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

该提案的目的是开发、模拟和技术验证一种用于磁粒子成像（MPI）的创新数据采集方法，将线圈拓扑结构的技术复杂性降低到与测量对象的连续平移相结合的2D设置，以便通过线性延长采样轨迹来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、高灵敏度和实时能力。结合这些标准，MPI有可能制定新的标准。该过程是基于可视化的纳米粒子的浓度与超顺磁性氧化铁（SPIO）制成的核心。SPIO最重要的物理特性是非线性磁化和饱和行为。由正弦磁场激发的颗粒磁化的非线性有助于信号生成，响应于磁化的非正弦变化，从中可以测量谐波。虽然高空间分辨率，高灵敏度和实时性的标准，在一个很好的方式使用MPI实现，实现的原型系统遭受从一个非常小的测量领域。因此，在该方案中，测量场在轴向方向上延伸。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布置来实现的，包围测量场，从而形成圆柱形通路。通过平面轨迹对二维测量场进行采样，同时通过测量场连续进给平移测量对象。所得到的线性轴向伸长和体积覆盖路径的采样点导致在横向平面中的二次采样。数据采集策略的一个关键要素是研究合适的插值策略来完成横截平面内的采样。对目前实施的三种MPI扫描仪拓扑结构（具有圆柱形测量场的FFP扫描仪、具有非对称线圈拓扑结构的单侧FFP扫描仪和具有圆柱形测量场的FFL扫描仪）进行基于模拟和测量的评估将是实现三维实时MPI的基本步骤，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.