[Positron emission tomography : from classical indications to new and future applications]

First clinical indications of positron emission tomography (PET) were in the fields of neurology and cardiology, but oncology is the domain in which PET got its recognition as an essential diagnostic tool. Its fast diffusion as an imaging method for diagnosis and follow-up of cancer has been facilitated by the existence of a single tracer for all kinds of oncological PET explorations. Nowadays, this tracer, fluorodeoxyglucose (FDG), is so largely distributed that non oncological PET indications have emerged. For instance, PET with FDG has totally supplanted gallium-67 for the evaluation of inflammatory conditions. Another non oncological domain in which PET with FDG has kept an important clinical role is neurology. The strong local relationship between neuronal activity and cerebral glucose uptake confers to PET with FDG a primordial role in neurological conditions in which structural changes are insufficient to establish a firm diagnosis. This is the case for focal epilepsy that remains an undisputed indication of PET with FDG, and for neurodegenerative disorders, in particular those that lead to dementia for which tracers detecting amyloid and tau depositions are now available. New tracers have enlarged PET indications in oncology, in particular for cancers that are not well evaluated with FDG. Since the early clinical PET introduction, patients with brain tumours are benefiting from PET exploration with amino-acid tracers, in particular for therapeutic tumour targeting. The recent development of tracers for neuroendocrine and prostatic cancers has opened a new field of applications for PET, linked to innovative radiotherapeutic approaches.