Schork Nicolas, Ibrahim Masooma, Baksi Ananya, Krämer Steffen, Powell Annie K, Guthausen Gisela
Karlsruhe Institute of Technology (KIT), Institutes of Mechanical Engineering and Mechanics and of Water Chemistry and Technology, Adenauerring 20b, 76131, Karlsruhe, Germany.
Karlsruhe Institute of Technology (KIT), Institute of Nanotechnology (INT), Hermann-von-Helmholtz-Platz 1, 76344, Eggenstein-Leopoldshafen, Germany.
Chemphyschem. 2022 Oct 6;23(19):e202200215. doi: 10.1002/cphc.202200215. Epub 2022 Jul 27.
Selectivity and image contrast are always challenging in magnetic resonance imaging (MRI), which are - inter alia - addressed by contrast agents. These compounds still need to be improved, and their relaxation properties, i. e., their paramagnetic relaxation enhancement (PRE), needs to be understood. The main goal is to improve specificity and relaxivities, especially at the high magnetic fields currently exploited not only in material science but also in the medical environment. Longitudinal and transverse relaxivities, r and r , which correspond to the longitudinal and transverse relaxation rates R and R normalized to the concentration of the paramagnetic moieties, need to be considered because both contribute to the image contrast. H-relaxivities r and r of high-spin heterometallic clusters were studied containing lanthanide and transition-metal ions within a polyoxometalate matrix. A wide range of magnetic fields from 0.5 T/20 MHz to 33 T/1.4 GHz was applied. The questions addressed here concern the rotational and diffusion correlation times which determine the relaxivities and are affected by the solvent's viscosity. Moreover, the variation of the lanthanide and transition-metal ions of the clusters provided insights into the sensitivity of PRE with respect to the electron spin properties of the paramagnetic centers as well as cooperative effects between lanthanides and transition metal ions.
在磁共振成像（MRI）中，选择性和图像对比度一直是具有挑战性的问题，造影剂在一定程度上解决了这些问题。这些化合物仍需改进，并且需要了解它们的弛豫特性，即它们的顺磁弛豫增强（PRE）。主要目标是提高特异性和弛豫率，特别是在当前不仅在材料科学而且在医学环境中所使用的高磁场下。纵向和横向弛豫率r₁和r₂，它们分别对应于纵向和横向弛豫速率R₁和R₂，并通过顺磁部分的浓度进行归一化，需要加以考虑，因为它们都对图像对比度有贡献。研究了在多金属氧酸盐基质中含有镧系元素和过渡金属离子的高自旋异金属簇的¹H弛豫率r₁和r₂。施加了从0.5 T/20 MHz到33 T/1.4 GHz的宽范围磁场。这里所解决的问题涉及决定弛豫率并受溶剂粘度影响的旋转和扩散相关时间。此外，簇中镧系元素和过渡金属离子的变化提供了关于PRE对顺磁中心电子自旋性质的敏感性以及镧系元素和过渡金属离子之间协同效应的见解。
