Gemini gxl

Whole-body FDG PET/CT, performed at baseline and during treatment, was acquired sequentially using a dedicated PET/CT system (Gemini GXL from December 2006 to December 2010 and Gemini TF from December 2010 to August 2013; Philips Medical Systems, Eindhoven, The Netherlands). Every patient included had their two PET/CT examinations acquired on the same system, if patients were scanned on the two different scanners they were excluded. Patients were instructed to fast except for glucose-free oral hydration for at least six hours before the intravenous injection of 5 MBq/kg (Gemini GXL) or 3 MBq/kg (Gemini TF) of FDG. Blood glucose levels were measured before the injection of the tracer to ensure levels below 10 mmol/L. PET was acquired 60±10 minutes following FDG injection, from brain to mid-thigh, with the patient supine. Conventional PET reconstruction was performed, emission data were all corrected for dead time, random and scatter coincidences and attenuation[12 (link)] before reconstruction with the RAMLA iterative method. Attenuation correction was calculated using a low-dose non-diagnostic CT acquisition (140 kV and 40–120 mA).

All patients stopped levodopa at least 16 h before their PET scan. All subjects took 2.5 mg/kg of oral carbidopa, a peripheral AADC inhibitor, 1 h before the FMT injection to increase the availability of the tracer. Prior to the emission scan, a 10 min transmission scan was obtained for attenuation correction. Subsequently, 0.12 mCi/kg of FMT in saline was infused into an antecubital vein, and a 30–90 min static three-dimensional acquisition scan was started simultaneously using a PET-CT scanner (GEMINI GXL, Philips, Amsterdam, Netherlands). Each subject also underwent 3.0-tesla MR imaging (Achieva 3.0 T, Philips) using an inversion recovery proton density-weighted pulse sequence to enhance the contrast of anatomical structures [11 (link)].

In the Pitié-Salpêtrière University Hospital in Paris, all the amyloid PET scans were acquired in a single session on a CT-PET scanner (Gemini GXL, Philips, Cleveland, USA) 50 ± 5 min after the injection of approximately 370 MBq (333–407 MBq) of 18F-florbetapir (AVID radiopharmaceuticals). PET acquisition consisted of 3 × 5-min frames, in a 128 × 128 acquisition matrix, with a voxel size of 2 × 2 × 2 mm³.
Images were then reconstructed using the iterative LOR-RAMLA algorithm (10 iterations). Reduction of noise was modulated by the relaxation parameter lambda, which was set to 0.7. All corrections (attenuation, scatter, and random coincidence) were integrated in the reconstruction [26 ]. The reconstructed PET image resolution was 7.5 mm FWHM.
MRI scans were acquired on a Siemens Verio 3 T scanner at the CENIR in the Brain and Spine Institute, Paris, France. A T1-weighted image was acquired using a fast three-dimensional gradient echo pulse sequence using a magnetization preparation pulse (Turbo FLASH) and with the parameters of TR = 2300 ms; TE = 2.98 ms; IT = 900 ms; flip angle = 9°; 1-mm isotropic voxel size; matrix 256 × 240; bandwidth 240 Hz/Px [26 ].

PET/CT studies were performed according to the European Association of Nuclear Medicine (EANM) guidelines [21 (link)]. Patients fasted for ≥6 h and their blood glucose levels were <200 mg/dL before the administration of 232 ± 42 MBq of ¹⁸F-FDG. Images were acquired at 60 ± 10 min of uptake time using a Gemini GXL (Philips Healthcare—LOR RAMLA reconstruction without PSF and TOF; 3 iterations, 33 subsets; 4 × 4 × 4 mm³ voxel size; Gaussian filter of 5 mm; reconstructed image matrix size of 128 × 128) or a Biograph mCT (Siemens Healthineers, Erlangen, Germany)—3D OSEM reconstruction with PSF modeling and TOF; 2 iterations, 21 subsets; 3.2 × 3.2 × 5 mm voxel size; application of Gaussian filter of 2 mm; reconstruction image matrix of 400 × 400) PET/CT scanner. A low-dose CT scan (120 kV, 50 mAs) was acquired similarly for both scanners, from the skull base to the mid-thighs, for anatomical localization of functional findings and attenuation correction. The reconstructed CT image had a matrix size of 512 × 512, a pixel size of 0.97 × 0.97 mm, and a slice thickness of 3 mm.

PET/CT studies were obtained on the following PET/CT devices: Gemini TF64 (Philips), Gemini GXL (Philips), Gemini TF16 (Philips), Discovery LS (GE Healthcare), and Biograph TP16 (Siemens). Subjects with fasting serum glucose <7.0 mmol/L >6 h received IV ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) 3.70−5.55 MBq/Kg. After 60 min whole-body PET/CT imaging was performed with a whole-body CT scan (120 KV and 140 mA) and a whole-body PET (in 3-dimensional mode, 120s/bed position). Acquisition of CT, PET and PET/CT fusion images including cross-section, sagittal-section and coronal-section used CT-based attenuation correction in reconstruction image by an iterative method.