Value of ultra-high b-value diffusion-weighted imaging for the evaluation of renal ischemia-reperfusion injury.

To explore the feasibility of ultra-high b-value diffusion-weighted imaging (ubDWI) in assessment of renal IRI. Thirty-five rabbits were randomized into a control group (n = 7) and a renal IRI group (n = 28). The rabbits in the renal IRI group underwent left renal artery clamping for 60 min. Rabbits underwent axial ubDWI before and at 1, 12, 24, and 48 h after IRI. Apparent diffusion coefficient (ADCst) were calculated from ubDWI with two b-values (b = 0, 1000 s/mm2). Triexponential fits were applied to calculate the pure diffusion coefficients (D), perfusion-related diffusion coefficient (D⁎), and ultra-high ADC (ADCuh). The interobserver reproducibility were evaluated. The repeated measurement analysis of variance and Spearman correlation analysis was used for statistical analysis. The ADCst, D, and ADCuh values showed good reproducibility. The ADCst, D, and D⁎ values of renal Cortex (CO) and outer medulla (OM) significantly decreased after IRI (all P < 0.05). The ADCuh values significantly increased from pre-IRI to 1 h after IRI (P < 0.05) and significantly declined at 24 h and 48 h after IRI (all P < 0.05). ADCuh was strongly positively correlated with AQP-1 in the renal CO and OM (ρ = 0.643, P < 0.001; ρ = 0.662, P < 0.001, respectively). ubDWI can be used to non-invasively evaluate early renal IRI, ADCuh may be adopted to reflect AQP-1 expression.

Renal ischemia-reperfusion injury in rabbits evaluated with quantitative susceptibility mapping: an animal study.

Background: There were no effective noninvasive methods to diagnose renal ischemia-reperfusion injury (IRI), which is a major clinical problem. The objective of this study was to explore the feasibility of the quantitative susceptibility mapping (QSM) technique in evaluating the dynamic changes in the renal IRI process. Methods: A total of 36 New Zealand rabbits were randomly assigned to the IRI group (n=30) and the sham group (n=6). All rabbits underwent magnetic resonance imaging (MRI) examination, including T2-weighted imaging and QSM before the operation (pre-IRI) and 1, 12, 24, and 48 h after the operation (IRI-1h, IRI-12h, IRI-24h, and IRI-48h, respectively). Regions of interest were manually delineated in the outer medulla. All specimens were stained with hematoxylin and eosin (HE) and glutathione peroxidase 4 (GPX4). The pathological score of renal injury and the average optical density value of GPX4 were calculated. The repeated measurement analysis of variance (ANOVA) and Spearman correlation analysis were used to compare the differences between the susceptibility values and determine the correlation. Results: In the IRI group, the susceptibility values of the outer medulla at the pre-IRI, IRI-1h, IRI-12h, IRI-24h, and IRI-48h time points were (42.83±7.83)×10-3, (-5.33±6.28)×10-3, (6.50±3.94)×10-3, (12.00±3.74)×10-3, and (22.00±6.81)×10-3 ppm, respectively. The susceptibility values significantly differed among the different time points (P<0.001). The susceptibility values had a negative correlation with the scores of cell edema (ρ=-0.61; P=0.002) and the average optical density value of GPX4 (ρ=-0.70; P<0.001). The susceptibility values had a positive correlation with iron content (ρ=0.79; P<0.001), the scores of cell necrosis (ρ=0.71; P<0.001), interstitial inflammation (ρ=0.60; P=0.002), cast (ρ=0.75; P<0.001), and the total pathological score of renal injury (ρ=0.51; P=0.01). Conclusions: QSM can be used as a noninvasive method to assess the dynamic changes of the outer medulla in the early stage of renal IRI in rabbits.