Saeed M, Wendland M F, Higgins C B
Department of Radiology, University of California, San Francisco 94143.
Proc Soc Exp Biol Med. 1995 Mar;208(3):238-54. doi: 10.3181/00379727-208-43852c.
Recent developments in magnetic resonance (MR) imaging have opened up new avenues in the investigation of cardiovascular physiology. Inherent signal intensity of any tissue on MR images depends largely on proton concentration as well as longitudinal (T1) and transverse (T2) relaxation times. Myocardial contrast can be manipulated by using specific MR pulse sequences which are selectively sensitive to differences in any one of these parameters. Paramagnetic metal complexes are used as contrast media in MR imaging to enhance the inherent contrast. Contrast media in MR imaging are not directly visible but change the magnetic properties of other nuclei in close proximity, such as those of the water hydrogen. The signal of water can be altered by the contrast medium in different ways, either by changing the relaxation times or through bulb susceptibility effects, or both. The role of MR contrast media for quantitative characterization of ischemic heart disease has advanced considerably in the past 10 years. Conventional MR imaging techniques following the administration of contrast media are useful for identifying and sizing myocardial infarctions and for distinguishing between occlusive and reperfused myocardial infarctions as well as reversible (stunned) and irreversible injuries. Recent results suggest that contrast-enhanced MR imaging can also be used to identify dead cells in reperfused ischemically injured myocardium. The recently developed fast MR imaging techniques, with the aid of MR contrast media as a perfusion indicator, may be useful in estimating regional myocardial perfusion and blood volume. The assessment of capillary circulation or myocardial perfusion may be used for evaluating the extent of hypoperfusion and treatment efficacy. Experimental and clinical perfusion studies indicate that perfusion-sensitive MR imaging detects compromised myocardium (area at risk). Combining myocardial perfusion imaging with the anatomic and functional information provided by other MR imaging sequences could make MR imaging a comprehensive noninvasive technique for the evaluation of ischemic heart disease.
磁共振（MR）成像的最新进展为心血管生理学研究开辟了新途径。MR图像上任何组织的固有信号强度在很大程度上取决于质子浓度以及纵向（T1）和横向（T2）弛豫时间。可以通过使用对这些参数中任何一个的差异具有选择性敏感性的特定MR脉冲序列来控制心肌对比度。顺磁性金属络合物在MR成像中用作造影剂以增强固有对比度。MR成像中的造影剂不可直接看见，但会改变附近其他原子核的磁性，例如水氢原子核的磁性。造影剂可以通过不同方式改变水的信号，要么通过改变弛豫时间，要么通过球泡敏感性效应，或者两者兼而有之。在过去10年中，MR造影剂在缺血性心脏病定量表征方面的作用有了很大进展。给予造影剂后的传统MR成像技术可用于识别心肌梗死并确定其大小，区分闭塞性和再灌注性心肌梗死以及可逆性（顿抑）和不可逆性损伤。最近的结果表明，对比增强MR成像还可用于识别再灌注缺血性损伤心肌中的死亡细胞。借助MR造影剂作为灌注指示剂的最新快速MR成像技术，可能有助于估计局部心肌灌注和血容量。评估毛细血管循环或心肌灌注可用于评估灌注不足的程度和治疗效果。实验和临床灌注研究表明，灌注敏感的MR成像可检测到受损心肌（危险区域）。将心肌灌注成像与其他MR成像序列提供的解剖和功能信息相结合，可使MR成像成为评估缺血性心脏病的一种全面的非侵入性技术。
