ARDMS Echo Doppler Principles and Applications

Question 1

What is the Nyquist limit in pulsed wave Doppler echocardiography?

Accepted Answer

Half the pulse repetition frequency

Answer

The Nyquist limit equals half the pulse repetition frequency (PRF); exceeding it causes aliasing in pulsed wave Doppler.

Question 2

Which Doppler modality is best suited for measuring high-velocity jets such as severe aortic stenosis?

Accepted Answer

Continuous wave Doppler

Answer

Continuous wave Doppler has no PRF limitation and can accurately measure high-velocity jets without aliasing.

Question 3

What effect does increasing the angle of insonation (θ) beyond 20° have on Doppler velocity measurements?

Accepted Answer

Underestimates true velocity

Answer

The Doppler equation uses cosine θ; as θ increases beyond 20°, cosine decreases, causing underestimation of true blood flow velocity.

Question 4

In color flow Doppler, what does aliasing (color reversal to the opposite color) indicate?

Accepted Answer

Velocities exceeding the Nyquist limit

Answer

Color aliasing occurs when detected velocity exceeds the Nyquist limit, causing the display to wrap to the opposite color.

Question 5

Which Doppler technique allows simultaneous visualization of flow direction and velocity across a 2D image?

Accepted Answer

Color flow Doppler

Answer

Color flow Doppler maps mean blood flow velocities across a 2D sector, color-coding direction and relative velocity.

ARDMS Echo - American Registry for Diagnostic Medical Sonography Echocardiography Practice Test