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Development of a novel MPI scanner based on a field free line

基于无场线的新型 MPI 扫描仪的开发

基本信息

批准号：
270315379
负责人：
Professor Dr. Thorsten Buzug
金额：
--
依托单位：
Institut für Medizintechnik (IMT)
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2015
资助国家：
德国
起止时间：
2014-12-31 至 2017-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/270315379?language=en
关键词：
Development novel MPI scanner based

项目摘要

The purposes of the presented project are the design, realization, and investigation of a real-time capable Magnetic Particle Imaging (MPI) scanner with an innovative topology, where for the first time rotating permanent magnets are used for construction. Of great relevance are the minimized power loss and the achievable size of the field of view. Essential criteria for a clinically successful tomographic imaging device are a high spatial resolution, a high sensitivity, the real-time capability and a minimal risk for the patient. Considering a combination of these criteria, Magnetic Particle Imaging (MPI) is setting new standards. The modality is based on the visualization of nanoparticles with a core that consists of super-paramagnetic iron oxide (SPIO).The most important physical characteristics of the SPIOs are the non-linear magnetization curve and the saturation behavior. The non-linearity of the particle magnetization enables signal generation, by causing the particles to emit a non-sinusoidal electromagnetic signal, when subjected to a sinusoidally oscillating magnetic field (drive field). The higher harmonics of this signal can then be measured. An additional magnetic gradient field (selection field) is used for spatial encoding. This field is generated in a way that all particles outside a distinct point, where the resulting magnetic flux density vanishes (FFP: field-free point), are in magnetic saturation. This way, spatial encoding is achieved, since only particles inside the FFP generate a signal.The sensitivity of the technique can be greatly improved by using a field-free line (FFL) instead of an FFP. Sufficient information for a CT-like spatial reconstruction of the particle distribution is acquired, when the FFL is slowly rotated and quickly shifted over the field of view.So far, the realization of real-time capable FFL-scanners failed worldwide, due to the high power losses in the selection field generating electromagnetic coils. The key point for the proposed research project is the development of the first dynamical FFL scanner that generates the FFL-selection-field with permanent magnets. For the geometry of the magnets an innovative scanner topology will be utilized.The reduction of the number of coils will reduce the coupling of the individual signal paths, which typically leads to a reduction of the magnetic field quality and to a very high energy demand. Additionally, no coils, power sources and analogue filters are needed for the generation of the selection field. However, the main advantage will be the reduction of power losses to below 0.1 % of a comparable scanner with electromagnetic selection field coils. Additionally, due to the mechanical FFL rotation, the influence of the time dependency of the selection field on the imaging process can be analyzed.

本项目的目的是设计，实现和研究具有创新拓扑结构的实时磁粒子成像（MPI）扫描仪，其中首次使用旋转永磁体进行施工。最小化的功率损耗和可实现的视场尺寸具有很大的相关性。临床上成功的断层成像设备的基本标准是高空间分辨率、高灵敏度、实时能力和对患者的最小风险。考虑到这些标准的组合，磁粒子成像（MPI）正在制定新标准。该模式是基于可视化的纳米粒子的核心组成的超顺磁性氧化铁（SPIO）的最重要的物理特性是非线性磁化曲线和饱和行为。当受到正弦振荡磁场（驱动场）时，通过使颗粒发射非正弦电磁信号，颗粒磁化的非线性使得能够产生信号。然后可以测量该信号的高次谐波。额外的磁梯度场（选择场）用于空间编码。这个场是以这样的方式产生的，即在所产生的磁通量密度消失的不同点（FFP：无场点）之外的所有粒子都处于磁饱和状态。由于只有FFP内部的粒子才会产生信号，因此可以实现空间编码。通过使用无场线（FFL）代替FFP，可以大大提高该技术的灵敏度。FFL在视场内缓慢旋转并快速移动，可获得足够的粒子分布信息，实现类似CT的空间重建。迄今为止，由于选择场产生电磁线圈的高功率损耗，FFL扫描仪的实时实现在世界范围内都失败了。该研究项目的关键点是开发第一台动态FFL扫描仪，该扫描仪使用永磁体产生FFL选择场。对于磁体的几何形状，将采用创新的扫描器拓扑结构。线圈数量的减少将减少各个信号路径的耦合，这通常会导致磁场质量的降低和非常高的能量需求。此外，不需要线圈、电源和模拟滤波器来产生选择场。然而，主要优点将是将功率损耗减少到具有电磁选择场线圈的可比扫描仪的0.1%以下。此外，由于机械FFL旋转，可以分析选择场的时间依赖性对成像过程的影响。