Detecting early kidney allograft fibrosis with multi-b-value spectral diffusion MRI

Kidney allograft fibrosis is a manifestation of chronic kidney disease (CKD) and predicts functional decline, and eventual allograft failure. This study evaluates whether spectral diffusion magnetic resonance imaging (MRI) detects early development and mild/moderate fibrosis in kidney allografts. In a prospective two-center study of kidney allografts, pathologic interstitial fibrosis and tubular atrophy (IFTA) was scored and eGFR was calculated from serum creatinine. Multi-b-value diffusion-weighted imaging (DWI) (bvalues=[0, 10, 30, 50, 80, 120, 200, 400, 800mm(2)/s]) was post-processed with spectral diffusion, intravoxel incoherent motion (IVIM), and apparent diffusion coefficient (ADC). Relationships between imaging parameters and biological processes were measured by Mann-Whitney U-test and Spearman’s rank; diagnostic ability was measured by five-fold cross-validation univariate and multi-variate logistic regression. Quality control analyses included volunteer MRI (n=4) and interobserver analysis (n=19). 99 patients were included (50±13yrs, 64 M/35F, 39 IFTA=0, 22 IFTA=2, 20 IFTA=4, 18 IFTA=6, 46 eGFR≤45mL/min/1.73m(2), mean eGFR=47.5±21.3mL/min/1.73m(2)). Spectral diffusion detected fibrosis (IFTA > 0) in patients with normal/stable eGFR > 45ml/min/1.73m(2) [AUC (95% CI)=0.72 (0.56, 0.87), p=0.007]. Spectral diffusion detected mild/ moderate fibrosis (IFTA=2–4) [AUC (95% CI)=0.65 (0.52, 0.71), p=0.023], as did ADC [AUC (95% CI)=0.71 (0.54, 0.87), p=0.013]. eGFR, time-from-transplant, and allograft size could not. Interobserver correlation was ≥0.50 in 24/40 diffusion parameters. Spectral diffusion MRI showed detection of mild/moderate fibrosis and fibrosis before decline in function. It is a promising method to detect early development of fibrosis and CKD before progression.