Transcranial Doppler Ultrasound (Ultrasonography Test)
What is a transcranial Doppler ultrasound?
Transcranial Doppler (TCD) ultrasound is a painless test that uses sound waves to examine blood flow in your brain. Your doctor has recommended that you have this test to diagnosis a medical condition that affects blood flow to and within the brain. The test is also used to monitor the results of certain treatments, for example, the breakup of clots inside brain arteries.
During TCD, sound waves are sent through the tissues of your skull. These sound waves reflect off blood cells moving within your blood vessels, allowing the radiologist or neurologist to interpret their speed and direction. The sound waves are recorded and displayed on a computer screen.
What medical conditions are diagnosed or monitored with transcranial Doppler ultrasound?
Transcranial Doppler ultrasound is used to diagnose or monitor a wide range of medical conditions affecting blood flow, including:
- Acute ischemic stroke: Acute ischemia stroke happens when a blood clot develops in a blood vessel in the brain, cutting off oxygen-rich blood flow to the brain.
- Vasospasm: This is the narrowing of a section of a blood vessel due to contraction. In this case, it’s a reaction to a brain bleed – a subarachnoid hemorrhage/brain aneurysm rupture.
- Stenosis in brain arteries: This is a narrowing or blockage of a section of an artery, most commonly due to atherosclerosis (hardening of the arteries).
- Cerebral microemboli: These are small blood clots that travel through the bloodstream and cause a transient ischemic attack (mini stroke).
- Stroke risk in adults and children with sickle cell anemia: The changed shape of blood cells in sickle cell anemia can lead to blood clots and blocked blood vessels, increasing the risk of stroke.
- Patent foramen ovale/right-to-left shunt detection: In this test, a solution is injected into a vein in the forearm. The presence of bubbles in the brain arteries indicates that blood is flowing in the wrong direction due to a hole in the wall between the two upper chambers of the heart (called a patent foramen ovale [PTO]). A PTO is a source of stroke in children.
- Brain death confirmation.
What happens during a transcranial Doppler ultrasound?
There is no special preparation for transcranial Doppler ultrasound.
- It is not necessary to change into a hospital gown or remove jewelry.
- Your ultrasound test is performed by specially trained technologists and interpreted by a board-certified radiologist or neurologist.
- You will either lie on a padded examining table or sit in a chair during the test.
- A small amount of water-soluble gel is applied to the skin over the area to be examined. The gel is usually applied to either the back of the neck, above the cheek bone, in front of the ear or over the eyelid. These are the blood vessel sites that supply the brain. The gel does not harm your skin or stain your clothes.
- A small microphone-looking-like device called a transducer is held in place on the exam area. The transducer sends high-frequency sound waves through the brain and captures the returning blood flow information. The ultrasound signal is turned into graphs or color pictures that are shown on the display screen.
- There is virtually no discomfort during the test. You may experience some minor pressure as the transducer is pressed against your skin.
- You will need to keep your head still and avoid talking during the test.
- The ultrasound takes about 30 to 60 minutes to complete.
- After the test, the gel will be wiped off your skin.
Results and Follow-Up
How will I get the results of my transcranial Doppler ultrasound?
A radiologist or neurologist will analyze the images and send a report to your healthcare provider who ordered the test. Your doctor will discuss the test results with you.
Sometimes a follow-up test is needed to get additional views or to monitor a particular medical condition for which the test was ordered or to see if treatment worked.
Are there any side effects from the transcranial Doppler ultrasound test?
Transcranial Doppler ultrasound is not hazardous. There are no harmful side effects. Ultrasound doesn’t use radiation, as X-ray tests do.