Biograph mmr pet mr scanner

All PET/MRI scans were performed at the National University of Singapore (NUS) Clinical Imaging Research Centre using a Siemens Biograph mMR PET/MR scanner (Siemens Healthcare, Erlangen, Germany). Prior to FDG PET/MRI, participants fasted for 6 h, following which an intravenous injection of 18F-FDG (mean activity 138.4 ± 9.4 MBq) was given to each participant. Fasting was not required prior to DOTANOC PET/MRI. An intravenous injection of 68Ga-DOTANOC (191.7 ± 9.3 MBq) was given. Scans for both radioligands were commenced immediately and data acquired up to 80 min post injection.
The PET images were reconstructed using Ordinary-Poisson Ordered-Subset Expectation–Maximisation (OP-OSEM) with 3 iterations and 21 subsets. A Gaussian post-smoothing filter of 6 mm full-width at half maximum (FWHM) was applied. The matrix size was 172 × 172, with a voxel size of 4.17 × 4.17 mm and slice thickness of 2.03 mm.
The MRI data was acquired using 12-channel body coils. Dixon images were collected for the purpose of MR-based Attenuation Correction (MRAC).

Participants underwent simultaneous three-dimensional (3D) [¹¹C] Pittsburg compound B (PiB)-positron emission tomography (PET) and 3D T1-weighted MRI scans using a 3.0T Biograph mMR (PET-MR) scanner (Siemens; Washington DC, WC, USA) at baseline and 2-year follow-up visit. The details of PiB-PET acquisition and preprocessing were previously described [36 (link)]. An automatic anatomic labeling algorithm [46 (link)] and a region combining method [47 (link)] were applied to determine regions of interests (ROIs) to characterize the PiB retention level in the frontal, lateral parietal, posterior cingulate-precuneus, and lateral temporal regions. A global Aβ retention value was the mean standardized uptake value ratio (SUVR) for all voxels of the four ROIs, calculated by dividing the mean uptake value of a reference region. For cross-sectional analysis of baseline data, the inferior cerebellar gray matter in the Spatially Unbiased Infratentorial Template for the cerebellum (SUIT) atlas [48 (link)] was used as the reference region for intensity normalization. For longitudinal analysis, the reference region included the inferior cerebellar grey matter in the SUIT, cerebellar white matter (thresholded at 50%) [49 (link)], pons, and cerebrum white matter (thresholded at 95% and eroded by 3 voxels) [50 (link), 51 (link)].

All participants underwent simultaneous three-dimensional (3D) [¹¹C] Pittsburgh compound B (PiB)-positron emission tomography (PET) and 3D T1-weighted MRI scan using a 3.0T Biograph mMR (PET-MR) scanner (Siemens), in accordance with the manufacturer’s guidelines. The details of the PiB-PET imaging acquisition and preprocessing were described previously (Park et al., 2019 (link)). An automatic anatomical labeling algorithm and a region-combining method (Reiman et al., 2009 (link)) were applied to determine regions of interest (ROIs) for characterization of PiB retention levels in the frontal, lateral parietal, posterior cingulate-precuneus, and lateral temporal regions. Standardized uptake value ratio (SUVR) values for each ROI were calculated by dividing the mean value for all voxels within each ROI by the mean cerebellar uptake value in the same image. A global cortical ROI consisting of the four ROIs was defined and a global Aβ retention value was generated by dividing the mean value for all voxels of the global cortical ROI by the mean cerebellar uptake value in the same image (Reiman et al., 2009 (link); Choe et al., 2014 (link)). Each participant was classified as Aβ-positive (Aβ+) if the SUVR value was > 1.4 in at least one of the four ROIs or as Aβ-negative (Aβ-) if the SUVR value was ≤ 1.4 for all four ROIs (Reiman et al., 2009 (link); Jack et al., 2014 (link)).