Using Ultrahigh b-Value Diffusion-Weighted Imaging to Noninvasively Assess Renal Fibrosis in a Rabbit Model of Renal Artery Stenosis

Abstract

Objective This study aimed to investigate the feasibility of diffusion-weighted imaging with ultrahigh b values (ubDWI) for the evaluation of renal fibrosis (RF) induced by renal artery stenosis (RAS) in a rabbit model. Methods Thirty-two rabbits underwent left RAS operation, whereas 8 rabbits received sham surgery. All rabbits underwent ubDWI (b = 0–4500 s/mm2). The standard apparent diffusion coefficient (ADCst), molecular diffusion coefficient (D), perfusion fraction (f), perfusion-related diffusion coefficient (D*) and ultrahigh apparent diffusion coefficient (ADCuh) were longitudinally assessed before operation and at weeks 2, 4, and 6 after operation. The degree of interstitial fibrosis and the expression of aquaporin (AQP) 1 and AQP2 were determined through pathological examination. Results In the stenotic kidney, the ADCst, D, f, and ADCuh values of the renal parenchyma significantly decreased compared with those at baseline (all P < 0.05), whereas the D* values significantly increased after RAS induction (P < 0.05). The ADCst, D, D*, and f were weakly to moderately correlated with interstitial fibrosis as well as with the expression of AQP1 and AQP2. Furthermore, the ADCuh negatively correlated with interstitial fibrosis (ρ = −0.782, P < 0.001) and positively correlated with AQP1 and AQP2 expression (ρ = 0.794, P < 0.001, and ρ = 0.789, P < 0.001, respectively). Conclusions Diffusion-weighted imaging with ultrahigh b values shows the potential for noninvasive assessment of the progression of RF in rabbits with unilateral RAS. The ADCuh derived from ubDWI could reflect the expression of AQPs in RF.