During your SPECT scan
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. 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 3-D images of your body.
How long your scan takes depends on the reason for your procedure.
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 few days.