Medically reviewed by Drugs.com. Last updated on Jul 27, 2022.
A single-photon emission computerized tomography (SPECT) scan lets your doctor analyze your body's organs, tissue and bones. A SPECT scan is a type of nuclear imaging test, which means it uses a radioactive substance and a special camera to create 3D pictures.
While imaging tests such as X-rays can show what the structures inside your body look like, a SPECT scan produces images that show how your organs are functioning. For instance, a SPECT scan can show how well blood is flowing to your heart; what areas of your brain are more active or less active; or what parts of your bone are affected by cancer.
Why it's done
Some of the most common uses of SPECT are to help diagnose or monitor brain disorders, heart problems and bone disorders.
A SPECT test creates a detailed, 3D map of the blood flow activity in your brain, which can be helpful in determining which parts of the brain are being affected by:
- Clogged blood vessels. SPECT scanning can detect altered blood flow in the brain and help diagnose or evaluate certain vascular brain disorders, such as moyamoya disease, a condition in which the arteries in the brain become blocked or narrowed.
- Seizure disorders. A SPECT scan can help diagnose and treat seizure disorders, such as epilepsy, by pinpointing the area of seizure activity in the brain.
- Parkinson's disease. In rare cases, your doctor may suggest a specific SPECT scan called a dopamine transporter scan (DaTscan) to help confirm a diagnosis of Parkinson's disease, a progressive neurological disorder that affects movement.
Some medical institutions may use SPECT scanning to help evaluate other brain conditions, such as dementia or head trauma.
Because the radioactive tracer highlights areas of blood flow, SPECT can check for:
- Clogged coronary arteries. If the arteries that feed the heart muscle become narrowed or clogged, the portions of the heart muscle served by these arteries can become damaged or even die.
- Reduced pumping efficiency. SPECT can show how completely your heart chambers empty during contractions.
Areas of bone healing or cancer progression usually light up on SPECT scans, so this type of test is being used more frequently to help diagnose hidden bone fractures. SPECT scans can also diagnose and track the progression of cancer that has spread to the bones and help identify sites for bone biopsy.
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
- Very rarely, an allergic reaction to the radioactive tracer
Be sure to tell your doctor or radiation technologist if there's a possibility you're pregnant or if you're breastfeeding.
Risks of radiation
Your health care team uses a small amount of radiation in order to perform a SPECT scan, and the test is not associated with any long-term health risks. 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.
In general, you should:
- Leave metallic jewelry at home.
- Inform the technologist if you're pregnant or breast-feeding.
- Bring a list of all the medications and supplements you take.
What you can expect
During the test
SPECT scans involve two steps: receiving a radioactive injection (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 intravenous (IV) infusion into a vein in your arm. The tracer dose is very small, and you may feel a cold sensation as it enters your body. You may be asked to lie quietly in a room for 20 minutes or more before your scan while your body absorbs the radioactive tracer. In some cases, you may need to wait several hours or, rarely, several days between the injection and your SPECT scan.
Your body's more active tissues will absorb more of the radioactive substance. For instance, during a seizure, the area of your brain causing the seizure may retain more of the radioactive tracer, which allows doctors to pinpoint the area of your brain causing your seizures.
Undergoing the SPECT scan
The SPECT machine is a large circular device containing a camera that detects the radioactive tracer your body absorbs. During your scan, you lie on a table while the SPECT machine rotates around you. 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 3D images of your body.
How long your scan takes depends on the reason for your procedure.
After the test
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 few days.
During a SPECT scan, your health care team positions you on a table. Then the SPECT machine rotates around you, taking pictures of internal organs and other structures highlighted by the radioactive tracer in your body.
A radiologist or doctor with advanced training in nuclear medicine will analyze the results of your SPECT scan and send them to your doctor. 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.
SPECT scan results can be in color or shades of gray. The varying shades or colors show your doctor which cells in your body are absorbing more or less of the radioactive tracer. This scan includes images of the kidneys, liver and spleen.