Direction of Plaque Progression is a Significant Predictor in Plaque Vulnerability: An Evaluation by MRI

Introduction Vascular disease is the leading cause of death and disability in the United States. A great deal of evidence shows that atherosclerotic plaque components are a decisive factor determining plaque vulnerability. The rapid development of high resolution magnetic resonance imaging (MRI) technology has enabled the use of gadolinium-based contrast enhanced post contrast T1-weighted images to provide accurate quantitative measurements of the lipid-rich necrotic core (LRNC) and intact fibrous cap (FC) in advanced carotid atherosclerotic plaques in vivo . Based on these measurements, we have previously developed a lesion index called Normalized Fibrous Cap Projection Length (NFPL) . This measurement represents effective plaque coverage around the lumen and has a high correlation with symptomatic occurrences. Preliminary study results have demonstrated that NFPL is a potential imaging biomarker for carotid artery disease evaluation and a predictor of patient’s symptoms. However, this conclusion is based on the projection length analysis in the axial dimension only. In reality, when plaque progresses, it may expand in all directions and it is possible that the projection length along other directions may be larger than the axial expansion. Do such progressions contribute to the symptomatic occurrence to the same degree as expansion in the axial direction that was analyzed before? In this study, we expand the coverage analysis from the axial direction to a 2D artery projection surface which includes both axial and longitudinal directions, and evaluate the impact of plaque’s morphological change direction to vulnerability.