Dedicated endoluminal coil for anal sphincter MR imaging

Results Minimum radial variation of signal intensity was found for an angle between 50 and 70°, depending on the radius. The quality factor Q of the “50° coil” embedded in salty water mimicking loading conditions was 124. SNR measured at the close vicinity of the coil (about 5 mm from the center) compared with SNR measured with the regular four-element phased array body coil used for abdominal clinical exams was 30 times higher. The sensitivity pattern falls off rapidly with distance from the coil. The sensitivity of the double loop coil was rather uniform to a fixed radius and improved compared to a signal loop coil. Moreover, it provides a better SNR than the four-element phased-array body coil up to about a radius of 30 mm from the coil centre. The anal sphincter complex was visualized with detail (Fig. 3). The high spatial resolution and excellent tissue contrast in images allowed excellent visualization of anal mucosa/submucosa complex, internal sphincter, and the external sphincter. Conclusion An endoluminal loop RF coil has been developed for the anal apparatus. The internal coil provides a dramatic increase in SNR local to the coil, compared to usual external coils. High-resolution magnetic resonance imaging acquired in the swine provides excellent visualizations of the normal anal sphincter complex anatomy. The results are promising and suggest useful applications in the management of anorectal diseases with minimally invasive procedure.