Modeling of the Magnetic Particle Imaging Signal Due to Magnetic Nanoparticles

 描述（由申请人提供）：磁性粒子成像（MPI）是一种新的断层成像技术，可真实的实时绘制氧化铁磁性纳米粒子（MNP）的空间分布，其空间分辨率与其他生物医学成像技术相当或更好。由于氧化铁MNP无毒，MPI是慢性肾病（CKD）患者的安全成像替代方案，并且由于其敏感性，它适用于 血管造影术、细胞追踪、癌症成像、炎症成像、主要器官成像和冠状动脉成像。最近，注意力已经转向具有理想MPI信号特性的MNP的开发。不幸的是，这些努力受到阻碍的理论，预测MPI信号由于MNP示踪剂，考虑到有限弛豫动力学的MNP在随时间变化的磁场典型的MPI。正因为如此，大多数关于开发MNP MPI示踪剂的先前工作仅限于合成颗粒的试错表征，而没有指导其合理设计的理论。所需要的是一个坚实的理论基础，这将允许合理设计未来几代的MNP MPI示踪剂和MPI磁场条件的调整，以产生最佳的图像对比度和分辨率。拟议的研究将发展一个理论基础，涉及MNP属性（例如，核尺寸、流体动力学直径、畴磁化、磁各向异性、粒子-粒子相互作用等）和MPI磁场条件（偏置和激励场强度、磁场梯度强度、扫描速率等）MPI信号强度和分辨率。所提出的方法是独特的，有别于其他工作，因为我们将开发随机计算机模拟模型的MNP的MPI典型的磁场的响应，考虑到纳米粒子的平移，物理旋转，内部偶极子旋转，和粒子-粒子磁相互作用。这些模型将使系统的大参数空间的粒子特性和磁场条件的MPI的典型研究。所提出的工作是有意义的，因为它将提供一个急需的理论理解之间的关系，船舶的粒子属性，MPI磁场条件，和MPI信号强度和分辨率。所提出的工作也是重要的，因为它将产生规则的MNP MPI示踪剂的合理设计与最佳的信号强度和分辨率，也可以建议新的应用程序的MPI超越成像的MNP示踪剂的位置和运动。所提出的工作是创新的，因为它将产生这个理论基础，通过计算机模拟平台的发展，通过结合布朗动力学模拟粒子的平移和旋转和Landau-Lifshitz-吉尔伯特方程描述内部磁偶极旋转，目前尚未探索的方法，在MPI中产生的磁场建模的MNP的响应。拟议的工作也是创新的，因为这些计算机模拟平台将被用来探索MPI信号对MNP属性和MPI磁场条件的依赖性，产生设计规则，以指导未来几代MPI示踪剂和MPI应用程序的开发。

 DESCRIPTION (provided by applicant): Magnetic Particle Imaging (MPI) is a new tomographic imaging technique that maps the spatial distribution of iron oxide magnetic nanoparticles (MNPs) in real time and with spatial resolution that is on par or better than other biomedical imaging techniques. Because iron oxide MNPs are nontoxic, MPI is a safe imaging alternative for Chronic Kidney Disease (CKD) patients and due to its sensitivity it is suitable for angiography, cell tracking, cancer imaging, inflammation imaging, imaging major organs, and imaging of coronary arteries. Recently attention has shifted towards development of MNPs with ideal MPI signal characteristics. Unfortunately, these efforts are hampered by a lack of theories that predict the MPI signal due to MNP tracers, taking into account the finite relaxation dynamics of MNPs in time-varying magnetic fields typical of MPI. Because of this, most prior work on development of MNP MPI tracers has been limited to trial-and-error characterization of synthesized particles, without a theory guiding their rational design. What is needed is a solid theoretical foundation that will allow rational design of future generations of MNP MPI tracers and tuning of MPI magnetic field conditions to yield optimal image contrast and resolution. The proposed research will develop a theoretical foundation relating MNP properties (e.g., core size, hydrodynamic diameter, domain magnetization, magnetic anisotropy, particle-particle interactions, etc.) and MPI magnetic field conditions (strength of bias and excitation field, magnetic field gradient strength, scan rate, etc.) to the MPI signal strength and resolution. The proposed approach is unique and distinct from other work because we will develop stochastic computer simulation models of the response of MNPs to the magnetic fields typical of MPI, taking into account nanoparticle translation, physical rotation, internal dipole rotation, and particle-particle magnetic interactions. These models will enable systematic study of the large parameter space of particle properties and magnetic field conditions typical of MPI. The proposed work is significant because it will provide a much-needed theoretical understanding of the relation- ship between particle properties, MPI magnetic field conditions, and MPI signal strength and resolution. The proposed work is also significant because it will yield rules for the rational design of MNP MPI tracers with optimal signal strength and resolution and could also suggest novel applications of MPI beyond imaging of MNP tracer location and motion. The proposed work is innovative because it will yield this theoretical foundation through development of computer simulation platforms to model the response of MNPs to the magnetic fields generated in MPI through a combination of Brownian dynamics simulations of particle translation and rotation and the Landau-Lifshitz-Gilbert equation describing internal magnetic dipole rotation, an approach that is currently unexplored. The proposed work is also innovative because these computer simulation platforms will be used to explore the dependence of the MPI signal on MNP properties and MPI magnetic field conditions, yielding design rules to guide development of future generations of MPI tracers and MPI applications.