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TCD ultrasound and sickle cell disease


Transcranial Doppler ultrasound is a test that uses sound waves to see the inside of the body. You will hear St. Jude staff call it a “TCD.” This test shows how fast blood moves through the blood vessels in your child’s brain.

Why does my child need a TCD?

When your child has sickle cell disease, she has a higher risk of having a stroke than other children. A TCD checks your child’s risk of a stroke. All children with sickle cell anemia (HbSS) or sickle beta thalassemia (SB-0) need this test starting at age 2. TCDs can help the doctor learn if there are:

  • Objects blocking normal blood flow, such as clots, and
  • Blood vessels that are getting narrow. 

Both these things raise your child’s risk of a stroke. So a TCD is important to learn your child’s risk.

How is a TCD done?

A nurse who is trained to do TCD does this test. If you or your child had regular ultrasound before, TCD works the same way. The test uses a small probe that records images of the blood flow inside your child’s head. The images show how well blood is flowing through the blood vessels.

Child having TCD

Read “Do You Know … Ultrasound” to learn more about ultrasound tests, including Doppler ultrasound.

How should my child get ready for a TCD?

Your child should wear comfortable, loose-fitting clothing and take off any hats or glasses. Hair clips and earrings might need to be taken off in areas where the nurse does the test. Your child can eat and drink normally before the test.

What happens during my child’s TCD?

Your child lies on her back on an exam table. The nurse puts a clear gel on your child’s head. This helps the ultrasound probe work better on the skin. The gel might feel cold at first. The nurse will wipe it off when the ultrasound is over. Next, the nurse presses the ultrasound probe firmly on your child’s skin. The nurse might move the probe back and forth in a certain place, or press more firmly in some places. This helps get the best measurement of how blood is moving. During the exam, your child needs to:

  • Be awake,
  • Lie still, and
  • Be as quiet as possible.

Your child cannot eat, drink, or suck on a pacifier during the exam. If your child has trouble lying still or being quiet, you can have a Child Life specialist in the room. The Child Life specialist can help distract your child.

Who sees the results and how do I get them?

A doctor trained to understand TCD and other imaging tests will see the results first. This doctor is called a “radiologist.” The radiologist will look carefully at how fast blood is moving through your child’s brain. Then the radiologist sends a report to the sickle cell doctor and other staff members who care for your child’s sickle cell disease.

What do the results mean?

Below is a list of the possible results and what each one means.

  • Normal—Your child has a low chance of having a stroke. She will have another TCD in one (1) year, or sooner if the sickle cell doctor thinks it is needed. The result will be in the clinic summary sent to your home.
  • Conditional—Your child has a medium chance of having a stroke. She needs another TCD in 3 to 6 months, or sooner if the sickle cell doctor thinks it is needed. A staff member will call to talk with you about your child’s stroke risk.
  • Abnormal—Your child has a high chance of having a stroke. She needs another TCD in 2 to 4 weeks, depending on what the sickle cell doctor decides. A staff member will call to talk with you about your child’s stroke risk.
  • Limited—The nurse could not take all the pictures needed to learn your child’s stroke risk. So your child’s stroke risk is not known. If this happens, the nurse will tell you at the exam. Your child’s sickle cell doctor will tell you when your child can have another TCD.

What are the benefits and risks of TCD?


  • Ultrasound gives a clear picture of your child’s blood vessels.
  • Ultrasound is extremely safe. It does not use radiation.
  • A TCD does not go inside the body. It does not use needles.
  • An ultrasound might be uncomfortable for a short time, but it almost never hurts.


TCD does not have any harmful effects.


If you have questions about your child’s TCD, please talk to your child’s doctor or nurse.


This document is not intended to take the place of the care and attention of your personal physician or other professional medical services. Our aim is to promote active participation in your care and treatment by providing information and education. Questions about individual health concerns or specific treatment options should be discussed with your physician.

St. Jude complies with health care-related federal civil rights laws and does not discriminate on the basis of race, color, national origin, age, disability, or sex.

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