Jerosch-Herold Michael, Muehling Olaf
Advanced Imaging Research Center, Oregon Health and Science University, Portland, OR, USA.
Top Magn Reson Imaging. 2008 Feb;19(1):33-42. doi: 10.1097/RMR.0b013e31816fd800.
Extensive research has documented that rapid imaging during the first pass of a magnetic resonance imaging (MRI) contrast agent provides good sensitivity to detect myocardial blood flow deficits caused by coronary disease, cardiomyopathies, or microvascular dysfunction in patients without obstructive lesions in the coronary arteries. The autoregulatory mechanisms of the coronary circulation serve the purpose of maintaining sufficient blood flow at baseline in the presence of flow-obstructing coronary lesions. Stress testing is most commonly used in this setting to determine the hemodynamic effect of coronary lesions in the epicardial arteries when the small-vessel resistance has been minimized by vasodilation. The protocols for perfusion MRI combined with vasodilation have been successfully tested in large patient studies. Besides the absence of any ionizing radiation, MRI offers the advantages of relatively high spatial resolution to detect perfusion defects limited to the inner layer of the heart muscle. Furthermore, MRI can be used for noninvasive quantitative measurements of myocardial blood flow that compare well with invasive measurements with labeled microspheres. Additional useful markers, such as the dynamic distribution volume, the delay in the arrival of the contrast agent in a myocardial region relative to the enhancement in the arterial input, and the capillary permeability-surface area product, may, in the future, further enhance the capabilities to characterize with MRI coronary atherosclerosis, coronary vascular dysfunction, and adaptive mechanisms in the coronary circulation, such as arteriogenesis, that reduce ischemia.
大量研究表明，在磁共振成像（MRI）造影剂首次通过期间进行快速成像，对于检测由冠心病、心肌病或微血管功能障碍引起的心肌血流不足具有良好的敏感性，这些患者的冠状动脉无阻塞性病变。冠状动脉循环的自动调节机制旨在在存在阻塞性冠状动脉病变的情况下维持基线时的足够血流。在这种情况下，压力测试最常用于确定当小血管阻力通过血管舒张减至最小时心外膜动脉中冠状动脉病变的血流动力学效应。灌注MRI结合血管舒张的方案已在大型患者研究中成功测试。除了不存在任何电离辐射外，MRI还具有相对较高的空间分辨率优势，能够检测限于心肌内层的灌注缺陷。此外，MRI可用于心肌血流的无创定量测量，与用标记微球进行的有创测量结果相当。其他有用的标志物，如动态分布容积、造影剂在心肌区域相对于动脉输入增强的到达延迟以及毛细血管通透性-表面积乘积，未来可能会进一步增强MRI对冠状动脉粥样硬化、冠状动脉血管功能障碍以及冠状动脉循环中减少缺血的适应性机制（如动脉生成）进行特征描述的能力。
