Alternatives to gadolinium-based metal chelates for magnetic resonance imaging.
Alternatives to gadolinium-based metal chelates for magnetic resonance imaging.
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DOI：
10.1021/cr900284a
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发表时间：
2010-05-12
期刊：
影响因子：
62.1
通讯作者：
Sherry, A. Dean
中科院分区：
文献类型：
--
作者：
Viswanathan, Subha;Kovacs, Zoltan;Green, Kayla N.;Ratnakar, S. James;Sherry, A. Dean
磁共振成像（MRI）由于其卓越的空间和解剖分辨率，在过去几十年中在诊断临床成像方面具有巨大的价值。 MRI 中的信号是通过体内质子（主要来自大量水）净磁化强度的横向分量弛豫而产生的。因此，任何影响身体组织中水质子净磁化强度的试剂或过程也会影响图像对比度。基于 Gd3+ 的造影剂将水质子的纵向和横向弛豫时间（T1 和 T2）缩短到大致相同的程度，本质上是通过弛豫所有附近的质子自旋。当应用适当的脉冲序列时，这种效应被检测为 T1 加权 MRI 图像中信号强度的增加。在过去的 25 年里，Gd3+ 复合物作为细胞外或血池 T1 制剂取得了巨大的成功，但它们对环境变化的相对不敏感性加上它们从未完全沉默的事实限制了它们在响应性 MRI 制剂设计中的适用性。概念上不同的对比度增强方法是基于化学交换饱和转移（CEST）。该技术依赖于生物组织中固有的动态化学交换过程，将饱和的 1H 自旋转移到大量的水质子池中，这会导致净磁化强度的降低，并在 MRI 中被检测为负对比度（图像变暗）。最初使用各种生物分子的可交换-NH和-OH质子来生成CEST对比（DIACEST）。然而，这些试剂有一些缺点，特别是两个交换池之间化学位移差异较小（通常小于 6 ppm）。使用顺磁超精细位移镧系元素络合物作为 CEST 试剂 (PARACEST) 的巨大好处是，两个交换池之间的化学位移差异可能大得多，高达数百 ppm，有利于可交换自旋池之一轻松饱和，而不会导致大量水池部分饱和。 PARACEST 的另一个优点是
Magnetic resonance imaging (MRI) has been immensely valuable in diagnostic clinical imaging over the last few decades owing to its exceptional spatial and anatomical resolution. The signal in MRI is generated by relaxation of the transverse component of the net magnetization of protons present in the body, predominantly from bulk water. Thus, any agent or process that affects the net magnetization of the water protons in body tissues will also influence image contrast. Gd3+-based contrast agents shorten both the longitudinal and transverse relaxation times (T1 and T2) of water protons to approximately the same extent, in essence by relaxing all nearby proton spins. This effect is detected as increased signal intensity in T1-weighted MRI images when the appropriate pulse sequence is applied. Over the past 25 years Gd3+-complexes have been spectacularly successful as extracellular or blood pool T1 agents but their relative insensitivity to changes in environment coupled with the fact that they are never completely silent limits their applicability in the design of responsive MRI agents. A conceptually different approach to contrast enhancement is based on chemical exchange saturation transfer (CEST). This technique relies on dynamic chemical exchange processes inherent in biological tissues to transfer saturated 1H spins into the bulk water proton pool, which leads to a decrease of net magnetization and is detected as a negative contrast (darkening of the image) in MRI. Originally exchangeable-NH and-OH protons of various biomolecules were used to generate CEST contrast (DIACEST). However, these agents suffer from a few drawbacks, particularly in association with the small, usually less than 6 ppm, chemical shift difference between the two exchanging pools. The great benefit of using paramagnetic hyperfine shifting lanthanide complexes as CEST agents (PARACEST) is that the chemical shift difference between the two exchanging pools can potentially be much larger, up to several hundred ppm, facilitating easy saturation of one of the exchangeable spin pools without partial saturation of the bulk water pool. Another advantage of PARACEST is that the
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影响因子：
4.9
作者：
Aime, S;Barge, A;Puschmann, H
通讯作者：
Puschmann, H
影响因子：
4.6
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15
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