MRIs take as long as you can afford. I have actually run ~3 hour MRIs for experiments, but we're being very fussy and trying to get the best possible image wit

MRIs take as long as you can afford. I have actually run ~3 hour MRIs for experiments, but we're being very fussy and trying to get the best possible image with the smallest possible voxel, which you do by acquiring tons of volumes and averaging them. Obviously, you can be in and out of there much quicker if you're just looking for a gaping hole.