude, sharp systolic peak with absent diastolic 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 70: Which component of an ultrasound transducer is specifically designed with an acoustic impedance intermediate between the piezoelectric crystal and the patient's skin to improve sound transmission?

The matching layer (Correct answer)
The damping material
The acoustic lens
The piezoelectric element

Correct answer: The matching layer

The matching layer has an acoustic impedance that is between that of the piezoelectric element (crystal) and the soft tissue of the patient. This intermediate impedance reduces the large impedance mismatch at the transducer-skin interface, which in turn decreases reflection and allows more sound energy to be transmitted into the body.

Question 71: Which display mode shows information about a moving reflector over time?

M-mode (Correct answer)
Z-mode
A-mode
B-mode

Correct answer: M-mode

M-mode, or Motion mode, displays a single scan line over time. The horizontal axis represents time, and the vertical axis represents depth, showing the movement of structures along that specific line. This display mode is ideal for visualizing and quantifying motion, such as cardiac wall movement or fetal heart rate, by tracking changes in reflector position over time.

Question 72: If the propagation speed of sound increases while frequency remains constant, what happens to wavelength?

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

Correct answer: Wavelength increases

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

Question 73: The term 'derated' intensity (e.g., ISPTA.3) in ultrasound safety refers to intensity that has been adjusted for:

Patient body habitus correction
Electronic noise subtraction
Assumed tissue attenuation of 0.3 dB/cm/MHz (Correct answer)
Transducer efficiency losses

Correct answer: Assumed tissue attenuation of 0.3 dB/cm/MHz

Derated values apply a standardized attenuation of 0.3 dB/cm/MHz to account for tissue absorption when reporting intensities in safety standards.

Question 74: To correct aliasing on a spectral Doppler display, which of the following would NOT be an effective solution?

Using a lower transmit frequency transducer
Increasing the pulse repetition frequency (PRF)
Shifting the spectral baseline
Decreasing the sample volume gate size (Correct answer)

Correct answer: Decreasing the sample volume gate size

Decreasing sample volume size changes the amount of vessel sampled but does not affect the PRF or the Nyquist limit, making it ineffective for correcting aliasing.

Question 75: What is the primary reason ultrasound QA records should be kept for a minimum of several years?

To comply with Medicare reimbursement rules for technical components
To track phantom consumable replacement schedules
To document trending of performance changes and support accreditation reviews (Correct answer)
To satisfy state radiation safety officer requirements

Correct answer: To document trending of performance changes and support accreditation reviews

Long-term QA records enable trending of gradual performance changes and are required by accreditation bodies such as the ACR and ICAVL during site reviews.

Question 76: Grating lobes in array transducers are caused by:

Excessive gain settings
Thermal noise in the electronic circuitry
Periodic spacing of array elements at or near the wavelength (Correct answer)
Refraction at tissue interfaces

Correct answer: Periodic spacing of array elements at or near the wavelength

When element spacing equals or exceeds one wavelength, constructive interference produces off-axis grating lobes that can create artifacts.

Question 77: At normal incidence, what determines the fraction of sound intensity reflected at an interface?

The difference in acoustic impedance between the two media (Correct answer)
The beam diameter at the interface
The depth of the interface
The frequency of the transducer

Correct answer: The difference in acoustic impedance between the two media

The reflection coefficient at normal incidence depends solely on the acoustic impedances of the two media.

Question 78: The pulsatility index (PI) is calculated as:

(PSV + EDV) / PSV
PSV / EDV
EDV / PSV
(PSV − EDV) / mean velocity (Correct answer)

Correct answer: (PSV − EDV) / mean velocity

The Pulsatility Index = (Peak Systolic Velocity − End Diastolic Velocity) / Mean Velocity, providing a measure of downstream resistance.

Question 79: Axial resolution in ultrasound is primarily determined by:

Beam width at the focal zone
Dynamic range setting
Spatial pulse length (Correct answer)
Frame rate

Correct answer: Spatial pulse length

Axial resolution equals half the spatial pulse length; shorter pulses (higher frequency, fewer cycles) yield finer axial resolution.

Question 80: In B-mode imaging, increasing the time gain compensation (TGC) at depth primarily compensates for:

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

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 81: Snell's Law in ultrasound describes the relationship between:

Intensity and attenuation
Pulse duration and bandwidth
Frequency and depth
Incident and refracted beam angles at a tissue boundary (Correct answer)

Correct answer: Incident and refracted beam angles at a tissue boundary

Snell's Law states that the sine of the angle of incidence to the sine of the angle of refraction equals the ratio of propagation speeds in the two media.

