Fibrosis in renal allografts confers risk of progression to allograft loss. The gold standard for evaluating renal fibrosis remains allograft biopsy, which is invasive, prone to sampling errors and difficult to repeat. We aimed to develop a quantitative multiparametric MRI (mpMRI) protocol for the comprehensive evaluation of renal transplant fibrosis. In this single center study, we enrolled 21 patients [15 with stable function (6-24 months post transplant, eGFR>45 ml/min; without rejection/BK/proteinuria) and 6 with established fibrosis on biopsy (biopsy < 6months before MRI; Banff Ci+Ct score > 2)]. To restrict the signal to fibrosis alone, we excluded all allografts with i score>0. All patients underwent mpMRI at 1.5T (Aera, Siemens) including advanced diffusion weighted imaging techniques [IVIM-DWI and diffusion tensor imaging (DTI)] and T1 mapping. IVIM-DWI parameters (true diffusion D, pseudodiffusion D*, perfusion fraction PF) and ADC were obtained. IVIM-DWI and T1 signal curves were measured in the cortex and medulla at the upper, middle and lower renal allograft poles, and were compared between functional and fibrotic allografts using the Mann-Whitney test. Spearman correlations were calculated between cortical MRI parameters and cortical biopsy score for individual Banff component scores. Cortical ADC, PF and D and medullary ADC were significantly decreased in fibrotic allografts. Test-Retest MRIs showed minimal coefficient of variation (<10%). There was significant decrease in [Delta]FA (fractional anisotropy) in fibrotic allografts. Cortical T1 values were significantly elevated, and [Delta]T1 significantly decreased in fibrotic allografts. There were no significant correlations between MRI parameters and pathology (p=0.06-0.99), due to the dichotomous nature of fibrosis in our cohort. Our preliminary data shows that IVIM-DWI and T1 parameters are sensitive to detect and quantify allograft fibrosis in renal transplant patients. Ongoing work is validating mpMRI-derived metrics in combination for characterizing renal transplant fibrosis in a larger cohort.

CITATION INFORMATION: Menon M., Bane O., Lewis S., Khaim R., Florman S., Kennedy P., Hectors S., Delaney V., Salem F., Taouli B. Multiparametric MRI for Assessment of Renal Transplant Fibrosis: A Pilot Am J Transplant. 2017;17 (suppl 3).

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