Free Practice Questions for ARDMS SPI Exam

Comprehensive and Detailed Explanation From Exact Extract:

Persistence is a frame averaging function that combines multiple sequential frames to smooth random noise and reduce speckle, particularly effective in stationary or slow-moving structures.

According to official Principles and Instrumentation guidelines:

"Persistence reduces random noise by averaging multiple frames over time, improving image clarity but potentially reducing temporal resolution."

Increasing frequency improves resolution but may increase attenuation.

Sector width affects frame rate.

Depth affects penetration but not noise reduction.

Therefore, the correct answer is D: Persistence.

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QUESTION NO22

Which adjustment produced the change from waveform A to waveform B?

A close-up of a graph Description automatically generated

A. Increased Doppler gain

B. Decreased Doppler gain

C. Increased wall filter

D. Decreased wall filter

Answer: A

Comprehensive and Detailed Explanation From Exact Extract:

Comparing waveform A to waveform B:

In image B, the Doppler spectral waveform is brighter, with stronger signal amplitude and more clearly visible Doppler shifts.

This indicates that the Doppler gain was increased, amplifying the strength of the returning Doppler signals displayed on the spectral waveform.

According to official sonography Principles and Instrumentation:

"Doppler gain controls the amplification of returning Doppler signals. Increasing the gain enhances signal amplitude, making weaker Doppler signals more visible."

Decreasing gain (B) would have produced a dimmer waveform.

Changes in wall filter (C and D) would primarily affect low-velocity signal display, not overall brightness.

Therefore, the correct answer is A: Increased Doppler gain.

QUESTION NO23

Which aspect(s) would best explain why the amplitude of the signal from reflector B in this diagram is less than that from reflector A?

A diagram of a transducer Description automatically generated

A. Attenuation

B. Elasticity of the medium

C. Propagation speed differences

D. Acoustic impedance differences

Answer: A

Comprehensive and Detailed Explanation From Exact Extract:

As ultrasound travels through tissue, it experiences attenuation — a reduction in signal amplitude due to absorption, scattering, and reflection. The deeper the reflector, the greater the attenuation. Therefore, the signal from reflector B (deeper structure) is weaker than from reflector A (shallower structure) primarily due to attenuation.

According to Principles and Instrumentation:

"Attenuation is the reduction in ultrasound beam strength as it propagates through tissue, resulting in decreased signal amplitude from deeper structures."

Elasticity affects stiffness but not amplitude directly.

Propagation speed differences cause refraction or displacement, not amplitude changes.

Acoustic impedance differences cause reflection strength variations at interfaces but do not account for depth-dependent amplitude reduction.

Therefore, the correct answer is A: Attenuation.

QUESTION NO24

Which adjustment would eliminate aliasing in the Doppler waveform in this image?

A close-up of an ultrasound Description automatically generated

A. Decrease Doppler gain.

B. Decrease wall filter.

C. Increase velocity scale.

D. Increase sample size.

Answer: C

Comprehensive and Detailed Explanation From Exact Extract:

Aliasing occurs when Doppler frequency shifts exceed the Nyquist limit (which equals half the pulse repetition frequency). Increasing the velocity scale (which increases PRF) raises the Nyquist limit, reducing or eliminating aliasing.

Principles and Instrumentation state:

"Aliasing in pulsed-wave Doppler can be corrected by increasing the pulse repetition frequency (velocity scale), allowing higher velocities to be displayed without wraparound."

Decreasing gain affects amplitude, not aliasing.

Wall filter adjustments remove low-velocity signals, not aliasing.

Increasing sample size affects spatial resolution and may reduce frame rate but does not address aliasing.

Therefore, the correct answer is C: Increase velocity scale.

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Enhancement artifact occurs when an anechoic (or low-attenuation) structure, such as a cyst or fluid-filled structure, allows the ultrasound beam to pass through it with minimal attenuation. As a result, the tissues located distal to this anechoic structure appear brighter (increased echo amplitude) on the ultrasound image because the sound waves are less attenuated by the anechoic structure, leading to higher intensity echoes returning from the distal tissue. This increased brightness beyond the anechoic area is known as enhancement.

ARDMS Sonography Principles and Instrumentation guidelines

Kremkau, F. W. (2015). Diagnostic Ultrasound: Principles and Instruments. Elsevier.

Comprehensive and Detailed Explanation From Exact Extract:

Slice thickness (elevational resolution artifact) occurs when the ultrasound beam partially includes surrounding tissue above or below the scan plane, falsely appearing as internal echoes within an otherwise anechoic cyst.

