ABSTRACT
The most commonly used radiotracer in PET technology, 18F-fl uorodeoxyglucose (FDG), is a glucose analog which is taken up by cells following the same initial metabolic pathway as glucose. After phosphorylation, given the lack of an oxygen atom at its C-2 position, the tracer molecule is unable to undergo further catabolism, thereby allowing accumulation of FDG within the cell. A subsequent decay of radioisotope occurs, during which positrons travel approximately 1 mm and collide with electrons in an annihilation reaction which produces two high-energy photons. These photons are emitted in opposite directions and can be detected during the wholebody scanning process as 3-D images representing the distribution of the radiotracer (6,7). Images also denote the intensity of FDG uptake and are reported as a standardized uptake value (SUV) representing metabolic data corresponding to both local and regional disease. Combining this process with CT (Fig. 21.1) allows correlation with anatomical data and increased accuracy of tumor detection. Indeed many studies have shown the combination of both the PET and CT modalities to have a higher sensitivity and specifi city than either modality alone (4,8,9). In breast cancer management FDGPET can be used in initial staging, follow-up staging, assessment of locoregional disease, and response to therapy.
