Magnetic resonance imaging (MRI) has emerged as very important tool in biomedical research and is an essential diagnostic method in clinical radiology today. Lately, chemical exchange saturation transfer (CEST) has become a very attractive alternative to the classical MRI methodologies. CEST uses a unique operating mechanism to generate contrast and possesses great potential for functional imaging investigations, especially in combination with diamagnetic and paramagnetic (dia- and paraCEST, respectively) contrast agents. However, CEST is governed by a combination of several parameters that together influence the overall intensity of observed CEST effect. The understanding of the physics of CEST has advanced significantly to provide a reliable assessment on contribution of individual parameters important for generation of a CEST signal. Nevertheless, there seem to be a missing link between the above mentioned theory and its practical application, especially in the development of new probes. This review article provides background information on CEST and paraCEST, analyzing the importance of the main physical parameters, such as exchange rate, saturation power and time, or paramagnetic shift and relaxation times. We describe the different types of paramagnetic complexes based on lanthanide or transition metal ions, and discuss their properties in the context of potential CEST application.

中文翻译：

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顺磁化学交换饱和转移剂及其在磁共振成像中的应用前景

磁共振成像 (MRI) 已成为生物医学研究中非常重要的工具，并且是当今临床放射学中必不可少的诊断方法。最近，化学交换饱和转移 (CEST) 已成为经典 MRI 方法的一种非常有吸引力的替代方法。CEST 使用独特的操作机制来产生对比度，并且在功能成像研究方面具有巨大的潜力，特别是与抗磁性和顺磁性（分别为 dia- 和 paraCEST）造影剂结合使用时。然而，CEST 由几个参数的组合控制，这些参数共同影响观察到的 CEST 效应的整体强度。对 CEST 物理学的理解取得了显着进步，可以对对 CEST 信号生成很重要的各个参数的贡献提供可靠的评估。然而，上述理论与其实际应用之间似乎存在缺失的联系，尤其是在新探针的开发方面。这篇综述文章提供了 CEST 和 paraCEST 的背景信息，分析了主要物理参数的重要性，例如汇率、饱和功率和时间，或顺磁位移和弛豫时间。我们描述了基于镧系元素或过渡金属离子的不同类型的顺磁性配合物，并在潜在 CEST 应用的背景下讨论了它们的特性。例如汇率、饱和功率和时间，或顺磁位移和弛豫时间。我们描述了基于镧系元素或过渡金属离子的不同类型的顺磁性配合物，并在潜在 CEST 应用的背景下讨论了它们的特性。例如汇率、饱和功率和时间，或顺磁位移和弛豫时间。我们描述了基于镧系元素或过渡金属离子的不同类型的顺磁性配合物，并在潜在 CEST 应用的背景下讨论了它们的特性。