RVT Ultrasound Physics and Instrumentation

Question 1

The piezoelectric effect in ultrasound transducers refers to the ability of certain crystals to:

Accepted Answer

Convert electrical energy into mechanical (sound) energy and vice versa

Answer

The piezoelectric effect describes how piezoelectric crystals (e.g., PZT) convert electrical pulses into mechanical vibrations (ultrasound) and convert returning echoes back into electrical signals.

Question 2

Which relationship best describes how ultrasound frequency affects axial resolution?

Accepted Answer

Higher frequency produces shorter wavelengths and better axial resolution

Answer

Higher frequency transducers produce shorter wavelengths, which improves axial resolution (ability to distinguish two structures along the beam axis), though at the cost of tissue penetration.

Question 3

The Nyquist limit in pulsed-wave Doppler is defined as:

Accepted Answer

Half the pulse repetition frequency (PRF)

Answer

The Nyquist limit is PRF/2; when the Doppler shift frequency exceeds this value, aliasing occurs and velocities are incorrectly displayed on the opposite side of the baseline.

Question 4

Acoustic impedance (Z) of a tissue is determined by:

Accepted Answer

The product of tissue density and the speed of sound in that tissue

Answer

Acoustic impedance Z = ρ × c, where ρ is tissue density and c is the propagation speed of sound; mismatches at tissue interfaces determine the magnitude of reflection.

Question 5

Ultrasound attenuation in soft tissue is approximately:

Accepted Answer

0.5 dB/cm/MHz

Answer

Soft tissue attenuates ultrasound at roughly 0.5 dB/cm/MHz, meaning a 5 MHz beam loses about 2.5 dB of intensity per centimeter traveled.

(RVT) Registered Vascular Technologist Practice Test

(RVT) Registered Vascular Technologist Practice Test

RVT Ultrasound Physics and Instrumentation