ARDMS SPI SPI Updated Exam

Comprehensive and Detailed Explanation From Exact Extract:

Defects in transducer crystals result in missing or weakened signals along the beam path produced by those elements, creating dropout. In array transducers, dropout typically appears as vertical or horizontal dark zones depending on which elements are affected.

According to sonography instrumentation reference:

“Crystal failure results in areas of signal dropout directly beneath the defective elements due to loss of transmitted or received signals.”

Therefore, the correct answer is D: Dropout.

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Comprehensive and Detailed Explanation From Exact Extract:

Using multiple focal zones improves lateral resolution but requires additional time for each focal zone acquisition, which reduces frame rate and therefore degrades temporal resolution.

According to sonography instrumentation reference:

“Multiple focal zones improve lateral resolution but at the expense of temporal resolution due to longer acquisition time for each frame.”

Therefore, the correct answer is D: Temporal.

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Which setting is the most likely cause of the artifact displayed in this image?

A close-up of a ultrasound Description automatically generated

A. Color gain set too low

B. Color gain set too high

C. Velocity scale set too high

D. Velocity scale set too low

Answer: D

Comprehensive and Detailed Explanation From Exact Extract:

The image shows color aliasing, where the colors abruptly change within the vessel indicating wrap-around of Doppler shifts. This happens when the velocity scale (PRF) is set too low, causing velocities exceeding the Nyquist limit to alias.

According to sonography instrumentation reference:

“Aliasing occurs in color Doppler when the flow velocities exceed the Nyquist limit, commonly due to a low velocity scale (PRF).”

Therefore, the correct answer is D: Velocity scale set too low.

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When a reflector (such as red blood cells) is moving toward the sound source, the frequency of the reflected sound waves increases. This phenomenon is known as the Doppler effect. The frequency shift occurs because the motion of the reflector compresses the sound waves, leading to a higher frequency than the emitted frequency. This increased frequency is what the Doppler ultrasound system detects and uses to calculate the velocity of the moving reflector.

ARDMS Sonography Principles and Instrumentation guidelines

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

Axial resolution refers to the ability to distinguish two structures that are close to each other along the path of the ultrasound beam.

Spatial pulse length (SPL) is the distance over which one pulse occurs, and it directly affects axial resolution.

Shorter SPL improves axial resolution because it allows better differentiation of closely spaced structures.

The axial resolution is improved by increasing the frequency of the transducer, which shortens the wavelength and hence the SPL.References:

ARDMS Sonography Principles and Instrumentation guidelines on resolution parameters and their impact on image quality.