HIGH-RESOLUTION MAGNETIC-RESONANCE-IMAGING OF THE ANAL-SPHINCTER USING AN INTERNAL COIL

An internal receiver coil was used to obtain high resolution transvers e and oblique coronal magnetic resonance images of the anal sphincter in five normal volunteers and five patients. The internal sphincter ha d a high signal intensity on T-1 weighted, T-2 weighted, and STIR sequ ences whereas the conjoined longitudinal muscle and external sphincter had a low signal intensity. The internal sphincter (but not the exter nal sphincter) showed contrast enhancement after administration of int ravenous gadopentetate dimeglumine. The oblique coronal plane was part icularly useful for showing the thickness and the relations of the ext ernal sphincter. Sphincteric abscesses as well as muscle defects, hype rtrophy, and atrophy were clearly shown. The coil was well tolerated b y most subjects. It has considerable potential for improving the diagn osis of anorectal disease.