VT Transcranial Doppler Imaging 3 — Questions and Answers
Question 1: During TCD-guided bubble study for patent foramen ovale (PFO), when should the patient perform the Valsalva maneuver?
- 5 seconds before agitated saline injection
- Simultaneously with injection
- 5–10 seconds after injection, during release (Correct answer)
- After all microbubbles have cleared
Correct answer: 5–10 seconds after injection, during release
The Valsalva maneuver should be released 5–10 seconds after injection to transiently raise right atrial pressure and maximize right-to-left shunt detection.
Question 2: A TCD study shows MCA mean velocity of 220 cm/s with a Lindegaard ratio of 2.5. This most likely represents:
- Severe vasospasm
- MCA stenosis
- Hyperemia (Correct answer)
- Normal variant
Correct answer: Hyperemia
High MCA velocity with a low Lindegaard ratio (<3) indicates hyperemia rather than vasospasm, as extracranial ICA velocity is proportionally elevated.
Question 3: The normal depth range for insonating the MCA M1 segment via the transtemporal window is approximately:
- 20–30 mm
- 35–60 mm (Correct answer)
- 65–80 mm
- 85–100 mm
Correct answer: 35–60 mm
The MCA M1 segment is typically found at depths of 35–60 mm through the transtemporal window.
Question 4: Which TCD waveform feature is most indicative of downstream arterial occlusion (distal high resistance)?
- High diastolic velocity with low pulsatility
- Blunted systolic upstroke with high resistance pattern
- Normal velocities with increased PI (Correct answer)
- Retrograde diastolic flow
Correct answer: Normal velocities with increased PI
Distal arterial occlusion creates high resistance outflow, manifesting as elevated pulsatility index (PI) with relatively preserved systolic but reduced diastolic velocity.
Question 5: In TCD assessment of cerebral autoregulation, the autoregulation index (ARI) is determined by measuring:
- Static response to CO2 changes
- Dynamic response of MCA velocity to rapid blood pressure changes (Correct answer)
- Bilateral MCA velocity symmetry
- Pulsatility response to head-of-bed positioning
Correct answer: Dynamic response of MCA velocity to rapid blood pressure changes
The autoregulation index assesses the dynamic cerebrovascular response (MCA velocity changes) following rapid blood pressure perturbations such as thigh-cuff deflation.
Question 6: What is the typical TCD finding in a patient with sickle cell disease at high risk for stroke?
- Decreased bilateral MCA velocities
- MCA or distal ICA time-averaged mean velocity ≥200 cm/s (Correct answer)
- Increased pulsatility index >1.5
- Absent MCA signal bilaterally
Correct answer: MCA or distal ICA time-averaged mean velocity ≥200 cm/s
STOP trial criteria define high stroke risk in sickle cell disease as TAMMV ≥200 cm/s in the MCA or distal ICA, indicating arterial narrowing from sickling.
Question 7: Which vessel is identified at approximately 60–80 mm depth with flow directed away from the probe on transtemporal insonation?
- MCA
- Anterior cerebral artery (ACA) (Correct answer)
- Posterior cerebral artery P1
- Ophthalmic artery
Correct answer: Anterior cerebral artery (ACA)
The ACA A1 segment is located at 60–80 mm depth and has flow directed away from the transtemporal probe (anterograde, away).
VT Transcranial Doppler Imaging 3
During TCD-guided bubble study for patent foramen ovale (PFO), when should the patient perform the Valsalva maneuver?