Positron emission tomography in oncology: the most sophisticated imaging technology.

The primary aim of this paper is to present a new nuclear medicine technology, which has just recently crossed over the clinical-research barrier. Positron emission tomography (PET) has become one of the routine functional imaging techniques in the most developed countries. The biggest advantage of PET is the usage of short-lived positron emission radionuclides, e.g., fluorine-18 (F-18), carbon-11 (C-11), nitrogen-13, and oxygen-15 (0-15). These radionuclides could be incorporated (H2O15) or linked (F-18 fluorodeoxyglucose (FDG) to different metabolically active molecules. In this way, it is possible to image and quantify the metabolic activity of various disorders and diseases including different types of tumors. The authors have concentrated on the PET rule in oncology. FDG and C-11 methionine are the most widely used PET radiopharmaceuticals in tumor imaging today, thus the results of human PET studies with FDG and C-11 methionine in the evaluation of tumors have been reviewed. The facts about the mechanism of uptake of both metabolic PET radiopharmaceuticals as well as the kinetics of tracers in normal and tumor tissue are described. The problem of accumulation of these tracers in some benign lesions is also mentioned. PET could be used for the evaluation of tumor response to therapy and duration of therapeutic effects in follow-up studies. PET offers a unique possibility to fully quantify the tumor metabolic activity, although semi-quantitative approaches are clinically more convenient. At the end, comparative studies of FDG and C-11 methionine in tumor evaluation are analyzed. A double-tracer FDG and C-11 methionine scanning protocol has been suggested as very useful for the assessment of brain tumor. This finding was also supported by the authors' data.