Fig 2.

(upper portion) Illustrative demonstration of the hand motor area isolation methodology using a fourth region of interest (ROI) in the precentral gyrus (cortical-ROI).

(left subsection) Detection of the “omega sign” in the precentral gyrus as indicated by the arrow (axial plane) (a). Confirmation of the correct localization via overlaying the FreeSurfer labelmap for each case that was a result of the automatic FreeSurfer subcortical segmentation. The purple color indicates the precentral gyrus (axial plane) (see the red arrow) (b).

(middle subsection) Drawing of the cortical-ROI in the cortical region of the “omega sign” (axial plane) (c). Detection of the same area in the coronal plane utilizing the “slice intersections” tool of 3D Slicer (coronal plane). Note that either a straight line covering the entire extent of the gyrus of interest or two bullets defining the gyrus of interest can be observed as illustrated in the image (d).

(right subsection) The remaining non-colored area of the gyrus of interest was filled in with the same color to complete the cortical-ROI (coronal plane) (e). In the axial plane, the correct area of interest, namely the hand motor area, was verified (f).

(lower portion) Spatial representation of all four ROIs after they were added to one labelmap in order to isolate the hand-related motor fiber tracts (HMFTs). HMFTs were defined in White Matter Query Language (WMQL) as the fiber tracts passing through all four ROIs, as demonstrated in the case of that HMFT. Posterior view of a 3D model of the four ROIs and the HMFT passing through all four in 3D Slicer software. Left and right sides are designated L and R, respectively (g). Lateral view (left side) of the same subject’s HMFT with an added sagittal MRI section of the subject’s b0 MRI image to illustrate spatial localization of the ROIs (h).