Investigation of particle mobility in Magnetic Particle Imaging (MPI)

该项目旨在借助已定义的粒子基质系统对MPS/MPI中的粒子迁移率进行量化。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水动力体积。通过分析MPS/MPI信号产生过程的相互作用和建模，可以从测量到的粒子信号中推断出粒子的迁移率。结果可以转移到成像系统中，允许对粒子-基质系统进行空间和及时的解析分析。1mm分辨率和1hz成像速率)。考虑粒子-基质相互作用的粒子迁移成像对于许多生物医学和技术应用具有重要意义。在项目背景下，将分析各种颗粒基质系统（包括商业颗粒以及来自SPP1681合作伙伴的颗粒）。介质的粘度提供了一个可调的参数，因此粘性颗粒-基质系统可以作为颗粒迁移率研究的参考系统。MPS/MPI中粘度估计的确定程度可以通过流变参考测量来验证。对于从MPS数据估计粘度，考虑了基于校准的方法，这需要测量和评估粘度系列。此外，我们试图在MPS信号中建立粘度贡献模型，这在颗粒迁移率和测量信号之间建立了直接联系。衍生的迁移率估计方法在MPS中的适用性将在生物颗粒基质系统（即血浆、细胞、组织）中进行测试。从MPS的黏度研究出发，提出了磁颗粒成像的方法和模型。移动感知MPI成像是MPI功能成像的重要一步，其中体素中的局部纳米/微粘度成像补充了磁性纳米颗粒示踪剂的空间浓度分布。体素平均宏观粘度与示踪剂局部迁移率之间的关系是非常有趣的，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可量化测定因颗粒-基质系统的非牛顿粘度或粘弹性而变得复杂。最后对粘弹性粒子系统和生物环境中的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.