Experimental Study of Intravoxel Incoherent Motion Diffusion Imaging Combined with Ultrasound Renal Resistance Index in Contrast-Induced Nephropathy

Objective This study explored the application of Intravoxel Incoherent Motion (IVIM) diffusion imaging combined with Ultrasound Renal Resistance Index (RRI) for monitoring the pathophysiological changes associated with early contrast-induced nephropathy (CIN). Methods In this study, forty-two male Sprague-Dawley (SD) rats were equally divided into two groups: a contrast media (CM) group and a control group, each containing 21 animals. The CM group was administered a tail vein injection of ioversol (370 mg I/ml, 1.5 ml/kg), while the control group received a saline solution in a similar volume. Assessments using IVIM-MRI and Doppler ultrasound were performed 24 hours before and at 1, 24, 48, and 72 hours post-injection. These assessments aimed to evaluate the true diffusion coefficient (D), pseudo-diffusion coefficient (D ^* ), perfusion fraction (f), apparent diffusion coefficient (ADC), and RRI. Concurrently, three rats from each group were sacrificed at these time points for renal histopathology, hypoxia-inducible factor-1α (HIF-1α) expression analysis, and the quantification of serum creatinine (SCr) and blood urea nitrogen (BUN) levels. Receiver operating characteristic (ROC) curves were plotted, and the area under the curve (AUC) was analyzed to evaluate the diagnostic performance of IVIM and RRI in predicting CIN. Results Post-ioversol administration, significant declines were noted in the D, D ^* , f, ADC across the renal cortex (CO), outer medulla (OM), and inner medulla (IM) from 1 to 48 hours (P < 0.05), with the lowest values observed at 48 hours. These parameters began to recover after 72 hours. Conversely, RRI values escalated from 1 to 48 hours, peaking at 48 hours (P < 0.05), and then diminished gradually after 72 hours. The control group showed no significant changes in these parameters. Furthermore, a negative correlation was observed between RRI, histopathological grades, HIF-1α expression levels, and the levels of SCr and BUN. In contrast, RRI exhibited a positive correlation with these pathological scores and the levels of SCr and BUN. ROC curve analysis revealed that the combined predictive performance of IVIM and RRI was superior to that of individual parameters. Conclusion The synergistic application of IVIM and RRI techniques offers a non-invasive approach for early detection of renal damage after ioversol exposure and is a potent method for observing the pathophysiological shifts associated with early-stage CIN.