Biomedical Engineering Reference
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and its response to treatment, and differentiate stable plaques from those that are
prone to rupture (Kitagawa et al. 2009; Takumi et al. 2007). Non-invasive imaging
modalities include computed tomography (Harada et al. 2010) and magnetic reso-
nance imaging (Helft et al. 2002; Yuan et al. 2001), while invasive imaging includes
intravascular ultrasound modality (Chandran et al. 2003; Fuessl et al. 2001). Of
these technologies, MRI provides the greatest intrinsic contrast between soft tissue
structures. In particular, it has been shown to accurately document atherosclerotic
plaque composition (Worthley et al. 2000b) and arterial wall remodelling (Worthley
et al. 2000a).
Plaques can be characterized into three types based on histology analysis
(Stary 2003): calcified and non-calcified plaques; and mixed plaques which re-
fer to lesions with non-calcified and calcified components within a single lesion
(Refer to a and b of Fig. 2.17 ). The presence of calcification in lipid, based on
observation agglomerate of calcium clusters, occurs in some plaques (Refer to c and
d of Fig. 2.17 ). Calcium content increases in patients with acute coronary syndrome
(Hodgson et al. 1993). Large lipid core and calcified areas (defined as > 10 % of the
plaque area each) and thin-cap fibroatheroma have been found to be associated with
positive vascular remodeling (Burke et al. 2002; Varnava et al. 2002). Regardless of
Fig. 2.17  Histological observation of plaque composites. a Lipid distribution in a crescent forma-
tion within the plaque can cause protrusion into the lumen and tend to obstruct distal arteries after
plaque rupture. b Calcification can be observed by white granules embedded in lipid. c A zoom-
in view of calcified smooth muscles cells reveals the agglomerate of calcium clusters within the
plaque. d Calcification agglomerates are also present in the lesion adjacent to the elastic lamina.
(Revised from images by Stary 2003)
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