PET-CT Amyloid Imaging

Amyloid PET imaging is a molecular neuroimaging technique that detects fibrillar beta-amyloid plaques in cerebral cortex, a hallmark neuropathology of Alzheimer disease (AD). FDA-approved radiotracers include florbetapir (Amyvid), florbetaben (Neuraceq), and flutemetamol (Vizamyl); pittsburgh compound B (PiB-C11) is used in research. Tracer is administered intravenously, and imaging is acquired 50-90 minutes post-injection depending on tracer.

Clinical indications according to Society of Nuclear Medicine and Alzheimer Association appropriate use criteria are: persistent or progressive unexplained mild cognitive impairment; possible AD with atypical clinical course or mixed features; progressive dementia with atypical early age of onset; and increasingly, eligibility assessment for anti-amyloid monoclonal antibody therapies (lecanemab, donanemab) where amyloid positivity is required. Inappropriate uses include screening asymptomatic patients, replacing genotyping, or determining dementia severity.

Interpretation uses standardized visual binary reading (positive vs negative) per tracer-specific criteria and quantitative methods (SUVR with cerebellum or whole-cerebellum reference, Centiloid scale for cross-tracer harmonization). A positive scan indicates amyloid pathology consistent with AD but not a clinical diagnosis; results are integrated with clinical assessment, structural imaging, FDG-PET, CSF biomarkers, and emerging plasma biomarkers. ARIA monitoring is critical when amyloid PET informs anti-amyloid therapy initiation.