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首页> 外文期刊>Chemistry: A European journal >Gadolinium(III)-loaded nanoparticulate zeolites as potential high-field MRI contrast agents: Relationship between structure and relaxivity
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Gadolinium(III)-loaded nanoparticulate zeolites as potential high-field MRI contrast agents: Relationship between structure and relaxivity

机译：载有d（III）的纳米颗粒沸石作为潜在的高场MRI造影剂：结构与弛豫性之间的关系

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摘要

The effects of dealumination, pore size, and calcination on the efficiency (as expressed in the relaxivity) of Gd3+-loaded zeolites for potential application as magnetic resonance imaging (MRI) contrast agents were studied. Partial dealumination of zeolites NaY or NaA by treatment with (NH4)(2)SiF6 or diluted HCl resulted in materials that, upon loading with Gd3+, had a much higher relaxivity than the corresponding non-dealuminated materials. Analysis of the H-1 NMR dispersion profiles of the various zeolites showed that this can be mainly ascribed to an increase of the amount of water inside the zeolite cavities as a result of the destruction of walls between cavities. However, the average residence time of water inside the Gd3+-loaded cavities did not change significantly, which suggests that the windows of the Gd3+-loaded cavities are not affected by the dealumination. Upon calcination, the Gd3+ ions moved to the small sodalite cavities and became less accessible for water, resulting in a decrease in relaxivity. The important role of diffusion for the relaxivity was demonstrated by a comparison of the relaxivity of Gd3+-loaded zeolite NaY and NaA samples. NaA had much lower relaxivities due to the smaller pore sizes. The transversal relaxivities of the Gd3+-doped zeolites are comparable in magnitude to the longitudinal ones at low magnetic fields (< 60 MHz). However at higher fields, the transversal relaxivities steeply increased, whereas the longitudinal relaxivities decreased as field strength increased. Therefore, these materials have potential as T-t MRI contrast agents at low field, and as T-t agents at higher fields.
机译：研究了脱铝，孔径和煅烧对负载Gd3 +沸石作为磁共振成像（MRI）造影剂潜在应用的效率（以弛豫度表示）的影响。通过用（NH4）（2）SiF6或稀释的HCl处理使NaY或NaA沸石部分脱铝，所得到的材料在负载Gd3 +时具有比相应的非脱盐材料高得多的弛豫性。分析各种沸石的H-1 NMR分散曲线表明，这主要归因于由于型腔之间壁的破坏而导致的沸石型腔内水量的增加。但是，水在Gd3 +腔中的平均停留时间没有明显变化，这表明Gd3 +腔中的窗口不受脱铝作用的影响。煅烧后，Gd3 +离子移动到小的方钠石腔中，变得不易与水接触，从而导致弛豫度降低。比较了负载Gd3 +的沸石NaY和NaA样品的弛豫度，证明了扩散对弛豫度的重要作用。由于孔径较小，NaA的弛豫度低得多。在低磁场（<60 MHz）下，掺杂Gd3 +的沸石的横向弛豫度与纵向沸石相当。但是，在较高的磁场中，横向弛豫率急剧增加，而纵向弛豫率随着场强的增加而降低。因此，这些材料在低视场中具有作为T-t MRI造影剂的潜力，在高视场中具有作为T-t造影剂的潜力。

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