RT Journal Article SR Electronic T1 Dr. Leighton Mark was invited to comment on this issue. JF American Journal of Neuroradiology JO Am. J. Neuroradiol. FD American Society of Neuroradiology SP 982 OP 984 VO 21 IS 5 A1 Mark, Leighton P. YR 2000 UL http://www.ajnr.org/content/21/5/982.3.abstract AB