Did you get this to work? I'm new to XTK and had problems with this when loading my own NRRD/NII files. I changed volume.range[0] to volume.dimensions[0] (etc.) and that worked fine for me, but not sure if that's a legit way of fixing things.
Edit: Actually, check which build you are using. I switched to xtk_edge.js and volume.range works fine with that build.