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MR colonography: baseline appearance of the unprepared rectosigmoid

Department of Radiology, University of Cambridge & Addenbrooke's Hospital, Cambridge, UK

View larger version (13K): [in a new window]   Figure 1. (a) The overall signal intensity of intraluminal material relative to the bowel wall for both T1 and T2 weighted studies. (b) The capacity of this luminal signal material to mimic tumour overall for T1 weighted and T2 weighted strategies individually, and for the combined analysis of T1 and T2 weighting. Wilcoxon signed rank test statistics were used to detect significant differences: intraluminal material of signal intensity similar to that of tumour occurred less frequently on T2 than T1 weighted imaging, with combined analysis providing a lower incidence of such tumour-mimicking material than either T1 weighted or T2 weighted alone (p<0.001 in each case).

View larger version (51K): [in a new window]   Figure 2. Location matched (a) T1 weighted and (b) T2 weighted images of the rectum and pelvic sigmoid colon with heterogeneous faecal material. These images also demonstrate the potential value of comparing multiple sequences to aid differentiation between lesions and intraluminal faeces. On T1 weighting (a) the area indicated (thick arrow) is of similar signal to the bowel wall and therefore could be tumour. T2 weighted (b) however demonstrates good negative luminal contrast in this region: no tumour is present. However this strategy is clearly limited: it would be impossible to exclude a lesion in either image at the area indicated by the thin arrow.

View larger version (13K): [in a new window]   Figure 3. (a) The presence of focal areas of luminal increased or decreased signal intensity compared with the remainder of intraluminal material. The majority of examinations demonstrated heterogeneous material, with foci of increased, decreased, or both increased and decreased signal present in T1 and T2 weighted studies. (b) The capacity of luminal foci to mimic colonic lesions in T1 and T2 weighted strategies.

View larger version (47K): [in a new window]   Figure 4. Location matched (a) T1 and (b) T2 weighted images of the rectosigmoid colon. A focus of slightly increased signal intensity relative to the bowel wall is demonstrated within the lumen on T2 weighting, whereas on T1 weighting this area is of similar signal to the wall. Consequently differentiation between faeces and a lesion is impossible.