Update the labeling protocol with the straightened view

[jcohenadad]

Manual labeling of nerve rootlets needs to be robust. There is a large variability between scans and raters.

One way to facilitate the labeling is to straighten the scan:

Other things to try:

• in the straightened space, average in the AP direction (test the number of slices for optimal visualization of ventral and dorsal rootlets)
• Include the PMJ in the straightened space. To do that, extend the centerline.