Discovery elite

¹⁸F-FDG PET imaging was performed using the Discovery Elite PET/computed tomography (CT) scanner (GE Healthcare) at the PET Center of Xiangya Hospital. The participants were advised to rest for 45–60 min with their eyes closed in the supine position on the PET scanner bed. The PET/CT scanning was conducted for 10 min using 3-dimensional (3D) mode after ¹⁸F FDG (3.7 MBq/kg) injection (intravenous). The images were reconstructed using the ordered subset expectation maximization algorithm with 6 iterations and 6 subsets method. Prior to image preprocessing, the DICOM images of PET were transformed into NIfTI images using the dcm2nii software (version 12¹). Preprocessing of PET images was performed with the statistical parametric mapping (SPM) software² implemented on MATLAB. Individual ¹⁸F-FDG PET image volumes were manually reset to the origin of 3-dimensional standard stereotactic Montreal Neurological Institute (MNI) spaces. The image intensity of all participants was globally normalized for a homogeneous comparison. A standard uptake value (SUV) image was generated for each participant. Then, the automated anatomical labeling (AAL) atlas was applied to parcellate all SUV images into 90 ROIs (45 per hemisphere without cerebellum), which were then defined as nodes of the individual metabolic network.

A GE Discovery Elite PET/CT scanner was used, whereby ¹⁸F‐FDG is produced by a GE Mini Tracer cyclotron and synthesized by an automatic synthesis module, with radiochemical purity >99%. Before examinations, patients fasted for more than 6 h, and the blood glucose was <15 mg/L. The ¹⁸F‐FDG injection dose was 3.7 MBq/kg body mass, and the patient was examined by routine PET/CT after 60 min of rest. CT scans were taken first with a tube voltage of 120 kV, automatic tube current (15 ~ 180 mA), tube rotation speed of 0.8 s/rot. The original voxel size is 3.65 mm × 3.65 mm × 3.27 mm. PET scans were conducted in 3‐dimensional mode, matrix of 192 × 192, 2 min/bed. The original voxel size is 0.98 mm × 0.98 mm × 3.27 mm. The scanning range covered from the upper part of both thighs to the top of the head. After scanning, the ordered subsets maximum expectation method iteration was used for image reconstruction. PET and CT images were then transferred to a Xeleris workstation for image fusion.

All patient data were obtained on a PET/CT scanner (GE Discovery Elite). Patients were instructed to fast for at least 6 h before the PET/CT imaging and to control fasting blood glucose concentration to <11.1 mmol/L. ¹⁸F-FDG (0.10–0.15 mci/kg) was injected through the cubital vein, after which the patient rested in a dark and quiet environment for approximately 60 min (the mean injection–acquisition time delay was 63.7 min; injection-collection time delay range was 50–73 min). All patients were scanned from the base of the skull to the distal femur. The spiral CT scan was performed with a tube current of 180 mAs, a tube voltage of 120 kV, and a layer thickness of 5 mm. The PET was scanned in eight bed positions, and each bed position needs 2 min with increments of 16.2 cm (3D mode). The ordered-subset expectation maximization (OSEM) iterative algorithm (with 6-mm full-width-at-half-maximum Gaussian filter) was used to reconstruct the PET images with CT values being used for attenuation correction, and the final PET voxel size was 5.3 mm × 5.3 mm × 2.5 mm.

¹⁸F-FDG PET/CT scanning was performed on either Gemini TF 64 (Philips, the Netherlands, 219 patients, 84.6%) from The First Affiliated Hospital of Wenzhou Medical University or General Electric Discovery Elite (Waukesha, WI, 40 patients, 15.4%) from Shaoxing People’s Hospital. All patients were instructed to fast for at least 6 h (blood glucose levels below 110 ml/dl) before being injected with ¹⁸F-FDG (3.7–5.55 MBq/kg). PET/CT images were acquired from the skull base to the mid-thigh after the injection with an average interval of 59.6 ( ± 7.8) min. Attenuation correction of the PET scan was based on the CT images. The detailed acquisition parameters are given in Supplementary Material Table 1, according to the Image Biomarker Standardization Initiative (IBSI) guidelines (24 ).

The patients fasted for approximately 6 h and had a blood glucose level < 11 mmol/L before undergoing the examination. A Discovery Elite PET/CT scanner (GE healthcare) was used to acquire images approximately 60 min after intravenous injection of ¹⁸F-FDG (4.2 MBq/kg). Unenhanced CT images were first acquired with 120 kVp, 80 mAs, and a slice thickness of 5 mm from the top of the skull to the middle femur during tidal breathing, and then full-ring dedicated PET images were obtained from the middle thigh to the top of the head during shallow breathing. PET/CT images were reconstructed using the ordered-subset expectation maximization algorithms and CT scans for attenuation correction.

Routine long-term video-electroencephalography (EEG) recording was performed with standard 10-20 system electrodes. Magnetic resonance imaging (MRI) was performed on each patient with a 3T MRI system (Signa HD xt 3T Volume, GE, GE Healthcare, USA) while ¹⁸F-FDG positron emission tomography (PET) scans were done using a PET/CT scanner in all except two patients due to concerns of radiation exposure (Elite Discovery, GE HealthCare, Fairfield, CT, USA).

PET images were acquired using a PET/CT scanner (Elite Discovery, GE HealthCare, USA) with a matrix size of 192 × 192 and a slice thickness of 3.27 mm. Patients fasted for at least 6 h and their serum glucose levels were maintained below 8 mmol/L. Patients were administered an intravenous injection of 310 MBq/70 kg of body weight of 18F-FDG. PET data reconstruction was performed using the ordered subset expectation maximization (OSEM) algorithm.
ASL scans were acquired using the 3D pseudo-continuous arterial spin labeling technique on a 3 T Siemens Magnetom Prisma MRI scanner (Siemens Healthineers, Germany) with a 64-channel head coil. No contrast agents were used, and patients were required to be stable during scanning. The scanning parameters were as follows: repetition time (TR) = 4705 ms; echo time (TE) = 11.2 ms; field of view (FOV) = 128 × 128 mm; number of excitations (NEX) = 1; 30 × 4.0 mm axial sections with whole brain coverage; scan duration, 6 min and 14 s.