Dynamic recording of lateral biomagnetic field distributions with integrated optical magnetometers (magnetic field camera)

厘米级物体的高磁场、高横向和高时间分辨率的磁场测量在物理和生物医学研究中具有重要意义。利用现有的基于SQUID阵列的测量技术，由于低温冷却，分辨率受到传感器尺寸和传感器-目标距离等技术因素的限制。光泵式磁强计(OPM)能够以毫米分辨率首次测量磁场。然而，这些测量目前是通过扫描感兴趣的对象来顺序执行的。这防止了具有高空间和时间分辨率的磁场的同步测量。在这个项目中，我们希望开发新的方法和技术，允许测量厘米大小的物体的磁场，横向分辨率在毫米范围内，磁场分辨率在皮特斯拉范围内，带宽在100赫兹。在大约50微特斯拉的外部磁场下，测量应该是可行的，这是我们纬度地球磁场的典型强度，而不需要昂贵的磁屏蔽。为了实现这一目标，需要开发新型的光泵磁强计。这既需要为光泵磁力计开发一种新的工作模式，首次允许并行动态记录二维磁场，也需要使集成的光学吸收池适应新的工作模式和目标横向分辨率的要求。此外，正在开发解决磁逆问题的新方法，这种方法一方面允许调整测量系统的参数，另一方面允许重建被检查物体内部的磁场来源。记录系统和重建算法将根据具有特殊技术模型的测量结果进行验证。这一创新测量系统的实现开辟了多种应用领域。一个重要的例子是动物实验研究中生物磁场的测量。具有高空间和时间分辨率的小动物(例如小鼠)的磁心图测量可用于监测具有高通过率的药物的效果。小动物脑磁图的测量对癫痫活动的神经科学研究具有很高的兴趣，由于小动物大脑皮层面积较小，需要以高空间分辨率重建皮质内电流。

The measurement of magnetic fields of centimeter-sized objects with high magnetic-field, lateral and temporal resolution is of great interest for physical and biomedical research. Using current measurement technologies based on SQUID arrays, the resolution is limited by technological factors such as the sensor size and the sensor-target-distance due to the cryogenic cooling. Optically pumped magnetometers (OPM) allow for first measurements of magnetic fields with a millimeter resolution. However, these measurements are currently performed sequentially by scanning the object of interest. This prevents a synchronous measurement of the magnetic field with high spatial and temporal resolution. In this project, we want to develop new methods and technologies that allow for the measurement of magnetic fields of centimeter-sized objects with lateral resolutions in the range of millimeters, a magnetic field resolution in the range of pico Tesla, and a bandwidth of 100 Hz. The measurements should be feasible at external magnetic fields of about 50 micro Tesla, the typical strength of the earth magnetic field in our latitudes, without the need of costly magnetic shielding. To realize this objective, novel optically pumped magnetometers need to be developed. This requires both the development of a new mode of operation for optically pumped magnetometers, which, for the first time, allows for the parallel dynamic recording of two-dimensional magnetic fields, as well as the adaptation of integrated optical absorption cells to the requirements arising from the new mode of operation and the targeted lateral resolution. In addition, new methods for solving the magnetic inverse problem are to be developed, which allow on the one hand to adjust the parameters of the measurement system and on the other hand to reconstruct the sources of the magnetic field inside the examined object. The recording system and the reconstruction algorithms are to be validated against measurements with special technical phantoms. The realization of this innovative measurement system opens up a variety of applications. An important example is the measurement of biomagnetic fields in animal experimental research. The measurement of magnetocardiograms of small animals (e.g. mice) with high spatial and temporal resolution could e.g. be used for monitoring the effect of drugs with high throughput rates. The measurement of magnetoencephalograms of small animals is of high interest for neuroscientific research on epileptic activity, for which intracortical currents need to be reconstructed with high spatial resolution due to the small size of cortical areas in small animals.