| Objective:Multi-b-value DWI was performed on rabbit models of acute superior mesenteric artery occlusion at different time periods by 1.5T magnetic resonance imaging.The correlation between DWI parameters and pathological changes of intestinal wall was observed and analyzed to explore the value of multi-b-value DWI in evaluating acute intestinal wall ischemic necrosis.Methods:35 New Zealand white rabbits,male and female,were randomly divided into two groups(experimental group,control group)and five time points(1h,2h,3h,4h,5h).15 rats in the control group,3 rats at each time point;20 rats in the experimental group,4rats at each time point,acute superior mesenteric artery occlusion model of intestinal ischemia was made by silk ligation method in the experimental group,the control group only separated and exposed superior mesenteric artery without ligation.Routine MRI plain scan(T1WI,T2WI)and different b values(0,200,400,600,800,1000 s/mm~2)DWI were performed at the corresponding time points of the two groups.ADC values of different time points and different b values were measured,and intestinal wall thickness and pathological scores were recorded at the corresponding time points.One-way ANOVA was used to compare the intestinal wall pathological score,intestinal wall thickness and ADC values between the control group and the experimental group.The ADC values of different b values in the control group and the experimental group were analyzed by independent sample t test;Pearson correlation analysis was used to compare the correlation between ADC value and intestinal wall thickness and pathological score in the experimental group.Results:(1)Control group:The intestinal wall was ruddy in color,with normal peristalsis,neat arrangement of small intestinal villi,and clear display of mucosal layer and muscular layer.No significant changes were observed in intestinal wall pathological score and intestinal wall thickness at each time point,and the difference was not statistically significant(P>0.05).In the control group,the ADC values of intestinal wall at each time point gradually decreased with the increase of b value,and the difference was statistically significant(P=0.000),while there was no statistically significant difference in the ADC values of intestinal wall at different time points under the same b value(P>0.05).(2)Experimental group:The colour of intestinal wall became dark red in 1 h-2 h ischemia group,and the scope of ischemia mainly involved mucosal layer and submucosal layer.The 3 h group gradually involved the muscular layer,the small intestine villi fell off,the structure was disordered,the muscle layer became thinner,and the inflammatory cells increased.In 4 h and 5 h group,the intestinal peristalsis was weakened,the intestinal wall was obviously thin and transmural necrosis occurred,the intestinal wall was dark purple,the intestinal tube was obviously dilated,and the peritoneal effusion and hemorrhage increased.There were statistically significant differences in pathological scores between the control group and the experimental group at each time point(P<0.05).There was no statistically significant difference in pathological scores between the experimental group at1 h and 2h(P=0.126),while there was statistically significant difference between the experimental group at 1h and 3h,4h and 5h(P<0.05).The differences of 2h,3h,4h and5h in the experimental group were statistically significant(P<0.05).The difference of 3h,4h and 5h in the experimental group was statistically significant(P<0.05).There was no significant difference in pathological score between the experimental group at 4h and 5h(P=1.000).The intestinal wall thickness of each group in the experimental group was thinner than that of the control group at the same time point,and the differences were statistically significant(P=0.000).Intestinal wall in the experimental group gradually thins with the extension of ischemia time,and the difference in intestinal wall thickness at each time point is statistically significant(F=1320.119,P=0.000).The intestinal wall ADC values of the experimental group at each time point gradually decreased with the increase of the b value,and the difference was statistically significant(P=0.000).There was no significant difference in the intestinal wall ADC values of the 1h group b=400 s/mm~2 and b=600 s/mm~2(t=1.374,P=0.190).The ADC value of the experimental group decreased gradually with the increase of time under the same b value,and there was no significant difference between the 4h and 5h groups when b=200 s/mm~2(t=1.246,P=0.232).Pearson correlation analysis showed that ADC values of different b values in the experimental group had a positive significant correlation with intestinal wall thickness(P=0.000),and b=800 s/mm~2 had the strongest correlation(r=0.979,P=0.000).Pearson correlation analysis showed that ADC values of different b values were negatively correlated with pathological scores,and the results were statistically significant(P=0.000).The correlation coefficient of b=800 s/mm~2 was the highest(r=-0.874,P=0.000).Conclusion:(1)The ADC value of the intestinal wall of the experimental group was significantly lower than that of the control group,and gradually decreased with the increase of b value and the prolongation of ischemia time;(2)The correlation coefficient between intestinal wall ADC value and intestinal wall thickness and pathological score in the experimental group was high,and the correlation was strongest when b=800 s/mm~2;(3)When the rADC value of>was 11.86%,it suggested that intestinal wall ischemia involved the muscle layer,while the rADC value of>was 23.34%,suggesting intestinal wall necrosis through the wall. |
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