Diffusion Weighted Imaging Based On Intravoxel Incoherent Motion For Evaluation Of Early Kidney Injury In Diabetic Rats

Purpose:The objective of this study was to explore the value of diffusion-weighted imaging based on intravoxel incoherent motion in the evaluation of renal function in diabetic rat models and the relationship between IVIM-DWI parametric changes and the related pathological findings.Materials and Methods:36 SD rats were randomly divided into 2 groups:the normal control(NC)and diabetic mellitus groups(DM).Rats in the DM group were given streptozocin(STZ)at a dose of 55mg/kg by intraperitoneal injection to establish the animal model of diabetes,whereas rats in the NC group were given an equal volume of a citric acid buffer by intraperitoneal injection.The 24-hour urine of each rat in the two groups was collected and its body weight was recordedat 4,8,and 12 weeks after the successful modeling before MR scanning.The scan sequences included axial T2-weighted imaging and intravoxel incoherent motion diffusion-weighted imaging(IVIM-DWI).The 12 frames of images were obtainedwith different b values(b=0,20,30,50,80,100,150,200,400,600,700 and 800s/mm~2).The IVIM imaging data were post-processed on a workstation(Sun Advantage Workstation 4.5;GE Medical Systems).D,D*,f,and ADC values were obtained by multiple ADC measurement tools.Blood was taken to measure BUN and Scr after the MR scan.And the kidneys were weighed and the kidney weight/body weight was calculated.The HE staining and Collagen IV immunohistochemistry were then performed.Interobserver variability for the IVIM parametric measurement was evaluated by using the method of Bland and Altman and calculating the intraclass correlation coefficient(ICC).One-way analysis of variance was used to compare the parameters of the NC and DM groups at each time point.Two independent sample t-test was used to compare the rats'weight,kidney weight ratio,urine volume,BUN,Scr,and IVIM-DWI parameters of CO,OS,IS,and IM between the two groups at each time point.The Pearson correlation analysis was performed between the parameters of IVIM-DWI in the DM group and glomerular sclerosis index,tubulointerstitial fibrosis index,and Collagen IV expression.Result:In the DM group,there was a significant decrease in the weight of rats and an increase in the ratio of kidney weight urine volume and the serum BUNover time..But the serum Scr didn'tchange in this group.Excellent interobserver agreement between the two observers in measuring all IVIM parameters and ADC values was found.There was no statistical difference in the IVIM-DWI parameters of the renal cortex and medulla at all time points in the NC group.Compared with the control group,except for the f value of CO at the 12th week,all other parameters of the renal cortex and medulla in the DM group were statistically different;at the 4th and 8th week,the renal cortex and medulla ADC values were not statistically different.The D values in the CO and OS were statistically different,while the D*and f values were significantly different in the renal cortex and medulla(P<0.05).The IVIM parameters of renal cortex and medulla in the DM group gradually decreased with the progression of diabetes.All parameters of CO in the DM group were negatively correlated with glomerular sclerosis index.Except for the ADC values of IS and IM,the IVIIM values of renal cortex and medulla in the DM group were negatively correlated with tubulointerstitial fibrosis index and Collagen IV expression.There was no correlation between the serum BUN and the pathological findings.Conclusion:IVIM-DWI may be helpful in assessing the early renal impairment of diabetes.D,D*and f values may be more sensitive than the traditional ADC value to detect early-stage injury.The glomeruli and adjacent renal tubules were damaged earlier and more obviously at the early stage of DM,.The D*and f values may be expected to be used as the indicators for early detection of the renal medulla.