Pet scan

A PET scan is a test that uses a doughnut-shaped special type of camera and a radioactive substance called a "tracer" to look at organs in the body. PET stands for positron emission tomography.

During the test, the tracer liquid is put into a vein in your arm. It moves through your body and collects in the specific organ or tissue. The tracer gives off tiny positively charged particles (positrons). As you lie in the "hole" of the machine, the camera records the positrons and turns the recording into pictures on a computer.

A computed tomography (CT) scan is often done at the same time as a PET scan.

A PET scan is done to:

• Study the brain's blood flow and metabolic activity. A PET scan can help a doctor find nervous system problems, such as Parkinson's disease, multiple sclerosis, transient ischemic attack (TIA), amyotrophic lateral sclerosis (ALS), Huntington's disease, stroke, and schizophrenia.
• Find changes in the brain that may cause epilepsy.
• Evaluate the extent of some cancers, especially lymphoma or cancers of the head and neck, brain, lung, colon, or prostate. In its early stages, cancer may show up more clearly on a PET scan than on a CT scan or an MRI.
• Determine whether a growth in an organ or in tissue is likely to be cancer, such as a growth in lung tissue.
• See how advanced a cancer is and whether it has spread to another area of the body (metastasized). Both CT and PET scans are often needed to evaluate cancer.
• Help a doctor choose the best treatment for cancer or to see how well treatment is working. PET scans may also be done to see whether surgery can be done to remove a tumor.
• Help diagnose Alzheimer's disease when the symptoms are not clear or when a person has dementia symptoms at a young age (usually younger than 65). This is called amyloid imaging.
• Find poor blood flow to the heart, which may mean coronary artery disease.
• Find damaged heart tissue, especially after a heart attack.
• Help choose the best treatment, such as coronary artery bypass graft surgery, for a person with heart disease.

• A radioactive tracer will be given in a vein (I.V.). You may need to wait 30 to 60 minutes for the tracer to move through your body. During this time, you will need to avoid moving and talking.
• You will lie on a table that is attached to a PET scanner.
• The table will pass slowly through the PET scanner, which is shaped like a doughnut. The scanner picks up signals from the tracer in your body. It is very important to lie still while each scan is being done.

• Tell your doctor ALL the medicines, vitamins, supplements, and herbal remedies you take. Some may increase the risk of problems during your test. Your doctor will tell you if you should stop taking any of them before the test and how soon to do it.
• Don't drink caffeine for 24 hours before a PET scan of your heart.
• Don't do any exercise or other strenuous activity for at least 48 hours before this test.
• Don't eat or drink (except water) for at least 6 hours before this test.
• If you are breastfeeding, you may want to pump enough breast milk before the test to get through 1 to 2 days of feeding. The radioactive tracer used in this test can get into your breast milk and is not good for the baby.
• Tell your doctor if you get nervous in tight spaces. You may get a medicine to help you relax. If you think you'll get this medicine, be sure you have someone to take you home.

The radiologist may discuss preliminary results of the PET scan with you right after the test. Complete results are usually available in 1 to 2 days.