[The use of 18F-fluorothymidine and 18F-fluorocholine in imaging with positron emission tomography]

Positron emission tomography (PET) with (18)F-fluorodeoxyglucose ((18)F-FDG) has proven useful for diagnosis, staging, restaging and therapy monitoring in a variety of tumors. Nevertheless there are some limitations. (18)F-FDG is not tumor selective and shows accumulation in inflammatory cells such as macrophages and fibroblasts that require glucose as their substrate for energy production. Furthermore, tissues with high background, such as brain may cause difficulties in image interpretation. Moreover, there are some tumors that are not avid for (18)F-FDG such as prostate cancer, hepatocellular carcinoma and some slow-growing tumors. This limitations motivated efforts to develop new oncologic tracers for PET imaging. Recently, (18)F-fluorothymidine ((18)F-FLT), a radiolabeled analog of thymidine, has been synthesized for imaging tumor cell proliferation. Another tracer that has been synthesized is (18)F-fluorocholine ((18)F-FCH) that can incorporate into tumor cell membranes by metabolic trapping. The purpose of this article is to report the role of these two new radiopharmaceuticals for PET imaging, (18)F-FLT and (18)F-FCH in the management of various malignancies.