Principles and Instrumentation:

"Slice thickness artifact occurs when off-axis echoes are included in the imaging slice, falsely creating internal echoes in cystic structures."

Refraction (A) causes displacement.

Enhancement (B) causes posterior brightening.

Range ambiguity (D) produces incorrect depth placement.

Therefore, the correct answer is C: Slice thickness.

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Comprehensive and Detailed Explanation From Exact Extract:

Output power directly affects the intensity of the ultrasound beam transmitted into the patient. Reducing output power lowers the risk of both thermal and mechanical bioeffects.

According to sonography instrumentation reference:

“Output power should be minimized following the ALARA (As Low As Reasonably Achievable) principle to reduce potential bioeffects while still obtaining diagnostic-quality images.”

Therefore, the correct answer is B: Output power.

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In this image, which characteristics of flow are represented by the upper right side of a variance mode color map?

A close-up of a screen Description automatically generated

A. Higher velocity, laminar with a positive Doppler shift

B. Higher velocity, laminar with a negative Doppler shift

C. Higher velocity, turbulent with a positive Doppler shift

D. Higher velocity, turbulent with a negative Doppler shift

Answer: C

Comprehensive and Detailed Explanation From Exact Extract:

In variance mode color Doppler, colors are assigned based on both flow direction (Doppler shift polarity) and flow character (laminar vs turbulent). In the image:

The vertical color bar shows standard Doppler shifts: positive shifts (toward the transducer) are displayed at the top, and negative shifts (away from the transducer) at the bottom.

The variance mode adds horizontal color variation (from left to right), where the right side indicates increasing turbulence.

Thus, the upper right portion of the color bar indicates:

Positive Doppler shift (flow toward the transducer)

High velocity

Turbulent flow

According to sonography instrumentation reference:

“In variance mode, the vertical axis represents flow direction and velocity, while the horizontal axis represents flow variance (turbulence). The upper right corner indicates high-velocity turbulent flow toward the transducer.”

Therefore, the correct answer is C: Higher velocity, turbulent with a positive Doppler shift.

A high wall filter is used in Doppler ultrasound to eliminate low-frequency signals that may be attributed to vessel wall motion or other low-velocity flows. However, if the wall filter is set too high, it can inadvertently eliminate desired low-frequency Doppler signals that represent real blood flow, particularly in smaller vessels or those with slower flow velocities. This results in a loss of valuable diagnostic information.

The Nyquist limit, which is the maximum detectable velocity before aliasing occurs, is directly related to the pulse repetition frequency (PRF). Increasing the color scale on the ultrasound machine effectively increases the PRF. When the PRF is increased, the Nyquist limit is also increased, allowing for the measurement of higher velocities without aliasing.

ARDMS Sonography Principles and Instrumentation guidelines

Kremkau, F. W. (2015). Diagnostic Ultrasound: Principles and Instruments. Elsevier.

Comprehensive and Detailed Explanation From Exact Extract:

Axial resolution is the system's ability to distinguish two structures located along the direction of the ultrasound beam (parallel to the beam axis). Test objects or phantoms contain closely spaced pins or reflectors along this axis to evaluate axial resolution.

Principles and Instrumentation state:

"Axial resolution is determined by the spatial pulse length and is tested using targets positioned along the beam axis."

Sensitivity (A) relates to detection of weak echoes.

Specificity (B) refers to diagnostic accuracy, not phantom testing.

Lateral resolution (C) is evaluated using side-by-side (perpendicular) targets.

Therefore, the correct answer is D: Axial resolution.

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A wall filter in Doppler ultrasound is designed to remove low-frequency signals that are often caused by tissue motion, vessel wall movement, or other forms of motion artifact. These low-frequency signals can clutter the Doppler spectrum, making it difficult to accurately interpret blood flow velocities. By filtering out these unwanted low-frequency signals, the wall filter helps to enhance the clarity of the Doppler signal, allowing for more accurate measurements of blood flow velocities.

American Registry for Diagnostic Medical Sonography (ARDMS). Sonography Principles and Instrumentation (SPI) Examination Review Guide.

Spectral Doppler mirroring, also known as crosstalk, occurs when the Doppler signal appears on both sides of the baseline. This can be caused by excessively high Doppler gain, which amplifies the signal and creates artificial mirror images. Decreasing the Doppler gain reduces the signal amplitude, thereby minimizing the mirroring artifact.

ARDMS Sonography Principles and Instrumentation guidelines

Hoskins, P. R., Thrush, A., Martin, K., & Whittingham, T. A. (2010). Diagnostic Ultrasound: Physics and Equipment.