An integrated PET/CT scan combines images from a positron emission tomography (PET) scan and a computed tomography (CT) scan that has been performed at the same time using the same machine. Because a CT scan provides detailed pictures of tissues and organs inside the body, while a PET scan reveals any abnormal activity that might be going on there, combining these scans creates a more complete image than either test can offer alone.
Like the individual tests it combines, an integrated PET/CT scan is a diagnostic tool used to detect cancer and find out the cancer’s stage (a way of describing where the cancer is located, if or where it has spread, and whether it is affecting the functions of other organs in the body). Knowing cancer’s stage helps you and your doctor decide what kind of treatment is best and helps predict prognosis (a patient’s chance of recovery). The scan can also be used to locate an area for a biopsy (the removal of a small amount of tissue for examination under a microscope to determine whether cancer is present) or to evaluate the effectiveness of cancer treatments, such as chemotherapy or radiation therapy. In addition, the CT portion of this scan is often used for radiation therapy treatment planning.
How a PET/CT works
A PET scan creates pictures of organs and tissues inside the body. A small amount of a radioactive substance is injected into a vein. This substance is absorbed mainly by organs and tissues that use the most energy. Because cancer cells tend to use more energy than healthy cells, they absorb more of the radioactive substance. A scanner then detects this substance to produce images of the inside of the body.
Meanwhile, a CT scan creates a three-dimensional picture of the inside of the body with an x-ray machine. A computer then combines these images into a detailed, cross-sectional view that shows any abnormalities or tumors. Sometimes, a contrast medium (a special dye) is injected into a patient’s vein to provide better detail in the images.