Excerpt

Nuclear imaging provides us with a unique ability to study various biochemical, metabolic and molecular processes, expression of cell membrane proteins and receptors, matrix composition, and gene expression, at a cellular, tissue and organ level in intact animals and humans under various physiological conditions.1‐6 This involves an identification of a target inside the body, which is highly specific for a particular disease process and is abundantly expressed and is amenable to an exogenously administered probe. The next step requires an identification or development of new ligand(s) specific for that particular target and its radiolabeling with a suitable radiotracer to image the target. These techniques allow us to study the metabolism of glucose, free fatty acids and various amino acids; nucleic acid synthesis as a marker of cell proliferation; activity of membrane transporters; expression of cell membrane associated and matrix-associated proteins and receptors and delivery of therapeutic interventions to these targets. These imaging techniques have greatly enhanced our understanding of tumor biology and pathophysiology and have also played a significant role in developing several highly effective novel cancer therapies.7 Fluorine-18 labeled deoxyglucose (¹⁸FDG) imaging has been the backbone of molecular imaging and is in extensive clinical use for diagnosing and staging of solid cancers and in evaluating response to therapy in patients with various malignancies.8¹⁸FDG imaging has also provided an interesting insight into the tumor microenvironment: a highly hypoxic and acidic milieu, primarily dependent upon anerobic glycolysis for meeting its energy demand. This requires a profound increase in glucose uptake, facilitated by an upregulation of cell membrane GLUT transporters and an upgraded system for clearance of lactic acid and other waste metabolites in the cancer cells. Although, ¹⁸FDG remains the key radiotracer used in oncology, a number of other radiotracers such as ¹⁸F-FLT (fluorothymidine), ¹⁸F-Methionine, ¹⁸F-fluoroestrodiol have been developed and are undergoing evaluation for studying various aspects of tumor biology.9‐11 …