Radionuclide Tests

These tests are also known as SPECT (single photon emission computed tomography) or MUGA (multiple-gated acquisition scans). Radionuclide tests are only available at some hospitals in the UK.

Common types of radionuclide tests include:

• Myocardial perfusion scan
• CT scans, which include CT coronary angiogram and coronary calcium scoring test

Myocardial perfusion scans

(Also known as thallium scan, MIBI scan, MPS or technetium scan)

What happens during the test?

There are two parts to the test - rest and stress.

For the rest part, a doctor, nurse or radiographer will inject a small amount of radioactive substance (isotope) into the blood. A large camera, positioned close to the chest, picks up the gamma rays sent out by the isotope as it passes through the heart. The camera can take different types of pictures of the heart.

For the stress part, you will be given another injection of isotope and will be asked to exercise on an exercise bike or treadmill. Or you may be given a drug which stimulates the heart to beat faster, (this is particularly useful if you cannot do much exercise). The camera will then take the same sort of pictures as before.

Various isotopes are used, these include technetium, tetrofosmin and thallium.

The staff will monitor your heart rate throughout the test and will also check your blood pressure.

What can the test show?

The camera can take pictures to: 

• help diagnose coronary heart disease
• look at how well your heart pumps, or
• look at the flow of blood to the walls of the heart muscle

CT scans (computerised tomography)

Also known as a CAT scan or EBCT (electron beam computerised tomography)

A CT scan is a sophisticated type of X-ray. It is useful for looking at the internal organs in your body, such as your heart and lungs. A cT scan can look at the heart muscle to see if it is enlarged or faulty in some way.

What happens during the test?

You will need to lie on a bed under the CT scanner. Usually, at the start of the scan, some dye (called a contrast) will be injected into your arm to show up the blood vessels on the surface of the heart. This may cause a warm, flushing sensation which some people find unpleasant. CT scans including the ones described below involve being exposed to a small amount of radiation.

Sometimes drugs to slow your heart down are also injected through a vein. The length of the test depends on the type of scanner used and exactly why you are having the scan. Many scanners are extremely fast now.

CT coronary angiogram

A CT coronary angiogram also uses a CT scan. The procedure is similar to the CT scan described above.

A CT coronary angiogram can produce more detailed images and show how well the blood flows through the coronary arteries (the coronary arteries supply the heart muscle with blood and oxygen). Overall, research has still not shown this test to be quite as helpful for all patients as the conventional coronary angiogram.

Coronary calcium scoring test

This is another test that uses a CT scan. The procedure is similar to the CT scan described above.

It is a way of measuring how much calcium there is in the coronary arteries. It is believed that the higher the calcium score the higher the risk of having coronary heart disease. Although the coronary calcium scoring test can tell how much calcium there is in the arteries, it can't usually tell you exactly where in the coronary arteries the calcium is or whether the plaque is causing a narrowing of the coronary arteries. If you get a high calcium score, you may need further tests.

Doing a CT scan just to get a calcium score is not usually done in the NHS. People usually have it done privately. It does not replace other well established tests such as exercise ECG and angiography.

Are there any risks in having a Radionuclide test?

Radionuclide tests are considered safe to have, however it does mean that you are exposed to some radiation. That's why it is important only to have tests that are really necessary. The basic principle is that, when having any medical test, the benefits of knowing the results of the test should outweigh the risks of having it done. Each person should be considered indvidually.

For more information about tests please see our booklet Tests for Heart Conditions.

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