Development of Magnetic Field Imaging System Using CT Technique.

本研究的目的是研制一种将CT技术应用于电磁感应测量的磁场成像系统。为了确定所研制系统的技术指标，进行了基础实验，并根据技术指标制作了磁场成像系统。在该系统中，重建区域的直径为10 cm，空间分辨率为0.5 mm。1990年，利用该系统进行的实验验证了该系统的有效性。在实验中，对永磁体泄漏的磁场进行了成像，并重建了磁通密度和磁势的分布。采集图像重建所需的全部投影数据需要2分钟，使用16位个人计算机计算重建需要20分钟。在空间分辨率设置为2 mm的情况下，采集投影数据和计算重建只需要3分钟。其次，对所开发的系统所获得的重建图像的定量精度进行了验证。将重建的图像与传统的磁场测量工具高斯计的测量结果进行比较，结果表明两者的测量结果基本相同，从而证实了本研究开发的磁场成像系统的有效性。但是，该系统在实际应用中还存在一些问题。要对物体周围的磁场成像是不可能的，因为需要在360^ﾟ的范围内投影。也不可能成像比重建区域更宽的磁场分布。这些问题将在未来的研究中得到解决。

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.