Exploration of Interstitial Fibrosis in Chronic Kidney Disease by Diffusion-Relaxation Correlation Spectrum MR...

Renal interstitial fibrosis is one of the most common pathways in the progression of chronic kidney disease (CKD). Noninvasive evaluation of interstitial fibrosis would help monitoring CKD progression and prognosis prediction.

To evaluate the severity of renal interstitial fibrosis by diffusion-relaxation correlation spectrum imaging (DR-CSI).

Prospective.

Forty patients with CKD and 10 healthy controls (average age 49.2 ± 14.8 years, 18 females).

3-T, DR-CSI with 36 axial spin-echo echo-planar diffusion-weighted images (6 b-values, 6 echo times).

Interstitial fibrosis level (IFL) was assessed from biopsy results (IFL = 1, fibrosis percentage <25%, defined as mild; IFL = 2, 25%-50%, moderate; IFL = 3, >50%, severe). Estimated glomerular filtration rate (eGFR) was calculated using serum creatinine. The regions of interest included cortex for both kidneys. The diffusivity-T2 spectrum was assessed considering three compartments (threshold: T2 30-40 msec, diffusivity 5-9 μm² /msec, according to visible peaks): A (low diffusivity, short T2), B (low diffusivity, long T2), and C (high diffusivity). Volume fractions V_i (i = A, B, C) were calculated.

Intra-class coefficient (ICC, >0.6 as good) to assess inter-reader agreement of DR-CSI V_i . Spearman's correlation to assess relationship of V_i to IFL and eGFR. Receiver operating characteristic analyses with the area under the curve (AUC) to discriminate patients with moderate-severe fibrosis from mild ones. Statistical significance criteria: P-value <0.05.

ICCs were good for all V_i . Correlations were found between IFL and V_B (r = 0.424, significant) and V_C (r = -0.400, significant), and between eGFR and V_B (r = -0.303, P = 0.058) and V_C (r = 0.487, significant). Regarding V_B and V_C , the AUCs were 0.903 and 0.824.

DR-CSI help distinguish patients with moderate or severe renal interstitial fibrosis from mild ones.

2 Technical Efficacy: Stage 2.