Investigation of particle mobility in Magnetic Particle Imaging (MPI)

该项目旨在借助已定义的粒子矩阵系统来量化MPS/MPI中的粒子迁移率。颗粒迁移率是通过布朗时间常数来定义的，它涵盖了介质的粘度和颗粒的流体动力学体积。通过分析MPS/MPI中的相互作用和信号产生过程的模型，可以从测量的粒子信号中推断出粒子的迁移率。结果可以被传输到成像系统，从而允许对颗粒-基质-系统(约.1 mm分辨率和1赫兹成像率)。考虑颗粒-基质-相互作用的颗粒迁移率成像对于许多生物医学和技术应用具有重要意义。在项目范围内，将对各种颗粒基质系统(包括商业颗粒以及来自SPP1681合作伙伴的颗粒)进行分析。介质的粘度提供了一个可调的参数，因此粘性颗粒基质系统可作为颗粒迁移率研究的参照系。MPS/MPI中粘度估算的确定程度可以通过流变学参考测量来验证。为了从MPS数据中估计粘度，考虑了一种基于校准的方法，该方法需要测量和评估粘度序列。此外，我们试图对MPS信号中的粘度贡献进行建模，这在粒子迁移率和测量信号之间建立了直接的联系。用于MPS中迁移率估计的衍生方法的适用性将针对生物颗粒-基质系统进行测试，即血浆、细胞、组织。在MPS粘度研究中，磁粉成像的方法和模型将被采用。迁移率感知的MPI成像是迈向MPI功能成像的重要一步，在MPI中，体素中的局部纳米/微粘度被成像为对磁性纳米粒子示踪剂的空间浓度分布的补充。体素平均宏观粘度和示踪剂的局部迁移率之间的关系是非常重要的，可以在SPP1681的框架内共同处理。在实际应用场景中，即在生物介质中，颗粒浓度和颗粒迁移率的定量确定因颗粒-基质-系统的非牛顿粘度或粘弹性而变得复杂。对生物环境中的粘弹性粒子系统和相互作用进行了总结分析。

The project aims for the quantification of the particle mobility in MPS/MPI with the help of defined particle-matrix-systems. Particle mobility is defined via the Brownian time constant and covers the viscosity of the medium and the hydrodynamic volume of the particles. By analyzing interactions and modelling of the signal generation process in MPS/MPI, particle mobility can be deducted from the measured particle signal. The results can be transferred into the imaging system allowing a spatially and timely resolved analysis of the particle-matrix-system (approx. 1 mm resolution and 1 Hz imaging rate). Imaging of the particle mobility considering particle-matrix-interactions is of great importance for numerous biomedical and technological applications. In the project context various particle-matrix-systems (including commercial particles as well as particles from partners in the SPP1681) are to be analyzed. The viscosity of the medium provides a tunable parameter, so that viscous particle-matrix-systems serve as a reference system for particle mobility studies. The degree of determination for viscosity estimation in MPS/MPI can be verified through rheological reference measurements. For the estimation of viscosity from MPS data a calibration-based approach is considered, which requires a viscosity series to be measured and evaluated. Furthermore, we seek to model the viscosity contribution in the MPS signal, which draws a direct connection between the particle mobility and the measurement signal. Applicability of the derived methods for mobility estimation in MPS will be tested against biological particle-matrix-systems, i.e. plasma, cells, tissue. From viscosity studies in MPS, the methods and models will be adopted for Magnetic Particle Imaging. Mobility-aware MPI imaging constitutes an important step towards functional imaging in MPI, where the local nano-/micro-viscosity in a voxel is imaged supplementary to the spatial concentration distribution of the magnetic nanoparticle tracer. The relation between a voxel-averaged macroscopic viscosity and the local mobility of the tracer is of great interest and can be dealt with collectively within the framework of the SPP1681. In practical application scenarios, i.e. in biological media, the quantifiable determination of particle concentration and particle mobility is complicated by non-Newtonian viscosity or viscoelasticity of the particle-matrix-system. A concluding analysis of viscoelastic particle systems and interactions in biological environments is projected.