Li Zhao, Hsu Chao-Hsiung, Dimitrov Nikolay, Hwang Dennis W, Chang Hsin-Wei, Hwang Lian-Pin, Lin Yung-Ya
Department of Chemistry and Biochemistry, University of California, Los Angeles, California, USA.
Department of Chemistry, National Tsing-Hua University, Hsinchu, Taiwan.
Magn Reson Med. 2015 Jul;74(1):33-41. doi: 10.1002/mrm.25632. Epub 2015 Apr 4.
Sensitive imaging of superparamagnetic nanoparticles or aggregates is of great importance in MR molecular imaging and medical diagnosis. For this purpose, a conceptually new approach, termed active feedback magnetic resonance, was developed.
In the presence of the Zeeman field, a dipolar field is induced by the superparamagnetic nanoparticles or aggregates. Such dipolar field creates spatial and temporal (due to water diffusion) variations to the precession frequency of the nearby water H magnetization. Sensitive imaging of magnetic nanoparticles or aggregates can be achieved by manipulating the intrinsic spin dynamics by selective self-excitation and fixed-point dynamics under active feedback fields.
Phantom experiments of superparamagnetic nanoparticles; in vitro experiments of brain tissue with blood clots; and in vivo mouse images of colon cancers, with and without labeling by magnetic nanoparticles, suggest that this new approach provides enhanced, robust, and positive contrast in imaging magnetic nanoparticles or aggregates for cancer detection.
The spin dynamics originated from selective self-excitation and fixed-point dynamics under active feedback fields have been shown to be sensitive to dipolar fields generated by magnetic nanoparticles. Magn Reson Med 74:33-41, 2015. © 2014 Wiley Periodicals, Inc.
超顺磁性纳米颗粒或聚集体的灵敏成像在磁共振分子成像和医学诊断中具有重要意义。为此，开发了一种概念上全新的方法，称为主动反馈磁共振。
在塞曼场存在的情况下，超顺磁性纳米颗粒或聚集体会感应出一个偶极场。这种偶极场会对附近水分子氢磁化的进动频率产生空间和时间（由于水扩散）上的变化。通过在主动反馈场下进行选择性自激发和定点动力学来操纵固有自旋动力学，可实现磁性纳米颗粒或聚集体的灵敏成像。
超顺磁性纳米颗粒的模型实验；有血凝块的脑组织的体外实验；以及有和没有磁性纳米颗粒标记的结肠癌小鼠体内图像表明，这种新方法在成像用于癌症检测的磁性纳米颗粒或聚集体时能提供增强的、稳健的和正性对比。
已证明，主动反馈场下源于选择性自激发和定点动力学的自旋动力学对磁性纳米颗粒产生的偶极场敏感。《磁共振医学》74:33 - 41, 2015。© 2014威利期刊公司。
