Signa hdxt mri

Four cognitively normal (CN), Aβ-negative subjects and five AD dementia
(Aβ-positive) patients underwent repeated dynamic
[¹⁸F]florbetapir PET scans (average interval: 4.5 ± 3.0 weeks)
with arterial blood sampling using a Philips Ingenuity TF PET/CT (Philips
Medical Systems, Best, the Netherlands). Prior to the start of a 90 minutes
dynamic PET scan, a low-dose CT was acquired. PET images were reconstructed
into 22 frames using the BLOB (rotationally symmetric volume elements)
ordered-subsets time of flight (BLOB-OS-TF) reconstruction algorithm, with
the vendors’ default settings.^{24 (link)}
T1-weighted MRI scans were acquired on either a Signa HDxt MRI
(General Electric, Milwaukee, WI) or an Ingenuity TF PET/MR (Philips Medical
Systems, Cleveland, OH) scanner.¹⁹

MRI data were obtained using a 3.0 Tesla GE Signa HDxt MRI scanner (GE, Milwaukee, WI, USA) equipped with an eight-channel head coil. All participants were instructed to keep their eyes closed without falling asleep and to think as little as possible during the scan. To minimize head movement and eliminate scanner noise, foam padding and ear plugs were used. The resting-state data were obtained using echo-planar imaging (EPI) at 2-s intervals for a total of 8 min, which comprised 240 contiguous EPI whole-brain functional volumes with the following parameters: repetition time (TR) = 2 s; echo time (TE) = 30 ms; field of view (FOV) = 240 × 240 mm²; flip angle (FA) = 80; matrix size = 64 × 64; slice thickness = 4 mm; gap = 0.6 mm. Three-dimensional (3D) T1-weighted images were acquired using a spoiled gradient recalled echo sequence with the following parameters: TR = 9.5 ms; TE = 3.9 ms; FA = 20; FOV = 256 × 256 mm²; matrix size = 512 × 512. The following structural brain sequences were also acquired: T2-weighted spin echo (TR = 3,500 ms; TE = 85 ms; echo train length = 15; FA = 90; 22 contiguous, 5-mm-thick, axial slices; matrix size = 512 × 512; and FOV = 230 × 184 mm²); FLAIR (TR = 11 s; TE = 120 ms; FA = 90; 22 contiguous, 5-mm-thick, axial slices; matrix size = 512 × 512; and FOV = 230 × 230 mm²).

The method for determining tumor architecture employed patient data from The Cancer Imaging Archive (TCIA) derived during The Cancer Genome Atlas (TCGA) glioblastoma study. From this dataset, 24 patients with pre-treatment diffusion tensor imaging (DTI) scans were identified from two institutions Henry Ford Hospital (19 subjects) on a GE scanner with 25 gradient directions and a b-value of 1000 s/mm² and from Case Western (5 subjects) on a Siemens scanner with 37 gradient directions and a b-value of 1200 s/mm². For clinical validation, and to assess the significance of tumor architecture in predicting clinical outcome, magnetic resonance imaging was conducted on a 3.0 T GE Signa HDxt MRI scanner (GE Healthcare, Waukesha, WI) with an 8-channel high-resolution brain coil (GE Healthcare) at University of Texas, MD Anderson Cancer Center (MDA). Ethical approval for this research was obtained for use with anonymous and retrospective glioblastoma patient data. The pulse sequence incorporated standard single-shot echo-planar (EPI) spatial encoding, employing a voxel size of 0.86×0.86×3.5mm, 27 gradient directions plus b-zero, and a b-value of 1200 s/mm².