PET/CT is a dual-purpose imaging device, a combination of PET (positron emission tomography) and CT (computed tomography) imaging techniques within a single piece of equipment. The scans, which are taken at the same time, can be presented separately or as a single, overlapping image. The two techniques offer different types of information about the complex human body. The highly sensitive PET detects the metabolic or physiologic activity within cancer growing cells of the body; CT provides a detailed picture of the body’s anatomy that reveals the location, size, and shape of abnormal cancerous growths. For example, a PET scan can highlight a tumor’s increased glucose consumption, while CT scan reveals the physical location.

A positron camera (tomography) is used to produce cross-sectional tomographic images, which are obtained from positron emitting radioactive tracer substances (radiopharmaceuticals) such as F18 fluorodeoxyglucose (FDG) that is administered intravenously to the patient. The tracer is very safe. Adverse reactions are essentially non-existent.

Alone, each imaging test has particular benefits and limitations, but when the results of PET and CT scans are “fused” together, the combined images provide complete information on cancer location and metabolism. PET/CT also eliminates the common problem of a delay between the two studies, during which time the patient’s condition may change.

In one continuous full-body scan (usually about 20-30 minutes), PET captures images of miniscule changes in the body’s metabolism caused by the growth of abnormal cells, while CT images simultaneously allow physicians to pinpoint the exact location, size, and shape of the diseased tissue or tumor.

Essentially, small lesions or tumors are detected with PET and then precisely located with CT.