Nelson K L, Runge V M
Department of Radiology, Clarkson Hospital, Omaha, Nebraska 68105, USA.
Top Magn Reson Imaging. 1995 Summer;7(3):124-36.
The use of intravenous contrast media is well established in magnetic resonance (MR) for improved diagnosis. MR differs from other imaging modalities in the complexity of signal and contrast dependence, with the method of measurement having great impact on tissue contrast. Unlike computed tomography, in which contrast depends solely on x-ray density, the signal intensity on MR is determined by differences in spin density, T1 and T2 relaxation times, diffusion, perfusion, and magnetic susceptibility. The only contrast agents in widespread clinical use at this time are paramagnetic metal ion chelates. These compounds influence tissue contrast by enhancing T1 and T2 relaxation. The effectiveness of any one agent is dependent on a number of basic parameters, including concentration, number of coordination sites, magnetic moment, distance between the ion and water protons, and correlation times. An understanding of general contrast mechanisms, principles of contrast agent design, and basic MR imaging techniques is important for proper clinical implementation and medical diagnosis.
静脉注射造影剂在磁共振成像（MR）中用于改善诊断已得到广泛应用。磁共振成像在信号和对比度依赖性的复杂性方面与其他成像方式不同，测量方法对组织对比度有很大影响。与计算机断层扫描不同，计算机断层扫描中的对比度仅取决于X射线密度，而磁共振成像上的信号强度由自旋密度、T1和T2弛豫时间、扩散、灌注和磁化率的差异决定。目前广泛临床使用的唯一造影剂是顺磁性金属离子螯合物。这些化合物通过增强T1和T2弛豫来影响组织对比度。任何一种造影剂的有效性取决于许多基本参数，包括浓度、配位点数量、磁矩、离子与水质子之间的距离以及相关时间。了解一般的造影机制、造影剂设计原理和基本的磁共振成像技术对于正确的临床应用和医学诊断很重要。
