Sorry for being a smartass, but it seems pretty obvious, how about you do an interventional radiology elective.
I wouldnt even bother with the general elective, I'm going into radiology and I'm not taking it. Perhaps its different at your school, but at my school you get bounced around so much you dont get to know anybody and 90% of the students who take the elective are jerkoffs looking for an easy month.
I did subspecialty months where you get lots of one on one time with big name faculty. I dont see how you could get a letter from the general elective, at my school you only spend 2-3 days on each service.