A nuclear medicine scan uses small amounts of radiation to create pictures of tissues, bones, and organs inside the body. The radioactive material collects in certain areas of your body, and special cameras find the radiation and make images that help your medical team diagnose and treat cancer and other illnesses. Other terms your doctor might use for a nuclear medicine scan are Nuclear scan, Nuclear imaging and Radionuclide imaging.
Nuclear medicine scans can help doctors find tumours and see how much cancer has spread in the body. They may also be used to decide if treatment is working. These tests are painless and usually done as an outpatient procedure. The specific type of nuclear scan you’ll have depended on which organ the doctor wants to look into.
How it works
Most scans don’t take more than an hour or so, though you may have to wait a few hours as health care workers prep you for the test. These scans are usually done at a nuclear medicine or radiology department at a hospital. Nuclear scans make pictures based on the body’s chemistry rather than on physical shapes and forms. These scans use liquid substances called radionuclides that release low levels of radiation. Body tissues affected by certain diseases, such as cancer, may absorb more or less of the tracer than normal tissues. Special cameras pick up the pattern of radioactivity to create pictures that show where the tracer travels and where it collects. If cancer is present, the tumour may show up on the picture as a “hot spot” – an area of increased cell activity and tracer uptake. Depending on the type of scan done, the tumour might instead be a “cold spot” – a site of decreased uptake (and less cell activity).
Nuclear scans may not find very small tumours, and cannot always tell whether a tumour is really cancer. These scans can show some internal organ and tissue problems better than other imaging tests, but they don’t provide very detailed images on their own. Because of this, they’re often used along with other imaging tests to give a more complete picture of what’s going on.
Before the scan, you’ll remove all jewellery and metal that could interfere with the images. Medical staff may ask you to wear a hospital gown, though in some cases you can wear your own clothes. You’ll lie on a table or sit on a chair for the scan. Technicians use a special camera, or “scanner,” on the appropriate parts of your body to detect gamma rays from the tracer. Technicians might ask you to change positions to get different angles as the scanner works. The scanner sends the information to computer software that creates pictures, sometimes in three dimensions (3D) and with colour added for clarity. A specialized doctor called a radiologist will review the pictures and talk to your doctor about what they show.
Types of scan commonly used for cancer:
Bone scans: Bone scans look for cancers that may have spread from other places to the bones. They can often find bone changes much earlier than regular x-rays. The tracer collects in the bone over a few hours, then the scans are done.
Positron emission tomography (PET) scans: PET scans usually use a form of radioactive sugar. Your medical team injects radioactive sugar into your body. Body cells take in different amounts of sugar, depending on how fast they are growing. Cancer cells, which grow quickly, are more likely to take up larger amounts of sugar than normal cells. You’ll be asked to not drink any sugary liquids for several hours before the test.
PET/CT scans: Doctors often use machines that combine a PET scan with a CT scan. PET/CT scanners give information on any areas of increased cell activity (from the PET), as well as show more detail in these areas (from the CT). This helps doctors pinpoint tumours.
Thyroid scans: This scan can be used to find thyroid cancers. Radioactive iodine can also be used to treat thyroid cancer. Radioactive iodine (iodine-123 or iodine-131) is swallowed. It goes onto the bloodstream and collects in the thyroid gland. This test may not work the way it should if you take in substances that contain iodine. Be sure you tell your doctor about any allergies to seafood or iodine. Talk to the doctor about what you need to do to be ready for this test.
MUGA scans: This scan looks at heart function. It may be used to check heart function before, during, and after certain types of chemotherapy. The scanner shows how your heart moves your blood as it carries the tracer, which binds to red blood cells. The test tells you your ejection fraction, which is the amount of blood pumped out of your heart. 50% or higher is normal. If you have an abnormal result, your doctor may switch you to a different kind of chemotherapy. You may be asked to not use tobacco or caffeine for 24 hours before the test.
Gallium scans: Gallium-67 is the tracer used in this test to look for cancer in certain organs. It can also be used for a whole-body scan. The scanner looks for places where the gallium has collected in the body. These areas could be infection, inflammation, or cancer.
- For the most part, nuclear scans are safe tests. The doses of radiation are very small, and the radionuclides have a low risk of being toxic or causing an allergic reaction.
- Some people may have pain or swelling at the site where the material is injected into a vein.
- Rarely, some people will develop a fever or allergic reaction when given a monoclonal antibody.
- Some people have an allergic reaction to the tracer material. But it’s usually mild and doesn’t last very long.
- Tell your doctor if you’re pregnant or breastfeeding because they may need to take certain safety precautions or change the timing and type of scan.