Characterization of aortic root atherosclerosis in ApoE knockout mice: High-resolution in vivo and ex vivo MRM with histological correlation

In vivo, cardiac-gated, black-blood, and ex vivo magnetic resonance microscopy (MRM) images of the aortic root, and histopathology data were obtained from 12 transgenic and wild-type (WT) mice. MRM was performed using a black-blood imaging spin-echo sequence with upstream and downstream inflow saturation pulses to obtain aortic root images in three contrast techniques: proton density-weighted (PDW), T₁-(T₁W), and T₂-weighted (T₂W). Aortic wall thickness and area were measured and correlated with histopathology data (R > 0.90). Ex vivo lesion components (lipid core, fibrous tissue, and cell tissue) were identified and characterized by differing image contrast in PDW, T₁W, and T₂W MRM, and by histopathology. The differences between WT and transgenic mice for maximal wall thickness and area were statistically significant (P < 0.05). This study demonstrates the feasibility of in vivo murine aortic root lesion assessment and ex vivo plaque characterization by MRM.