Transcranial dopplers (TCD) : University College London Hospitals NHS Foundation Trust

This page is for parents and carers of children with sickle cell disorder. It explains what happens during a Transcranial Doppler Scan.

As part of your child’s care in the Sickle Cell Clinic we offer TCD as a regular screening test starting at the age of two. TCD helps to identify children who are at an increased risk of having a stroke. By using screening tests, such as blood tests and TCD, we aim to detect and treat any problems at an early stage.

A Doppler machine uses sound waves, much like the ultrasound used during pregnancy, to check how fast blood is flowing in the vessels in the brain. This helps us to measure the speed of blood flow in some of the arteries that supply blood to the brain. If arteries are narrow, the blood travels faster and the machine makes a higher pitched sound.

In most children with sickle cell disorder, the TCD results are normal. If the scan shows something unusual, we may need to repeat it or do more tests to check the arteries. If the results are borderline (known as ‘conditional’), we will repeat the test within a few weeks.

We recommended that all children with SCD have this screening test at the age of two, and then once a year after that. This can be less frequent for children with HbSC disease.

The TCD test helps us find early signs of blood flow problems in the brain. We can then talk to you about more detailed tests and treatment options to help prevent serious problems like a stroke. For example, large studies in America have shown that children with high blood flow who receive regular blood transfusions have a much lower risk of having a stroke.

TCD is safe and there are no risks associated with it.

The scans are only performed once a month so if your child is unable to make the appointment, please contact us as soon as possible.

Your child will have the scan in the Children’s Outpatient Department, Elizabeth Garrett Anderson Wing, University College Hospital. You will see your child’s consultant and CNS but the scan will be performed by a doctor from another hospital. This gives your child's consultant more time to talk with you during the consultation.

The scan usually takes about 30 minutes but it may take longer with younger children. It is painless and your child needs to be relaxed and still during the scan. They will be awake and lying on a couch, and you will be able to stay with them the entire time.

The consultant will review the results of the scan during your clinic visit, usually on the same day.

If the results are normal, we will plan to repeat the test every year or so.

We will schedule another TCD test within a few weeks if:

the results show fast blood flow, which might indicate narrowing of the blood vessels, or
the results are not clear.

You will have a summary of the results in your clinic letter.

We may also arrange other tests, including:

MRI and MR Angiography (MRA) – these are painless scans to check the brain and its blood vessels in more detail
imaging TCD (TCDi) – this is another painless scan to identify the blood vessels if the traditional TCD is difficult to interpret.

If the scans show narrowing of blood vessels, it could mean reduced blood flow to part of the brain and an increased risk of stroke in the future. If this is the case, we will explain the results to you and tell you about the available treatment options to help reduce this risk.

Haematology admin team:

uclh.redcelladminteam@nhs.net

Haematology clinical nurse specialists (CNSs):

uclh.redcell.cnsteam@nhs.net

Haematology advice line (office hours, children and adults):

020 3447 7359

Adult haematology advice line (out of hours):

07852 220 900

Paediatric helpline (out of hours):