ABSTRACT

Since its introduction by Aaslid and colleagues in 1982, transcranial Doppler (TCD)

ultrasonography has rapidly evolved as a noninvasive technique for measuring blood flow

velocity (FV) in the major intracranial arteries. TCD has been described as a stethoscope

of the brain, allowing the clinician to “listen” for the changes in cerebral circulation. The

main advantages are that it is safe, noninvasive, easy to use, portable, reproducible, and

versatile; provides continuous online beat-to-beat information; and does not involve the

use of radioactive substances. It is particularly useful in the investigation of vascular

reactivity because it can detect rapid changes in FV instantaneously (1).