Use of FDG PET as an imaging biomarker in clinical trials of Alzheimer's disease.

PET with the glucose analog FDG as a tracer is a mature and increasingly available clinical imaging technique that can improve the diagnostic accuracy for Alzheimer's disease, which is of particular value at an early stage of the disease when clinical symptoms are still mild and nonspecific. It can also monitor progression of Alzheimer's disease, and the findings are closely related to clinical symptoms. FDG PET, therefore, could also potentially be used as an imaging biomarker for selection of patients and assessment of outcome in clinical trials. Several published intervention studies indicate a good correspondence between clinical outcome and FDG PET findings, but study designs and methods used for data analysis vary widely. Recent developments towards standardization of largely user-independent methods for quantification of regional metabolic impairment on FDG PET scans will allow a new generation of studies that could provide the required evidence for full qualification of FDG PET as an imaging biomarker in clinical trials.