Study Of Normal Human Kidney And Renal Allograft Function Early After Transplantation With Diffusion Tensor Imaging At3.0T

Part I Diffusion Tensor Imaging in Normal Human Kidney at3.0TObjective:To evaluate the feasibility of diffusion tensor imaging (DTI) in kidney, and to observe the characteristics of DTI parameters and diffusion tensor tractography (DTT) in normal human kidney at3.0T magnetic resonance imaging (MRI) system. Subjects and Methods:DTI of the normal kidney of30healthy volunteers were obtained with3.0T MRI scanners using respiration-triggered acquisition (b-values0and300s/mm2, diffusion direction of6).Fractional anisotropy (FA) and apparent diffusion coefficient (ADC) values of both the renal cortex and the medulla of bilateral kidney were measured and compared. Meanwhile, the DTT features of bilateral kidney were observed.Results:The corresponding parameters of bilateral kidney was similar with each other (P>0.05). In all volunteers, FA values were significantly higher in the medulla (0.70±0.05) than in the cortex (0.32±0.04)(P<0.01), whereas the ADC values were higher in the cortex (2.83±0.20X10-3mm2/s) than in the medulla (2.50±0.18X10-3mm2/s)(P<0.01). DTT typically revealed a radial preferred direction of medullary diffusion basically reflecting medullary microstructure.Conclusion:This study shows the feasibility of renal DTI with a3.0T MR system and the normative FA and ADC values of cortex and medulla of the normal kidney. DTI of kidneys with3.0T scanners using respiration-triggered acquisition is feasible with excellent cortex-medulla differentiation.Renal DTI is an effective method to reflect diffuse characteristics of both the cortex and the medulla, and to visually demonstrate microstructure of the medulla.Part II Evaluation of renal allograft function early after transplantation with diffusion tensor imaging--initial study Objective:To prospectively evaluate the feasibility of diffusion tensor imaging (DTI) as an noninvasive way for assessment of renal allograft function early after transplantation, and to explore the differential diagnostic efficacies value of DTI in discriminate transplants with varied function.Subjects and Methods:This study was approved by the local ethics committee; written informed consent was obtained for all subjects. Between March and November in2012,51renal allograft recipients2-3weeks after transplantation and26age-matched healthy volunteers were included in this study and examined using a fat-saturated echo-planar DTI sequence in oblique-coronal orientation at3.0Tesla magnetic resonance (MR) imager (diffusion directions=6, b=0,300s/mm2). The secrum creatinine (Scr) concentrations of renal allograft recipients on the examined day were recorded, and then used to calculate the estimated glomerular filtration rate (eGFR) according to the modification of diet in renal disease (MDRD) formula. All subjects were divided into four groups according to allograft function, determined by the eGFR:Group1, healthy volunteers; Group2, eGFR≥60ml/min/1.73m2; Group3,30≤eGFR<60ml/min/1.73m2; Group4, eGFR<30ml/min/1.73m2. Mean apparent diffusion coefficient (ADC) and mean fractional anisotropy (FA) were determined separately for the cortex and the medulla and compared among4groups. Relationships between ADC, FA and eGFR of renal allografts were assessed by using Pearson correlation coefficient. Meanwhile, The receiver operating characteristic (ROC) curves was used to analyze the differential diagnostic efficacies of medullary FA value、cortical ADC value and medullary ADC value for renal allografts with different renal function. P<0.05indicated a statistically significant difference.Results:(1) Mean FA values in the medulla were higher than in the cortex in all four groups (P<0.01). Mean ADC value in the medulla was higher than in the cortex in Group1(P<0.01), while mean ADC value in the medulla was lower than in the cortex in Group2(P<0.01). Meanwhile, in Group3and Group4, the differences of mean ADC values between medulla and cortex were equal to each other (P>0.05)(2) Mean FA value in the cortex was significantly higher in Group1than in other three groups (P<0.01), while there were no significant differences among Group2to Group4(P>0.05) (3) Mean FA values in the medulla and mean ADC values in the cortex between Group1and Group2didn’t show pronounced differences (P<0.01), but they were both higher than Group3and Group4(P<0.01). Furthermore, mean FA value in the medulla in group4was obviously lower than other three groups(4) There were no significant differences of mean ADC values in the medulla between Group1and Group3(P>0.05), while mean ADC value in the medulla in Group1was lower than that in Group2, and the difference was significant (P<0.05). Meanwhile, mean ADC value in the medulla of Group4was significantly lower than other three groups (P<0.01)(5) In renal allografts, there was a significant negative correlation between Scr and medullary FA (r=-0.702, P<0.01), cortical ADC (r=-0.644, P<0.01) and medullary ADC (r=-0.555, P<0.01), meanwhile, a significant positive correlation between eGFR and medullary FA (r=0.812, P<0.01), cortical ADC (r=0.756, P<0.01) and medullary ADC (r=0.757, P<0.01)(6) Medullary FA value、cortical ADC value and medullary ADC value could distinguish renal allogafts with different renal function, and the sensitivity、 specificity、positive and negative predictive values were all more than70%. However, the differential diagnostic efficacies of these three parameters were almost same with each other (P>0.05)(7) Diffusion tensor tractography (DTT) revealed that the radial diffusion tracts in the medulla of Group3and Group4obviously broke off and reduced, especially in Group4Conclusion:DTI is a promising way to assess renal allograft function early after transplantion noninvasively, and can quantitatively and visually distinguish transplants with different function.