Combined MRI and fibreoptic colonoscopy: technical considerations and clinical feasibility

A method of fibre-optic colonoscopy with simultaneous high resolution MRI has been developed to obtain cross-sectional information of the intramural and extramural extent of lesions, for diagnostic and therapeutic purposes. An MR-compatible colonoscope with receiver coil was designed, developed and used in ex vivo studies to scan a section of large bowel in transverse and longitudinal planes with T1 and T2 weighted spin-echo sequences. In vivo five patients were followed-up after excision of large bowel cancer. The patients were three men and two women aged 50-77 years, (mean 65.6 years) who were studied on a 0.5 T scanner (Picker Asset, OH, USA). The coil and colonoscope were inserted into the rectum. After routine visual inspection of the colon, T1 weighted spin-echo images and radio-frequency spoiled gradient-echo images of the bowel wall were obtained. Ex vivo: three layers of bowel wall were identified: an intermediate to high signal-intense mucosa, a high signal intensity layer on T1 weighting which corresponded to the submucosa, and a low signal intensity muscularis propria. In vivo: On T1 weighted images three layers could be identified that corresponded to the layers seen on the ex vivo imaging. This pilot study demonstrates that MR colonoscopy is feasible and allows delineation of bowel wall structure, thus providing a useful adjunct to conventional colonscopy.

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