Question 82: During a renal ultrasound, a sonographer places the color Doppler box over a suspected kidney stone. A rapidly changing, mosaic pattern of color appears immediately posterior to the hyperechoic structure, despite the absence of true blood flow. This specific finding is known as:

Power Doppler bloom
Twinkle artifact (Correct answer)
Crosstalk artifact
Reverberation artifact

Correct answer: Twinkle artifact

The twinkle artifact is a color Doppler phenomenon seen as a rapidly changing mixture of red and blue pixels posterior to a strongly reflecting, rough-surfaced object like a kidney stone. [17, 21] It is thought to be caused by intrinsic machine noise or random phase shifts from the rough surface creating a 'noisy' Doppler signal. [20] It is a useful sign that increases confidence in identifying calcifications. [21]

Question 83: Which of the following properties of a medium has the most significant influence on the propagation speed of an acoustic wave?

Density
Viscosity
Temperature
Stiffness (Correct answer)

Correct answer: Stiffness

Propagation speed is primarily determined by the stiffness (or bulk modulus) and density of the medium. Of these two, stiffness has the greater influence. Sound travels faster in stiffer materials. While density does affect speed (higher density generally leads to slower speed), its effect is less pronounced than that of stiffness. For example, bone is much denser than soft tissue, but it is also significantly stiffer, resulting in a much higher propagation speed. [11, 13]

Question 84: Which of the following acoustic wave types does diagnostic ultrasound primarily use for imaging?

Surface (Rayleigh) waves
Longitudinal (compressional) waves (Correct answer)
Plate (Lamb) waves
Transverse (shear) waves

Correct answer: Longitudinal (compressional) waves

Diagnostic ultrasound uses longitudinal waves in which particle displacement occurs parallel to the direction of wave propagation, as these travel efficiently through soft tissue.

Question 85: Which property of ultrasound contrast agents (microbubbles) makes them effective Doppler signal enhancers?

Their large size relative to red blood cells
Their strong non-linear oscillation and backscatter at diagnostic pressures (Correct answer)
Their ability to absorb all ultrasound energy
Their high acoustic impedance similar to bone

Correct answer: Their strong non-linear oscillation and backscatter at diagnostic pressures

Microbubbles oscillate non-linearly under ultrasound pressure, producing strong harmonic backscatter that greatly enhances Doppler signals.

Question 86: 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?

Dynamic range
Registration accuracy (Correct answer)
Uniformity
Axial resolution

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 87: In color Doppler, increasing the color box angle (steering) away from perpendicular to the vessel:

Improves Doppler angle and increases color sensitivity (Correct answer)
Reduces the detectable velocity range
Eliminates aliasing
Increases the PRF automatically

Correct answer: Improves Doppler angle and increases color sensitivity

Steering the color box to achieve a smaller insonation angle increases the cosine factor, producing larger frequency shifts and better color filling.

Question 88: In a standard spectral Doppler display, the vertical (y-axis) represents:

Doppler frequency shift (displayed as velocity after angle correction) (Correct answer)
Relative signal power or amplitude
Time elapsed during the cardiac cycle
Depth of the sample volume gate

Correct answer: Doppler frequency shift (displayed as velocity after angle correction)

The y-axis in spectral Doppler displays the Doppler frequency shift, which is converted to velocity using angle correction, while the x-axis represents time.

Question 89: Which of the following functions is considered a preprocessing function because it can only be performed on a live image before the data is stored in the scan converter?

Read Magnification
Adjusting the grayscale map
Adding caliper measurements
Write Magnification (Correct answer)

Correct answer: Write Magnification

Preprocessing functions manipulate the image data before it is stored in the scan converter memory. Write Magnification (or Write Zoom) is a classic example of preprocessing; it rescans the selected region of interest with a higher line density to generate a new, higher-resolution image. This can only be done on a live image. Read magnification, caliper placement, and grayscale map adjustments are postprocessing functions that can be applied to a frozen image.

Question 90: Stable cavitation differs from inertial cavitation in that stable cavitation involves:

Immediate tissue destruction at the focal zone
Bubbles oscillating in a sustained, non-destructive manner (Correct answer)
Violent bubble collapse that produces free radicals
Complete vaporization of the liquid medium

Correct answer: Bubbles oscillating in a sustained, non-destructive manner

Stable (non-inertial) cavitation describes gas bubbles that oscillate repetitively without collapsing, whereas inertial cavitation involves violent implosion.

