Imaging processing: Target ROI selection
MetaROI
Another component of characterizing OTS was exploring the relationship between OTS ROIs and target ROIs. In this study we focused on 3 target ROIs: ERC, hippocampus and the temporal MetaROI. We chose to examine ERC and hippocampus because these are among the earliest regions to accumulate tau, including in unimpaired older adults. Notably, with MK6240, unlike flortaucipir, quantification of hippocampal signal is feasible because MK6240 OTS is minimal in choroid plexus, which has been shown to contaminate hippocampal signal with flortaucipir. ERC and hippocampus were defined using FreeSurfer and the MetaROI was created by combining the following FreeSurfer ROIs: amygdala, ERC, fusiform gyrus and inferior and middle temporal gyri. The MetaROI is a summary measure of overall AD-specific tau burden (