PET/CT and MRI Data Acquisition

The patient population consisted of 45 patients (19 males and 26 females, 63 ± 9 years and 71 ± 13 years, respectively) presenting with cognitive symptoms of possible neurodegenerative disease who underwent brain ¹⁸F-FDG PET/CT and MRI examinations collected between April 2017 and September 2019 at Geneva University Hospital. The detailed demographic information of the patients is summarized in Table ​Table1.1. The study protocol was approved by the institution’s ethics committee and all patients gave written informed content. PET/CT acquisitions were performed on a Biograph mCT scanner (Siemens Healthcare, Erlangen, Germany) about 35 min post-injection. A low-dose CT scan (120 kVp, 20 mAs) was performed for PET attenuation correction. The patients underwent a 20-min static brain PET scan after injection of 205 ± 10 MBq of ¹⁸F-FDG. PET data were acquired in list-mode format and reconstructed using the e7 tool (an offline reconstruction toolkit provided by Siemens Healthcare) to produce FD PET images. Subsequently, a subset of PET data containing 5% of the total events was extracted randomly from the list-mode data to produce the LD images using a validated code [25]. Both FD and LD PET images were reconstructed into a 200 × 200 × 109 image matrix (2.03 × 2.03 × 2.2 mm³ voxel size) using an ordinary Poisson ordered subsets-expectation maximization (OP-OSEM) algorithm (5 iterations, 21 subsets) with point spread function (PSF) modelling. PET images underwent post-reconstruction Gaussian filtering with 2 mm FWHM similar to the clinical protocol. MRI data acquisition was carried out on a 3T MAGNETOM Skyra (Siemens Healthcare, Erlangen, Germany) with a 64-channel head coil. The MRI scans included a 3D T1-weighted magnetization prepared rapid gradient-echo, MP-RAGE (TE/TR/TI, 2.3 ms/1930 ms/ 970 ms, flip angle 8°; NEX = 1, voxel size 0.8 × 0.8 × 1 mm³) and a 3D T2-weighted (TE/TR, 386 ms/5000 ms, NEX = 1; voxel size 0.5 × 0.5 × 1 mm³).

Demographics of patients included in this study protocol