MR findings of bowel ischemia with mesenteric vascular occlusion: comparison with pathologic findings in a cat model

초록

Purpose: To assess whether changes in the MR enhancement, T1 and T2 signal intensity of the bowel wall layer can be used to diagnose acute bowel ischemia due to mesenteric vascular occlusion in a cat model. Materials and Methods: Twelve cats were assigned to the either normal control group (no ischemic period, n=2), the acute ischemic group (ligation of mesenteric vessels for 3 hours, n=6) or the subacute ischemic group (ligation of mesenteric vessels for 10 hours, n=4). Under the general anesthesia, the laparotomy was performed. The ileal artery and vein were ligated, and a columnar surface coil was applied to the expected bowel ischemia. Using a 4.7 T MR scanner, contrast enhanced T1WI was obtained at 10, 20, 30, 60, and 90 minutes after bolus injection of contrast media. T1WI and T2WI were obtained from the extracted bowel, and the specimen was pathologically examined. MR signal intensity was measured at each layer of the bowel wall, and compared with the pathologic findings. Results: On contrast enhanced T1WI, the submucosal layer showed most intensive enhancement, followed-in decreasing order of signal intensity-by muscle and mucosal layer. Time to peak enhancement of bowel wall was 10 minutes in the normal control group, 20 and 60 minutes in acute and subacute ischemic groups, respectively. On T1WI, no significant differences in signal intensity were observed between the ischemic group and the normal control group (p>0.05). On T2WI, the signal intensity of the submucosal layer of acute ischemic group was significantly higher than that of the normal control or subacute ischemic group, and the signal intensity of the muscular layer of the ischemic group was significantly higher than that of the normal control group (p<0.05). Conclusion: Time to peak enhancement of bowel wall was helpful criterion for assessment of the ischemic period. Analysis of the signal intensity of the bowel wall layer was useful for the early detection of the acute bowel ischemia.