SPECT scan

Find out what to expect during and after a SPECT scan in order to reduce any anxiety you might be feeling about your test.

A single-photon emission computerized tomography (SPECT) procedure lets your doctor analyze the function of your internal organs. A SPECT scan is a type of nuclear imaging test, which means it uses a radioactive substance and a special camera to create pictures of your organs. While imaging tests such as X-rays can show what the structures inside your body look like, a SPECT scan produces three-dimensional images that show how your organs work — for instance, how blood flows to your heart or what areas of your brain are more active or less active.

Who is a SPECT scan for?

Your doctor may order a SPECT scan to help diagnose or monitor a number of diseases and conditions, including:

• Brain disorders such as Alzheimer's disease, epilepsy, head injury, Huntington's disease, memory loss, migraine, Parkinson's disease and schizophrenia.
• Heart problems such as blockages in the arteries of the heart, chest pain and heart attack.
• Cancer, including primary tumors and cancer that has spread to other areas of the body (metastasized).

How do you prepare for a SPECT scan?

How you prepare for a SPECT scan depends on your particular situation. In many cases, no restrictions are placed on what you can eat or drink before the procedure. Other times you may be allowed only water after midnight before the procedure. Before a SPECT scan of your heart, you may be asked to avoid caffeine or to stop taking certain medications. Ask your health care team whether you need to make any special preparations before your SPECT scan.

How is a SPECT scan done?

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SPECT scan

Most SPECT scans involve two steps: receiving a radioactive dye and using a SPECT machine to scan a specific area of your body.

Receiving a radioactive substance
Before you undergo the actual SPECT scan, you'll receive a radioactive substance through an injection or through an intravenous (IV) infusion into a vein in your arm. In some cases you may inhale the substance through your nose.

The radioactive substance, called a tracer, is processed by your body, with your body's more active tissues absorbing more of the substance. For instance, during a seizure, the area of your brain causing the seizure may absorb more of the radioactive tracer, which allows doctors to pinpoint the area of your brain causing your seizures. In another example, cancer cells may absorb more radioactive tracer than other cells because cancer cells may grow and multiply at a much quicker rate than healthy cells.

What specific radioactive tracer you receive before your SPECT scan will depend on what type of procedure you're undergoing and what part of your body is being scanned. You may be asked to lie quietly in a room for 15 minutes or more while your body absorbs the radioactive tracer.

Undergoing the SPECT scan
Members of your health care team position you on a table in the room where you'll undergo your SPECT scan. Depending on your specific case, you may have your head or other parts of your body strapped into place so that you don't move during the procedure. In some cases you may receive a sedative before your SPECT scan to make you more comfortable while lying still.

The SPECT machine is a large circular device that contains a special camera called a gamma camera that detects the amount of radioactive tracer absorbed by your body. During your scan, the SPECT machine rotates around you as you lie on the table. The SPECT machine takes pictures of your internal organs and other structures. The pictures are sent to a computer that uses the information to create 3-D images of your body.

How long your scan takes depends on your procedure. Most SPECT scans take 30 to 90 minutes.

Other types of SPECT procedures
Special types of SPECT scans may be conducted differently, such as a:

• Nuclear stress test. This test measures how well the blood flows into your heart. During this test you receive an injection of radioactive tracer after exercising on a treadmill or stationary bicycle. You undergo the SPECT scan and then wait a few hours and undergo another scan. This allows your doctor to compare blood flow to your heart during stress and during rest.
• Seizure scan. A SPECT scan may help doctors determine what area of your brain is causing your seizures if you have epilepsy. To do this, you receive an injection of radioactive tracer when you have a seizure. Then you undergo a SPECT scan. You receive another injection and undergo another scan 24 hours later. Your doctor then compares the two scans.

What can you expect during a SPECT scan?

You may feel some discomfort during your injection or infusion of radioactive tracer when the needle is inserted in your vein. Some people are allergic to the chemicals in the tracer, so tell your doctor about any allergies you have.

The SPECT scan won't hurt. But you may feel uncomfortable lying still for an extended period. You may be offered a sedative to relax you.

Results

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SPECT scan results

Your doctor analyzes the results of your SPECT scan. Pictures from your scan may show colors that tell your doctor what areas of your body absorbed more of the radioactive tracer and which areas absorbed less. For instance, a brain SPECT image might show a lighter color where brain cells are less active and darker colors where brains cells are more active. Some SPECT images show shades of gray, rather than colors.

Your results may be available in about a week, though that may vary. Ask your health care team how long to expect to wait for your results.

Risks

For most people, SPECT scans are safe. If you receive an injection or infusion of radioactive tracer, you may experience bleeding, pain or swelling where the needle was inserted in your arm. Rare allergic reactions to the radioactive tracer are possible, so tell your doctor about any allergies you have.

SPECT scans aren't safe for women who are pregnant or breast-feeding because the radioactive tracer may be passed to the developing fetus or the baby. Women of childbearing age may be required to take a pregnancy test before a SPECT procedure.

Most of the radioactive tracer leaves your body through your urine within a few hours after your SPECT scan. Your doctor may instruct you to drink more fluids, such as juice or water, after your SPECT scan to help flush the tracer from your body. Your body breaks down the remaining tracer over the next day or two.

Your health care team uses the lowest amount of radiation possible in order to perform the scan. How much radiation you're exposed to depends on many factors, such as your particular SPECT procedure and your own body. In general, a SPECT scan exposes you to radiation levels similar to those you might encounter naturally in the environment over the course of a year. Talk to your doctor if you're concerned about your exposure to radiation during a SPECT scan.