RVT Ultrasound Physics and Instrumentation 5

Question 1

Which of the following best describes the duty factor in pulsed ultrasound?

Accepted Answer

The ratio of pulse duration to the pulse repetition period

Answer

Duty factor is the fraction of time the transducer is actively transmitting, calculated as pulse duration divided by the pulse repetition period.

Question 2

The spectral broadening seen in Doppler waveforms from a stenotic vessel is primarily caused by:

Accepted Answer

Turbulent flow creating a wide range of velocities within the sample volume

Answer

Turbulence disorganizes flow so that red blood cells move at many different velocities simultaneously, filling in the spectral window and causing spectral broadening.

Question 3

Which AIUM/NEMA safety index estimates the likelihood of cavitation in tissue?

Accepted Answer

Mechanical index (MI)

Answer

The Mechanical Index (MI = peak negative pressure / √frequency) estimates the potential for cavitation, with values above 0.3 suggesting increased risk.

Question 4

In the context of Doppler ultrasound, the angle of insonation should ideally be kept at or below:

Accepted Answer

60 degrees

Answer

Doppler angle correction is most accurate when the angle is ≤60°; beyond 60° the cosine function changes rapidly, introducing large velocity measurement errors.

Question 5

A hypoechoic structure on ultrasound indicates that it:

Accepted Answer

Reflects fewer echoes than surrounding tissue

Answer

Hypoechoic means the structure appears darker (fewer/lower amplitude echoes) compared to adjacent tissue, not completely echo-free.

(RVT) Registered Vascular Technologist Practice Test

(RVT) Registered Vascular Technologist Practice Test

RVT Ultrasound Physics and Instrumentation 5