While a CT scan provides anatomical detail (size and location of the tumor, mass, etc.), a PET scan provides metabolic detail (cellular activity of the tumor, mass, etc.). Combined PET/CT is more accurate than PET and CT alone.
Anatomical: CT Scanners send x-rays through the body, which are then measured by detectors in the CT scanner. A computer algorithm then processes those measurements to produce pictures of the body's internal structures.
Metabolic: PET images begin with an injection of FDG, an analog of glucose that is tagged to the radionuclide F18. Metabolically active organs or tumors consume sugar at high rates, and as the tagged sugar starts to decay, it emits positrons. These positrons then collide with electrons, giving off gamma rays, and a computer converts the gamma rays into images. These images indicate metabolic "hot spots," often indicating rapidly growing tumors (because cancerous cells generally consume more sugar/energy than any other organs or tumors).
The PET/CT examination provides comprehensive diagnostic information to your healthcare team very quickly. The PET/CT system provides exceptional image quality and accuracy of diagnostic information.