18F-FDG PET for Dementia Evaluation: Co-pathologies, New Diseases, and Its Roles in the Era of Antiamyloid Treatment.

Dementia, which impairs a person's cognition and ability in daily tasks and is often caused by neurodegenerative disorders, remains one of the most challenging neuropsychiatric conditions. The prevalence of dementia has been steadily increasing in aging societies. Recently, antiamyloid treatment has been developed and approved for the treatment of Alzheimer's disease (AD), which is known as the major cause of dementia. Such therapeutic developments have accelerated the use of in vivo biomarkers in research, clinical trials, and clinical practice. Past and recent developments of several biomarkers, including ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET), have played a pivotal role in understanding the underlying mechanisms of dementing disorders and accelerating progress in both research and clinical practice, leading to more accurate clinical diagnosis, recognition of co-pathologies, better understanding of new diseases, treatment planning, and response evaluation. This article reviews the roles of brain FDG PET, one of the well-established imaging biomarkers, as a valuable tool for studying brain metabolism and its applications in clinical and research settings, particularly for the treatment of dementia.