An-Najah Staff

PURPOSE
Distension of the colonic lumen for MR colonography has to date been accomplished with water. However, it has been suggested that distending the colon with water is associated with more discomfort compared to air or CO2. The aim of this study was to assess air-distended MR colonography in terms of image quality and patient acceptance and to compare it with water-distended MR-colonography.
METHOD AND MATERIALS
In 5 volunteers the colon was imaged twice: once after distending the colon with air and a second time with water. 50 patients, who had been referred to colonoscopy for a suspected colorectal pathology were randomised into a water-distension (n = 25) and air-distension (n = 25) groups. All examinations were performed in prone position using 2500 ml of room air or tap water to distend the colon. A contrast-enhanced T1w 3D GRE sequence (TR/TE/flip: 3.1/1.2ms/12) was collected using a 1.5T Scanner (Sonata, Siemens, Germany). Comparative analysis was based on qualitative ratings of image quality and bowel distension based on a three-point scale as well as CNR measurements for the colonic wall with respect to the colonic lumen. In addition, patient acceptance was evaluated using a standardized questionnaire.
RESULTS
Inflammatory changes and colorectal masses were correctly identified on MRC in eight patients of each group. One 4 mm polyp identified at colonoscopy was missed on water-distended MRC. There were no false positive findings. No differences were found between air- and water-distension regarding discomfort levels and image artifacts (p>0.05). The presence of air in the colonic lumen was not associated with susceptibility artifacts. However, mean CNR of the contrast-enhanced colonic wall (36.3 vs 43.5) as well as bowel distension (1.07 vs 1.52) were superior on air-distended 3D data sets, and proved a statistical significant difference compared to the water-based MRC group (p<0.05).
CONCLUSIONS
MR colonography can be performed using either water or air for colonic distension. Both techniques permit assessment of the colonic wall and identification of colorectal masses. While discomfort levels are similar for both agents, MRC with air provides higher CNR and better colonic distension