Modeling of the Magnetic Particle Imaging Signal Due to Magnetic Nanoparticles

 描述(申请人提供)：磁粒子成像(MPI)是一种新的断层成像技术，它实时绘制氧化铁磁性纳米颗粒(MNPs)的空间分布，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MNPs无毒，MPI是慢性肾脏疾病(CKD)患者的一种安全的成像选择，由于其敏感性，它适合于 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，人们的注意力转向了具有理想MPI信号特性的MNPs的开发。不幸的是，由于缺乏理论来预测由于MNP示踪剂引起的MPI信号，考虑到MNPs在典型的MPI典型的时变磁场中的有限松弛动力学，这些努力受到阻碍。正因为如此，以前开发MNP MPI示踪剂的大部分工作都局限于对合成颗粒进行反复试验表征，而没有一个指导其合理设计的理论。需要的是一个坚实的理论基础，以便合理设计未来几代MNP MPI示踪剂，并调整MPI磁场条件，以产生最佳的图像对比度和分辨率。拟议的研究将建立与MNP特性(例如，核尺寸、流体动力学直径、磁化强度、磁各向异性、颗粒-颗粒相互作用等)相关的理论基础。和MPI磁场条件(偏置和激励磁场强度、磁场梯度强度、扫描速率等)。至MPI信号强度和分辨率。该方法是独特的，与其他工作不同，因为我们将建立MNPs对MPI典型磁场响应的随机计算机模拟模型，考虑纳米粒子平移、物理旋转、内部偶极旋转和粒子-粒子磁相互作用。这些模型将使人们能够系统地研究MPI典型的粒子性质和磁场条件的大参数空间。这项拟议的工作意义重大，因为它将为粒子性质、MPI磁场条件和MPI信号强度和分辨率之间的关系提供亟需的理论理解。这项拟议的工作也具有重要意义，因为它将为合理设计具有最佳信号强度和分辨率的MNP MPI示踪剂提供规则，并可能建议MPI在MNP示踪剂位置和运动成像之外的新应用。这项拟议的工作具有创新性，因为它将通过开发计算机模拟平台来模拟MNPs对MPI中产生的磁场的响应，从而产生这一理论基础，通过结合粒子平移和旋转的布朗动力学模拟以及描述内部磁偶极旋转的Landau-Lifshitz-Gilbert方程，这是一种目前尚未探索的方法。这项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特性和MPI磁场条件的依赖性，产生指导未来几代MPI示踪剂和MPI应用的设计规则。

 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.