transcranial Doppler ultrasonography
Non-invasive ultrasound technique for measuring blood flow velocities in major intracranial arteries through the skull.
Full Definition
Transcranial Doppler ultrasonography (TCD) is a non-invasive diagnostic technique that uses ultrasound to measure blood flow velocities and detect emboli in the major intracranial arteries. TCD transmits ultrasound waves through thin areas of the skull (temporal windows) to interrogate vessels including the middle cerebral artery, anterior cerebral artery, posterior cerebral artery, and basilar artery. The technique provides real-time assessment of cerebral hemodynamics and can detect vasospasm, stenosis, emboli, and changes in cerebral autoregulation. In neurocritical care, TCD is particularly valuable for monitoring vasospasm after subarachnoid hemorrhage, assessing cerebral circulatory arrest in brain death evaluation, and detecting microemboli during cardiac procedures. Results are typically reported as mean flow velocities and pulsatility indices.
Usage
Usage note: Commonly abbreviated as TCD. Distinct from transcranial color duplex which provides additional imaging capabilities.
In Context
- "Daily TCD monitoring revealed progressive increase in middle cerebral artery velocities consistent with vasospasm." — Neurocritical care progress note
- "Transcranial Doppler ultrasonography confirmed absent intracranial flow supporting the diagnosis of brain death." — Brain death evaluation report