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SPECT scan
By Mayo Clinic staffMayo Clinic Health Manager
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Definition
A single-photon emission computerized tomography (SPECT) scan 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 3-D images that show how your organs work. For instance, a SPECT scan can show how blood flows to your heart or what areas of your brain are more active or less active.
Why it's done
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, stroke and seizure
- 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)
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
- Rarely, an allergic reaction to the radioactive tracer
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 nursing baby. Women of childbearing age may be required to take a pregnancy test before a SPECT procedure.
Risks of radiation
Your health care team uses the lowest amount of radiation possible in order to perform the scan. 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.
How you prepare
How you prepare for a SPECT scan depends on your particular situation. Ask your health care team whether you need to make any special preparations before your SPECT scan.
What you can expect
During your SPECT scan
Most SPECT scans involve two steps: receiving a radioactive dye (called a tracer) and using a SPECT machine to scan a specific area of your body.
Receiving a radioactive substance
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.
Your body processes the radioactive substance, 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 usually grow and multiply at a much quicker rate than do healthy cells.
What specific radioactive tracer you receive depends 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 before your scan 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.
The SPECT machine is a large circular device that contains a special camera called a gamma camera, which 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 the reason for your procedure. In some cases, you may undergo more scans hours or days later.
After your SPECT scan
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.
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.
Ask your health care team how long to expect to wait for your results.
- Wernick MN, et al. Emission Tomography: The fundamentals of PET and SPECT. San Diego, Calif.: Elsevier; 2004:146.
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- Nuclear medicine. American Society of Radiologic Technologists. https://www.asrt.org/content/ThePublic/AboutRadiologicProcedures/Nuclear_Medicine.aspx. Accessed Jan. 9, 2009.
- What is nuclear medicine? Society of Nuclear Medicine. http://interactive.snm.org/index.cfm?PageID=1110&RPID=3106&FileID=5932. Accessed Jan. 12, 2009.
- Computer imaging/tomography. American Heart Association. http://www.americanheart.org/presenter.jhtml?identifier=4554. Accessed Jan. 9, 2009.
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