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Please note:

Transcranial doppler (TCD) studies are only done in hospitals.


What is an TCD Test?

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. It may also show how the blood vessels react to medicines or position changes. 


How to prepare for your TCD test?

You or a close family member will be asked to sign a legal document called a consent form. It gives healthcare providers permission to do the procedure. It also explains the problems that may happen, and your choices.


Make sure all your questions are answered before you sign this form. 

Tell your healthcare provider what medicines you take. Also tell him or her if you have diabetes, COPD, emphysema, or any other lung condition. Tell him or her if you smoke or have high blood pressure. These factors may affect your test results.


What are the risks of TCD testing?

You may be at risk for an infection if TCD is done near your eyes or open wounds. 

What do I expect in TCD test? TCD is performed on the outside of your head. Your healthcare provider will place gel on the tip of the TCD probe. He or she will gently move the probe across your temple, neck, eyelid, chin, or ear. He or she may hold the probe during a test, or secure it in place to monitor you during the test. 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.

He or she may ask you to open and close your eyes, hold your breath, or breathe heavily. He or she may also ask you to strain as if you are lifting something heavy.


You may be given medicine to widen or shrink your blood vessels. Healthcare providers may place blood pressure cuffs on your thighs. 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.

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