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Fig 1. A, ROI segmentation for corticospinal tract tractography. Polygonal ROIs are placed on transverse b = 0 images (TR/TE, 7000 ms/79 ms). The first "OR" ROI (blue) is placed at either side of the cerebral peduncle on the plane where the characteristic 
shape of the central sulcus is at the center of cerebral hemisphere (top left). The second "AND" ROI (blue) is placed at the ipsilateral precentral gyrus (top right). Left and right ROI segmentations were separately performed. "NOT" ROIs (green) are placed on midline structures connecting right and left corticospinal tracts on sagittal reconstructed image (bottom left) and fibers projecting into ipsilateral cerebellar peduncle on coronal reconstructed image (bottom right). Examples of bilateral corticospinal tract overlaid on coronal reconstructed image are shown (bottom right).
B, ROI segmentation for optic radiation tractography. The 4 kinds of ROIs (white polygon) are placed on coronal or sagittal color-coded maps. Cross lines indicate the orthogonal planes. The first "OR" ROI is placed at either side of the occipital lobe, including the calcarine cortex on the coronal plane through the anterior edge of the occipital-parietal sulcus (top left). The second "AND" ROI is placed at the ipsilateral temporal stem, including the Meyer loop on the sagittal plane (top right). Temporal stem is identified as green, and the Meyer loop is identified as a small red area inside the temporal stem (red arrow). The third and fourth "NOT" ROIs are placed on the same coronal plane through the dorsal end of the Sylvian fissure (bottom left). Bilateral Meyer loops are indicated as red arrows. Occipital-frontal connections medial to the Meyer loop and fibers projecting to the temporal horn passing through lateral to the Meyer loop are removed using the "NOT" operation. Examples of bilateral optic radiation overlaid on transverse b = 0 images (TR/TE, 7000 ms/79 ms) are shown (bottom right).
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