Development of an EPR imager for the cerebral function analysis

这项研究的目标是开发一种用于脑功能分析的EPR成像仪。解决了EPR成像中图像重建的一个关键问题。系统地研究了获得最佳图像分辨率的滤波函数的选择。直接傅里叶变换重构(DFTR)方法适用于了解滤波器特性的影响。在滤波函数中，我们考虑了光谱的信噪比来确定截止频率。虽然用这种技术重建图像的有效性应该在更逼真的样本成像中得到验证，但我们的基本概念是可信的。噪声的频率特性可以看作是白噪声。此外，使用能够远程控制谐振频率的光学设备的技术被开发用于诸如环隙谐振器之类的体积线圈。通过磁场调制实现了电磁感应较小的调谐电路，这成为变容二极管使用中的一个问题。采用自动调谐控制，降低了灵敏度，但提高了测量的稳定性。今后有必要提高灵敏度。虽然这是为了一个很大的目标，即开发用于脑功能分析的EPR成像仪而进行的研究，但我们解决了一些技术问题。在图像重建中选择截止频率的系统方法和控制共振频率的光学技术对于EPR研究是有用的。

The goal of this study was the development of an EPR imager for the cerebral function analysis. A key problem of the image reconstruction in EPR imaging was tacked. A systematic selection of filtering function to obtain the optimum image resolution was investigated. The direct Fourier transformation reconstitution(DFTR)method is suitable to understand the effect of the filter characteristics. We paid attention to the signal-to-noise ratio of the spectra to determine the cut-off frequency in the filter function. Although the usefulness of the image reconstruction by this technique should be verified in the imaging of more realistic samples, our fundamental concept was confiemed. The frequency characteristics of the noise can be treated as the white noise. Moreover, the technology using the optical device that enables remote control of the resonant frequency was developed for of the volume coil such as a loop-gap resonator. This realized the tuning circuit with less electromagnetic induction by magnetic field modulation which becomes a problem in the use of a varactor diode. The sensitivity was decreased by using the automatic tuning control, but the stability of the measurements was improved. It is necessary to improve the sensitivity in the future. Although it was a research for a very large goal, namely, the development of the EPR imager for the cerebral function analysis, we solved some technical problems. The systematic approach to selecting the cut-off frequency in image reconstruction and the optical technique to control the resonance frequency are useful for EPR study.