This software enables you to view your tomography DICOM data as 3D visualization. Description: DICOM 3D viewer https://github.com/Slicer/Slicer
I checked myself and it will likely result in more than one ebuild, also the cmake build looks from my side not really friendly for the use case. Sadly I'm not experienced with creating ebuilds, so I can't start ere on my own. On the other hand it looks like a real useful DICOM tool, sth that is missing currently on gentoo.
AFAIK, there is no program in Gentoo to explore MRI scans, so this one may be very (even though rarely) useful.