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

Abstract

BackgroundIschemia 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.PurposeTo longitudinally evaluate IRI‐AKI in rats by renal structure, function, and metabolites using multi‐parametric MRI (mpMRI).Study TypeProspective.Animal ModelForty‐eight rats undergoing IRI‐AKI.Field Strength/Sequence7‐T, T1 mapping, and arterial spin labeling (ASL): echo planar imaging (EPI) sequence; blood oxygen level‐dependent (BOLD): gradient recalled echo (GRE) sequence; T2 mapping, quantitative magnetization transfer (qMT), and chemical exchange saturation transfer (CEST): rapid acquisition with relaxation enhancement (RARE) sequence.AssessmentThe 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 TestsPearson 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.ResultsCompared with control kidneys, the T1 and T2 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 ConclusionMulti‐parametric MRI may show comprehensive variations in IRI‐AKI, and amine‐CEST may exhibit the highest accuracy for diagnosis of IRI‐AKI.Level of Evidence1Technical EfficacyStage 2

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Multi-parametric MRI-based machine learning model for prediction of pathological grade of renal injury in a rat kidney cold ischemia-reperfusion injury model

“…The potential of multi-parametric quantitative magnetic resonance imaging (MRI) has been extensively discussed as a diagnostic tool in renal function. Functional MRI techniques without the use of exogenous contrast agents, can indirectly re ect renal injury reduced by acute kidney injury, chronic kidney disease, renal allograft dysfunction, and so on, by quantitatively assessing blood ow with arterial spin labeling(ASL) 5 , blood oxygen with blood oxygen level-dependent (BOLD) 6,7 , water content with longitudinal relaxation time (T1) mapping and water molecule diffusion with diffusion weighted imaging(DWI) 8,9 . Intravoxel incoherent motion (IVIM), which applies a bi-exponential model using multiple b-values, can incorporate the pure diffusion of water molecules as well as the pseudo-diffusion component formed by microcirculation or perfusion, microvascular dynamics 10,11 .…”

Editorial for “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”

“…In the present study, 4 multi‐parametric MRI (mpMRI), including T1 and T2 mapping, blood oxygen level‐dependent (BOLD) contrast or functional MRI (fMRI), arterial spin labeling (ASL), quantitative magnetization transfer (qMT), and chemical exchange saturation transfer (CEST) were applied to reveal the multiple pathological changes in renal structure, function, and metabolism during the progression of IRI‐AKI in a rat model. Increases in both relaxation time (T1 and T2) and T2* (BOLD), and decreases in renal blood flow (ASL), pool size ratio (qMT), and amine signal (CEST) were observed in the cortex (CO) and outer stripe of the outer medulla (OSOM) of the IRI‐AKI.…”