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

• Applicants: Professor Dr.-Ing. Matthias Gräser; Professor Dr.-Ing. Tobias Knopp
• Subject Area: Medical Physics, Biomedical Technology
• Term: from 2019 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 428087693

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.

• DFG Programme: Research Grants