ARDMS SPI - ARDMS Sonography Principles and Instrumentation Color Doppler and Artifacts Questions and Answers

Question 1

A sonographer performing a color Doppler study of the carotid artery observes a mosaic pattern of colors in the center of the vessel where flow velocity is highest. This artifact is most likely:

Accepted Answer

Aliasing, which should be corrected by increasing the PRF/Scale.

Answer

The mosaic pattern in the area of highest velocity is the classic appearance of aliasing. This artifact occurs when the Doppler shift frequency exceeds the Nyquist limit (PRF/2). [12] The most direct way to correct this is to increase the Pulse Repetition Frequency (PRF), also known as the velocity scale, which raises the Nyquist limit and allows the system to display higher velocities correctly. [4]

Question 2

Which of the following is a primary advantage of Power Doppler when compared to conventional Color Doppler?

Accepted Answer

It is more sensitive to slow flow and is not subject to aliasing.

Answer

Power Doppler displays the amplitude or strength of the Doppler signal, not the frequency shift (velocity). [10] This makes it more sensitive to the presence of flow, especially slow flow. [2] Because it does not measure velocity, it is not limited by the Nyquist criterion and therefore does not alias. [9] Its main disadvantages are the lack of directional/velocity information and increased susceptibility to motion artifact. [2]

Question 3

While evaluating blood flow, a sonographer notices low-frequency, high-amplitude color signals originating from the vessel walls that obscure the true flow within the lumen. Which control should be adjusted to mitigate this specific artifact?

Accepted Answer

Wall Filter

Answer

The artifact described is clutter, or ghosting, which is caused by strong, low-frequency Doppler shifts from moving anatomy like vessel walls. [15] The Wall Filter is a high-pass filter specifically designed to eliminate these low-frequency signals, allowing the weaker, higher-frequency signals from blood flow to be displayed more clearly. [16]

Question 4

During a renal ultrasound, a sonographer places the color Doppler box over a suspected kidney stone. A rapidly changing, mosaic pattern of color appears immediately posterior to the hyperechoic structure, despite the absence of true blood flow. This specific finding is known as:

Accepted Answer

Twinkle artifact

Answer

The twinkle artifact is a color Doppler phenomenon seen as a rapidly changing mixture of red and blue pixels posterior to a strongly reflecting, rough-surfaced object like a kidney stone. [17, 21] It is thought to be caused by intrinsic machine noise or random phase shifts from the rough surface creating a 'noisy' Doppler signal. [20] It is a useful sign that increases confidence in identifying calcifications. [21]

Question 5

A sonographer is optimizing a color Doppler image and notices that the color extends beyond the vessel walls into the surrounding stationary tissue. Which of the following adjustments should be made FIRST to correct this?

Accepted Answer

Decrease the color gain

Answer

When color appears in stationary tissue outside the vessel lumen, it is known as color bleed, blooming, or flash artifact. [13, 16] This is caused by the color gain being set too high, which over-amplifies the signal and noise. [7] The first and most appropriate action is to incrementally decrease the color gain until the color is confined within the vessel walls. [7, 13]

ARDMS SPI - ARDMS Sonography Principles and Instrumentation Practice Test

ARDMS SPI - ARDMS Sonography Principles and Instrumentation Practice Test

ARDMS SPI - ARDMS Sonography Principles and Instrumentation Color Doppler and Artifacts Questions and Answers