CET Doppler Echocardiography & Spectral Analysis 1 — Questions and Answers
Question 1: Which Doppler modality is best suited for measuring high-velocity jets such as severe aortic stenosis?
- Pulsed-wave Doppler
- Continuous-wave Doppler (Correct answer)
- Color flow Doppler
- Tissue Doppler imaging
Correct answer: Continuous-wave Doppler
Continuous-wave Doppler has no aliasing limit and can accurately measure high-velocity jets exceeding the Nyquist limit.
Question 2: The Nyquist limit in pulsed-wave Doppler is equal to:
- The pulse repetition frequency (PRF)
- One-half the pulse repetition frequency (PRF/2) (Correct answer)
- Twice the pulse repetition frequency (2×PRF)
- The transducer frequency divided by depth
Correct answer: One-half the pulse repetition frequency (PRF/2)
Aliasing occurs when the sampled velocity exceeds half the PRF (Nyquist limit), causing velocity wrap-around on the spectral display.
Question 3: On a pulsed-wave Doppler spectral display, flow moving toward the transducer is displayed:
- Below the baseline
- Above the baseline (Correct answer)
- As a bidirectional signal
- With no baseline shift
Correct answer: Above the baseline
By convention, flow directed toward the transducer produces a positive Doppler shift and is displayed above the baseline.
Question 4: Which of the following best describes the term 'angle of incidence' in Doppler echocardiography?
- The angle between the ultrasound beam and the cardiac wall
- The angle between the ultrasound beam and the direction of blood flow (Correct answer)
- The angle between two ultrasound beams
- The angle of the transducer footprint
Correct answer: The angle between the ultrasound beam and the direction of blood flow
The angle of incidence is the angle between the ultrasound beam and the direction of blood flow; accuracy is greatest when this angle is less than 20 degrees.
Question 5: The modified Bernoulli equation used in echocardiography is expressed as:
- ΔP = 2V²
- ΔP = 4V² (Correct answer)
- ΔP = 8V²
- ΔP = V²/4
Correct answer: ΔP = 4V²
The simplified Bernoulli equation ΔP = 4V² converts peak Doppler velocity (m/s) to pressure gradient (mmHg), widely used to estimate stenotic and regurgitant jet gradients.
Question 6: In color flow Doppler imaging, aliasing is indicated by:
- A uniform blue color throughout the cardiac chamber
- A mosaic or variance map pattern where colors reverse at high velocities (Correct answer)
- Complete absence of color signal
- A purely red signal at all velocities
Correct answer: A mosaic or variance map pattern where colors reverse at high velocities
Aliasing in color flow Doppler appears as a mosaic of colors, particularly where flow velocities exceed the Nyquist limit and colors wrap from red to blue or vice versa.
Question 7: Tissue Doppler imaging (TDI) differs from conventional Doppler primarily because it measures:
- High-velocity blood flow
- Low-velocity myocardial wall motion (Correct answer)
- Turbulent regurgitant jets
- Pressure gradients across valves
Correct answer: Low-velocity myocardial wall motion
TDI uses a low-velocity, high-amplitude filter to display myocardial motion rather than blood flow, making it useful for diastolic function assessment.
CET Doppler Echocardiography & Spectral Analysis 1
Which Doppler modality is best suited for measuring high-velocity jets such as severe aortic stenosis?