ARDMS SPI Exam Dumps

Comprehensive and Detailed Explanation From Exact Extract:

At greater depths, pulse repetition frequency (PRF) is automatically reduced due to longer pulse travel times, lowering the Nyquist limit and increasing the likelihood of aliasing.

Principles and Instrumentation state:

'As sample depth increases, PRF decreases, lowering the Nyquist limit and increasing the risk of aliasing in pulsed-wave Doppler.'

Doppler shift depends on flow velocity and angle, not depth.

Actual velocity measurements do not increase with depth.

Signal strength typically decreases (not increases) due to attenuation.

Therefore, the correct answer is A: Increased aliasing.

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:

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.

Comprehensive and Detailed Explanation From Exact Extract:

The Doppler equation demonstrates that the Doppler shift frequency is directly proportional to the velocity of the moving reflector (typically red blood cells).

The Doppler shift formula is:

Doppler shift = (2 transducer frequency reflector velocity cos ) / propagation speed

According to sonography instrumentation references:

''The Doppler shift frequency increases as the velocity of the moving reflector increases. This relationship is linear when all other factors remain constant.''

Therefore, the correct answer is D: Velocity of the moving reflector.

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Color aliasing in Doppler ultrasound occurs when the velocity of blood flow exceeds the Nyquist limit, causing the color display to wrap around and display high velocities incorrectly as the opposite direction. This phenomenon is characterized by a mix of colors that indicate flow in both directions at the same location. In the provided image, there is a clear presence of color aliasing, as evidenced by the abrupt color change across the vessel, which is not consistent with normal flow patterns. Reference:

American Registry for Diagnostic Medical Sonography (ARDMS) Sonography Principles and Instrumentation guidelines.