RVT - Registered Vascular Technologist Hemodynamics and Doppler Principles Questions and Answers

Question 1

A sonographer measures a peak systolic velocity in the common carotid artery and notes that the Doppler angle of insonation is 75 degrees. What is the most likely consequence of using this angle for the velocity measurement?

Accepted Answer

The velocity will be significantly underestimated.

Answer

The Doppler equation uses the cosine of the angle between the ultrasound beam and the direction of blood flow to calculate velocity. As this angle increases towards 90 degrees, its cosine value decreases sharply. Angles above 60 degrees introduce a large potential for error, leading to a significant underestimation of the true velocity.

Question 2

According to the Bernoulli principle as it applies to hemodynamics, what is the relationship between pressure and velocity at the point of maximum arterial stenosis?

Accepted Answer

Velocity is highest and pressure is lowest.

Answer

The Bernoulli principle describes the conservation of energy, stating that an increase in velocity (kinetic energy) must be accompanied by a decrease in pressure (potential energy). In an arterial stenosis, blood accelerates to pass through the narrowed segment, resulting in the highest velocity and, consequently, the lowest pressure at that specific point.

Question 3

Based on Poiseuille's law, which of the following factors has the greatest influence on resistance to blood flow?

Accepted Answer

Vessel radius

Answer

Poiseuille's law demonstrates that resistance to flow is inversely proportional to the vessel radius raised to the fourth power (r⁴). This exponential relationship means that even a very small change in the radius of a vessel will cause a very large change in resistance, making it the most impactful factor.

Question 4

While performing a spectral Doppler evaluation, a sonographer encounters aliasing. Which of the following adjustments is LEAST effective for correcting this artifact?

Accepted Answer

Increasing the overall Doppler gain.

Answer

Aliasing occurs when the Doppler shift exceeds the Nyquist limit. Increasing the PRF (scale), shifting the baseline, and using a lower frequency transducer are all effective methods to correct for or reduce aliasing. Increasing the Doppler gain only amplifies the entire signal, including the artifact, and does not change the parameters that cause aliasing.

Question 5

In spectral Doppler, the filling-in of the clear space under the systolic peak is known as spectral broadening. This finding is most commonly associated with:

Accepted Answer

Disturbed or turbulent blood flow.

Answer

The clear area under the systolic peak, or 'spectral window,' represents the uniform velocity of red blood cells in laminar flow. Turbulent flow involves red blood cells moving at a wide variety of speeds and in multiple directions. This range of velocities fills in the spectral window, causing the appearance of spectral broadening.

(RVT) Registered Vascular Technologist Practice Test

(RVT) Registered Vascular Technologist Practice Test

RVT - Registered Vascular Technologist Hemodynamics and Doppler Principles Questions and Answers