What is a SPECT scan?

Professor Joanna Wardlaw explains to Senior Cardiac Nurse Emily McGrath how these scans can diagnose blocked arteries, dementia and more.

Single photon emission computed tomography (SPECT) scans create 3D images that show how certain parts of your body are working. This can be useful to look for evidence of narrowings or blockages in your coronary arteries, or to see how your heart is functioning after a heart attack. They are also used for conditions such as dementia, seizures, some psychiatric problems, or problems with bones or joints.

In your heart, SPECT scans may be used to look at the flow of blood, for example to check the amount of narrowing of your coronary arteries. This is a myocardial perfusion scan. A myocardial perfusion scan can also be done using PET (positron emission tomography) imaging. SPECT scans can also help to diagnose amyloidosis.

In your brain, the scans can show blood flow, which is useful because blood flow is closely linked to areas of activity in your brain.

SPECT scan images of the heart
This SPECT scan shows horizontal layers of the heart during a heart attack. Normally the heart looks like a ring; the gap on the left (14 – 17) shows part of the heart muscle dying due to lack of blood.

1. What does a scan involve?

You have an injection of a radioactive dye, so your blood flow shows up in the scanner. You wait a while, then lie down in the ring-shaped scanner – you need to keep very still while inside. For some SPECT scans of the heart, you may be asked to exercise before the scan.

Image of a PET scanner

2. Do I need to do anything to prepare?

Your appointment letter will tell you anything you need to do. Drink plenty of fluids so you are well hydrated, and continue to keep hydrated afterwards.

3. What will it tell my doctor?

A SPECT scan can show many different things. For example, it will show a reduced blood flow to a particular area if you have narrowings of the arteries that supply your heart or your brain. Different types of dementia will also show up on a SPECT scan as reduced blood flow in certain areas of the brain, which will depend on the particular area affected. This can be very helpful in diagnosing which type of dementia you have.

These scans can also be used in people with epilepsy, to show in which areas of the brain the seizures are happening.

4. Does it hurt?

You may feel a prick from the injection, but that’s all.

5. How long does a SPECT scan last?

You may need to wait half an hour or, in some cases, as long as several hours, after the injection and before the scan, depending on how long it takes for the dye to travel to the cells. Usually the actual scan takes 30 to 40 minutes.

6. Who shouldn’t have one?

Pregnant women shouldn’t have a SPECT scan. If you are breastfeeding, ask your doctor.

7. Are there any risks?

The risk is very low. It’s an extremely low dose of radiation that shouldn’t pose a risk to your health, and the benefit to you will outweigh any risk.

Professor Joanna Wardlaw

  • Professor Joanna WardlawProfessor of Applied Neuroimaging, Head of Division of Neuroimaging Sciences and Director of the Brain Research Imaging Centre, University of Edinburgh
  • Honorary Consultant Neuroradiologist at NHS Lothian
  • Author of more than 400 publications
  • Recipient of University of Edinburgh Chancellor’s award for research and the British Society of Neuroradiologists President’s medal
  • Her groundbreaking studies have changed how patients with stroke are treated all over the world

Discover Professor Wardlaw's research into lacunar stroke and dementia.

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