Radionuclide tests are one of several types of tests
performed to assess your heart condition.
The test that is offered to you will depend
on your condition and symptoms, as well as on what tests and
equipment are available.
Radionuclide tests are considered safe.
However, during the test you will be exposed to some radiation.
Every day we are exposed to a small amount of
radiation which occurs naturally in the environment. Our risk of
cancer can increase if we're exposed to plenty of radiation, but
the amounts used in these tests are small.
Your doctor will only suggest you have the
test if he or she feels it's really necessary, and if its benefits
outweigh any risks.
Types of radionuclide tests
There are two types of radionuclide tests: a myocardial
perfusion scan and a computerised tomography (CT)
scan. There are lots of different names for these
The names we mention below are some of the more common ones. If
the name of your test isn't mentioned here, check with your doctor
or radiographer what your test involves.
Myocardial perfusion scan
This is also known as a thallium scan,
MIBI scan, MPS or
technetium scan. A camera takes pictures
- look at the pumping action of your heart
- look at the flow of blood to your heart muscle
- see how your heart functions when it has to work harder - for
example, when you're being more active, or
- help diagnose coronary heart
What happens during a myocardial perfusion scan?
There are two parts to the test - stress and
For the stress part, you will be given an
injection of a small amount of isotope
(radioactive substance) and be asked to exercise on an exercise
bike or treadmill. Or, you may be given a drug that
stimulates your heart to beat faster (this is useful if you cannot
do much exercise).
A large camera, positioned close to your chest, picks up
the gamma rays sent out by the isotope as it passes
through your heart. The camera takes pictures of the
different parts of your heart.
For the rest part, you will be given a
small amount of isotope while you're resting. The camera will
then take the same sort of pictures as before.
Various isotopes are used, including technetium and
During the test, the staff will monitor your heart rate
and check your blood pressure.
When might I be offered this test?
You may be offered this test if you haven't previously been
diagnosed with CHD and you go to A&E with chest pain. If
the doctors think it's very likely that your chest pain is caused
by CHD this test may be used to confirm if you have
You may also be offered this test if you have CHD and your
doctor wants to find out if you'll benefit from having a procedure
such as an angioplasty or coronary bypass graft.
CT scans (computerised tomography)
A CT scan is also known as a CAT
scan. It's a sophisticated type of X-ray, which can
produce detailed images of your heart. It can look at:
- the pumping action of your heart
- the structure of your heart - its muscle, valves and coronary
arteries (the arteries that supply your heart muscle with blood and
- the flow of blood through your heart and your coronary
A CT scan can see how well your heart is
working and can help to diagnose various heart
conditions such as an enlarged heart, heart valve
problems or coronary heart disease (CHD).
This test can also measure how much
calcium there is in your coronary arteries - this is
called a coronary calcium scan. The higher your
calcium score, the higher your risk of having CHD. If you have a
high or medium calcium score, you may need further tests. If you
have a low calcium score, it's unlikely that you have CHD.
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. This allows
the camera to easily see the heart's structure and blood
flow. This may cause a warm, flushing sensation which some
people find unpleasant.
You may be given a medicine to slow your heart rate down. This
is to ensure that the doctors are able to get the best possible
image of your heart.
How long the test is, depends on the type of
scanner used and why you are having the scan.
When might I be offered this test?
You may be offered a CT scan if doctors are
not entirely sure that your chest pain is caused by CHD. So this
test is often used to make sure that you don't have CHD.
If your doctor is reasonably sure that you do
have CHD, he or she is more likely to offer you a
myocardial perfusion scan or a conventional