The transcranial (through the skull) Doppler ultrasound test uses reflected sound waves—the same used to see the fetus during pregnancy—to measure how blood is flowing through the blood vessels in the brain. The test does not require entering the body (it is noninvasive). Transcranial Doppler ultrasound is often done together with carotid Doppler ultrasound.
How does transcranial Doppler ultrasound work?
Transcranial Doppler ultrasound works the same way as carotid Doppler ultrasound, except it is done on the head instead of the neck. A small hand-held device (called a probe) is placed lightly on your head, where it gives off ultrasound waves that pass into the body and bounce off the arteries and the red blood cells moving through them, like an echo. The echo from the moving blood is detected by the device. A computer converts the echoes into moving images of the insides of the blood vessels in the brain. Colors in the graphs may be used to show the speed and direction of blood flow.