BOLD And ASL MRI For Longitudinal Evaluation Of Parental Renal Functions In Remaining And Donated Kidneys

Purpose:To evaluate the longitudinal functional changes of remaining and donated kidneys associated with parental kidney transplantation by BOLD and ASL MRI.Materials and Methods:30 healthy kidney donors and their corresponding recipients who underwent parental kidney transplantation were included.MRI examinations were performed supine with a 3.0T machine to acquire BOLD,ASL images in the oblique sagittal planes.All donors underwent MRI within 3 days prior to transplantation.And all subjects underwent MRI at 2 weeks after transplantation,in addition,15 pairs of whom underwent MRI respectively again at 3 and 6 months after transplantation.All donors underwent preoperative nuclear medicine examination to acquire GFR.The eGFR was calculated by the SCr value according to the simplified MDRD at 2 weeks after transplantation.The R2~*and RBF values were measured both by two physicians.The consistencies of the BOLD and cortical ASL values measured by the two physicians were analyzed using ICC analysis.The correlations between R2~*values and GFRs,RBF values and GFRs before transplantation were analyzed using Pearson correlation analysis.The correlations between R2~*values and eGFRs,RBF values and eGFRs at 2 weeks after transplantation were analyzed using Pearson correlation analysis.Before transplantation,the differences between the two kidneys,the differences between cortex and medulla were analyzed using two-independent-sample t test.The differences in corticomedullary R2~*values and RBF values between pre-transplantation and 2 weeks post-transplantation were analyzed using paired sample t test.The correlations between the change in R2~*values and RBF values of both remaining and donated kidneys at 2 weeks after transplantation were analyzed using linear regression analysis.For the 15 pairs of subjects,the differences in R2~*values and RBF values of the cortex and medulla between pre-transplantation,2weeks,3 and 6 months post-transplantation were analyzed using one factor repeated measures ANOVA analysis.Significance threshold was taken at P<0.05.Results:(1)The consistencies of the values measured by the two physicians are both good.(2)Before transplantation,the R2*values and RBF values were both correlated with their GFRs.(3)At 2 weeks after transplantation,the R2~*values and RBF values in remaining kidneys were both correlated with their eGFRs,and the renal medullary R2~*values and corticomedullary RBF values in donated kidneys were also correlated with their eGFRs.(4)Before transplantation,there was no significant difference of R2~*values and RBF values between two kidneys,while medullary R2~*values were higher than cortical R2~*values.(5)In remaining kidneys,corticomedullary R2~*values at 2 weeks after transplantation were lower than that at pre-transplantation,while RBF values were higher than that at pre-transplantation;And in the donated kidneys,corticomedullary R2~*values at 2 weeks after transplantation were lower than that at pre-transplantation,as well as RBF values.(6)At 2 weeks after transplantation,only the change of cortical R2~*values in remaining kidneys was negatively correlated with the change of RBF values(7)For remaining kidneys in the 15 pairs of subjects:the R2~*and RBF values at 3 months post-transplantation were approaching and still different to that at pre-transplantation.The values have no significant differences between 3 and 6 months post-transplantation.(8)For donated kidneys in the 15 pairs of subjects:the R2~*and RBF values at 3 months post-transplantation were approaching and still different to that at pre-transplantation.The values have no significant differences between 3 and 6months post-transplantation.Conclusions:BOLD?ASL MRI can reflect longitudinal changes of blood flow and blood oxygen level in remaining and donated kidneys non-invasively.For the remaining kidneys,the increases of blood oxygen level are associated with the increase of blood flow,whereas for the donated kidneys,the changes of blood oxygen level are inconsistent with the changes in blood flow due to the function's reduction.