Well sort of I had gone to a normal ER twice in two weeks and gotten a head CT twice based on the whole crazy thing but they didn't treat me...then I got admitted to the psych ward and was supposed to have an MRI...I filled out the paperwork but never got it...pdoc asked why and I didn't know and he found out on the question with are you pregnant yes no I had written in maybe....because of my rape delusion... well we got to talking and I said I already had a head scan and he wanted to know exactly what and then he said oh well you don't need an MRI then...so in this case they are pretty interchangeable but the MRI is much more sensitive but since they are pretty much trying to rule out tumors which are big or large missing sections or bleeding which is apparent etc a CT is apparently good enough.