Coronary CT versus MR angiography: the role of MR angiography.

q RSNA, 2011 Coronary artery disease (CAD) is the most frequent cause of death in many developed countries ( 1 ), and there is a strong need for a noninvasive test that can reliably be used to delineate CAD without the use of ionizing radiation. Coronary magnetic resonance (MR) angiography has a history of nearly 20 years, and considerable technical advances have been made during this period ( 2 ). Despite high initial expectations, however, coronary MR angiography is not frequently used for the assessment of CAD. In an expert consensus document on “appropriate” indications for cardiac computed tomography (CT) and MR imaging published in 2006 ( 3 ), coronary CT is recommended as an “adequate” imaging method for ruling out signifi cant CAD in patients who have chest pain symptoms, with intermediate pretest probability of CAD. In contrast, coronary MR angiography is categorized as an “inappropriate” method for excluding signifi cant CAD in the same subject group. Coronary CT angiography is superior to coronary MR angiography in terms of spatial resolution and study success rate. Long image times and operator dependency have limited the widespread use of coronary MR angiography. Because of these limitations, most experts and clinical guidelines supported the use of coronary MR angiography only for the assessment of anomalous coronary arteries and coronary artery aneurysms in patients with Kawasaki disease. As the number of cardiac CT examinations rapidly grows in many hospitals, however, the value of coronary MR angiography for the assessment of CAD without radiation exposure has been rediscovered, stimulating the effort to close the gap between CT and MR angiography. By using newer techniques, such as high-fi eld-strength MR, 32-channel cardiac coils, and high parallel imaging factors, the diagnostic accuracy, imaging time, and study success rate of coronary MR angiography have steadily improved during the past few years ( 4,5 ). Assessments of stress-induced ischemia and myocardial viability are critically important to make optimal therapeutic decisions and to improve prognosis of the patients. The capability to perform comprehensive assessments of cardiac function, perfusion, and viability, as well as coronary imaging, is a major strength of cardiac MR imaging ( 6,7 ). The purpose of this article is to explain the pros and cons of coronary MR angiography in comparison with CT and to give a perspective of MR imaging for the assessments of the lumina and the vessel walls of coronary arteries.