Development of L-band Electron Spin Resonance Imaging System for Small Animals

本课题研制了一种利用l波段微波对大鼠或小鼠进行ESR成像的新型系统。ESR成像系统的结构本课题研制的系统由l波段ESR光谱仪、场梯度线圈和数据处理器组成。该光谱仪配备了环隙谐振器，环隙谐振器中有一个电屏蔽，工作频率为700- 800hz，频率约为30 mT.2。使用了几种氮氧自由基，并分别静脉注射到大鼠体内。将老鼠的头插入谐振器。成功地对头部进行了ESR观测，获得了较好的信噪比。ESR信号随时间衰减。我们发现，大鼠对硝基化合物的代谢和排泄可以通过观察其衰变率来分析。ESR成像(1)二维图像：在生理盐水溶液中使用硝基3-氨基甲酰-2,2,5,5，-四甲基吡啶- 1-酰氧基（CPROXYL）作为显像剂。通过在XY、YZ和ZX平面上的投影，获得了小鼠腿部和头部自由基分布的二维图像。图像与受试者体内氮氧化物自由基的位置和分布吻合较好。(2)ESR-CT图像：大鼠腹腔注射CPROXYL。在横切面（水平和横轴，厚度1.5mm）上进行成像。这些图像是名副其实的ESR-CT。在大鼠头部的横切面图像中，富氮氧化物区与缺氮氧化物区明显区分开。缺乏氮氧化物的区域与大鼠的大脑相对应。由于大脑有血脑屏障，CPROXYL可能在这里保留，其在大脑中的浓度很低，因此ESR信号较弱。它在血液中的高浓度会发出强烈的ESR信号。我们相信我们的系统已经发展成为一种l波段ESR成像系统，可用于研究含有外源性自由基的大鼠或小鼠。少

We developed a novel ESR imaging system for rats or mice using the L-band microwave.l.Construction of ESR imaging system The system developed in this project is composed of an L-band ESR spectrometer, a field gradient coil and a data processor. The spectrometer is equipped with a loop-gap resonator having an electric shield in the loop, and is operated at 700-800NHz under ca. 30 mT.2.in vivo ESR spectroscopy Several kinds of nitroxide radicals were used and each was intravenously injected into the rat. The rat head was inserted into the resonator. ESR was successfully observed for the head and obtained the spectra with a good S/N ratio. The ESR signal decayed with time. We showed that the metabolism and /or the excretion in the rat for the nitroixed can be analyzed by the observation of the decay rate.3.ESR imagings (1)Two dimensional images: A nitroxide radical, 3-carbamoyl-2,2,5,5,-tetramethylpyrrolidine- 1-yloxy (CPROXYL), was used as an imaging agent in saline solution. Two dimensi … More onal images of the distribution of the radical in the mouse legs or the rat head were made by the projection to the XY, YZ and ZX planes. The images corresponded well to the location and the distribution of the nitroxide radical in the subjects. (2)ESR-CT images: The rat received the intraperitoneal administration of CPROXYL. The imaging was made on the distribution in the cross sectional plane (horizontal and transaxial, 1.5mm in thickness). The images deserve the name of ESR-CT. In the cross-sectional image of the rat head the nitroxide rich region was clearly distinguished from the deficient region. The nitroxide deficient areas corresponded well to brain of the rat. Since the brain holds the blood brain barrier, CPROXYL may be retained here and its concentration in the brain is quite low, which gives weak ESR signals.Its high concentration in the blood gives strong ESR signals.We believe our system has been well developed as an L-band ESR imaging system and is available to studies on a rat or a mouse containing exsogenous radicals. Less