Allegra mri

Thirty-six participants were scanned at the MGH Martinos Center for Biomedical Imaging (Charlestown, MA, USA).^{64, 65, 68} Their self-identified ethnic makeup was: 3 African American; 5 Asian; 27 Caucasian; 1 multiracial. The mean age of this cohort was 40.5 years (range: 18–74). Thirty-three participants were right-handed, two were left-handed, and one was ambidextrous. Twenty participants were female; 16 were male. Thirty-one participants were scanned on a Siemens Tim Trio MRI; five participants were scanned on a Siemens Allegra MRI. This cohort was utilized to establish the tractographic method described below; this method was then tested using Cohorts B and C. Fourteen of these participants were scanned a second time, always utilizing the same MRI scanner for both acquisitions. We compared voxel location between the two scans to assess the longitudinal validity of the technique.

Each child was transported to the Cape Universities Brain Imaging Centre (CUBIC) together with his/her mother at mean age 10.1 ±1.0 years. After familiarization with the scanning procedures on a mock scanner, data were acquired using two DTI acquisitions with alternating phase encoding directions (i.e., anterior–posterior and posterior–anterior (AP-PA)) on a 3 T Allegra MRI (Siemens, Erlangen, Germany). For each acquisition, the following parameters were used: 4 reference images with b = 0 s/mm² and 30 diffusion-weighted images (DWIs) with b = 1000 s/mm²; 72 slices; field of view (FOV) = 230 ×230 ×130 mm³; slice thickness 1.8 mm; 1.8 ×1.8 mm² in-plane resolution; TR 10,000 ms; TE 88 ms. A 3D echo planar imaging (EPI) navigated [Tisdall et al., 2009 ] multi-echo magnetization prepared rapid gradient echo (MEM-PRAGE) [van der Kouwe et al., 2008 (link)] structural image (resolution 1.3 ×1.3 ×1.0 mm³, FOV = 256 ×256 × 167 mm³, 128 slices, TR 2530 ms, TI 1100ms, TEs 1.53/3.21/4.89/6.57 ms, flip angle 7°) was also acquired for each subject.

The children and their mothers were transported to the Cape Universities Brain Imaging Center (CUBIC), a research-dedicated, child-friendly facility where they were familiarized with the scanning procedures by first practicing in a mock scanner. The children were imaged on a 3T Allegra MRI (Siemens, Erlangen, Germany). Diffusion weighting was performed in 30 directions; 36 slices were acquired in an oblique axial orientation that included primarily infra-tentorial structures to provide high-resolution cerebellar data. The first 18 children (3 FAS, 6 PFAS, 3 HE, 6 Controls) were imaged using five DTI acquisitions; the others, using six acquisitions with alternating phase encoding directions (i.e., anterior-posterior and posterior-anterior) to reduce echo planar imaging distortions. Voxelwise analyses repeated without the 18 children for whom the imaging protocol differed, yielded differences between the same groups in regions overlapping with those found for the whole sample. Further, analyses relating oz AA/day to the DTI measures in the regions where group differences were found were virtually unchanged with these 18 children included or excluded. Cerebellar T2-weighted structural images were acquired with a matched spatial resolution and slice position as the DTI in order to improve co-registration between the cerebellar DTI and whole-brain structural data.