Transcranial Doppler Ultrasonography
Transcranial Doppler ultrasonography (TCD) is a test that measures the speed of blood flow through the cerebral blood vessels. It can be used to support, establish, or confirm diagnoses of cerebral embolism, carotid artery stenosis (blockage), cerebral vasospasm, and subarachnoid hemorrhage.
TCD is usually used with other imaging tests (e.g., MRI, MRA, and CT) to confirm diagnoses. It is noninvasive, involving no radiation or injection of foreign substances, relatively inexpensive, and easy to perform. It can be done using a portable machine and can be completed in a relatively short time frame. The ultrasound probe sends high-pitched inaudible and invisible sound waves into the body, which “bounce” off of the tissues in varying patterns. The timing, amount, and pattern of the returning sound waves are recorded by the sensor in the probe, and the appearance of these returning sound waves reflects various changes in the tissues. When an image is...