VT Transcranial Doppler Imaging 2 — Questions and Answers
Question 1: Which TCD parameter is most useful for detecting cerebral vasospasm after subarachnoid hemorrhage?
- Pulsatility index
- Mean flow velocity (Correct answer)
- End-diastolic velocity
- Resistance index
Correct answer: Mean flow velocity
Mean flow velocity (MFV) >120 cm/s in the MCA is the primary TCD criterion for detecting cerebral vasospasm after subarachnoid hemorrhage.
Question 2: The Lindegaard ratio is calculated by dividing MCA mean velocity by which vessel's velocity?
- Posterior cerebral artery
- Anterior cerebral artery
- Extracranial internal carotid artery (Correct answer)
- Vertebral artery
Correct answer: Extracranial internal carotid artery
The Lindegaard ratio = MCA MFV / ipsilateral extracranial ICA MFV, used to distinguish vasospasm from hyperemia.
Question 3: A Lindegaard ratio greater than 6 is most consistent with which condition?
- Hyperemia
- Severe vasospasm (Correct answer)
- Occlusion
- Normal perfusion
Correct answer: Severe vasospasm
A Lindegaard ratio >6 indicates severe vasospasm, while a ratio <3 with elevated MCA velocity suggests hyperemia.
Question 4: During TCD monitoring for microemboli, what is the characteristic appearance of a HITS signal?
- Bidirectional signal below baseline
- Unidirectional high-intensity transient signal lasting <300 ms (Correct answer)
- Sustained decrease in velocity >50%
- Low-frequency oscillating signal
Correct answer: Unidirectional high-intensity transient signal lasting <300 ms
High-intensity transient signals (HITS) appear as unidirectional, brief (<300 ms) high-intensity signals at least 3 dB above background noise.
Question 5: Which acoustic window is used to insonify the basilar artery during TCD?
- Transtemporal
- Transorbital
- Suboccipital/transforaminal (Correct answer)
- Submandibular
Correct answer: Suboccipital/transforaminal
The suboccipital (transforaminal) window provides access to the vertebral arteries and basilar artery through the foramen magnum.
Question 6: Normal TCD flow direction in the posterior communicating artery (PComA) when acting as collateral is:
- Anterior to posterior, away from probe
- Posterior to anterior, toward probe from transtemporal window (Correct answer)
- Variable with respiration
- Always bidirectional
Correct answer: Posterior to anterior, toward probe from transtemporal window
When the PComA serves as collateral (e.g., ICA stenosis), flow travels from posterior to anterior, appearing as flow toward the probe on transtemporal insonation.
Question 7: Which TCD finding is characteristic of increased intracranial pressure?
- Increased diastolic velocity with normal systolic
- Decreased pulsatility index
- Reverberating or to-and-fro flow pattern (Correct answer)
- Symmetric bilateral flow acceleration
Correct answer: Reverberating or to-and-fro flow pattern
As ICP rises critically, diastolic flow reverses, creating a reverberating (to-and-fro) waveform pattern indicating near-zero or absent net cerebral perfusion.
VT Transcranial Doppler Imaging 2
Which TCD parameter is most useful for detecting cerebral vasospasm after subarachnoid hemorrhage?