Positron emission tomography with [18F]flutemetamol and [11C]PiB for in vivo detection of cerebral cortical amyloid in normal pressure hydrocephalus patients

Background and purpose This study determined the correlation between uptake of the amyloid positron emission tomography (PET) imaging agent [18F]flutemetamol and amyloid- measured by immunohistochemical and histochemical staining in a frontal cortical biopsy. Methods Fifteen patients with possible normal pressure hydrocephalus (NPH) and previous brain biopsy obtained during intracranial pressure monitoring underwent [18F]flutemetamol PET. Seven of these patients also underwent [11C] Pittsburgh compound B (PiB) PET. [18F]Flutemetamol and [11C]PiB uptake was quantified using standardized uptake value ratio (SUVR) with the cerebellar cortex as a reference region. Tissue amyloid- was evaluated using the monoclonal antibody 4G8, Thioflavin-S and Bielschowsky silver stain. Results [18F]Flutemetamol and [11C]PiB SUVRs correlated with biopsy specimen amyloid- levels contralateral (r=0.86, P<0.0001; r=0.96, P=0.0008) and ipsilateral (r=0.82, P=0.0002; r=0.87, P=0.01) to the biopsy site. Association between cortical composite [18F]flutemetamol SUVRs and [11C]PiB SUVRs was highly significant (r=0.97, P=0.0003). Conclusions [18F]Flutemetamol detects brain amyloid- in vivo with moderate to high sensitivity and high specificity. This agent, therefore, represents a valuable new tool to study and verify the presence of amyloid- pathology, both in patients with possible NPH and among the wider population.