Virtual MR elastography with diffusion-weighted imaging to evaluate chronic kidney disease fibrosis and dysfunction

Renal stiffness declines with chronic kidney disease (CKD) progression. Magnetic resonance elastography (MRE) enables quantitative assessment of tissue stiffness but requires external hardware, limiting routine clinical use.

To develop a diffusion-derived virtual shear modulus (µ_diff) for vibration-free renal virtual MR elastography (vMRE) and evaluate its ability to assess dysfunction and fibrosis across CKD stages.

This prospective single-center study included 53 healthy volunteers and 114 CKD patients, stratified by estimated glomerular filtration rate (eGFR) into early-stage CKD (CKD_1-2, eGFR 60-120 mL/min/1.73 m²) and moderate-to-advanced CKD (CKD_3-5, eGFR < 60 mL/min/1.73 m²). Renal biopsy results performed for clinical care were collected. Magnetic resonance elastography and multi-b-value diffusion-weighted imaging (DWI) (b = 0-2000 s/mm²) were performed on a 3T MRI (MAGNETOM Prisma, Siemens). Cortical shifted apparent diffusion coefficient (csADC) across b-value combinations correlated with cortical MR elastographic shear modulus (cµ_MRE) to identify the optimal combination and derive µ_diff. Age-adjusted analysis of covariance (ANCOVA) compared MRI parameters. Partial correlations with eGFR and Spearman correlations with interstitial fibrosis (IF) were performed. Diagnostic performance was evaluated by receiver operating characteristic (ROC) analysis.

A significant correlation (R ² = 0.94, P < .001) was observed between cµ_MRE and csADC derived from DWI at b-values of 200 (S₂₀₀) and 800 (S₈₀₀) s/mm² (csADC_200-800), yielding ${\mu }_{\mathrm{diff}} \left(\mathrm{kPa}\right)=4.91 \ln (S_{200}/S_{800})+0.92.$ Cortical µ_diff (cμ_diff) correlated with eGFR (r = 0.602, P < .001) and IF (r = -0.809, P < .001). In biopsied patients (n = 51), cμ_diff showed comparable diagnostic performance to cµ_MRE in differentiating mild from moderate-to-severe IF (area under the curve [AUC], 0.910 [95% CI, 0.822-0.998] vs 0.901 [95% CI, 0.813-0.989]; P > .05).

Diffusion-weighted imaging-derived µ_diff enables vibration-free renal vMRE, offering a stiffness-related surrogate that correlates with renal dysfunction and fibrosis. Diagnostic performance is comparable to MRE, including in early-stage CKD. If validated externally, this may provide a scalable alternative for CKD evaluation.