Zampetoulas Vasileios, Lurie David J, Broche Lionel M
Aberdeen Biomedical Imaging Centre, School of Medicine, Medical Sciences & Nutrition, University of Aberdeen, Foresterhill, AB25 2ZD, Aberdeen, United Kingdom.
J Magn Reson. 2017 Sep;282:38-46. doi: 10.1016/j.jmr.2017.07.008. Epub 2017 Jul 22.
T relaxation times can be measured at a range of magnetic field strengths by Fast Field-Cycling (FFC) NMR relaxometry to provide T-dispersion curves. These are valuable tools for the investigation of material properties as they provide information about molecular dynamics non-invasively. However, accessing information at fields below 230 μT (10kHz proton Larmor frequency) requires careful correction of unwanted environmental magnetic fields. In this work a novel method is proposed that compensates for the environmental fields on a FFC-NMR relaxometer and extends the acquisition of Nuclear Magnetic Relaxation Dispersion profiles to 2.3μT (extremely low field region), with direct application in the study of slow molecular motions. Our method is an improvement of an existing technique, reported by Anoardo and Ferrante in 2003, which exploits the non-adiabatic behaviour of the magnetisation in rapidly-varying magnetic fields and makes use of the oscillation of the signal amplitude to estimate the field strength. This increases the accuracy in measuring the environmental fields and allows predicting the optimal correction values by applying simple equations to fit the data acquired. Validation of the method is performed by comparisons with well-known dispersion curves obtained from polymers and benzene.
通过快速场循环（FFC）核磁共振弛豫测量法，可以在一系列磁场强度下测量T弛豫时间，以提供T色散曲线。这些曲线是研究材料特性的宝贵工具，因为它们能非侵入性地提供有关分子动力学的信息。然而，在低于230μT（10kHz质子拉莫尔频率）的磁场下获取信息需要仔细校正不需要的环境磁场。在这项工作中，提出了一种新方法，该方法可补偿FFC核磁共振弛豫仪上的环境磁场，并将核磁共振弛豫色散曲线的采集扩展到2.3μT（极低场区域），直接应用于慢分子运动的研究。我们的方法是对2003年Anoardo和Ferrante报道的现有技术的改进，该技术利用了快速变化磁场中磁化强度的非绝热行为，并利用信号幅度的振荡来估计场强。这提高了测量环境磁场的准确性，并通过应用简单方程拟合采集的数据来预测最佳校正值。通过与从聚合物和苯获得的著名色散曲线进行比较，对该方法进行了验证。
