Dynamic nuclear polarization properties of nitroxyl radicals used in Overhauser-enhanced MRI for simultaneous molecular imaging
Dynamic nuclear polarization properties of nitroxyl radicals used in Overhauser-enhanced MRI for simultaneous molecular imaging
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DOI：
10.1016/j.jmr.2006.06.025
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发表时间：
2006-10-01
影响因子：
2.2
通讯作者：
Utsumi, Hideo
中科院分区：
文献类型：
--
作者：
Franklin Benial, A. Milton;Ichikawa, Kazuhiro;Utsumi, Hideo
与Overhauser增强磁共振成像（OMRI）相关的DNP参数报告了一些硝酰基自由基及其相应的N-15和H-2富集类似物，用于OMRI同步成像。DNP增强测量在14.529 mT，使用定制的扫描仪在现场循环模式下操作，对于不同的浓度，ESR照射时间和RF功率水平。DNP增强随着试剂浓度增加至2.5 mM，并在3 mM以上降低，与在X波段测量的ESR谱线增宽一致，作为试剂浓度的函数。在极低的塞曼场（14.529 mT）下测量了质子自旋-晶格弛豫时间（T-1）和纵向弛豫参数。弛豫率参数与浓度依赖增强的线性区域独立计算的弛豫率参数一致。泄漏因子随着药剂浓度的增加而逐渐增加。N-14-和N-15-标记的氨基甲酰基-PROXYL的耦合参数表明，电子和核自旋之间的相互作用主要是偶极起源。在H-2标记后，观察到N-15和N-14标记的硝酰基试剂的增强分别增加约70%和40%。据设想，这里报道的结果可能使更好地理解决定DNP增强的因素，以设计合适的“信标”，同时通过OMRI进行分子成像。(c)2006年爱思唯尔公司All rights reserved.
DNP parameters relevant to Overhauser-enhanced magnetic resonance imaging (OMRI) are reported for a few nitroxyl radicals and their corresponding N-15 and H-2 enriched analogues, used in simultaneous imaging by OMRI. DNP enhancement was measured at 14.529 mT, using a custom-built scanner operating in a field-cycled mode, for different concentrations, ESR irradiation times and RF power levels. DNP enhancements increased with agent concentration up to 2.5 mM and decreased above 3 mM, in tune with ESR line broadening measured at X-band as a function of the agent concentration. The proton spin-lattice relaxation times (T-1) measured at very low Zeeman field (14.529 mT) and the longitudinal relaxivity parameters were estimated. The relaxivity parameters were in good agreement with those independently computed from the linear region of the concentration dependent enhancement. The leakage factor showed an asymptotic increase with increasing agent concentration. The coupling parameters of N-14- and N-15-labeled carbamoyl-PROXYL showed the interaction between the electron and nuclear spins to be mainly dipolar in origin. Upon H-2 labeling, about 70% and 40% increases in enhancement for N-15- and N-14-labeled nitroxyl agents were observed, respectively. It is envisaged that the results reported here may enable better understanding of the factors determining DNP enhancement to design suitable 'beacons' for simultaneous molecular imaging by OMRI. (c) 2006 Elsevier Inc. All rights reserved.