Research Of3.0T Magnetic Resonance Imaging In Rat Model Of Dextran Sulfate Sodium-induced Acute Ulcerative Colitis

Objective We investigated the MRI findings and diagnostic value of the acute colitis in rat model in order to develop a preclinical imaging method for evaluating colitis, and provide valuable information for further exploration of the MRI features of human UC.Materials and Methods24male SD rats were treated with8%dextran sulfate sodium in their drinking water for7days to induce colitis.MRI scanning were performed before treatment and7day after treatment using GE3.0T HDx superconducting magnet.Scan sequences and parameters include:①T1WI and T2WI;②Axial DWI scanning:using a single excitation of the SE-EPI sequences with b=1000s/mm2, the DWI images and ADC maps were obtained;③Dynamic contrast-enhanced MRI performed by LAVA (live aquisition with volume acceleration)series, pre-scan finished before a dose of0.13mmol/kg of the body weight of Gd-DTPA contrast agent was injected via the catheter,then fist scan began at30s after injection, each collection time interval was1minute and collected a total of nine times. The following data were analyzed:①To observe the shape of bowel, the wall thickness and signal intensities of T2WI in skeletal muscle and colonic tissues.to analyses single intensity ratio (SIR)of colon to muscle;②To analysis the ADC value of colon;③To observe the time-signal intensity curve(TIC). and measured the signal intensities (SI) of the intestinal wall, muscle and fat at unenhanced and enhanced peak level, to calculate the relative maximum enhancement ratio.Results:1. Normal rats before modeling showed low signal in the intestine of rats; after modeling16rats shows high signal intensity both in T1WI and T2WI. suggesting the blood in the intestine. Wall thickness was (1.58±0.33) mm before modeling while (0.47±0.08)mm.after modeling. wall thickness was significantly greater than before modeling (t=-17.176. P<0.001).2. T2signal intensity of intestinal wall higher than muscle, before modeling the intestinal wall/muscle signal ratio was (1.59±0.35), after modeling the intestinal wall/muscle signal ratio was (3.55±0.60), the SI were also significantly different in inflamed colons compared to normal colon (t=-8.504, p<0.001), that means the T2WI signal in inflamed colons was higher than the normal intestinal wall.3. With b=1000s/mm2, the ADC value of inflamed colons was inferior to normal colon, ADC value distinguished normal colon from diffusely thickened colonic wall occurring in colitis (t=14.915, P<0.001).4. Both of the type of TIC were flat type, The TTP of the intestinal wall were different (p=0.002)between normal (3.25±0.45s) and inflamed colons (4.05±0.51s).5. On the condition of using dorsal muscle and fat independently at the same slice of bowel as the reference, the relative maximum enhancement ratio of normal bowel wall differ from colitis bowel wall(t=-9.328,p<0.001; t=-2.614,p=0.024).Conclusions:1. The results demonstrate that T2WI、DWI and dynamic contrast-enhanced MRI can be a successful method for evaluating colitis. The colorectal of normal rat is straight and natural expansion, the intestinal wall is slightly high signal intensity. By means of injecting gas through the anus to intestine.we also can obtain the satisfied imaging of inflamed colon.2.8%DSS(w/v) can successfully induce rats acute phase of UC. Axial T2WI can measure the thickness of the intestinal wall of rats colorectal and signal intensities.3.The results demonstrate that quantitative analysis of ADC value can successfully distinguish colitis from normal colon in rats.4.Application of LAVA dynamic enhancement techniques can evaluate the intestinal wall of nomal rats and colitis model.