Combining Aquaporin Theory And Non-Gaussian Distribution Model DWI To Evaluate HIRI Model In Rats

CHAPTER ONE:Study on the model ofHepatic Ischemia Reperfusion Injury Model in Rats by Non-Gaussian Distribution Model Diffusion Weighted ImagingObjective:To investigate the imaging features of hepatic ischemia reperfusion injury(HIRI)model in rats,and to study the changes in cellular and molecular levels combining with many non-Gaussian distribution models diffusion weighted imaging(DWI)such as biexponential model,threxponential model,stretched-exponential model diffusion weighted imaging and diffusion kurtosis imaging.Methods:Forty-two SD rats weighing 250-300g were divided into 7 groups,6 rats in each group.The experimental groupunderwent right hepatic portal vein and hepatic artery ligation for 3 hours(h),and the control group underwent sham operation.3.0T MRI scans were performed at Oh,6h,12h,1 day(d),3d,7d and 14d after reperfusion,including T1WI,T2WI,conventional DWI(0 s/mm2,1000 s/mm2)and 15 b-value DWI(0 s/mm2-4500s/mm2).Standard apparent diffusion coefficient(ADCs),pure diffusion coefficients(D),pseudodiffusion coefficients(D*),perfusion fraction(f),ultra-high apparent diffusion coefficient(ADCu),distributed diffusion coefficient(DDC),water diffusion heterogeneity index(a),mean diffusion coefficient(MD)and mean diffusion kurtosis(MK)were measured based on single b-value DWI and 15 b-value DWI respectively.The dynamic variation of each parameter at each time point was observed.Executed immediately after scanning,liver specimens were taken and pathological hematoxylin-eosin staining(HE)was performed.Results:ADCs began to be higher than that of the control group at 6h after HIRI,and returned to normal on 7d.D values at each time point in the experimental group were significantly higher than those in the control group,which were highest on Id.In addition,D*values were lower than that in the control group at 6h after reperfusion and returned to normal on 14d.f was lower than that of the control group at 6h after operation which were highest at 6h and returned to normal on 7d.However,ADCu began to increase at 6h after operation and recovered on 14d.The value of a in the experimental group was higher than those of the control group starting from 6h after operation and returned to normal on 14d after operation.The value of DDC in the experimental group was lower than those of the control group starting from 6h after operation and returned to normal on 7d after operation.The MD in the experimental group were higher than those of the control group starting from 6h after operation and returned to normal at 14d after operation and reached the highest level on 1d after operation.The MK in the experimental group were lower than those of the control group starting from 6h after operation and returned to normal at 14d after operation and reached the lowest level on 1d after operation.Conclusion:The model of HIRI in rats evaluated by non-Gaussian distribution model DWI is superior to conventional DWI.The characteristics of its parameters reflect indirectly the molecular changes of HIRI in rats and evaluated it from the angle of imaging.CHAPTER TWO:Study on the Correlation between Ultra-High B-value Diffusion Weighted Imaging and Aquaporin-4 in A Hepatic Ischemia Reperfusion Injury Model in RatsObjective:To study the expression of aquaporin-4(AQP-4)in hepatic ischemia reperfusion injury tissue,and to explore the correlation between ultra-high b-value magnetic resonance diffusion-weighted imaging(DWI)and AQPs.Methods:Forty-two SD rats weighing 250-300 g were divided into 7 groups(n=6).The right lobe portal vein and hepatic artery were ligated for 3hin the experimental group.The rats in the experimental group were treated with ligating the right lobe portal vein and hepatic artery for 3h.The rats in the control group were treated with sham operation.3.0T MRI scanning including plain scan T1-weighted imaging,T2-weighted imaging,conventional diffusion weighted imaging(DWI)(b=0 s/mm2,1000 s/mm2)and 15 b-values DWI(b=0 s/mm2-4500 s/mm2)were performed in both groups at Oh,6h,12h,1 day(d),3d,7d and 14d after reperfusion.ADCs and ADCuwere measured based on single b-value DWI and 15 b-value DWI respectively.The dynamic changes of each parameter were observed at each time point.After scanning,the animals were euthanized and liver specimens were taken for HE staining.The morphological changes of the liver were noted under light microscope.The expression of AQP-4 was measured qualitatively and quantitatively by Western blot.Results:The ADCS in the experimental group were higher than those of the control group starting from 12 hours after operation and returned to normal at 1 week after operation.ADCu in the experimental group began to significantly higher than those in the control group at 6 h after operation and returned to normal at 2 weeks after operation.The expression of AQP-4 in the experimental group decreased gradually at 6h,12h,1d and 3d after operation but still higher than that in the control group and began to approach normal at 1 week after operation.ADCs did not correlate with AQP-4 expression(P=0.416),but ADCu was significantly correlated with AQP-4 expression(P=0.034)and the correlation coefficient was 0.721.Conclusion:The ultra-high b-value DWI can reflect the transport of water though AQPs.