Image processing: OTS ROI creation
PATHOLOGY, CORTEX
The overarching goals of this project were to 1) characterize MK6240 OTS and 2) optimize MK6240 quantification in POINTER Imaging participants.To accomplish the first goal, we created novel OTS ROIs to measure meningeal signal across the whole scan (‘whole OTS’) and adjacent to key regions including the entorhinal cortex (ERC), a meta temporal region often used to stage tau pathology (MetaROI; We used the whole OTS mask as an exclusive mask for MK6240 scans to exclude OTS signal in some of our candidate pipelines (described below) and also for quantifying OTS itself. In addition to measuring OTS in native space using the whole OTS mask created in template space, we created novel OTS ROIs defined in native space that were adjacent to the ERC, MetaROI and inferior cerebellar gray matter by first smoothing each subject-specific, FreeSurfer-defined region with a 6mm FWHM Gaussian kernel, thresholding at 0.05, and then capturing the overlap between the smoothed ROI and the reverse-normalized whole OTS mask. Importantly, when quantifying OTS, we excluded cortical voxels since we were only interested in signal outside the brain. All OTS ROI SUVRs were created by normalizing by inferior cerebellar gray.