First Low Field Magnetic Particle Imaging System for Neurological Applications in Humans

磁性粒子成像（MPI）是一种成像技术，可以确定磁性纳米粒子的局部分布。经过快速的技术发展，该方法目前正在进行临床前试验，其中它已经在各种医疗应用中显示出很高的潜力。特别是，MPI已经在诸如颅脑创伤和中风等神经问题以及脑动脉瘤成像方面取得了开创性的成果。然而，到目前为止，这些结果只能在小动物模型中显示，因为迄今为止开发的MPI扫描仪太小，无法对大型动物或人类进行测量。本项目的目标是开发一种用于神经问题的MPI扫描仪，它也适用于人体检查。基于已经证明可行性的原型，我们将设计一个最适合神经重症监护室监测任务的系统。由于其体积小和优化的线圈，它不需要专门的冷却，因此可以直接安装在病人的床上。由于有效的信号路由和对室内干扰的检测，该系统也可以在屏蔽室外运行。这使得在中风治疗后的几个小时内对患者进行永久监测，而不是暴露于X射线。到目前为止，这些病人的CT图像只在病情急性恶化的情况下才拍摄，而且费用高昂。现有的原型是以低场MPI系统实现的，在水平方向上达到高达6毫米的空间分辨率，在垂直方向上达到28毫米，选择场的梯度强度约为10毫米。0.2 T/m。在该项目中，将设计一个二维激励单元和一个三维接收单元，满足三个基本要求。它们非常高效，不需要主动冷却，电气安全，也可以毫不犹豫地用于人体实验，并且经过噪声优化，可以进一步提高现有原型的灵敏度。由于二维激励和三维接收，头部扫描仪将实现约为2.5的各向同性分辨率。通过优化测量序列，扫描仪将实现约5 mm的高时间分辨率。对于边长为100 mm的三维测量体积，250 ms。对于数据重建算法，开发了考虑磁场缺陷的算法。所开发的MPI扫描仪和重建算法进行了测试，在现实的模拟人体头部的血管系统的脑电波幻影。

Magnetic Particle Imaging (MPI) is an imaging technique that allows the local distribution of magnetic nanoparticles to be determined. After rapid technological development, the method is currently undergoing preclinical trials, in which it has already shown a high potential in various medical applications. In particular, MPI has already achievedpioneering results in neurological questions such as craniocerebral trauma and stroke, as well as in the imaging of brain aneurysms. So far, however, the results could only be shown in small animal models because the MPI scanners developed so far are too small for measurements on large animals or humans.The goal of this project is the development of an MPI scanner for neurological questions, which is also suitable for human examination. Based on a prototype with which the feasibility has already been demonstrated, we will design a system that is optimally suited for monitoring tasks in the neurological intensive care unit. Due to its small sizeand optimized coils, it does not require a dedicated cooling and can therefore be mounted directly on the patient’s bed. The system can also be operated outside shielded rooms thanks to efficient signal routing and the detection of disturbances in the room. This enables permanent monitoring of the patient in the hours following stroke treatmentwithout exposure to X-rays. Up to now, CT images of these patients are only taken in cases of acute deterioration and at great expense.The existing prototype is implemented as a low-field MPI system and achieves a spatial resolution of up to 6mm in the horizontal direction and 28 mm in the vertical direction with a gradient strength of the selection field of approx. 0.2 T/m. Within the project, a two-dimensional excitation unit and a three-dimensional receiver unit will be designed which meets three essential requirements. They are highly efficient and do not require active cooling, they are electrically safe and can also be used in human experiments without hesitation and they are noise optimized so that the sensitivity of the existing prototype can be further increased. Due to the two-dimensional excitation and three-dimensional reception, the head scanner will achieve an isotropic resolution of approx. 5 mm. By optimizing the measurement sequence, the scanner will achieve a high temporal resolution of approx. 250 ms for a three-dimensional measurement volume with an edge length of 100 mm. For data reconstruction algorithms are developed, which consider imperfections of the magnetic fields. The developed MPI scanner and the reconstruction algorithms are tested on realistic flow phantoms, which simulate the vascular system of a human head.