Introduction

Kidney transplantation is currently considered as the preferred treatment for End-Stage Renal Disease (ESRD). With the improvement and maturity of renal transplantation surgical technology[1], especially the application of new immunosuppressants, the survival rate of early transplantation patients has increased significantly [2]. However, most kidney transplant patients still develop chronic kidney disease (CKD), and even face the risk of renal failure due to postoperative complications and other related factors[3,4],In the past, diffusion-weighted magnetic resonance imaging (DWI) and apparent diffusion coefficient (ADC) were used to access the transplanted kidneys, and the long-term outcome after Kidney transplantation has not been improved[5]. The progression of CKD is a process of renal interstitial fibrosis caused by pathophysiological processes such as ischemia and hypoxia, leading to a decrease in local blood flow[6].Therefore, this study aims to explore the performance of blood oxygen level dependent functional MRI (BOLD-fMRI) and intravoxel incoherent motion (IVIM) MRI of renal transplants kidney patients with CKD, and provide a basis for the application of fMRI in the evaluation of renal transplant function.

Method

104 patients of stable disease after renal transplantation more than 3 months were retrospectively considered as the case group. The case group was divided into 3 groups according to eGFR: eGFR ≥ 60 ml / (min · 1.73 m2) for mild CKD group 1, 11 patients; 30 ml / (min · 1.73 m2) ≤ EGFR ＜ 60 ml / (min · 1.73 m2) for moderate CKD group 2, 61patients; eGFR ＜ 30ml / (min · 1.73 m2) for severe CKD group 3, 32 patients. 36 healthy volunteers were selected as control named 0 group，as shown in Table1. Clinical Routine MRI, BOLD-fMRI and IVIM MRI were performed in both cases and controls to measure the cortical and medullary, all data were collected on a 3T MR scanner (MAGNETOM Prisma, Siemens Healthcare, Erlangen, Germany) through an 18-element abdominal coil array. An integrated prototypical slice-by-slice shimming (iShim) technique was used which dynamically updatesthe frequency and the linear shim terms prior to the acquisition of each slice during the imaging phase. The parameters are as follows: TR/TE =3700/59ms, slice thickness=4mm, FOV=245×350mm2, Bandwidth = 2195 Hz/px, b-values = 0, 50, 100, 150, 200, 400, 800, 1200, 2000, 3000 s/mm2. BOLD were acquired using a multi-echo GRE protocol with the following parameters: TR=440ms, TE=2.46ms, 4.95ms, 7.39ms, 9.88ms, slice thickness=4 mm, in-plane resolution= 1.1×1.1 mm2, FOV=250×250mm2, flip angle= 25 deg, slices= 20, distance factor=10%. R2* values, D values, D* values, and fp values of kidneys in the control and case groups were acquired, as shown in Fig 1 and Fig 2. The analysis of these parameters between cortex and medulla in the control and case groups were performed by using SPSS 22.0 statistical software, t test, the One-Way ANOVA and LSD method.

Result

Table 2 and 3,figure 1 and 2 show analysis results of R2* values, D values, D* values, and fp values of control and case groups. R2* values of renal medulla and D values of renal cortex between each group are statistically significant (all p ＜ 0.05). D* values and fp values of renal cortex and medulla in control group are higher than group 2 and 3 (all p < 0.05). For case groups, R2* values of renal cortex、D values of renal medulla、D* values and fp values of renal cortex and medulla are also analyzed, there was no statistically significant difference (all p＞0.05).

Discussion and Conclusions

In this study，R2* value and D value can well distinguish the normal kidney tissue from the kidney tissue with functional impairment. BOLD-fMRI and IVIM can provide a more accurate and comprehensive understanding of the functional information of the chronic kidney metabolism, which is beneficial to selection treatment drug，and provides an important reference value for the diagnosis, staging, treatment and prognosis of CKD in transplanted kidneys.

Acknowledgements

We sincerely thank the participants in this study.

References

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