What is PET/CT?
PET/CT is a new imaging tool that combines two scan techniques in one exam - a PET scan and a CT scan. PET/CT is mainly used for diagnosis, staging or restaging malignant disease and metastases and evaluation of treatment response. It may also be used to differentiate dementia verses Alzheimer's disease. The two procedures together provide information about the location, nature of and the extent of the lesion. In other words, it answers questions like: Where is the tumor, how big is it, is it malignant, benign or due to inflammatory change, and has the cancer spread?
How does PET/CT work?
PET/CT combines or merges a PET scan and a CT scan into one set of images.
How does CT work?
CT stands for Computerized Tomography (commonly known as a CAT scan). During the CT scan, the scanner emits X-rays, which go through the patient to detectors. The computer uses this information to generate cross-sectional images of anatomical structures. Your body will not come in contact with the scanner itself. You will be lying on a narrow table, which will move through the scanner or dectors. Each cross-sectional picture or slice gives detailed anatomic location and changes in the anatomy. The use of oral and IV contrast agents can enhance the details by highlighting the gastrointestinal tract (filled by oral contrast) and other organs and blood vessels (filled with IV contrast).
How does PET work?
PET stands for Positron Emission Tomography. PET scans measure metabolic activity and molecular function by using a radioactive glucose injection. The F-18 FDG is injected into the patient. The PET scanner detects the radiation emitted from the patient, and the computer generates three-dimensional images of tissue function or cell activity in the tissues of your body. These functional images can detect disease earlier than the anatomic information gained from CT alone. Like the CT scanner, your body will never come in contact with scanner itself. There are no side effects from this injection and procedure.
All cells use glucose as an energy source. However, cancer cells grow faster than normal healthy cells and they use glucose at much higher rate than normal cells. This is the basis of imaging with F-18 FDG for cancer detection in PET scan.