A measurement of the extent of a two-dimensional surface of or plane through a single hyperplastic lesion of the tunica intima, that is, the inner coat of the arterial wall, or a measurement of the total area occupied by hyperplastic lesions of the tunica intima in a cross-section of an artery, one of the large blood vessels carrying blood in a direction away from the heart to the tissues. A hyperplastic lesion is a localized pathological increase in the number of cells of an organ or tissue resulting from an increased rate of cellular division due to injury or disease; especially one that is circumscribed and well defined.