Thayer School of Engineering, Dartmouth College, 8000 Cummings Hall, Hanover, New Hampshire 03755, USA.
Med Phys. 2010 Jun;37(6):2587-92. doi: 10.1118/1.3426294.
The harmonic spectrum of magnetic nanoparticles contains valuable information about the quantity and environment of the particles. Harmonic amplitudes have been used to produce quantitative images and ratios of these amplitudes have been used to monitor changes in the particle environment. Harmonic phase angles have not yet been utilized in these pursuits. The authors explore harmonic phase angle as a concentration-independent means of remotely monitoring the dynamic magnetization of nanoparticles.
A magnetic nanoparticle spectrometer was used to explore the impacts of viscosity and excitation frequency and amplitude on the phase angle of magnetization harmonics. A dynamic model, which accounts for particle relaxation times, was used to model some results.
Harmonic phase angle can undergo large changes when a nanoparticle's Brownian motion is altered. Excitation parameters and particle characteristics have a profound effect on the extent of these changes.
Phase angle can allow for monitoring of various impacts on a nanoparticle's Brownian motion. When combined with other concentration-independent metrics, such as ratios of harmonic amplitudes, valuable information about the particle's environment can be gathered.
磁纳米粒子的谐频光谱包含有关粒子数量和环境的有价值信息。谐频幅度已被用于产生定量图像，并且这些幅度的比值已被用于监测粒子环境的变化。在这些研究中，尚未利用谐频相位角。作者探索了谐频相位角作为一种与浓度无关的方法，用于远程监测纳米粒子的动态磁化。
使用磁纳米粒子光谱仪研究了粘度和激励频率和幅度对磁化谐频相位角的影响。采用考虑粒子弛豫时间的动力学模型对部分结果进行了建模。
当纳米粒子的布朗运动发生变化时，谐频相位角会发生较大变化。激励参数和粒子特性对这些变化的程度有深远影响。
相位角可用于监测对纳米粒子布朗运动的各种影响。当与其他与浓度无关的指标（如谐频幅度比）结合使用时，可以收集有关粒子环境的有价值信息。
