I work with medical images daily and resizing can mean different things to different people. It could possibly mean:
There isn't necessarily a one size fits all solution. Do all of the medical images have the identical voxel spacing and is that spacing isometric? This is a key consideration for how you can handle the data while preserving its relation to anatomical space.
I'm happy to try and help, but I just want to be sure I understand what you're trying to achieve.