Transcranial Doppler ultrasound evaluates blood circulation in the brain. A device called a transducer is passed lightly across different areas of your head, directing high-frequency sound waves (ultrasound) at particular cerebral arteries. The sound waves are reflected back at frequencies that correspond to the velocity of blood flow, and are converted into audible sounds and graphic recordings.
Duplex scanning combines Doppler ultrasound with real-time ultrasound imaging of the arteries. Images are displayed on a viewing monitor and may also be recorded on film or video for later examination.
Purpose of the Transcranial Doppler Ultrasound
- To provide important information and help diagnose and determine the best treatment for stroke or stroke warning signs
- To evaluate blood flow in the brain and the major arteries and veins of the neck, arms and legs
- To identify abnormalities, such as narrowing (vasospasm), blockages, or arteriovenous malformation (a congenital blood vessel defect), in arteries within the brain
- To monitor progression of cerebral vasospasm
Who Performs It
- A radiologist, a neurologist, or a trained technician
Before the Transcranial Doppler Ultrasound
- No special preparation is necessary.
What You Experience During Transcranial Doppler Ultrasound
- You will either lie on a bed or table or sit in a reclining chair.
- A small amount of water-soluble gel is applied to the skin on certain portions of your face and head to enhance the transmission of sound waves.
- The examiner then moves the transducer back and forth over your head—typically, the forehead, eye socket region, and base of the skull—to obtain different views of the artery or arteries being studied.
- Once clear images are obtained, they are recorded on film or video for later analysis.
- The test usually takes less than 1 hour.
Risks and Complications of Transcranial Doppler Ultrasound
- Ultrasound is painless, noninvasive, and involves no exposure to radiation. There are no associated risks.
After the Transcranial Doppler Ultrasound
- The examiner removes the conductive gel from your skin.
- You may resume your normal activities.
Results of Transcranial Doppler Ultrasound
- A radiologist reviews the recorded images and other test data for evidence of any abnormality. High blood flow velocity suggests that blood flow is too turbulent or that the blood vessel is too narrow. This finding may indicate a blockage, vasospasm, or an arteriovenous malformation.
- If a definitive diagnosis can be made, appropriate treatment will be initiated.
- In many cases—particularly before surgical treatment—additional tests, such as arteriography of the cerebral blood vessels, are required to further evaluate abnormal findings and to provide more specific information.
The Johns Hopkins Consumer Guide to Medical Tests
Simeon Margolis, M.D., Ph.D., Medical Editor
Updated by Remedy Health Media