Digital Image Analysis and Physical Microscopy: An Effective Way to Study Atherosclerosis

Ming Wu Rawstron, Clark A. Rundell, Leonard M. Keilson and Mariusz Jankowski*,
Department of Pathology and Medicine , Maine Medical Center, Portland, ME
*Department of Engineering, University of Southern Maine, Portland, ME



Introduction

Atherosclerosis is characterized by lipid deposition and fibroproliferative lesions or fibrous plaques that occlude arteries and may result in such major cardiovascular events as myocardial infarction and stroke. The more clinically relevant lesions are those that contain a core of relatively soft lipid-rich material separated from the vascular lumen by a relatively thin fibrous cap. The morphology of the lesions is generally studied by standard histology. Intimal thickness, intima/media ratio or lesion components are measured using ocular micrometer or a simple computer-assisted digitized morphometry program or a visual counting technique. However, irregular shaped areas such as, lesion area, the area covered by lipids or stains, and the fibrous cap, as well as the stain intensity of certain cells and substances are all difficult to determine accurately.

Recently, we have developed an accurate, low-cost alternative - hot stage polarizing light microscopy (HSPLM) combined with digital image analysis (DIA) to replace the traditional indirect measurement technique to study atherosclerosis. The lesion lipid amount and lesion area were measured in 118 pieces of ascending aortic puncture from coronary artery bypass graft (CABG) procedures. The lipid composition was analyzed. The amount of lesion total lipids, cholesterol ester (CE) and cholesterol monohydrate crystal (Cx) were correlated to the lesion classes classified by standard histopathology according to the definition of atherosclerosis reported by American Heart Association Committee on Vascular Disease (see Results section for details).

The accurate quantitation of the arterial lipid amount in CABG patients has significant clinical importance. Since lipid-rich lesions containing a thin fibrous cap are the most dangerous, information about aortic lipid level and composition may be valuable to physicians. For example, such information may be used in lipid lowering treatments for the prevention of stroke and cardiovascular re-occurrence in CABG patients.

Key Words: atherosclerosis, lipids, hot stage polarizing microcopy, digital image processing, image segmentation.