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A PET (positron emission tomography) scan is a test that shows how organs and tissues function inside the body. These tests help doctors diagnose and treat cancer because they can see and track the activity of cancer and other cells. The processes that can be measured include blood flow, tumor growth rate, and the action of chemotherapy drugs.
Sometimes a PET scan is performed at the same time as a computed tomography (CT) scan. A PET-CT scan collects images from both PET and CT scans and combines them, giving doctors information about the function, size, shape, and location of cancer and surrounding structures. CT is done first to create anatomic pictures of the organs and structures in the body, and then PET is done to create colored pictures that show metabolic or other functional changes in tissues.
A PET-CT scan collects images from both PET and CT scans and combines them.
PET scans can measure the level of glucose, or sugar, in cells. Before the PET scan, patients are injected with a radioactive tracer — a form of glucose with a small amount of radioactive material attached. Because cancer cells grow and divide so quickly, they absorb much more glucose than normal cells. The radioactive material attached to the glucose molecule causes the glucose to light up on the PET scan.
The level of radiation is very small, and the doctor will discuss the risks and benefits involved. Patients and families should talk to their care team if they have any concerns. The radioactive material is taken up by the cells and does not stay in the body long. Through the natural process of radioactive decay, it will lose its radioactivity over time. It may also pass out of the body through urine or stool during the first few hours following the test. The medical team will likely tell patients to drink plenty of water to help flush out the radioactive material.
Even though the amount of radioactivity is very low, it is recommended that parents follow these precautions when caring for their child after the scan:
A radiologist who has specialized training in nuclear medicine will analyze the images and send a report to the referring physician. The doctor will go over the information during the patient’s next appointment.
Reviewed: June 2018