Relative 11C-PiB Delivery as a Proxy of Relative CBF: Quantitative Evaluation Using Single-Session 15O-Water and 11C-PiB PET
Journal of Nuclear Medicine
The primary goal of this study was to assess the suitability of 11 C-Pittsburgh compound B ( 11 C-PiB) blood-brain barrier delivery (K 1 ) and relative delivery (R 1 ) parameters as surrogate indices of cerebral blood flow (CBF), with a secondary goal of directly examining the extent to which simplified uptake measures of 11 C-PiB retention (amyloid-b load) may be influenced by CBF, in a cohort of controls and patients with mild cognitive impairment (MCI) and Alzheimer disease (AD). Methods:
... eteen participants (6 controls, 5 AD, 8 MCI) underwent MR imaging, 15 O-water PET, and 11 C-PiB PET in a single session. Fourteen regions of interest (including cerebellar reference region) were defined on MR imaging and applied to dynamic coregistered PET to generate time-activity curves. Multiple analysis approaches provided regional 15 O-water and 11 C-PiB measures of delivery and 11 C-PiB retention that included compartmental modeling distribution volume ratio (DVR), arterial-and reference-based Logan DVR, simplified reference tissue modeling 2 (SRTM2) DVR, and standardized uptake value ratios. Spearman correlation was performed among delivery measures (i.e., 15 O-water K 1 and 11 C-PiB K 1 , relative K 1 normalized to cerebellum [Rel-K 1-Water and Rel-K 1-PiB ], and 11 C-PiB SRTM2-R 1 ) and between delivery measures and 11 C-PiB retention, using the Bonferroni method for multiple-comparison correction. Results: Primary analysis showed positive correlations (r ≈0.2-0.5) between 15 O-water K 1 and 11 C-PiB K 1 that did not survive Bonferroni adjustment. Significant positive correlations were found between Rel-K 1-Water and Rel-K 1-PiB and between Rel-K 1-Water and 11 C-PiB SRTM2-R 1 (r ≈0.5-0.8, P , 0.0036) across primary cortical regions. Secondary analysis showed few significant correlations between 11 C-PiB retention and relative 11 C-PiB delivery measures (but not 15 O-water delivery measures) in primary cortical areas that arose only after accounting for cerebrospinal fluid dilution. Conclusion: 11 C-PiB SRTM2-R 1 is highly correlated with regional relative CBF, as measured by 15 O-water K 1 normalized to cerebellum, and cross-sectional 11 C-PiB retention did not strongly depend on CBF across primary cortical regions. These results provide further support for potential dual-imaging assessments of regional brain status (i.e., amyloid-b load and relative CBF) through dynamic 11 C-PiB imaging.