![]() ![]() The approach is illustrated for amyloid-β (Aβ)–positive cognitively unimpaired (CU) individuals. The interval that resulted in the highest annual percentage change in tau-PET SUVR across participants was then selected for use. In order to limit the number of intervals, 0.2 to 0.4 (ie, 0.2, 0.3, 0.4) and 0.7 to 1 (ie, 0.7, 0.8 0.9, 1) were used as lower and upper start values, respectively. B, In the probability-based approach, GMM-based probabilities of being tau positive were first extracted from the FreeSurfer (Laboratory for Computational Neuroimaging) atlas and change in tau–positron emission tomography (PET) standardized uptake value ratio (SUVR) calculated across different probability intervals. After calculating the connectivity-based distance of each ROI to the participant-specific epicenters, ROIs were grouped into nonoverlapping quartiles on the basis of their connectivity-based distance to the epicenter (ie, quartile 1 is closest to the epicenter). A, In the quartile 1 approach, we extracted gaussian mixture modeling (GMM)–based probabilities of being tau positive from all brain regions in the Schaefer brain atlas and defined the top 10% of ROIs as tau epicenters (ie, brain regions in which tau emerges first). ![]()
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