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Transcranial Doppler Ultrasound


Transcranial Doppler (TCD) ultrasound is a test that uses sound waves to measure blood flow in your brain. It shows the speed and direction of blood through the blood vessels in your brain. It may also show how the blood vessels react to medicines or position changes. Your healthcare provider may use this test to learn if you are at risk for a stroke. TCD may reveal blood clots or areas of your brain that need more oxygen. TCD may also show narrowed blood vessels, injury, or internal bleeding in your brain. This test may help find and prevent serious health problems, or monitor how well other treatments are working for you.


Before the test:

  • Informed consent is a legal document that explains the tests, treatments, or procedures that you may need. Informed consent means you understand what will be done and can make decisions about what you want. You give your permission when you sign the consent form. You can have someone sign this form for you if you are not able to sign it. You have the right to understand your medical care in words you know. Before you sign the consent form, understand the risks and benefits of what will be done. Make sure all your questions are answered.
  • Tell your healthcare provider what medicines you are taking. Also tell him if you have diabetes, COPD, emphysema, or any other lung condition. Tell him if you smoke or have high blood pressure. These factors may affect your test results.

The day of the test:

  • Vital signs: Healthcare providers will check your blood pressure, heart rate, breathing rate, and temperature. They will also ask about your pain. Vital signs give information about your current health.
  • Heart monitor: This is also called an ECG or EKG. Sticky pads placed on your skin record your heart's electrical activity.

During the test:

  • TCD is performed on the outside of your head. Your healthcare provider will place gel on the tip of the TCD probe. Your healthcare provider will gently move the probe across your temple, neck, eyelid, chin, or ear. He may hold the probe during a test, or secure it in place to monitor you during surgery. Your healthcare provider may ask you to change positions to increase or decrease the blood flow in your brain. You may be asked to lie down, squat, sit, or stand during this test. Your healthcare provider may also ask you to lie on your side, with your chin tucked towards your chest.
    Transcranial Doppler Ultrasound
  • Your healthcare provider may ask you to open and close your eyes, or read for several seconds. He may ask you to breathe heavily, or strain as if you are lifting something heavy. Your healthcare provider may ask you to breathe carbon dioxide through a face mask. You may also receive medicine to widen or shrink your blood vessels. You may receive pressure cuffs to wear on your legs. These will tighten and loosen around your legs to change your blood pressure. Your healthcare provider may perform activities around you, such as turning on a light. The TCD sound waves appear in patterns on a monitor, showing how your blood vessels respond to these activities.

After the test:

You may need other tests to help healthcare providers learn more about your condition.


Heat from the TCD probe may burn your skin. You may be at risk for an infection if TCD is done near your eyes or open wounds. Talk to your healthcare provider if you have questions or concerns about these risks.


You have the right to help plan your care. Learn about your health condition and how it may be treated. Discuss treatment options with your healthcare providers to decide what care you want to receive. You always have the right to refuse treatment.

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The above information is an educational aid only. It is not intended as medical advice for individual conditions or treatments. Talk to your doctor, nurse or pharmacist before following any medical regimen to see if it is safe and effective for you.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.