Transcranial Doppler Ultrasonography for Measuring Blood Velocity
Transcranial Doppler ultrasonography (TDU), a noninvasive technology used to record blood velocities from intracranial arteries through selected cranial foramina and thin regions of the skull using a handheld pulsed low frequency Doppler transducer.
The results obtained from Transcranial Doppler ultrasonography allows display, calculation and analysis of peak systolic, peak diastolic, and mean velocities and pulsitility indices. Doctors can locate the major brain arteries in three dimensions by mapping the sampled velocities as a color display of spectra in lateral, coronal and horizontal views. This medical test is conducted to measure the velocity of blood flow through the brain's blood vessels. This is a suitable medical test that helps doctors in the diagnosis of emboli, stenosis, vasospasm from a subarachnoid hemorrhage. This is a quick and inexpensive test. The equipments used for Transcranial Doppler ultrasonography test is potable making it possible for the doctor to carry it anywhere, be it the hospital or the nursing home for both inpatient and outpatient studies. Often this test is used in conjunction with other tests such as MRI, MRA, carotid duplex ultrasound and CT scans.
In 1982, Aaslid and his colleagues demonstrated the transcranial Doppler (TCD) ultrasound examination of the intracranial arteries. The value obtained for a particular artery showed the velocity of blood flowing through the vessel. However, the diameter of that blood vessel is required to determine the actual blood flow. So, Transcranial Doppler ultrasonography is a technique primarily used for measuring relative changes in blood flow.
The clinical utility of the technique has widened and has established value in the assessment of patients with intracranial stenosis, collaterals, subarachnoid hemorrhage, and brain death