Transcranial Doppler ultrasound

What is Transcranial Doppler Ultrasound?

Transcranial Doppler ultrasound (TCD) is a type of ultrasound imaging used to measure the flow of blood in the brain. It works by sending high-frequency sound waves through the skull into the brain’s blood vessels, which then reflect the echoes off the moving red blood cells. The TCD machine then produces a visual image of the moving blood cells, showing the direction, speed, and volume of the blood flow.


No special preparation is required for a TCD ultrasound. Most people can comfortably have a TCD test performed while sitting in a reclining chair. A gel will be applied to the skin on the forehead to help with the transmission of ultrasound waves.


During the procedure, the technician will apply a round probe to the patient’s forehead and will place earphones on the patient’s ears. The technician will move the probe around the forehead, using a pattern determined by the doctor to produce an image. The doctor will look at the images on a monitor and any changes in the blood flow can be noted. The procedure usually takes 10-20 minutes.

Types of Transcranial Doppler Ultrasound

There are two types of TCD ultrasound, Color Doppler and Power Doppler. Color Doppler is used to measure the velocity of the blood flow, while Power Doppler measures the rate at which the blood moves.


TCD ultrasound is considered a safe procedure with minimal potential risks. Possible side effects include headaches and dizziness. However, these side effects are rare, and the scan does not involve the use of radiation or any type of contrast agents.

Why It Is Done?

Transcranial Doppler ultrasound is used to diagnose a variety of conditions, including stroke, aneurysm, and intracerebral hemorrhage. It can also detect blood clots, detect narrowing of the arteries, and track changes in blood pressure. It is also used to identify abnormalities in the heart and vascular system.

When Should It Be Done?

A TCD ultrasound should be done any time there is a suspicion of a neurological or cardiovascular disorder. It is often used if a patient is having recurrent or severe headaches, has a family history of stroke, or is undergoing certain types of treatment such as chemotherapy or radiation.