18F-FDG-PET/CT.

[18F]FDG has been the first radiopharmaceutical used for human brain PET studies and still is the most used radiotracer worldwide for PET and PET/CT oncologic applications. In the assessment of brain tumors, in spite of its low sensitivity in some histological exams, chiefly low-grade lesions, its prognostic value remains of high clinical impact. Moreover, the reliability of [18F]FDG in examining not only the tumor itself, but also the functional state of the whole brain, makes this tracer a valuable tool for treatment decisions and patient management, even nowadays when new tracers (especially amino-acids) are available. In addition, [18F]FDG has a role in the differential diagnosis between relapse and necrosis when assessing aggressive tumors and to establish dedifferentiation in low-grade lesions. With the growing of available therapies, another emerging application of [18F]FDG is the monitoring of response to treatment, even though more evidence is needed to assess the best scanning time. Finally, the implementation of CT in PET devices most likely will improve the sensitivity and specificity of [18F]FDG, even though more data are needed to better understand which is the real advantage of PET/CT with respect to multimodality imaging. Currently, the possible added value of PET/CT is in the study of secondary brain lesions. It is believable that in the future we will keep on speaking about this "old" radiotracer, still alive.