VIRTUAL COLONOSCOPY WITH MAGNETIC-RESONANCE-IMAGING - IN-VITRO EVALUATION OF A NEW CONCEPT

Background & Aims: Screening for colonic polyps is desirable. A new co ncept based on cross-sectional and endoscopic analysis of a magnetic r esonance (MR) data set is presented. Methods: Ex vivo autopsy colonic specimens, containing artificially placed polyps, were obtained and fi lled with a gadolinium-containing solution. Forty-four thin-section MR images were obtained in a 1.5-T MR scanner in 28 seconds. A three-dim ensional endoscopic fly-through of these images was rendered. Fly-thro ughs and two-dimensional cross-sectional images were analyzed by two o bservers for the presence of polyps. Results: The average sensitivity and specificity for the detection of polyps based on three-dimensional endoscopic MR colon imaging were 87% and 96%, respectively. Analysis of cross-sectional images showed an overall sensitivity and specificit y of merely 57% and 84%, respectively. The difference in the interpret ation of three-dimensional MR colonoscopy and two-dimensional cross-se ctions was statistically significant (P < 0.001). With three-dimension al MR colonoscopy, overall sensitivity for detection of polyps measuri ng less than or equal to 5 mm in length and diameter was 70%; for larg er polyps, it increased to 95% (P < 0.01). Conclusions: The feasibilit y of an MR-based endoluminal assessment of the colon is shown. Minimal invasiveness, lack of radiation exposure, and high in vitro diagnosti c accuracy warrant further investigation of this novel concept.