Study Of Diffusion And Perfusion Properties Of Different Functional Allografts Early After Kidney Transplantation With Functional MRI

Objective: To assessment of diffusion and perfusion properties of normal kidneys and different functional allografts early after kidney transplantation with intravoxel incoherent motion?IVIM? and arterial spin labeling?ASL? MR imaging.Subjects and methods: From May in 2014 to December in 2015, a total of 76 renal allograft recipients and 26 age-matched healthy volunteers were included in this prospective study. All subjects were underwent conventional MRI and IVIM?11 b values? and ASL MRI which was performed in the oblique-sagittal plane at 3.0T MR scanner. In all recipients, serum creatinine?SCr? concentrations were obtained on the day of the MR scan and were used to calculate the estimated glomerular filtration rate?e GFR? according to the modification of diet in renal disease?MDRD? formula. Recipients were divided into 3 groups based on the e GFR and chronic kidney disease: group 1, recipients with good allograft function?e GFR ?60 ml/min/1.73m2,n=44?; group 2, recipients with mild to moderate impaired allograft function?30?e GFR<60 ml/min/1.73m2,n=19?; group 3, recipients with severe impaired allograft function?e GFR <30 ml/min/1.73m2,n=13?; at the same time, healthy volunteers?n=26? were selected as the cortrol group in group 0. Apparent diffusion coefficient?ADC?,pure diffusion coefficient(ADC_slow), pseudo-diffusion coefficient(ADC_fast),perfusion fraction?PF?,renal blood flow?RBF? and T1 values in the cortex and medullar were measured. An intra-class correlation coefficient?ICC? was calculated to confirm the reproducibility of the measured results from two doctors. A paired-t test was used to compare the difference of cortical or medullary index values between the bilateral kidneys in healthy volunteers, as well as between the cortex and medulla in the four groups. One-way analysis of variance?ANOVA? and least significant difference?LSD? were used to compare the difference of the index values among four groups. Pearson correlation coefficients were used to evaluate the correlation of index values with e GFR, as well as the correlation of cortical ADC_fast, PF and RBF. The receiver operating characteristic?ROC? curve was performed to assess the diagnostic efficacy of using IVIM and ASL index values to discriminate different renal function. The ROC curve and binary logistic regression analyses were performed to assess the diagnostic efficacy of using IVIM, ASL alone or their combination to distinguish allografts with different renal function.Results:?1? All index values showed good reproducibility between doctors with an ICC larger than 0.75;?2? ADC, ADC_slow, ADC_fast, PF, RBF and T1 values in the cortex or medulla of the bilateral kidneys showed no significant difference?P>0.05?;?3? ADC, ADC_slow, ADC_fast, PF and T1 values between cortex and medulla were significantly different in both group 0 and 1?P<0.05?; excepting T1 values, other index values were no significantly different?P>0.05? in group 2; ADC, ADC_slow, ADC_fast and T1 values between cortex and medulla were significantly different in group 3?P<0.05?, while PF was not?P>0.05?;?4? ADC, ADC_slow in the cortex and medulla, ADC_fast, PF in the cortex were no significant difference?P>0.05? in group 1 and 0, while ADC_fast,PF in medulla and RBF in the cortex, T1 in the cortex and medulla were not?P<0.05?; ADC, PF in the cortex and medulla, ADC_slow, ADC_fast, RBF, T1 in the cortex were significant different between group 2 and 1?P<0.05?, while ADC_slow, ADC_fast and T1 were not?P>0.05?;ADC, ADC_slow, ADC_fast in the cortex and medulla, PF, RBF and T1 in the cortex were significant different between group 3 and 2?P<0.05?, while PF and T1 in the medulla were not?P>0.05?;?5? ADC, ADC_slow, ADC_fast, PF in the cortex and medulla, RBF and T1 in the cortex exhibited a correlation with renal function as determined by e GFR for recipients?R was 0.603,0.590,0.604,0.457,0.552,0.552,0.579,0.425,0.673,-0.450 respectivily,P<0.01?;?6? Both cortical ADC_fast, PF showed a positive correlation relationship with RBF for recipients?R was 0.501,0.423,respectively,P<0.01?;?7? ADC in the cortex and medulla, ADC_slow, ADC_fast, PF, RBF and T1 in the cortex showed a relatively high diagnostic efficacy to discriminate renal allografts with different function. Cortical ADC showed a better diagnostic efficacy?z=2.699,P=0.007? than cortical ADC_slow when distinguish group 1 from 2, while other index values showed no difference in other allografts groups?P>0.05?;?8? The combination IVIM and ASL MRI showed a better diagnostic efficacy to distinguish group 1 from 2 than IVIM and ASL MRI alone, with an AUC of 0.969, a sensitivity of 76.0% and a specificity of 86.5%?P<0.05?; while IVIM,ASL and their combination showed no significantly different for distinguish other allografts groups?P>0.05?Conclusion: IVIM and ASL MRI can evaluate the diffusion and perfusion properties for normal kidneys and allografts early after kidney transplantation. Combined IVIM and ASL MRI can better distinguish different functional allografts.