PET/CT is a procedure that can help locate abnormal cell activity at the basic metabolism level in a patient. In cancer and some other diseases like Alzheimer’s, the way cells metabolize or process food changes before the tumor mass forms.

PET/CT can detect these changes and can often identify the presence of disease earlier than tests, which look for a tumor mass. Growing cells use glucose (a type of sugar) as a main source of energy. Cancer cells grow faster than normal cells, and as a result use more glucose. FDG is a special form of glucose that emits or gives off particles called positrons within the body’s cells. The FDG is active for a short period of time, which makes it very important that the patient be on time for their scan appointment. This special glucose is injected about 1 hour before the PET exam.

The PET/CT scanner takes a time exposure of the body and produces a map of where the FDG was consumed in the body.  During the same exam a CT scan is done with the same equipment and then the two images are combined to give the radiologist a better view of where the FDG was used by the body.  PET/CTs are used looking for cancer or Alzheimer’s disease.  PET/CT scans are also used to demonstrate effectiveness of cancer therapy.  For this reason physicians may sometimes order repeat PET/CT exams.