14800-DvRappard

128 Chapter 8 Control subjects at 1.5T had normal MRI and neurological examination. Controls at 3T had experienced a non-neurological trauma and were included in a previous study. 20 Acquisition Between January 2007 and April 2013, 19 patients and 20 controls were examined at 1.5T (Siemens Sonata, Erlangen, Germany). BetweenMay 2013 and April 2017, 9 patients and 27 controls were examined at 3T (GE Signa HDxt and MR750, Milwaukee, WI). Conventional imaging included sagittal 3-dimensional (3D)-T1 and axial FLAIR, using the same spatial resolution at both field strengths. 20,21 FLAIR imaging was not performed for control subjects at 3T. DTI was obtained with a multi-slice echo planar imaging sequence and isotropic 2.5x2.5x2.5mm 3 voxels. At 1.5T we obtained 1 b0 volume and 12 gradient directions with b-value 750s/mm 2 , 2 acquisitions, TR/TE 6700/81 ms.(21) At 3T we obtained 5 b0 volumes and 30 gradient directions with b-value 750s/mm 2 , 1 acquisition, TR/TE 5100/75 ms, and parallel imaging factor 2. 20 Analysis: DTI data were analyzed using FMRIB’s software library FSL after correction of distortion and subject motion. The diffusion tensor was fitted resulting in maps of FA, AD, RD and MD. Tract based spatial statistics (TBSS) was used to align FA images from all subjects into a common space and to create a mean FA skeleton. Each participants’ aligned FA data were projected onto this skeleton and fed into voxel-wise cross participant statistics using randomise (see statistical analysis). 22 Based on the regional differences found in the TBSS analyses we further analyzed diffusion measures in the following regions of interest (ROIs): normal-appearing white matter (NAWM, corpus callosum and thalamus in all subjects, and abnormal cerebral WM in patients. In addition, we analyzed the pyramidal tracts, which were determined for each subject by tractography between motor cortex and cerebral peduncles (see below). To determine these ROIs in DTI subject space, we first outlined abnormal WM on 2D FLAIR images of patients using clusterize. 23 The mask of abnormal WM was registered to the corresponding 3DT1, and filled with signal intensity of NAWM. This 3DT1 image was then segmented with the FSL tools FAST 24 and FIRST 25 to obtain WM, grey matter (GM) and deep GM (DGM) structures, including the thalamus. DGM and abnormal WM were subtracted from the WM mask to obtain NAWM. ROIs for corpus callosum and cerebral peduncles were identified using the Johns Hopkins University (JHU)WM atlas defined in standard Montreal Neurological Institute (MNI) space. 26 The motor cortex was identified