To determine the correspondence of in vivo quantitative estimates of brain uptake of fluorine 18–labeled flutemetamol with immunohistochemical estimates of amyloid levels in patients who underwent previous biopsy.
Cross-sectional study of 18F-flutemetamol positron emission tomography (PET) findings in patients with prior cortical biopsy specimen stained for the presence or absence of amyloid plaques.
Seven patients who previously had a prior right frontal cortical biopsy at the site of ventriculoperitoneal placement for presumed normal pressure hydrocephalus were recruited. Inclusion criteria included an adequate biopsy specimen for detection and quantification of β-amyloid pathology and age older than 50 years.
All patients underwent an 18F-flutemetamol PET scan.
Main Outcome Measures
Quantitative measures of 18F-flutemetamol uptake (standardized uptake value ratio, a ratio of mean target cortex activity divided by that in a cerebellar reference region) were made at a location contralateral to the biopsy site and compared with estimates of amyloid load based on immunohistochemical and histological staining.
There was complete agreement between visual reads of 18F-flutemetamol PET scans (3 blinded readers with majority rule) and histology. A regression model, including time from biopsy as a covariate, demonstrated a significant relationship (P = .01) between 18F-flutemetamol uptake and percentage of area of amyloid measured by a monoclonal antibody raised against amyloid (NAB228). Similar results were found with the amyloid-specific monoclonal antibody 4G8 and Thioflavin S.
To our knowledge, these data are the first to demonstrate the concordance of 18F-flutemetamol PET imaging with histopathology, supporting its sensitivity to detect amyloid and potential use in the study and detection of Alzheimer disease.