Axially unlimited elongation of a volume-covering sampling trajectory for a novel 3D MPI scanner with cylindrical field-of-view

本提案的目的是开发，模拟和技术验证磁颗粒成像（MPI）的创新数据采集方法，将线圈拓扑的技术复杂性降低到二维设置，并结合测量对象的连续平移，以便通过采样轨迹的线性延伸实现轴向无限的圆柱形测量场。成像系统的基本标准是高空间分辨率、高灵敏度和实时性。综合这些标准，MPI有可能制定新的标准。该过程是基于可视化纳米颗粒浓度，其核心由超顺磁性氧化铁（SPIO）制成。spio最重要的物理特性是非线性磁化和饱和行为。在正弦磁场的激励下，粒子磁化的非线性有助于信号的产生，并以非正弦的磁化变化响应，由此可以测量谐波。虽然MPI很好地满足了高空间分辨率、高灵敏度和实时性的要求，但所实现的原型系统的测量范围很小。因此，本文在轴向上扩展了测量范围。这是通过传统几何形状的梯度线圈和激励线圈的二维对称排列来实现的，它们包围了测量场，从而形成了圆柱形通道。利用平面轨迹对二维测量场进行采样，同时利用连续进给将测量对象平移通过测量场。所得到的采样点的线性轴向延长和体积覆盖路径导致在所述横向平面上的子采样。数据采集策略的关键是研究合适的插值策略来完成横断面的采样。对目前实现的三种MPI扫描仪拓扑（带圆柱形测量场的FFP扫描仪、带非对称线圈拓扑的单面FFP扫描仪和带圆柱形测量场的FFL扫描仪）进行基于仿真和测量的评估，将是实现三维实时MPI的基础一步，为人体全身MPI铺平道路。

The aim of this proposal is the development, simulation, and technical validation of an innovative data acquisition method for Magnetic Particle Imaging (MPI), reducing the technical complexity of the coil topology to a 2D setup combined with a continuous translation of the measuring object, in order to achieve an axially unlimited cylindrical measuring field by a linear elongation of the sampling trajectory. Essential criteria for an imaging system are a high spatial resolution, a high sensitivity, and real-time capability. Combining these criteria, MPI has the potential to set new standards. The procedure is based on visualizing the concentration of nanoparticles with cores made of superparamagnetic iron oxide (SPIO). The most important physical characteristics of the SPIOs are a non-linear magnetization and saturation behavior. The non-linearity of the particle magnetization, excited by a sinusoidal magnetic field, contributes to the signal generation, responding with a non-sinusoidal variation of the magnetization, from which harmonics can be measured. Although the criteria of high spatial resolution, high sensitivity and real-time capability are fulfilled in an excellent way using MPI, the realized prototype systems suffer from a very small measuring field. Due to this, the measuring field is extended in axial direction in this proposal. This is achieved by a two-dimensional, symmetrical arrangement of gradient coils and excitation coils in conventional geometry, enclosing the measuring field resulting in cylindrical access. The two-dimensional measuring field is sampled by a planar trajectory, while translating the measuring object with a continuous feed through the measuring field. The resulting linear axial elongated and volume covering path of the sampling point leads to a subsampling in the transversal plane. A key element of the data acquisition strategy is to research suitable interpolation strategies to complete the sampling in the transversal plane. Performing a simulation and measuring based evaluation of three currently implemented MPI scanner topologies (FFP scanner with cylindrical measuring field, single-sided FFP scanner with asymmetric coil topology, and FFL scanner with cylindrical measuring field) will be a fundamental step towards the realization of three-dimensional real-time MPI, paving the way for human full-body MPI.