The development of an ESR NMR hybrid imaging system for observation of free radicals in biological systems

本研究的目的是开发一种ESR/NMR混合成像系统，在该系统中，人们可以在不移动样品的情况下获得样品的ESR图像（自由基成像）和NMR图像（解剖成像）。首先，制备了ESR/NMR谐振腔。它由ESR谐振器、桥式环隙谐振器（730 MHz）、核磁共振谐振器、电磁线圈和可变电容器组成的LC电路（27 MHz）组成。前者位于后者的内部。通过使用ESR/NMR谐振器，可以对幻影进行CW-ESR， CW-NMR和脉冲NMR测量。其次，制备了用于核磁共振成像的场梯度线圈。为了在屏蔽盒中对样品施加脉冲状场梯度，必须在屏蔽盒中安装场梯度线圈，因此制作了可用于屏蔽盒侧壁的包含3个梯度线圈和屏蔽的四层电板。利用ESR/NMR谐振器、核磁共振梯度线圈和ESR主电磁铁，对幻体和小鼠进行核磁共振成像（自旋回波和二维FFT）。由于ESR主磁体磁场的不均匀和不稳定，所得到的图像显示出强度不均匀和畸变。为了克服这一问题，需要开发可切换到下场进行ESR测量的核磁共振主线圈。

The aim of this study is development of an ESR/NMR hybrid imaging system, where one can obtain ESR image (free radical imaging) and NMR images (anatomical imaging) of a sample without moving the sample. First, an ESR/NMR resonator was fabricated. It consisted of an ESR resonator, a bridged loop-gap resonator (730 MHz), and an NMR resonator, an LC circuit (27 MHz) of a solenoid coil and variable capacitor. The former was located inside the latter. By using the ESR/NMR resonator, CW-ESR, CW-NMR, and pulsed NMR measurements of a phantom could be made. Second, field gradient coils for NMR imaging were fabricated. To apply pulse-shaped field gradients to a sample in a shield case, field gradient coils must be located in the case, so four-layered electric board including 3 gradient coils and shield that could be used for side wall of the shield case was fabricated. By using the ESR/NMR resonator, the NMR gradient coils and main electromagnet for ESR, NMR imaging (spin echo and 2D FFT) of the phantom and mice was performed. Because of inhomogenous and unstable field caused by the ESR main magnet, the images obtained showed inhomogenous intensity and distortion. To overcome this problem, development of NMR main coil that can be switch to lower field for ESR measurement will be needed.