Comprehensive and Detailed Explanation From Exact Extract:
The end-diastolic velocity represents the lower velocity portion of the Doppler waveform. The wall filter (or high-pass filter) removes low-frequency Doppler shifts from the spectral display. When the wall filter is increased, it filters out these low-velocity signals - including diastolic flow components. According to sonography Principles and Instrumentation reference materials:
"The wall filter eliminates low-velocity signals from the Doppler spectrum. Increasing the wall filter may completely eliminate end-diastolic velocities, especially in low-resistance arterial flow." Therefore, the correct answer is D: Increased wall filter.
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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.

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.
References:
ARDMS Sonography Principles & Instrumentation Guidelines
Hedrick WR, Hykes DL, Starchman DE.Ultrasound Physics and Instrumentation. 4th ed. Philadelphia, PA:
Elsevier Saunders; 2005.

The color Doppler image shows an artifact where high-velocity blood flow exceeds the Nyquist limit, resulting in color wrap-around or aliasing. This artifact is visualized as a mosaic pattern of colors that abruptly change, indicating that the velocity exceeds the color Doppler scale's maximum. Aliasing occurs when the sampling rate (pulse repetition frequency) is insufficient to accurately capture the high velocities, causing the display to cycle back to lower velocities.
References:
ARDMS Sonography Principles & Instrumentation Guidelines
Hagen-Ansert SL. Textbook of Diagnostic Ultrasonography. 8th ed. St. Louis, MO: Mosby; 2017.

Power Doppler, unlike color Doppler, is less angle dependent because it detects the strength of the Doppler signal rather than the velocity of the blood flow. This means it is more sensitive to detecting low-velocity flow and flow in smaller vessels, regardless of the angle between the ultrasound beam and the flow direction.
Color Doppler provides information on flow direction and velocity but is highly dependent on the angle of insonation, making it less reliable when the angle is suboptimal.
ARDMS Sonography Principles and Instrumentation guidelines
Zwiebel, W. J., & Pellerito, J. S. (2017).Introduction to Vascular Ultrasonography. Elsevier.