P1‐405: regional association of cerebral blood flow with amyloid and tau in alzheimer's disease

Changes in regional cerebral blood flow (CBF) have been reported as an early prodromal finding in Alzheimer's disease (AD). There is evidence for compensatory increases in CBF during early stage AD, whereas decreased CBF has been a consistent finding in symptomatic stages. Our goal was to evaluate the relationship between CBF, measured using pseudo-continuous arterial spin labeled (pCASL) MRI and amyloid and tau burden on PET, in older adults along the AD continuum including cognitively normal (CN), subjective cognitive decline (SCD), amnestic mild cognitive impairment (MCI) and AD. Participants included 21 CN, 14 SCD, 10 MCI, and 6 AD. pCASL MRI scans were obtained on a Siemens 3T Prisma scanner and processed to create CBF maps for each individual. The amyloid (Florbetapir or Florbetaben – processed using the Centiloid method) and tau (Flortaucipir) PET scans were obtained and processed to calculate global cortical mean amyloid centiloid value and a medial temporal lobe (MTL) Flortaucipir SUVR value for each individual. Relationships between independent factor CBF and dependent factors amyloid and tau were assessed using multiple regression with age, sex, APOEε4 status as covariates on a voxel-based analysis in SPM12. Voxel-wise results showed that amyloid and tau are correlated with CBF in various brain regions. Regions of association between CBF and tau (Fig. 2, p<0.05 uncorrected) are more widespread and diffuse than those between CBF and amyloid (Fig. 1, p<0.05 uncorrected). When participants were stratified into CN/SCD vs MCI/AD groups, there was a shift from positive to negative associations between AD-related pathology and CBF between groups. In addition, amyloid and tau are uniquely associated with CBF in different brain regions in individuals in the later stages of the disease. In general, amyloid pathology is primarily associated with altered CBF in parietal and temporal regions while tau pathology is also associated with altered CBF in frontal regions.