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

该方案的目的是开发、模拟和技术验证用于磁粒子成像(MPI)的创新数据采集方法，将线圈拓扑的技术复杂性降低到2D设置，并结合测量对象的连续平移，以通过线性延长采样轨迹来实现轴向无限圆柱形测量场。成像系统的基本标准是高空间分辨率、高灵敏度和实时能力。结合这些标准，MPI有可能制定新的标准。这一过程是基于以超顺磁性氧化铁(SPIO)为核心的纳米颗粒浓度的可视化。SPIO最重要的物理特性是非线性磁化和饱和行为。由正弦磁场激发的粒子磁化的非线性有助于信号的产生，响应于磁化强度的非正弦变化，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，在本方案中，测量场沿轴向扩展。这是通过传统几何中的梯度线圈和励磁线圈的二维对称排列来实现的，将测量场包围起来，从而形成圆柱形通道。通过平面轨迹对二维测量场进行采样，同时以连续馈送的方式平移测量对象通过测量场。由此产生的采样点的线性轴向拉长和体积覆盖路径导致在横向平面上的次采样。数据采集策略的一个关键是研究合适的插补策略，以完成横截面上的采样。对目前实现的三种MPI扫描器(柱面测量场的FFP扫描器、非对称线圈的单面FFP扫描器和柱面测量场的FFL扫描器)进行仿真和测量评估将是实现三维实时MPI的基础步骤，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.