VT Diagnostic Imaging Techniques 2 — Questions and Answers
Question 1: Which Doppler mode provides a visual map of flow velocities superimposed on a B-mode image?
- Spectral Doppler
- Color flow Doppler (Correct answer)
- Continuous wave Doppler
- Power Doppler
Correct answer: Color flow Doppler
Color flow Doppler encodes velocity and direction as colors overlaid on the grayscale B-mode image.
Question 2: A vascular sonographer notes aliasing on color Doppler. The BEST corrective action is to:
- Increase gain
- Increase the color scale (PRF) (Correct answer)
- Decrease transducer frequency
- Switch to power Doppler mode
Correct answer: Increase the color scale (PRF)
Aliasing occurs when the PRF is too low; increasing the color scale (PRF) raises the Nyquist limit and eliminates wrap-around.
Question 3: Which imaging modality uses gadolinium contrast and is considered the gold standard for evaluating renal artery stenosis in patients who cannot receive iodinated contrast?
- CT angiography
- Duplex ultrasound
- MR angiography (Correct answer)
- Catheter angiography
Correct answer: MR angiography
MR angiography with gadolinium provides excellent vessel detail without iodinated contrast, making it preferred for patients with iodine allergy.
Question 4: The angle of insonation recommended for accurate arterial Doppler velocity measurements is:
- 0–15 degrees
- 30–45 degrees
- 60 degrees or less (Correct answer)
- Greater than 70 degrees
Correct answer: 60 degrees or less
A Doppler angle of 60 degrees or less is used because angles above 60 degrees introduce large cosine-related velocity errors.
Question 5: B-flow imaging (B-flow) differs from color Doppler in that it:
- Uses higher frequency pulses only
- Displays moving blood without Doppler processing (Correct answer)
- Requires contrast agents
- Cannot image slow venous flow
Correct answer: Displays moving blood without Doppler processing
B-flow uses coded excitation to directly visualize moving blood cells in grayscale without Doppler processing, providing high temporal resolution.
Question 6: When performing CTA of the aorta, the timing bolus technique ensures that:
- Radiation dose is minimized
- Images are acquired at peak arterial enhancement (Correct answer)
- Venous contamination is avoided
- Slice thickness is optimized
Correct answer: Images are acquired at peak arterial enhancement
A timing bolus or automated bolus-tracking triggers data acquisition when contrast reaches peak concentration in the target vessel.
Question 7: Intravascular ultrasound (IVUS) is particularly useful for:
- Screening peripheral arterial disease non-invasively
- Assessing plaque morphology and stent apposition from within the vessel (Correct answer)
- Measuring ankle-brachial index
- Detecting deep vein thrombosis
Correct answer: Assessing plaque morphology and stent apposition from within the vessel
IVUS provides cross-sectional images from inside the vessel, making it ideal for evaluating plaque composition and confirming stent wall apposition.
VT Diagnostic Imaging Techniques 2
Which Doppler mode provides a visual map of flow velocities superimposed on a B-mode image?