Multimodal Imaging of Amyloid Deposition in WRAP Cohort

Acquisition of ¹¹C-PiB-PET and MRI imaging data in the WRAP cohort has been described in detail previously [23 (link)]. Briefly, ¹¹C-PiB-PET scans were acquired in a 3-D mode with a dynamic 70-min acquisition protocol after an injection of a 15-mCi target dose of ¹¹C-PiB bolus. Dynamic acquisition frames consisted of 17 time frames, including 5 × 2 min and 12 × 5 min frames. A filtered back-projection algorithm was used for reconstructing the data. For anatomical reference, a high-resolution T1-weighted MRI scan was acquired using a 3.0-Tesla GE MR750 scanner with an 8 or 32 channel head coil. The 3-D inversion recovery prepared fast spoiled gradient-echo sequence had the following parameters: inversion time (TI) = 450 ms, repetition acquisition matrix = 256 × 256 × 156 mm, field of view (FOV) = 256 mm, and slice thickness = 1.0 mm. The reconstructed time series of ¹¹C-PiB-PET data were realigned, corrected for motion, de-noised, and coregistered to the subject’s T1-weighted MRI scan based on co-registration of the time-integrated PET scan utilizing the Statistical Parametric Mapping software (SPM12; www.fil.ion.ucl.ac.uk/spm). Parametric distribution volume ratio (DVR) maps were generated using Logan graphical analysis methods [24 (link), 25 (link)] with t* = 35 min and cerebellar gray matter as a reference region of non-displaceable binding.