Transcranial Doppler
Transcranial Doppler (TCD) was invented by Rune Aaslid in the late 1970's. TCD primarily measures the mean flow velocity of the major basal vessels of the Circle of Willis, providing physiological data of the intracranial hemodynamics.
APPLICATIONS
Bubbleometry- TCD is the gold standard for right to left shunt detection. When performed correctly it is the most sensitive diagnostic tool for R-L shunt detection.
Intracranial stenosis- TCD uses velocity to determine presence and or degree of intracranial stenosis. TCD has certain advantages of MRA/CTA, and can be used as a compliment to MR's and CT's to increase overall diagnostic accuracy.
Emboli detection- TCD is the only way to visualize emboli in real time. Emboli detection is commonly performed intraopertivley, post embolic stroke, and on patients with know carotid stenosis.
TCD with Duplex Imaging of the Carotids- TCD's performed with carotid ultrasound has become the standard in many advanced institutions. In normal CUS studies, the TCD detects intracranial stenosis that could potentially be the cause of symptoms. In abnormal CUS studies, the TCD intracranial hemodynamic shifts resulting from proximal stenosis, evaluation of collaterals, vasomotor response, and spontaneous emboli resulting from the carotid plaque.
Vasospasm- TCD has been a standard tool for assessing vasospasm post subarachnoid hemorrhage for decades. TCD velocity shifts will occur up to three days prior to symptoms onset, and decrease the patients exposure to radioactive isotopes.
Vasomotor Reactivity - With TCD a simple procedure to assess vasodilatory reserve capacity, can be performed with breath holding maneuvers.