Intravoxel Incoherent Motion-Diffusion-Weighted MRI for Investigation of Delayed Graft Function Immediately after Kidney Transplantation

Abstract

Purpose. A non-invasive way of assessing post-transplant renal graft function has been needed. This study aimed to assess the micro-structural and micro-functional status of graft kidneys by using intravoxel incoherent motion- (IVIM-) diffusion-weighted imaging (DWI) to investigate delayed graft function (DGF) immediately after transplantation. Method. A prospective study was conducted on 37 patients, 14 with early graft function (EGF) and 23 with DGF (9 with complication, 14 without) who underwent IVIM-DWI, most often within 1-7 days after kidney transplantation. A total of 37 cases were collected and all the participants have been well-informed and signed their consents. In addition, the study conducted in this paper was approved by the Ethics Committee of Clinical Research, Taichung Veterans General Hospital (IRB number: CE14065). Using biexponential analysis of slow diffusion coefficient ( $D_{\text{slow}}$ ), fast diffusion coefficient ( $D_{\text{fast}}$ ), and perfusion fraction was performed. The apparent diffusion coefficient ( $\text{ADC}$ ) was calculated by use of a monoexponential model. All parameters were measured from three different regions-of-interest (ROI), covering the entire renal parenchyma, cortex, and medulla. Results. $D_{\text{slow}}$ , perfusion fraction, and $\text{ADC}$ were significantly higher in patients with EGF than DGF (all $p$ values values <0.001). Especially, $\text{ADC}$ measured from ROI covering the entire kidney parenchyma had the best cut-off value (1.93μm2/msec) with the highest area under the receiver operating characteristic curve ( $\text{AUC}$ 0.943) in differentiating EGF from DGF. For analysis of pair-wise differences, only the perfusion fraction values, measured from the ROI covering the renal cortex, were significantly higher in 14 DGF patients with no complications than in the 9 DGF patients with complications, with the best cut-off value of 12.3% and the $\text{AUC}$ of 0.844. Conclusion. Noninvasive IVIM-DWI reliably differentiates DGF from EGF after kidney transplantation, and it may aid in identifying posttransplant complications and indications for renal biopsy.