Development of Magnetic Field Imaging System Using CT Technique.

本研究的目的是开发将CT技术应用于电磁感应测量的磁场成像系统。在1989年。首先进行了基础实验，确定了所研制系统的规格，然后根据规格制作了磁场成像系统。该系统重构区域直径为10cm，空间分辨率为0.5mm。1990年，利用该系统进行的实验证实了所开发系统的有效性。实验对永磁体泄漏磁场进行了成像，重建了永磁体的磁通密度和磁势分布。采集图像重建所需的整个投影数据需要2分钟，使用16位个人计算机计算重建需要20分钟。当空间分辨率设置为2mm时，收集投影数据和计算重建只需要3分钟。然后，验证了所开发的系统所获得的重建图像的定量精度。将重建图像与传统磁场测量工具高斯计的测量结果进行了比较，两者的测量结果基本一致。由此，研究中所开发的磁场成像系统的有效性得到了证实。然而，该系统在实际应用中还存在一些问题。由于需要360^ <s:1>范围内的投影，因此不可能对某些物体周围的磁场进行成像。对比重构区域更宽的磁场进行成像也是不可能的。这些问题将在今后的研究中得到解决。

The purpose of this study is to develop the magnetic field imaging system which applies CT technique to the electromagnetic induction measurement.In 1989. The basic experiment was performed for deciding the specifications of the developed system, and then, the magnetic field imaging system was produced according to the specification. In this system, the diameter of the reconstructed region is 10cm and the spatial resolution is 0.5mm.In 1990, the efficacy of the developed system was confirmed by the experiment performed using the system. In the experiment, the magnetic fields leaking from permanent magnets were imaged and the distribution of the magnetic flux density and the magnetic potential were reconstructed. It took 2 minutes to collect whole projection data which was required for image reconstruction, and 20 minutes to calculate the reconstruction using 16 bit personal computer. In case that the spatial resolution is set to 2mm, only 3 minutes were required for both collecting the projection data and calculating the reconstruction. Next, the quantitative accuracy of the reconstructed image obtained by the developed system was demonstrated. The comparison of the reconstructed image to the measurement using a gauss meter, which is a conventional tool for magnetic field measurement, shows that the both measurements were almost same.Consequently, the efficacy of the magnetic field imaging system developed in the research confirmed. However, there are some problems for the practical use of the system. It is impossible to image the magneic field surrounded by some object, since the projections in the range of 360^ﾟ are required. It is also impossible to image the magnetic field distributing wider than the reconstructed region. The problems will be solved in the future research.