A PET scan is an imaging and diagnostic method that evaluates the metabolic activity (i.e, breakdown and production of certain molecules) inside cells in order for an image of certain organs (such as the breast, ovary, and brain) or the whole body to be produced.
For example, a small amount of a tracer chemical (such as a radioactive mineral attached to a sugar molecule) is injected intravenously (IV; i.e., into a vein). As the cells use and change the sugar into other substances, the PET instrument measures the metabolic activity of the cells (i.e., the rate at which the tumor utilizes the sugar) and produces an image that is viewed on a computer screen.
Usually, cells of high-grade (i.e., more aggressive) cancers use more sugar than do normal cells. Cells of low-grade (i.e., less aggressive) cancers tend to use less sugar than do cells of high-grade tumors.
Specific purposes of PET scanning include:
• Determine the aggressiveness (grade) of the cancer
• Determine the degree of spread of certain solid tumors within the body
• Monitor the effects of treatment on cancer
1. American Cancer Society. Glossary.