QA output: images you need to determine whether b vectors are oriented correctly

[arokem]

We want to produce an image of the DTI ellipsoids around the posterior corpus callosum in a horizontal section. If these are pointing orthogonal to the posterior callosum, rather than swinging back like we would expect, the b vectors need to be reoriented.

Might be useful to provide example images that tell you exactly what you should do (i.e., what you should provide as keyword arguments to dmriprep upon re-running it).