For most clinical PET scans, a small amount of radioactive sugar (“tracer”) is introduced into the body through an I.V.. The tracer then travels through your body. After the tracer has been processed (usually 60-90 minutes), a PET scanner detects radioactive tracers’ distribution and displays a computerized image of that distribution on a computer monitor. These images are then review by an experienced PET-trained physician and/or radiologist to diagnose, stage, evaluate treatment, or rule out recurrence of disease.
 Most clinical PET studies in oncology utilize [18F] 2-Fluoro-2-Deoxy-D-Glucose - more commonly known as “FDG”. This molecule is shown above. The green atom is the radioactive (positron-emitting) Fluorine-18 atom whose emissions the PET scanner detects.
The foundation of PET imaging with FDG rests with the observation as long ago as the 1920s that malignant tissue has a higher metabolic rate for glucose than the normal tissues from which those tumors arise.
FDG, an analog of glucose, becomes trapped in the cells that try to metabolize it. Its concentration is tissue builds up in proportion to the rate of glucose metabolism. Because tumors have a high rate of glucose metabolism, they concentrate FDG, and appear as “hot spots” in PET images.
 PET is a “tracer” imaging methodology. This means we only use TINY (non-pharmacological) quantities of radioactive tracer in a PET study. For example, when we use FDG, a glucose analog, for our PET studies, we inject less than a millionth of a single grain of sugar!!
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