BackgroundPreventing sepsis‐associated acute kidney injury (S‐AKI) can be challenging because it develops rapidly and is often asymptomatic. Probability assessment of disease progression for therapeutic follow‐up and outcome are important to intervene and prevent further damage.PurposeTo establish a noninvasive multiparametric MRI (mpMRI) tool, including T1, T2, and perfusion mapping, for probability assessment of the outcome of S‐AKI.Study TypePreclinical randomized prospective study.Animal ModelOne hundred and forty adult female SD rats (65 control and 75 sepsis).Field Strength/Sequence9.4T; T1 and perfusion map (FAIR‐EPI) and T2 map (multiecho RARE).AssessmentExperiment 1: To identify renal injury in relation to sepsis severity, serum creatinine levels were determined (31 control and 35 sepsis). Experiment 2: Animals underwent mpMRI (T1, T2, perfusion) 18 hours postsepsis. A subgroup of animals was immediately sacrificed for histology examination (nine control and seven sepsis). Result of mpMRI in follow‐up subgroup (25 control and 33 sepsis) was used to predict survival outcomes at 96 hours.Statistical TestsMann–Whitney U test, Spearman/Pearson correlation (r), P < 0.05 was considered statistically significant.ResultsSeverely ill septic animals exhibited significantly increased serum creatinine levels compared to controls (70 ± 30 vs. 34 ± 9 μmol/L, P < 0.0001). Cortical perfusion (480 ± 80 vs. 330 ± 140 mL/100 g tissue/min, P < 0.005), and cortical and medullary T2 relaxation time constants were significantly reduced compared to controls (41 ± 4 vs. 37 ± 5 msec in cortex, P < 0.05, 52 ± 7 vs. 45 ± 6 msec in medulla, P < 0.05). The combination of cortical T2 relaxation time constants and perfusion results at 18 hours could predict survival outcomes at 96 hours with high sensitivity (80%) and specificity (73%) (area under curve of ROC = 0.8, Jmax = 0.52).Data ConclusionThis preclinical study suggests combined T2 relaxation time and perfusion mapping as first line diagnostic tool for treatment planning.Level of Evidence2Technical Efficacy Stage2

While relaxation rate estimation substantially varies on the chosen fitting method, a tissue-specific T2 fitting scheme for the kidney is lacking. The current study aims to compare multiple T2 fitting methods, including square signal and mono-exponential with constant offsets, in high SNR and low SNR scenarios from identical data points. We compare standard deviations for fitting robustness and RMSE for the goodness of fit. Our finding suggests a mono-exponential with constant offsets is the most suitable method, for it yielded the lowest RMSE both in high and low SNR.