3.0t biograph mmr pet mr scanner

All subjects underwent simultaneous three-dimensional (3D) [¹¹C] Pittsburgh compound B (PiB)-PET and 3D T1-weighted magnetization-prepared rapid acquisition with gradient echo (MPRAGE) sequence MRI scans using a 3.0T Biograph mMR (PET-MR) scanner (Siemens, Washington DC, USA) according to the manufacturer’s approved guidelines. 3D T1-weighted images were acquired in the sagittal orientation, and the acquisition parameters were as follows: repetition time = 1670 ms, echo time = 1.89 ms, field of view = 250 mm, and a 256 × 256 matrix with a 1.0-mm slice thickness. For PiB-PET, a 30-minute emission scan was obtained 40 minutes after intravenous administration of 555 MBq of [¹¹C]PiB (range, 450–610 MBq). The PiB-PET data collected in list mode were processed for routine corrections such as uniformity, UTE-based attenuation, and decay corrections and were reconstructed into a 344 × 344 image matrix using iterative methods (5 iterations with 21 subsets).

Participants underwent simultaneous three-dimensional (3D) [¹¹C] Pittsburgh compound B (PiB) positron emission tomography (PET) and 3D T1-weighted MRI using a 3.0T Biograph mMR (PET-MR) scanner (Siemens, Washington, DC, USA) according to the manufacturer’s guidelines. Details of PiB-PET image acquisition and preprocessing are described in the Supplementary material.
The automatic anatomic labeling algorithm and a region-combining method40 were applied to determine regions of interest (ROIs) to characterize the PiB retention level in the frontal, lateral parietal, posterior cingulate-precuneus, and lateral temporal regions. The standardized uptake value ratio (SUVR) for each ROI was calculated by dividing the mean value for all voxels within the ROI by the mean cerebellar uptake value in the same image. 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 values was ≤1.4 for all four ROIs.40 ,41 A global cortical ROI comprising the four ROIs was also defined, and a global cerebral 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.

All participants underwent simultaneous three-dimensional (3D) [¹¹C] Pittsburg compound B (PiB)-positron emission tomography (PET) and 3D T1-weighted MRI using a 3.0T Biograph mMR (PET-MR) scanner (Siemens, Washington DC, USA) according to the manufacturer’s protocols. We have described the details of PiB-PET image acquisition and preprocessing previously [24 (link)]. The automatic anatomic labeling algorithm and the region combination method [25 (link)] were used to determine regions of interest (ROIs) and to characterize PiB retention in the frontal, lateral parietal, posterior cingulate-precuneus, and lateral temporal regions. A global cortical ROI (consisting of the four smaller ROIs) was also defined. A global Aβ retention value, the standardized uptake value ratio (SUVR) for the global cortical ROI, was calculated by dividing the mean values for all voxels of the global cortical ROI by the mean cerebellar uptake value evident in the same images [26 (link)]. A participant was classified as Aβ positive if the SUVR of the global ROI was >1.21 [27 (link)].