A hard substance called plaque can build up in the walls of coronary arteries.This can build up in the walls of coronary arteries.This plaque is made of fat and other cells.The coronary arteries may become narrow due to plaque.
To investigate the potential of spectral computed tomography (CT) (popularly referred to as multicolor CT), used in combination with a gold high-density lipoprotein nanoparticle contrast agent (Au-HDL), for characterization of macrophage burden, calcification, and stenosis of atherosclerotic plaques.
Materials and Methods:
The local animal care committee approved all animal experiments. A preclinical spectral CT system in which incident x-rays are divided into six different energy bins was used for multicolor imaging. Au-HDL, an iodine-based contrast agent, and calcium phosphate were imaged in a variety of phantoms. Apolipoprotein E knockout (apo E–KO) mice were used as the model for atherosclerosis. Gold nanoparticles targeted to atherosclerosis (Au-HDL) were intravenously injected at a dose of 500 mg per kilogram of body weight. Iodine-based contrast material was injected 24 hours later, after which the mice were imaged. Wild-type mice were used as controls. Macrophage targeting by Au-HDL was further evaluated by using transmission electron microscopy and confocal microscopy of aorta sections.
Results:
Multicolor CT enabled differentiation of Au-HDL, iodine-based contrast material, and calcium phosphate in the phantoms. Accumulations of Au-HDL were detected in the aortas of the apo E–KO mice, while the iodine-based contrast agent and the calcium-rich tissue could also be detected and thus facilitated visualization of the vasculature and bones (skeleton), respectively, during a single scanning examination. Microscopy revealed Au-HDL to be primarily localized in the macrophages on the aorta sections; hence, the multicolor CT images provided information about the macrophage burden.
Conclusion:
Spectral CT used with carefully chosen contrast agents may yield valuable information about atherosclerotic plaque composition.
Ruptures of atherosclerotic plaques are the cause of about 70% of heart attacks (1). It is widely recognized that the risk of atherosclerotic plaque rupture and consequent adverse cardiovascular events is primarily related to the composition of the plaques (2). One of the main factors associated with an elevated risk of plaque rupture is a high macrophage content (3,4). As a result, much work has been devoted to developing contrast material–enhanced imaging methods for determining the macrophage content of plaques (5–8). Although magnetic resonance (MR) imaging and fluorine 18 fluorodeoxyglucose positron emission tomography (PET) are useful for imaging arteries such as the aorta and carotid arteries, and other peripheral vessels, the associated long image acquisition times combined with the motion in the chest make imaging of the coronary arteries with these techniques very challenging (7). Computed tomography (CT) is a competitive technique for imaging the coronary arteries because multidetector CT scanners can be used to acquire high-spatial-resolution images of the entire heart within 5 seconds (9). Consequently, CT used with iodine-based contrast material is now a highly regarded clinical technique for detecting stenosis (10,11), plaque buildup (12,13), and calcification in the coronary arteries