CIN remains a serious complication following the use of contrast agents in diagnostic imaging, often leading to acute kidney injury. Early detection is critical but remains challenging. This study sought to bridge that gap by assessing whether IVIM-MRI parameters and RRI could capture early pathophysiological changes in the kidneys.
The research involved 42 male Sprague-Dawley rats, divided equally into a contrast media (CM) group and a control group. Rats in the CM group were injected with ioversol, a commonly used contrast agent, while the control group received an equivalent volume of saline. IVIM imaging and Doppler ultrasound assessments were conducted before and at several time points (1, 24, 48, and 72 hours) after the injections.
The imaging analysis focused on key diffusion parameters—true diffusion coefficient (D), pseudo-diffusion coefficient (D*), perfusion fraction (f), and apparent diffusion coefficient (ADC)—as well as RRI values. Additionally, kidney tissue was examined for histopathological damage, hypoxia-inducible factor-1α (HIF-1α) expression, and changes in serum creatinine (SCr) and blood urea nitrogen (BUN) levels.
The following were the notable findings of the study:
- Significant reductions in diffusion parameters were observed in the renal cortex, outer medulla, and inner medulla beginning at 1 hour post-injection, with the most pronounced changes occurring at 48 hours.
- These diffusion parameter values began to gradually recover by 72 hours.
- RRI values increased during the same time frame, peaking at 48 hours, and then started to decline.
- Changes in RRI and IVIM parameters showed strong correlations with biochemical markers, histological damage, and HIF-1α expression levels.
- The diagnostic accuracy improved when IVIM and RRI were combined, as shown by ROC curve analysis.
While the findings are promising, the authors acknowledged several limitations. Respiratory motion in rats affected imaging quality, despite efforts to stabilize the abdomen. The study was also limited to a single species, and technical challenges, such as low signal-to-noise ratio and insufficient b-value sampling in IVIM imaging could impact accuracy.
Nonetheless, the study provides compelling evidence that combining IVIM and RRI offers a valuable, non-invasive strategy for detecting early-stage CIN. The authors suggest that further research in diverse animal models and clinical settings is needed to validate these techniques for broader use.
Reference:
Chen, J., Song, X., Wang, Z. et al. Experimental study of intravoxel incoherent motion diffusion imaging combined with ultrasound renal resistance index in contrast-induced nephropathy. BMC Nephrol 26, 401 (2025). https://doi.org/10.1186/s12882-025-04329-3
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