RT Journal Article SR Electronic T1 MR appearance of the retroisthmic cleft. JF American Journal of Neuroradiology JO Am. J. Neuroradiol. FD American Society of Neuroradiology SP 397 OP 398 VO 17 IS 2 A1 C W Horner A1 V M Haughton YR 1996 UL http://www.ajnr.org/content/17/2/397.abstract