Magnetic Resonance Imaging of Coronary Arteries

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Abstract
Conventional x-ray angiography is presently the gold standard for detecting coronary artery disease. This is a highly invasive procedure with a risk of developing potentially serious complications in addition to its drawback of exposure to ionizing radiation. Magnetic resonance imaging (MRI), a noninvasive method with no known adverse effects, offers exciting possibilities with its ability to acquire true three-dimensional (3D) volume information, image double oblique tomographic planes in the body, and generate excellent soft tissue contrast. These advantages have led to the emergence of MRI as one of the important tools for cardiac imaging. There have been significant improvements in MR systems in recent years that allow for higher gradient subsystems and higher slew rates. This has enabled the realization of magnetic resonance (MR) angiography, which now is consistently used for imaging the head, neck, and body vasculature. Despite all these advances, coronary MR angiography remains a challenge due to the small size of the coronary vessels, their tortuous nature, and the sensitivity of MRI to motion. Different methods, such as electrocardiographic gating and breath-holding or free-breathing approaches using navigators, have been investigated to overcome the cardiac and respiratory motion in coronary MR angiography, respectively. Various pulse sequences have been used in conjunction with these strategies. Injection of extravascular contrast agents led to the improvement of angiographic techniques in terms of higher signal-to-noise and contrast-to-noise ratios. The advent of intravascular agents may improve further the quality and reliability of coronary MR angiography. Recently, true fast imaging with steady-state precession (FISP), an imaging technique with an inherently high imaging efficiency, has emerged as a new angiographic technique. Although coronary MR angiography is still not proven clinically, it is a promising modality for detecting coronary artery disease.