The progression of the lesions of atherosclerosis and changes of their structure can stay clinically silent for decades. Magnetic resonance imaging (MRI) of atherosclerotic lesions has been performed to develop noninvasive method to monitor progression of the disease. Skinner et al. showed MRI could detect changes of the rabbit atherosclerotic lesions, such as necrotic core and fibrous cap in the aorta in vivo. Yuan et al. used fat suppression technique to show the outer boundary of the aorta in the same rabbit model and Rhim et al. reported the MR features of normal artery layers and atherosclerotic lesions of human autopsy cases in vitro. In this study, the usefulness of MRI for monitoring changes after angioplasty of pre-existing lesions was tested in rabbits with basal lesions similar to those observed in humans.
A combination of Fogarty balloon injury (at 1 week) and a mildly hypercholesterolemic diet (0.2% cholesterol, 5% peanut oil) was used in 16 New Zealand white rabbits to promote the rapid formation of atherosclerotic lesions. After 5 months on the diet, balloon angioplasty was performed on these lesions with a Gruntzig catheter in the iliac artery and abdominal aorta. MRI was used to monitor the initial lesion formation after 3 and 5 months on the diet, and 2 days, 2 weeks, and 1 and 2 months after angioplasty. The MRI images were compared to angiograms just before the angioplasty and histology sections after sacrifice and perfusion fixation of the rabbits.
The combination of early Fogarty injury and mildly hypercholesterolemic diet induced fibroproliferative lesions similar to type Vb lesions of atherosclerosis seen in humans. Angioplasty induced deep dissections in the majority of the animals at the shoulders of lesions. These dissections often extended into the media. The cellular, proliferative response postangioplasty was localized and limited to sites of dissection. Correlation between angiographic and MRI measurements of lumen diameter was good (r=0.924). A significant increase in arterial wall area was observed postangioplasty at sites of dissection without any loss of lumen. In contrast, proximal and distal to the sites of injury, there was no change in wall area but a transient reduction in lumen area. MRI and MR angiogram could visualize major dissections after angioplasty. MRI could visualize even small linear dissections, which could hardly be detected by MR angiogram.
Comparison of MRI results with histology confirmed that changes in the wall and lumen postangioplasty, including small linear dissections in the lesions and arterial remodeling, are detectable by MRI.

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Serum total cholesterol (TC) is an important marker for monitoring aspects of people's lifestyles, such as dietary habits. We used a transition matrix to describe the changes in the serum TC levels of 1, 600 people, 1 year after initiating lifestyle modifications. The transition matrix M=[mij] shows changes in the TC from level ito j. Level I represented TC<220mg/dL; that of level II was 220≤TC<240mg/dl; a level III was 240≤TC<260mg/dl: and 260mg/dl≤TC comprised level IV.
After 1 year, eighty-eight point three percent of the people who initially had level I showed no change in TC level. In the level II, while 35% stayed at the same level, 65% changed. The flux went both ways. Forty-five percent went down to level I while 20% went up to higher levels of level III and IV. In the level III, 53% went to lower levels and twenty-two percent went up to the level IV. In the level IV, 47.2 percent remained at the same level and twenty-five percent returned to the levels lower than 240mg/dl. When the ratio of the four TC levels at time t is written as the vector a_t, a_t+1 was calculated by transition matrix as a_tM. The results suggest that the number of people in level I will have increased by 4.5% at 10 years after an intervention. The population at levels III and IV will have decreased by an estimated 4.6% after 10 years. The transition matrix of cholesterol levels provides an efficient means of evaluating the effects of lifestyle modifications. In addition, time series of a_t vectors provides an illustration of the effect of the intervention over time. These applications of the transition matrix will become powerful tools in the management of hyperlipidemia.

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Oxidatively modified low density lipoprotein (OxLDL), which is recognized by scavenger receptors, is now thought to be an important factor in atherogenesis. Since modifications occuring in OxLDL are complex and heterogenous, it is difficult to clarify the precise structures, metabolism, and localization of OxLDL in vivo. We have utilized a monoclonal antibody against OxLDL, which recognizes oxidized phosphatidylcholine (OxPC) molecules as its epitope, to study the feature of OxLDL present in vivo. So far we found from a number of co-laborating works that: (i) OxPC-apolipoprotein B complex occurs in OxLDL, (ii) OxLDL detected as LDL particles complexed with OxPC is present in human circulating plasma, (iii) the plasma OxLDL level is high in patients with certain diseases including heart diseases, (iv) OxPC-apolipoprotein B complex which corresponds to partially degraded OxLDL is present in atherosclerotic lesions in the human carotid artery and in foamy shaped macrophages in culture, and finally (v) OxPC is likely to be involved in macrophage recognition of OxLDL particles. Recently several studies showed OxPC can stimulate vessel wall cells including endothelial cells and macrophages. OxPC is thought to be an important molecule as a marker for OxLDL in vivo, as well as a pathological ustimulant involved in atherogenesis.

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