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A transcranial Doppler, or TCD, is a noninvasive ultrasound test that measures blood flow in and around the brain. It uses sound waves to evaluate how fast blood is moving through certain brain arteries. The test does not use radiation and does not require an incision. It is performed by trained clinicians or technologists and interpreted with the patient’s symptoms and other test results.
read more about transcranial doppler ...A transcranial Doppler is used to evaluate blood flow problems that can affect the brain. It can help assess stroke risk, narrowed blood vessels, vasospasm after subarachnoid hemorrhage, and blood flow changes linked to certain conditions. In some patients, it is also used to monitor blood flow during treatment or after a diagnosis. The test is one part of a wider neurologic or vascular evaluation.
The test uses a handheld ultrasound probe placed on specific areas of the head where sound waves can pass through the skull. These areas are sometimes called acoustic windows. The device measures changes in reflected sound waves as blood cells move through the vessels. Those measurements help estimate the speed and direction of blood flow.
The patient usually lies down or sits while gel is placed on the skin. The technologist moves the probe around the temples, back of the head, neck, or closed eyelid depending on which vessels need to be checked. The test is usually painless, though light pressure from the probe can feel uncomfortable. Results are reviewed by a clinician who looks for abnormal flow patterns or speeds.
Transcranial Doppler is generally safe and does not expose the patient to ionizing radiation. The test can be limited if the ultrasound signal cannot pass well through the skull. It measures blood flow speed, but it does not show every detail that CT angiography, MR angiography, or catheter angiography can show. Sudden weakness, severe headache, trouble speaking, vision loss, or facial drooping needs emergency care.
No. It is usually painless, though the probe can create mild pressure on the skin during the exam.
No. It uses ultrasound sound waves, not ionizing radiation.
It can help evaluate blood flow linked to stroke risk or stroke-related problems, but it is usually used with other clinical findings and imaging tests.
The time can vary, but the test is usually completed in under an hour. More complex monitoring can take longer.
Transcranial Doppler (TCD) Ultrasound. Cleveland Clinic. https://my.clevelandclinic.org/health/diagnostics/4998-transcranial-doppler-ultrasound-ultrasonography-test. Date Accessed June 15, 2026.
About Transcranial Doppler (TCD). Johns Hopkins Medicine. https://www.hopkinsmedicine.org/neurology-neurosurgery/specialty-areas/neurovascular-laboratory/transcranial-doppler. Date Accessed June 15, 2026.
Doppler Trans-Cranial Assessment, Protocols, and Interpretation. StatPearls (NCBI Bookshelf). https://www.ncbi.nlm.nih.gov/books/NBK570636/. Date Accessed June 15, 2026.
Transcranial Doppler Ultrasound: Technique and Application. PubMed Central. https://pmc.ncbi.nlm.nih.gov/articles/PMC3902805/. Date Accessed June 15, 2026.
Doppler Ultrasound. MedlinePlus Medical Test. https://medlineplus.gov/lab-tests/doppler-ultrasound/. Date Accessed June 15, 2026.