Identification of Diffusion-Relaxation Compartments Based on Correlation to Renal Pathological Scores: An Explorative...

Renal histologic findings are beneficial in the diagnosis and treatment of lupus nephritis (LN), but require an invasive biopsy. Diffusion-relaxation correlated spectrum imaging (DR-CSI) has previously been applied to assess renal fibrosis, yet current approaches for compartment identification lack quantified standards.

This exploratory study is aimed at establishing a spectrum-pathology correlation analysis for identifying possible DR-CSI compartments, and explore the diagnostic value of the compartment fractions on common pathologic features.

Cross-sectional.

66 LN patients (58 females) and 20 healthy volunteers (17 females).

3 T scanner/Axial renal DR-CSI scan with 34 contrasts (TE 55~170 ms, b-values 0~1200 s/mm²).

Pathologic classification, activity index, and chronicity index were obtained through biopsy. The estimated glomerular filtration rate (eGFR) was assessed, representing renal function. Four compartments, short-T2 (S), restricted-diffusion (R), long-T2 (L), and pseudo-diffusion (PD), were identified. Compartment fractions F _X were calculated (X: compartment label).

Spearman correlation for spectrum-pathology relationship. Student's t-test or Mann-Whitney U-test for group comparison. ROC analysis for diagnostic performance. Significance criteria: p < 0.05.

LN patients had significantly higher F _R (12.3% ± 5.6% vs. 7.6% ± 2.3%), lower F _PD (36.3% ± 9.1% vs. 29.6% ± 13.0%), lower F _L (30.1% ± 12.1% vs. 24.8% ± 7.6%), and higher ADC (1.95 ± 0.19 vs. 1.78 ± 0.22 μm²/ms) than healthy volunteers. Patients with impaired renal function had significantly higher F _R (11.1% ± 5.3% vs. 15.4% ± 5.2%), higher F _L (27.8% ± 10.8% vs. 36.0% ± 13.5%), lower F _PD (32.3% ± 12.3% vs. 23.3% ± 12.7%), and lower ADC (1.82 ± 0.19 vs. 1.69 ± 0.23 μm²/ms). Proliferative LN patients had significantly increased F_L (31.8% ± 12.1% vs. 24.8% ± 11.2%) than non-proliferative ones. For identifying patients with impaired function, F _R showed numerically highest AUC (0.736), sensitivity (0.842), and balanced accuracy (0.730) at optimal point for Youden index. For identifying proliferative patients, F _L showed numerically highest AUC (0.679), sensitivity (0.800), and negative predictive value (0.474) among single univariate models.

The compartment fractions can identify proliferative LN and impaired function, highlighting the potential of a histology-driven compartment identification strategy.

2.

Stage 2.