A dual-purpose imaging device, PET/CT is literally the combination of PET (positron emission tomography) and CT (computed tomography) imaging techniques within a single machine. The individual scans, which are taken simultaneously, can be presented separately or as a single, overlapping image. The two techniques present different types of information about the human body: PET shows metabolic or chemical activity in the body; CT shows the body's anatomical structures. For example, a PET scan would highlight a tumor's increased glucose consumption, while a CT scan would reveal its physical mass.

Taking the two scans virtually simultaneously ensures that the patient remains in place and, therefore, that the two images form a precise computer overlay—that the tumor "hot spot" on the PET scan corresponds directly to the physical mass on the CT scan. This fused image provides a more reliable alternative to the traditional side-by-side visual comparison of PET and CT images. PET/CT also eliminates the common problem of a delay between the two studies, during which time the patient's condition may change.

Older imaging techniques such as CT or MRI work by showing anatomic detail of a patient’s body. PET is unique in that it is the only imaging technique that can identify areas of increased metabolic activity—often times identifying evidence of disease before anatomic changes are seen on more traditional imaging studies. In many cases the result will be that PET imaging will provide a more accurate assessment of disease, often changing your physician’s treatment plans to better suit your true condition.

You will receive radiation exposure in an amount equivalent to about two chest x-rays.

Although various natural compounds such as water and amino acids (the building blocks of protein) can be used in PET imaging, the most common PET imaging procedures utilize a natural sugar compound known as FDG, or fluorodeoxyglucose. To satisfy their increased metabolic rates, many cancers devour these simple sugars at abnormally high rates. By tracking the accumulation of the sugar compound, PET imaging can safely and easily detect areas of cancer that might otherwise go undetected using more common CT or MRI imaging.