AV-1451 PET-TAU IMAGING QUANTIFICATION AND CORRELATIONS

Abstract

Tau and amyloid are pathological hallmarks of Alzheimer's disease. Emerging imaging techniques recently have enabled visualizing intracellular neurofibrillary tau tangles in human brains in vivo with PET tracers. Purpose of this study is to quantify pathological tau depositions in brain regions and to investigate age effect as well. 51 individuals (mean ± std of age: 75.4±7.6 years; 18 women) with [18-F] AV-1451 PET ligand for imaging intracellular hyper-phosphorylated tau, were downloaded from ADNI website (www.adni.loni.usc.edu). Amyloid imaging with [18-F]-Florbetapir (AV-45) PET ligand and FDG PET images for the available subjects that have both tau and amyloid or both tau and FDG data were downloaded as well. Neuropsychological tests including two composite scores of executive function and memory domains, and multi parametric MRI imaging metrics were downloaded for correlational analyses. PET Images were analyzed to derive the ratio of standard uptake value (SUVR) choosing cerebellum as the tissue reference, after normalization to the standard MNI space, with 116-ROI cortical and subcortical parcellations. Group mean tau pattern identified higher temporal deposition especially in the hippocampus, the inferior temporal and subcortical putamen/palladium regions compared to mean cortical deposition (Figure 1). Quantitative Braak stage-based regional analyses found highest tau deposition in the Braak stage II in the preclinical samples (Figure 2). There are also age related increases of tau deposition (r=0.46–0.48, P=0.02) for a few brain regions including temporal cortex and subcortical putamen regions (off-target binding), while non-significant correlation with age in mean cortical region (P=0.1). Significant correlations between tau deposition and memory score (Figure 3) was found, as well as executive function score, especially from middle and inferior temporal cortex. Significant correlations were also found between tau deposition and amyloid/FDG, and with multiple MRI metrics including diffusion, perfusion, functional and structural connectivities.