Positron Emission Tomography, also called PET-CT imaging, is a diagnostic exam that visualizes metabolic activity from various tissues, allowing a physician to distinguish between benign and malignant disorders.  PET-CT's whole-body capability is useful for the detection of metastasis and the staging of various cancers, assess myocardial viability, and patterns of brain metabolism.  Alone, each imaging examination has particular benefits and limitations but by combining these two state-of the-art technologies, physicians can more accurately diagnose, localize and monitor cancer, as well as heart disease and certain brain disorders including dementia and Alzheimer’s disease.  Because a PET scan images the biology of disorders at the molecular level, it can help a physician detect abnormalities in cellular activity at a very early stage, generally before anatomic changes are visible.