1. Subject recruitment and screening procedures. Subjects will be recruited from community dwelling persons from Northern Manhattan, men and women, aged 55 to 69 years, who have already undergone or agreed to undergo, brain magnetic resonance imaging (MRI) and Florbetaben positron emission tomography (PET) as part of Columbia IRB protocol AAAQ2950 (PI: Luchsinger). Recruitment of participants for these studies and all study procedures, including brain MRI, Florbetaben PET, and tau PET, are funded by existing grant from the National Institutes of Health awarded to PI Luchsinger (R01AG050440, RF1AG051556-01S2, R01AG055299)
2. Imaging procedures related to 18F-MK-6240 PET. One brain MRI will be performed on each subject using a 3 T Philips scanner. Sequences performed will include 3D T1 (MPRAGE, 180 slice 1 mm resolution, 256 x 256 voxel count) for volumetric analysis and clinical sequences to exclude subjects with significant intracranial pathology unrelated to AD, such as malignant brain tumor of subdural hematoma. PET scans will take place on a Biograph mCT PET scanner (Siemens Healthcare) at the CUMC Kreitchman PET Center. Subjects will have one PET scan with 18F-MK-6240 (injected activity up to 5 mCi = 185 MBq). PET imaging will be performed without arterial sampling. Vital signs (blood pressure, heart rate, respiratory rate, and temperature) will be checked prior to injection of 18F-MK-6240, then at the completion of the PET scan. 18F-MK-6240 will be purchased from Cerveau Technologies, Inc. via a licensed production facility. Subjects will not be informed of 18F-MK-6240 PET scan results, as this scan is used only in research and have not yet been validated for clinical use. Subjects will be informed if a clinically important abnormality is detected on MRI or PET imaging (e.g., brain tumor).
3. Image processing FreeSurfer (http://surfer.nmr.mgh.harvard.edu/), the MRI software package comprising a suite of automated tools for segmentation, reconstruction, and derivation of regional volumes and surface-based rendering, will be used for derivation of regions-of-interest (ROIs). Eleven ROIs will be extracted from the structural T1 image: entorhinal cortex, hippocampus, inferior temporal cortex, combined superior and middle temporal cortex, superior parietal lobule, inferior parietal lobule, precuneus, occipital cortex, prefrontal cortex, striatum, and thalamus. 18F-MK-6240 PET images will be analyzed as follows: Freesurfer based ROIs will be applied to coregistered PET images. Correction for partial volume effects using a region-based voxel-wise method92 will be applied to compare to partial volume uncorrected data. Regional time-activity curves will be extracted from the PET scans, including cerebellum which will be used as a reference region. Standardized uptake value ratio (SUVR) values will be calculated by dividing SUV values for each target region by that of the cerebellum. Alternative analytic methods such as Logan DVR and Simplified Reference Tissue Method may also be applied to compare to SUVR data.
