Clinical applications of positron emission tomography-computed tomography in oncology.

Positron emission computed tomography (PET) is a functional diagnostic imaging technique, which can accurately measure in vivo distribution of a variety of radiopharmaceuticals. The ability of PET to study various biological processes (glucose, amino acid, phospholipids, receptors etc.) opens up new possibilities for both day-to-day clinical use and research applications in the practice of oncology. Addition of CT to PET has resulted in better specificity and sensitivity than either of the modalities alone, as the combined approach has the ability to demonstrate functional and structural details in the same setting. F-18 fluoro-2-deoxy-D-glucose (FDG), an analogue of glucose, is the most commonly used radiotracer in PET-CT imaging. The F-18 FDG uptake in tumor cells is directly proportional to glucose metabolism in the cells. Since glucose metabolism is increased several folds in the malignant tumors, PET-CT images show preferential higher FDG uptake in malignant cells as compared to normal cells. F-18 FDG PET-CT has been found to be useful in the initial staging, detection of recurrent disease and monitoring the response to the therapy in malignancies including lung cancer, colorectal cancer, lymphoma, melanoma, esophageal cancer, head and neck cancer, breast cancer.