Multi‐Parametric MRI for Evaluating Variations in Renal Structure, Function, and Endogenous Metabolites in an Animal Model With Acute Kidney Injury Induced by Ischemia Reperfusion

Background Ischemia reperfusion injury (IRI)‐induced acute kidney injury (AKI) may occur after renal ischemic injury. There is a lack of an accurate and comprehensive detection technique for IRI‐AKI. Purpose To longitudinally evaluate IRI‐AKI in rats by renal structure, function, and metabolites using multi‐parametric MRI (mpMRI). Study Type Prospective. Animal Model Forty‐eight rats undergoing IRI‐AKI. Field Strength/Sequence 7‐T, T 1 mapping, and arterial spin labeling (ASL): echo planar imaging (EPI) sequence; blood oxygen level‐dependent (BOLD): gradient recalled echo (GRE) sequence; T 2 mapping, quantitative magnetization transfer (qMT), and chemical exchange saturation transfer (CEST): rapid acquisition with relaxation enhancement (RARE) sequence. Assessment The mpMRI for IRI‐AKI was conducted at 0 (control), 1, 3, 7, 14, and 28 days, all included eight rats. The longitudinal mpMRI signal of manually outlined cortex, outer stripe of the outer medulla (OSOM), inner stripe of the outer medulla, and medulla plus pelvis were calculated and compared, their diagnosis performance for IRI‐AKI also been evaluated. Statistical Tests Pearson correlations analysis for correlation between mpMRI signal and renal injury, unpaired t ‐tests for comparing the signal changes, and receiver operating characteristics (ROC) analysis was used to identify most sensitive indicator of mpMRI. A P ‐value <0.05 was considered statistically significant. Results Compared with control kidneys, the T 1 and T 2 values of the cortex and medulla in IRI kidneys increased and reached their highest values on day 14, and the kidneys also showed the most severe edema and segments blurred. The RBF in the cortex and OSOM showed a significant decline after day 3. The BOLD signal in the OSOM largest increased on day 28. The cortical PSR and the amine‐CEST both decreased with IRI‐AKI progression, and amine‐CEST achieved the highest AUC for the diagnosis (0.899). Data Conclusion Multi‐parametric MRI may show comprehensive variations in IRI‐AKI, and amine‐CEST may exhibit the highest accuracy for diagnosis of IRI‐AKI. Level of Evidence 1 Technical Efficacy Stage 2