RVT Ultrasound Physics and Instrumentation 2

Question 1

The Doppler equation used to calculate flow velocity is: v = (f_d × c) / (2 × f_0 × cos θ). What does 'θ' represent?

Accepted Answer

The angle between the ultrasound beam and the direction of blood flow

Answer

The angle between the transducer face and the vessel wall

Answer

The angle of incidence at the tissue boundary

Answer

The beam divergence angle beyond the focal zone

Question 2

Aliasing in color flow Doppler imaging appears as:

Accepted Answer

An abrupt color reversal in the center of a high-velocity jet

Answer

A complete absence of color within the vessel lumen

Answer

A uniform increase in red signal intensity throughout the vessel

Answer

Acoustic shadowing distal to a calcified plaque

Question 3

Which technique is most effective for eliminating aliasing in pulsed-wave Doppler without switching to continuous-wave mode?

Accepted Answer

Increasing the pulse repetition frequency (PRF)

Answer

Decreasing the transducer operating frequency

Answer

Reducing the Doppler gain

Answer

Widening the sample volume gate

Question 4

Power Doppler differs from conventional color flow Doppler primarily in that it displays:

Accepted Answer

The amplitude (power) of the Doppler signal rather than frequency shift

Answer

Bidirectional flow with higher velocity sensitivity

Answer

Mean velocity values averaged across the vessel diameter

Answer

Pulsatility index mapped in color across the image

Question 5

The range resolution (axial resolution) of a pulsed ultrasound system is primarily determined by:

Accepted Answer

Spatial pulse length

Answer

Transducer aperture size

Answer

Pulse repetition period

Answer

Focal zone depth

Question 6

A duplex ultrasound system combines which two imaging modalities?

Accepted Answer

B-mode (gray-scale) imaging and pulsed-wave Doppler

Answer

Continuous-wave Doppler and M-mode imaging

Answer

Color Doppler and CT angiography

Answer

Power Doppler and contrast-enhanced ultrasound

Question 7

Time gain compensation (TGC) in ultrasound imaging is used to:

Accepted Answer

Compensate for the increasing attenuation of sound with depth

Answer

Increase the pulse repetition frequency for deeper structures

Answer

Reduce side-lobe artifacts from high-amplitude reflectors

Answer

Adjust the Doppler angle automatically for angle correction