In the last 15 years, slightly modified radiolabeled glucose molecules (F-18 labeled deoxyglucose or FDG) have been shown to be the best available tracer for detecting cancer and its metastatic spread in the body.Ī combination instrument that produces both PET and CT scans of the same body regions in one examination (PET/CT scanner) has become the primary imaging tool for the staging of most cancers worldwide. In fact, the degree of aggressiveness for most cancers is roughly paralleled by their rate of glucose utilization. Glucose utilization depends on the intensity of cellular and tissue activity so it is greatly increased in rapidly dividing cancer cells. The major purpose of PET scans is to detect cancer and monitor its progression, response to treatment, and to detect metastases. SPECT agents have recently become available for aiding in the diagnosis of Parkinson's disease in the brain, and distinguishing this malady from other anatomically-related movement disorders and dementias. There are also radiotracers to detect disorders in bone, gall bladder disease and intestinal bleeding. SPECT scans are primarily used to diagnose and track the progression of heart disease, such as blocked coronary arteries. The tracer that is used determines whether the patient receives a SPECT or PET scan.
The nuclear medicine physician will select the tracer that will provide the most specific and reliable information for a patient’s particular problem. Researchers demonstrate that combined PET/CT (right) of a mouse provides a more complete view of the spine than CT (left) or PET (middle) alone.Īpproved tracers are called radiopharmaceuticals since they must meet FDA’s exacting standards for safety and appropriate performance for the approved clinical use. The mode of tracer administration will depend on the disease process that is to be studied. However a radioactive tracer may also be administered by inhalation, by oral ingestion, or by direct injection into an organ. Any accumulation of radioactivity in the intestines informs doctors of where the problem lies.įor most diagnostic studies in nuclear medicine, the radioactive tracer is administered to a patient by intravenous injection. They then reinject the blood and use a SPECT scan to follow the path of the blood in the patient. For example, in cases where doctors need to know the exact source of intestinal bleeding, they may radiolabel (add radioactive atoms) to a sample of red blood cells taken from the patient. Some tracers employ molecules that interact with a specific protein or sugar in the body and can even employ the patient’s own cells.
These carrier molecules vary greatly depending on the purpose of the scan. Radioactive tracers are made up of carrier molecules that are bonded tightly to a radioactive atom.