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Transcranial Doppler (TCD) Bubble Study

Transcranial Doppler (TCD) is a test that uses sound waves to study the blood flow in your brain. The sound waves bounce off blood cells, sending information to a computer for analysis. This test may help to determine possible causes of stroke, for example, an abnormal connection between your arteries and veins.


How should I prepare for the test?

  • No fasting is required for the test.
  • Continue with your regular diet and medications.

What will happen during the test?

The test is done by a doctor and a sonographer and takes up to 30 minutes.

  • This test is done while you lie down.
  • An intravenous line (IV) is inserted into a blood vessel in your arm.
  • A small amount of gel is applied onto your scalp and a headset is fitted (Figure 1).
  • A salt solution containing tiny bubbles is injected into your blood vessel, through the IV (Figure 2). You may feel a slight discomfort but there should be no pain. If there is pain, let the doctor know.
  • The headset detects if any of the tiny bubbles reach your brain.
  • Once done, the headset and IV is removed and the gel is cleaned.
  • A report will be sent to your doctor and he/she will discuss the results with you at your next appointment.

Figure 1. A headset is fitted.
Image for illustration purposes only

Figure 2. A salt solution is injected.
Image for illustration purposes only.


Frequently Asked Questions

What happens after the procedure?

  • You may resume your usual activities.

Is the test safe?

  • The test is generally safe. Some patients may experience pain at the area where the IV is inserted or infection of the site. If there is discomfort, let the doctor know or call us.
  • Complications are rare but can occur:
    • 1 to 2 patients per 1,000 cases (0.15%1) may experience a stroke or transient ischaemic attack (mini stroke).
    • Blood clots in the lungs are extremely rare.

1Romero et al. Cerebral Ischemic Events Associated With ‘Bubble Study’ for Identification of Right to Left Shunts. Stroke. 2009;40:2343-2348.

Can I undergo the test if I am feeling unwell?

No. If you are feeling unwell e.g. fever, cough, do not proceed with the test. Call to reschedule your appointment.


Have questions or concerns? Call:

Tel: 6330 6363

Office Hours:
8.00am – 5.30pm, Mon – Wed, Fri
8.00am – 5.00pm, Thurs
Closed on Sat, Sun, Public Holidays

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The information is correct as of July 2021 and subject to revisions without notice.