| Objective To investigate the feasibility of using intravoxel incoherent motion(IVIM)imaging to evaluate the kidney cold ischemia reperfusion injury(CIRI)in rats.Methods 40 healthy male SD(Sprague Dawley)rats of 8-10 weeks old(weighing about 200-250g)were selected.20 rats in left kidney cold ischemia-reperfusion model group(experimental group)and 20 rats in right kidney resected and left kidney preserved group(sham operation group)were made.Using Siemens magnetom prism 3T superconductive MRI scanner,five rats were randomly selected for kidney T2 WI and IVIM MRI scanning at 1st hour,1st,2nd and 5th day after operation.FSE sequence was used in T2 WI,and single shot plane echo diffusion weighted sequence was used in IVIM.The images are transmitted to the post-processing workstation to generate parameter values images,including apparent diffusion coefficient(ADC),real diffusion coefficient(D value),perfusion related diffusion coefficient(D*)and perfusion fraction(f).After scanning,blood was collected from abdominal aorta.The content of blood urea nitrogen(BUN)and superoxide dismutase(SOD)in all rats was obtained by test.At the same time,the left kidney was removed for pathology examination.Data were measured by two radiologists with experience in MRI diagnosis of kidney.The ROIs were placed in the upper pole of kidney,the level of hilus and the lower pole of kidney respectively.Each level includes cortex,outer stripe of outer medullary and inner stripe of outer medullary.T-test of two independent samples was used to compare the differences of parameters of two groups at the same time point.One-way analysis of variance(ANOVA)and least significant differences(LSD)were used to compare the differences of parameters of different parts at different time points in each group.Pearson correlation analysis was used to evaluate the correlation between biochemical indexes(BUN、SOD)and imaging parameters.Results(1)Two doctors showed a good consistency in the measurement results of MRI parameters of rats with ICC above 0.85;(2)The ADC and D values of all parts in the sham operation group were the lowest in 1h,which was statistically different from those on the 1d,2d and 5d(P all<0.01),they were the highest on the 5d,there were no statistical differences among the other time groups(P>0.05);there were no statistical differences in the D * value of each part between the time groups(P>0.05);(3)The f value of each part in the sham operation group was the highest in the 1d group,and the f value of cortex was statistically different between the adjacent time points of 1h,1d and 2d(P <0.05),there were no statistical differences between the 5th day and other time groups(P > 0.05);the f value of the outer stripe of outer medullary was the lowest in 1h group,which was significantly different from that in 1d,2d and 5d groups(P < 0.01);there was no significant difference in the f value of the inner stripe of outer medullary(P > 0.05);(4)The ADC and D values of each part in the experimental group were the lowest at 1 hour after operation,and there was a statistical difference between them at day 1,day 2 and day 5(P < 0.01),and the highest at the day 5;the ADC and D values of the inner stripe of outer medullary in the day 5 group were higher than those in the day 2 group(P all < 0.01);the ADC and D values of cortex in 1h group were significantly higher than those in the inner stripe of outer medullary(P < 0.01);(5)The D * value of each part in the experimental group was the highest in the 1d group,and the D * value of the cortex and inner stripe of outer medulla in the 1d group was significantly higher than that in the 2d and 5d groups(P < 0.05);but there were no statistical significances among the groups of the outer stripe of outer medulla(P > 0.05);(6)In the experimental group,the f value of each part was the lowest in the 1h,and the outer and inner stripes of outer medullary increased to the highest on the day 1(P < 0.01);but the f value of the cortex increased to the peak on the day 2,which was statistical significances with 1h group(P < 0.05);(7)On the day 1,the ADC and D values of the inner stripe of and outer stripe of outer medulla in the experimental group were significantly lower than those in the sham operated group(P < 0.05);the D* value of inner stripe of outer medulla in the experimental group was significantly higher than that of the sham operated group(P < 0.01);the f value of cortex and outer stripe of outer medulla in experimental group was significantly lower than that in sham operation group(P < 0.05);on the day 2,the D* and f of the outer stripe of outer medulla in the experimental group were significantly lower than those in the sham operated group(P < 0.05);there were no significant differences between the two groups in the 1h and 5d after operation;(8)The D* value of cortex was positively moderate correlated with urea nitrogen in the experimental and shame operated groups(r = 0.461,P < 0.01);in the experimental group,the f value of outer stripes of outer medulla was negatively moderate correlated with SOD(r =-0.455,P < 0.05);Conclusions IVIM technology can dynamically observe the time trend changes of renal cortex and medulla in CIRI models about the diffusion of water molecules and the level of microcirculation perfusion;in the acute stage of CIRI,renal repair is mainly compensatory;CIRI influences microcirculation more than water molecules diffusion;the parameters of IVIM have a certain correlation with biochemical indicators,which indicating IVIM plays an important role in monitoring renal injury,compensation and recoverability. |
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