ARDMS Updated SPI Exam Questions and Answers by elsie-rose

Temporal resolution refers to the ability of an ultrasound system to distinguish between events occurring closely in time. It is primarily affected by the frame rate, which is the number of frames displayed per second. One of the main factors that influence the frame rate is the display depth. The deeper the imaging depth, the longer it takes for the ultrasound pulses to travel to the target and back, thus reducing the frame rate and temporal resolution. Shallower imaging depths allow for higher frame rates and better temporal resolution.

References

ARDMS Sonography Principles and Instrumentation (SPI) Exam Study Guide

"Diagnostic Ultrasound: Principles and Instruments" by Frederick W. Kremkau

Comprehensive and Detailed Explanation From Exact Extract:

Color Doppler detects flow based on the Doppler shift, which is dependent on the cosine of the angle between the ultrasound beam and the direction of blood flow. At 90 degrees, the cosine value is zero, resulting in no Doppler shift and therefore no detectable color flow signal.

According to sonography instrumentation reference:

“When the insonation angle is 90 degrees, the Doppler frequency shift is zero because the cosine of 90 degrees equals zero. As a result, no flow is displayed.”

Therefore, the correct answer is D: 90 degrees.

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Write magnification, or pre-processing zoom, involves rescanning the region of interest (ROI) with more scan lines, thus acquiring new data for that specific area. This process increases the spatial resolution of the image in the magnified area because it gathers more detailed data by adjusting the scan parameters, resulting in improved image quality. This is different from read magnification (post-processing zoom), which simply enlarges the existing image data without increasing resolution.

Increased Sweep Speed: This affects the display of the waveform over time but does not impact the appearance of the spectral Doppler signal in the way shown.

Decreased Pulse Repetition Frequency (PRF): Lowering the PRF can lead to aliasing, which is evident as the waveform wrapping around in the spectral display from image A to image B. This makes the velocity appear higher than it actually is.

Decreased Wall Filter: This adjustment primarily affects the elimination of low-frequency Doppler signals but does not typically cause the kind of changes seen in the images.

Increased Spectral Gain: Increasing the gain would result in a brighter spectral display but not the wrapping of the signal as seen.