Tau accumulation in the brain is a pathologic hallmark of Alzheimer disease and other tauopathies. Quantitative visualization of tau pathology in humans can be a powerful method as a diagnostic aid and for monitoring potential therapeutic interventions. We established methods of PET quantification of tau pathology with (11)C-PBB3 (2-((1E,3E)-4-(6-((11)C-methylamino)pyridin-3-yl)buta-1,3-dienyl) benzo[d]thiazol-6-ol), considering its radiometabolite entering the brain.
Methods: Seven Alzheimer disease patients and 7 healthy subjects underwent dynamic (11)C-PBB3 PET scanning. Arterial blood was sampled to obtain the parent and metabolite input functions. Quantification of (11)C-PBB3 binding was performed using dual-input models that take the brain metabolite activity into consideration, traditional single-input models without such considerations, and the reference tissue model (MRTMO) and standardized uptake value ratio (SUVR). The cerebellar cortex was used as the reference tissue for all methods.
Results: The dual-input graphical models estimated binding parameter ([Formula: see text]) stably (∼0.36 in high-binding regions). The MRTMO [Formula: see text] matched the corresponding [Formula: see text] by the dual-input graphical model (r(2) = 1.00). SUVR minus 1 correlated well with MRTMO [Formula: see text] (r(2) > 0.97). However, BPND by the single-input models did not correlate with [Formula: see text] by the dual-input graphical model (r(2) = 0.04).
Conclusion: The dual-input graphical model [Formula: see text] is consistent with the reference tissue [Formula: see text] and SUVR-1, suggesting that these parameters can accurately quantify binding of (11)C-PBB3 despite the entry of its radiometabolites into the brain.
Keywords: 11C-PBB3; Alzheimer disease; PET quantification; tau.
© 2015 by the Society of Nuclear Medicine and Molecular Imaging, Inc.