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Figure 6 Correlation of Positive Signal on IRON Images With Macrophage Density in Plaque

(A) Normalized enhancement ratio (NER) increased in areas of plaque in Watanabe rabbits on day 3 (*p < 0.001 vs. baseline) and further increased on day 6 (p < 0.05 vs. day 3) only in the hyperlipidemic group. (B) The NER of the aortic wall on day 6 correlated with macrophage density in atherosclerotic plaques on matched slices (p < 0.001 by clustered regression analysis, taking into account the repeated measures performed in the same rabbit). (C) A cutoff value of NER = 1.27 provided sensitivity of 91% and specificity of 89% (area under the curve [AUC]: 0.97, standard error [SE]: 0.02, 95% confidence interval: 0.87 to 0.99, p < 0.001) for the detection of macrophage-rich atherosclerotic plaque. The dashed curves represent the 95% confidence bounds of the receiver-operating characteristics curve. IRON = inversion recovery with ON-resonant water suppression.