In Vivo Human Amyloid Imaging

PET imaging agents such as Pittsburgh compound B (PiB) allow detection of fibrillar beta-amyloid (A beta) in vivo. In addition to quantification of A beta deposition in mild cognitive impairment and Alzheimer's disease, PiB has also increased our understanding of A beta deposition in older adults without cognitive impairment. In vivo A beta deposition has been studied in relation to genotype, structural and functional brain changes, as well as alterations in biomarker levels. To date, several studies have reported changes in A beta burden over time. This, together with investigation of the relationship between A beta deposition and cognition, sets the stage for elucidation of the temporal sequence of the neurobiological events leading to cognitive decline. Furthermore, correlation of A beta levels detected by PiB PET and those obtained from biopsy or postmortem specimens will allow more rigorous quantitative interpretation of PiB PET data in relation to neuropathological evaluation. Since the first human study in 2004, in vivo amyloid imaging has led to advances in our understanding of the role of A beta deposition in human aging and cognitive decline, as well as provided new tools for patient selection and therapeutic monitoring in clinical trials.