Question 91: What is the primary mechanism of attenuation in blood?

Refraction at the plasma-cell boundary
Scattering by red blood cells (Correct answer)
Absorption by hemoglobin
Reflection at vessel walls

Correct answer: Scattering by red blood cells

Red blood cells act as Rayleigh scatterers, and scattering is the dominant mechanism of attenuation in blood.

Question 92: When the Doppler angle approaches 90°, what happens to the measured Doppler shift?

It doubles
It equals the transmitted frequency
It reaches its maximum value
It approaches zero, making velocity measurement unreliable (Correct answer)

Correct answer: It approaches zero, making velocity measurement unreliable

At 90°, cos 90° = 0, so the calculated Doppler shift approaches zero regardless of actual flow velocity, making angle correction and velocity measurement unreliable.

Question 93: Which setting would a sonographer adjust to reduce aliasing in pulsed wave Doppler without switching to CW Doppler?

Increase PRF (Correct answer)
Increase ensemble length
Decrease wall filter
Decrease overall gain

Correct answer: Increase PRF

Increasing PRF raises the Nyquist limit, allowing higher velocities to be measured before aliasing occurs.

Question 94: A tissue-mimicking phantom contains hyperechoic spherical masses. These targets are primarily used to test which system performance parameter?

Contrast resolution for high-reflectivity lesions (Correct answer)
Dead zone depth
Temporal resolution
Doppler sensitivity

Correct answer: Contrast resolution for high-reflectivity lesions

Hyperechoic spherical targets surrounded by uniform background material test the system's ability to detect and resolve high-amplitude echoes against background speckle.

Question 95: Microstreaming as a non-thermal ultrasound bioeffect is best described as:

Large-scale fluid motion driven by overall radiation pressure through a vessel
Shear wave propagation perpendicular to the sound beam
Localized, high-velocity fluid currents generated near an oscillating bubble interface (Correct answer)
Steady heating of tissue adjacent to a gas-filled reflector

Correct answer: Localized, high-velocity fluid currents generated near an oscillating bubble interface

Microstreaming is the high-shear localized fluid motion that occurs immediately around a cavitating or oscillating bubble, capable of disrupting cell membranes.

Question 96: Frame rate in real-time ultrasound imaging is primarily limited by:

The transducer element impedance
The patient's body habitus
The speed of sound and imaging depth (Correct answer)
The analog-to-digital conversion speed

Correct answer: The speed of sound and imaging depth

Because sound must travel to the maximum depth and return before the next pulse is fired, greater depth forces a lower pulse repetition frequency and thus a lower frame rate.

Question 97: A research study reports a 'free-field' ISPTA value versus a 'derated' ISPTA.3 value. Which statement is correct?

Derated values apply only to cardiac applications
The two values are identical for all clinical probes
Derated values are lower because they account for tissue attenuation between the transducer and target (Correct answer)
Free-field values are always lower because water attenuates sound more than tissue

Correct answer: Derated values are lower because they account for tissue attenuation between the transducer and target

Derated (ISPTA.3) values are calculated by applying 0.3 dB/cm/MHz attenuation to free-field water measurements, producing a lower, more clinically realistic intensity estimate.

Question 98: Which of the following best describes the transmission coefficient when sound passes from one medium to another?

It is always less than the reflection coefficient
It depends on frequency but not impedance
It equals the product of the two impedances
It equals 1 minus the reflection coefficient (Correct answer)

Correct answer: It equals 1 minus the reflection coefficient

Conservation of energy requires that the transmission coefficient T = 1 − R, where R is the reflection coefficient.

Question 99: Dynamic range in ultrasound refers to:

The maximum frame rate achievable at a given depth
The bandwidth of frequencies included in the transmit pulse
The ratio of the largest to smallest echo amplitudes the system can process and display (Correct answer)
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 100: Which of the following operator adjustments would lead to a degradation of lateral resolution?

Decreasing the overall gain
Increasing the imaging depth (Correct answer)
Activating tissue harmonic imaging
Increasing the number of focal zones

Correct answer: Increasing the imaging depth

Lateral resolution is the ability to distinguish two structures that are side-by-side, perpendicular to the beam's axis. It is determined by the beam width. As the ultrasound beam travels deeper into the body, it naturally diverges or widens, especially in the far field beyond the focal zone. This increased beam width at greater depths degrades lateral resolution.

Question 101: The pulse repetition frequency (PRF) setting directly affects which Doppler parameter?

