Early-Phase 11C-PiB PET in Amyloid Angiopathy-Related Symptomatic Cerebral Hemorrhage: Potential Diagnostic Value?

Although late-phase (>35min post-administration) 11C-PiB-PET has good sensitivity in cerebral amyloid angiopathy (CAA), its specificity is poor due to frequently high uptake in healthy aged subjects. By detecting perfusion-like abnormalities, early-phase 11C-PiB-PET might add diagnostic value. Early-frame (1-6min) 11C-PiB-PET was obtained in 11 non-demented patients with probable CAA-related symptomatic lobar intracerebral haemorrhage (70±7yrs), 9 age-matched healthy controls (HCs) and 10 HCs <55yrs. There was a significant decrease in early-phase atrophy-corrected whole-cortex SUV relative to cerebellar vermis (SUVR) in the CAA vs age-matched HC group. None of the age-matched controls fell below the lower 95% confidence limit derived from the young HCs, while 6/11 CAA patients did (sensitivity = 55%, specificity = 100%). Combining both early- and late-phase 11C-PiB data did not change the sensitivity and specificity of late-phase PiB, but combined early- and late-phase positivity entails a very high suspicion of underlying Aβ-related clinical disorder, i.e., CAA or Alzheimer disease (AD). In order to clarify this ambiguity, we then show that the occipital/posterior cingulate ratio is markedly lower in CAA than in AD (N = 7). These pilot data suggest that early-phase 11C-PiB-PET may not only add to late-phase PiB-PET with respect to the unclear situation of late-phase positivity, but also help differentiate CAA from AD.