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Transcranial doppler ultrasound (TCD)

Transcranial doppler ultrasound (TCD) is a safe, non-invasive way of investigating the circulation in your head. It measures the speed and direction of blood flow around the base of your brain, and can be a useful diagnostic test if you have a circulation disorder.

A TCD is mainly carried out if you have one of three conditions:

Subarachnoid haemorrhage (SAH)

In subarachniod haemorrhage, where there is bleeding into the brain, the arteries often narrow (spasm) because of the presence of blood in the space outside the arteries. Spasm resolves as you recover, but TCD measurements help identify the extent to which it is present so that you can have appropriate treatment.

Vascular disorders

In vascular disorders (problems with blood vessels), TCD can help to identify abnormalities of the circulation in your head, whether caused by atherosclerosis (hardening of the arteries) or by congenital abnormalities of the circulation. Using TCD we can help to establish whether an artery is narrowed or blocked. TCD is also used if you are undergoing carotid endarterectomy (surgery to remove blockages in your neck arteries), enabling the surgeon to monitor the blood supply to your brain during surgery.

Sickle cell disease

In children with sickle cell disease it has been shown that the presence of high blood velocities, measured by TCD, indicates an increased risk of stroke. We monitor velocities in these children on a regular basis to help ensure they are getting the treatment they need.

Having a transcranial doppler ultrasound

The transcranial doppler measurement is simple, painless and non-invasive, and takes between 10 and 40 minutes. An ultrasound detector will be put on your head, close to the temple. Most of our TCD measurements are carried out on inpatients.

Meet the team

Dr Tony Birch is head of the transcranial doppler ultrasound service.

We also offer TCD training courses for clinicians interested in learning to use this technique, for example in neurological intensive care, stroke medicine or sickle cell disease.

Contact us

You can email Dr Birch at

Telephone for appointments on 023 8120 6109. Please note that this is a specialised test, and referrals can only be accepted from hospital consultants.