Fig. 3

Segmentation of the sciatic nerve. Tensor fitting was performed with DTI Studio (www.mristudio.org) to obtain DTI maps after motion and distortion correction by linearly registering all gradient directions to the b = 0 map. Sciatic nerves were manually segmented using the fractional anisotropy (FA) map (left panel) as a mask by thresholding the nerve (minimum, maximum FA = 0.3, 0.8) and using the reversed fast imaging with steady state free precession sequence for anatomical nerve localization (right panel). A region-growing algorithm, using a custom code written in Interactive Data Language (www.harrisgeospatial.com), was employed to segment the entire nerve length. DTI measurements were extracted from voxels between the 25th and the 75th percentiles of the FA histogram to mitigate partial volume effects at the peripheral margins of the nerve. The surgical site was located proximal to the midpoint between a line drawn between the greater trochanter and ischial tuberosity (right panel, white arrows). Similarly, the distal site was located 3 mm distal to the surgical site on the FA map. Only the voxels inside the mask were included in the analysis