Maximum detectable velocity (Nyquist limit) (Correct answer)
Beam steering angle
Spectral baseline position only
Wall filter cutoff

Correct answer: Maximum detectable velocity (Nyquist limit)

The Nyquist limit is equal to PRF/2, so increasing PRF raises the maximum velocity that can be displayed without aliasing.

Question 102: The primary function of the scan converter in an ultrasound system is to:

Convert electrical signals into acoustic pulses.
Amplify the weak returning echo signals.
Calculate the Doppler shift from moving red blood cells.
Format the echo data from the spoke format into a video format for display. (Correct answer)

Correct answer: Format the echo data from the spoke format into a video format for display.

The scan converter, or image processor, is a digital memory component that receives echo data from the receiver. Its main job is to reformat this data, which is acquired in a spoke or line-by-line format (like polar coordinates for a sector transducer), into a standard raster scan or video format (Cartesian coordinates) that can be displayed on a monitor.

Question 103: Elevational (slice-thickness) resolution is primarily controlled by:

Dynamic receive focusing
Fixed focus in the elevation plane (Correct answer)
Time gain compensation
Pulse repetition frequency

Correct answer: Fixed focus in the elevation plane

Most arrays cannot steer or focus electronically in the elevation plane, so slice thickness is fixed by the lens curvature.

Question 104: The acoustic streaming artifact in color Doppler is seen as:

Color aliasing in a deep vessel
Twinkling behind a stone
Color signal within a fluid-filled cyst caused by acoustic radiation force (Correct answer)
Color bleed from a hyperechoic mass

Correct answer: Color signal within a fluid-filled cyst caused by acoustic radiation force

Acoustic streaming occurs when ultrasound radiation force displaces fluid within a cyst, producing color Doppler signal in an otherwise avascular structure.

Question 105: What is the effect of increasing the pulse repetition frequency (PRF) on maximum detectable depth in PW Doppler?

Maximum depth is unaffected by PRF
Maximum depth decreases because less time is allowed for echoes to return from deep structures (Correct answer)
Maximum depth increases
Maximum depth doubles

Correct answer: Maximum depth decreases because less time is allowed for echoes to return from deep structures

Increasing PRF sends pulses more frequently, leaving less time for echoes from deep structures to return before the next pulse is sent, which reduces the maximum detectable depth.

Question 106: Which of the following best defines 'insonation angle' in Doppler ultrasound?

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
The angle of the spectral display baseline

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 107: Which acoustic parameter is determined solely by the medium through which sound travels?

Amplitude
Frequency
Period
Propagation speed (Correct answer)

Correct answer: Propagation speed

Propagation speed depends entirely on the medium's density and stiffness, not on the sound source.

Question 108: Coded excitation (e.g., chirp pulses) is used in ultrasound primarily to:

Widen the beam for panoramic imaging
Increase frame rate at low frequency
Improve signal-to-noise ratio and penetration while maintaining resolution (Correct answer)
Eliminate harmonic content

Correct answer: Improve signal-to-noise ratio and penetration while maintaining resolution

Coded excitation transmits a long modulated pulse and uses pulse compression on receive to achieve high SNR with good axial resolution.

Question 109: Side lobes in ultrasound transducers are most problematic because they:

Reduce the dynamic range of the system
Create artifact echoes that appear to originate from the main beam (Correct answer)
Increase axial resolution
Improve lateral resolution at depth

Correct answer: Create artifact echoes that appear to originate from the main beam

Side lobes radiate energy off-axis; reflectors in their path produce echoes that the system incorrectly places along the main beam axis, creating artifacts.

Question 110: In pulsed-wave Doppler, the sample volume (gate) is positioned within the vessel of interest. What determines the axial length of the sample volume?

The gate length (time duration of the listening window) (Correct answer)
The transducer frequency
The Doppler angle
The pulse repetition frequency

Correct answer: The gate length (time duration of the listening window)

The axial length of the PW Doppler sample volume is determined by the gate length — the longer the listening window (in time), the larger the axial sample volume.

Question 111: Which of the following is a recognized method to correct for aliasing in color Doppler without switching to power Doppler?

Decreasing the transmit frequency
Increasing the color scale (velocity range / PRF) or shifting the baseline (Correct answer)
Lowering the color scale (velocity range) further
Increasing the color gain

Correct answer: Increasing the color scale (velocity range / PRF) or shifting the baseline

Increasing the color scale raises the Nyquist limit for color Doppler, and shifting the color baseline allows more dynamic range in one direction to accommodate higher velocities without aliasing.

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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