Transcranial Doppler (TCD)

What is a Transcranial Doppler test?

Transcranial Doppler test is a valuable diagnostic test that involves making an ultrasound recording of blood flow in the brain before and during peripheral venous injection of agitated saline (which contains micro bubbles).

How do I prepare for the test?

There is no special preparation required. You should come as you are and eat or drink as you normally do. If you take medications, you should continue to take them as normal unless your doctor specifies otherwise.

How much time the test will take?

The test will last 30 minutes but expect to be at London Heart Centre for 45 minutes.

What happens during the test?

You will be escorted into an Ultrasound room by our Cardiac Physiologist (technician).  An IV (intravenous line) will be inserted into a peripheral vein (e.g. arm). The agitated saline will be administered through this line. During the test, you will lie comfortably on a bed. From time to time, you may be asked to move into different positions. A gel that washes off with water will be put on your temples. Ultrasound does not travel well through air, so the gel is used to keep air bubbles from blocking the sound waves. The gel may feel cold on your temples. A small probe, called the transducer, will be gently placed on various positions of the temples, to record blood flow in the brain in real-time. As this is done, you may hear a “whooshing” sound. This sound relates to the movement of blood within your brain. When all the necessary information is obtained, the gel and IV line will be removed.

What are the risks from the test?

There are no known risks or after effects from either the ultrasound or saline injection.

What happens after the test?

The ultrasound recordings will be sent to our cardiologist who is a specially-trained physician in reading these recordings. He or she will interpret the recordings and will then provide your physician with a written report. The cardiac physiologist will not be able to provide you with any results at the time of the test.