[…] High resolution T1 MPRAGE volumes from each patient were normalized to Montreal Neurological Institute (MNI) standard space using FSL FLIRT (FMRIB's Linear Image Registration Tool; http://fsl.fmrib.ox.ac.uk/fsl/fsl-4.1.9/flirt/) (). A two-step registration procedure was implemented: (i) a mask was drawn over the lesion area and any surrounding craniotomy defect to prevent a bias in the transformation caused by the presence of these defects; and (ii) voxels within the mask were given a weight of 0 and ignored during 12° affine transformation of the lesioned brain to the standard MNI 1 mm reference volume. Lesions were then manually traced by a neuropsychologist (K.E.B.) on individual slices of the patient’s brain overlaid on to the standard template, with crosschecking across all three planes. Tracing produced a 3D volume with ‘1’ indicating the presence of the lesion and ‘0’ the presence of normal tissue. These images were smoothed (8 mm Gaussian isotropic) using SPM8 software (www.fil.ion.ucl.ac.uk/spm) for visual display of lesions. Lesion overlap maps were constructed by generating a proportion overlap score at each voxel (lesion/no lesion) ranging from 0 to 1.We further quantified the overlap between lesions and anterior PFC as defined by the boundaries of BA 10 in the MRIcron atlas (http://www.mccauslandcenter.sc.edu/mricro/mricron/), subdivided into lateral (x > 20 or x < −20) and medial sectors (). We additionally computed the overlap with neighbouring BA 46 (). We stress that this assay of lesion encroachment into Brodmann areas is at best probabilistic, as the normalization pipeline and individual differences in sulcal location predict only an approximate correspondence between stereotaxic coordinate and Brodmann area. Figure 4 […]
| Software tools | SPM, MRIcron |
|---|---|
| Application | Magnetic resonance imaging |
| Organisms | Homo sapiens |
| Diseases | Brain Diseases |
