T1ρ mapping for assessment of renal allograft fibrosis

Background There is an unmet need for noninvasive methods to diagnose and stage renal allograft fibrosis. Purpose To investigate the utility of T-1 rho measured with MRI for the assessment of fibrosis in renal allografts. Study Type Institutional Review Board (IRB)-approved prospective. Subjects Fifteen patients with stable functional allograft (M/F 9/6, mean age 56 years) and 12 patients with allograft dysfunction and established fibrosis (M/F 6/6, mean age 51 years). Field Strength/Sequence T-1 rho imaging at 1.5T using a custom-developed sequence. Assessment Average T-1 rho in the cortex and medulla was quantified and T-1 rho repeatability (expressed by the coefficient of variation [CV]) was measured in four patients. Statistical Tests Differences in T-1 rho values between the 2 groups were assessed using Mann-Whitney U-tests. Diagnostic performance of T-1 rho for differentiation between functional and fibrotic allografts was evaluated using receiver operating characteristic (ROC) analysis. Spearman correlations of T-1 rho with Masson's trichrome-stained fractions and serum estimated glomerular filtration rate (eGFR) were assessed. Results Higher T-1 rho repeatability was found for cortex compared with medulla (mean CV T-1 rho cortex 7.4%, medulla 13.3%). T-1 rho values were significantly higher in the cortex of fibrotic vs. functional allografts (111.8 +/- 17.2 msec vs. 99.0 +/- 11.0 msec, P = 0.027), while there was no difference in medullary T-1 rho values (122.6 +/- 20.8 msec vs. 124.3 +/- 20.8 msec, P = 0.789). Cortical T-1 rho significantly correlated with Masson's trichrome-stained fractions (r = 0.515, P = 0.044) and eGFR (r = -0.546, P = 0.004), and demonstrated an area under the curve (AUC) of 0.77 for differentiating between functional and fibrotic allografts (sensitivity and specificity of 75.0% and 86.7%, using threshold of 106.9 msec). Data Conclusion Our preliminary results suggest that T-1 rho is a potential imaging biomarker of renal allograft fibrosis. These results should be verified in a larger study. Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2019;50:1085-1091.