THE ROLE OF POSITRON EMISSION TOMOGRAPHY IN UROLOGY

Abstract

Positron emission tomography (PET) is a nuclear medical imaging technique that produces a three-dimensional image or picture of functional processes in the body. The system detects pairs of gamma rays emitted indirectly by a positron-emitting radionuclide (tracer), which is introduced into the body on a biologically active molecule. Three-dimensional images of tracer concentration within the body are then constructed by computer analysis. In modern scanners, three dimensional imaging is often accomplished with the aid of a CT or X ray scan performed on the patient during the same session, in the same machine. The usefulness of PET in RCC remains unclear. In local staging, there is no evidence to support its use, but novel radiotracers are showing promising results regarding the identification of RCC before surgery. In monitoring and re-staging advanced disease, PET has already shown good results, which might lead a potential role for this technique within the ‘targeted therapy’ era. Further research is needed before clinical use of PET/ CT, as current results show that it cannot be used in primary diagnosis or follow-up outside of clinical trials. Additionally, its role in monitoring response with target therapy has to be examined. In Cancer bladder, 18F-FDG PET is useful for identifying distant metastases due to increased 18F-FDG uptake by the lesions, but it is not useful in detecting primary tumors because urinary excretion of 18F-FDG interferes with local staging. 11C choline and 11C-methionine may prove to be more effective than 18F-FDG, but further studies are needed. Positron Emission Tomography (PET) has emerged as a promising imaging tool for prostate cancer, however, the most commonly used PET radiotracer, 18F-Fluoro-deoxy-glucose (FDG), has limited sensitivity for prostate cancer due to low glucose consumption in early PCa, compounded by artifacts created from high bladder activity . Preliminary studies have demonstrated promising results with the PET agent, 11C Acetate, for the diagnosis of recurrent or metastatic PCa , but its role in primary PCa detection and staging is less well established . Poor PET results study show that PET cannot be considered a validated diagnostic tool for NSGCT, PET seems to be one of the most promising tools in the evaluation of patients with SGCT . Currently, the only established role for PET in urological oncology is for follow-up of patients with seminomas GCT . Smaller studies have shown the potential for PET to be used as an adjunct to CT and serum tumor markers in the management of NSGCT, but further studies are necessary. The development of newer radiotracers with different metabolic pathways may be promising in the evaluation of NSGCT .