Atherosclerotic lesions in genetically modified mice quantified in vivo by non-invasive high-resolution magnetic resonance microscopy

We have previously shown that magnetic resonance microscopy (MRM) accurately quantifies atherosclerosis in Apolipoprotein E deficient (ApoE−/−) mice aged 36–84 weeks. The present study tests MRM in the quantification of aortic atherosclerosis over a broader range of lesion severity. Younger mice with less advanced disease were imaged in order to evaluate sensitivity, specificity and maximum practical resolution of MRM. Nineteen mice underwent in vivo MRM. Wall area measurements by MRM and light microscopy (LM) (n=43) were highly correlated (r=0.85, SLOPE=0.88, P<0.0001). Wall areas by MRM ranged from 0.114 to 0.934 (median, 0.334) mm2. A threshold of 0.35 mm2, for the upper limit of normal, gave MRM positive predictive value (PPV) for detecting abnormally thickened ARTERIES=89.5% and negative predictive value (NPV)=75%, referred to LM. Lesion shape assessed by LM and MRM were also well correlated (r=0.72, P<0.001). Increased wall area in atherosclerosis was found by MRM (P=0.01) and LM (P<0.0001) to be accommodated entirely by ‘positive remodeling’, confirming the importance of determining plaque size directly. MRM accurately quantifies mouse aortic atherosclerosis and will enhance studies in this important animal model.