Positron: an electrically charged particle that has the opposite charge as an electron. Photon: a particle that travels at the speed of light. Damaged tissues have reduced metabolic activity therefore, gamma radiation from these areas is reduced or absent. Positron emission tomography (PET): a nuclear medicine test in which tissue function can be imaged. Gamma rays: electromagnetic radiation emitted during radioactive decay and having an extremely short wavelength.
If you have further questions about this diagnostic test, contact the doctor that ordered the test or visit. The nuclear medicine doctor will promptly review your images and communicate directly with your referring doctor, who in turn will discuss the results with you. Some people may have an allergic reaction to the tracer or the contrast agent. Women who are pregnant or nursing should not undergo a SPECT scan. If you have concerns about your cumulative radiation exposure, talk to your doctor. Your exposure risk could vary, however, depending on how many CT or other scans you have had. The long-term risk of radiation exposure is usually worth the benefits of diagnosing serious medical conditions. They breakdown quickly and are removed from the body through the kidneys. This exposure is limited, however, because the radioactive chemicals have short half-lives. The tracer is radioactive, which means your body is exposed to radiation. Be sure to drink plenty of fluids to flush the tracer from your body. Once the scan is complete, you can leave. Be sure to remain as still as possible so that the machine can take accurate pictures. Next, you'll lie comfortably on a scanner table while a special camera rotates around your head. You'll be asked to rest for about 10-20 minutes until the tracer reaches your brain. What happens during the test?įirst, you will receive an injection of a small amount of radioactive tracer. Wear comfortable clothing and be prepared to stay for 1 to 2 hours. Who performs the test?Ī specially trained nuclear medicine technologist will perform the test in the Nuclear Medicine department of the hospital, or at an outpatient imaging center. This type of scanning is also useful in diagnosing stress fractures in the spine (spondylolysis), blood deprived (ischemic) areas of brain following a stroke, and tumors. The temporal lobe on the left side of the brain shows less blood flow than the right, confirming for the surgeon the nonfunctioning area of the brain causing seizures. A SPECT scan of a patient with uncontrolled complex partial seizures. The test can be performed between seizures (interictal) or during a seizure (ictal) to determine blood flow to areas where the seizures originate.įigure 1.
SPECT scanning is also useful for presurgical evaluation of medically uncontrolled seizures (Fig. Tests have shown that it might be more sensitive to brain injury than either MRI or CT scanning because it can detect reduced blood flow to injured sites.
What does a SPECT scan show?Ī SPECT scan is primarily used to view how blood flows through arteries and veins in the brain. SPECT scans are cheaper and more readily available than higher resolution PET scans. The test differs from a PET scan in that the tracer stays in your blood stream rather than being absorbed by surrounding tissues, thereby limiting the images to areas where blood flows. For example, if your doctor is looking at a tumor, he or she might use radiolabled glucose (FDG) and watch how it is metabolized by the tumor. The type of tracer used depends on what your doctor wants to measure. Various drugs and other chemicals can be labeled with these isotopes. These radioactive forms of natural elements will pass through your body and be detected by the scanner. The radioisotopes typically used in SPECT to label tracers are iodine-123, technetium-99m, xenon-133, thallium-201, and fluorine-18. These cross-sections can be added back together to form a 3D image of your brain. The computer collects the information emitted by the gamma rays and displays it on the CT cross-sections. The tracer is radiolabeled, meaning it emits gamma rays that can be detected by the CT scanner. The tracer is what allows doctors to see how blood flows to tissues and organs.īefore the SPECT scan, a tracer is injected into your bloodstream. SPECT is a nuclear imaging scan that integrates computed tomography (CT) and a radioactive tracer. It may be used to help diagnose seizures, stroke, stress fractures, infections, and tumors in the spine. SPECT (single photon emission computed tomography) scan OverviewĪ single photon emission computed tomography (SPECT) scan is an imaging test that shows how blood flows to tissues and organs.