Time-Domain Radio Frequency EPR Imaging-猫眼课题宝

时域射频 EPR 成像

DOI：

发表时间：

2003

期刊：

影响因子：

通讯作者：

中科院分区：

文献类型：

作者：

S. Subramanian;James B. Mitchell;M. Krishna

本文描述了用于活体应用的300 MHz射频时域EPR光谱仪/成像仪的研制。概述了我们解决非成对自旋系综弛豫时间很短的挑战的方法，如宽带低Q谐振器的设计，提供亚微秒脉冲的必要性，减少接收器恢复时间(谐振器死区时间和前置放大器恢复时间)，以千兆采样/S速率采样时间响应的需要等。通过将测量频率降低到射频范围来降低灵敏度，需要使用快速信号平均策略。光谱仪/成像仪可以定位整个鼠标大小的物体，并且可以使用基于三芳基甲基的窄线自旋探针、在静态梯度存在的情况下使用体积激发和过滤反投影技术来获得分辨率良好的二维和三维图像。概述了成像模式，并给出了来自体模和活体研究的典型例子。还描述了使用由组织pO2的变化带来的局部弛豫时间差来提供图像中的对比度。时间域射频FT-EPR方法是一种重要的成像工具，可以提供肿瘤缺氧、血管血流分布和体内pO2的有价值的信息，并将作为CT、BOLD-MRI和PET的有用辅助手段。

The development of a radio frequency time domain EPR spectrometer/imager operating at 300 MHz for in vivo applications is described. The ways we have addressed the challenges originating from the very short relaxation times of the unpaired spin ensemble such as the design of broad band low Q resonators, the necessity of providing ultra short pulses of sub microsecond duration, reduction of the receiver recovery time (resonator dead time and preamplifier recovery time), the need to sample the time response at Gigasamples/s rates, etc., are outlined. The reduction in the sensitivity by lowering the frequency of measurement to radio frequency regime necessitates the use of fast signal averaging strategies. The spectrometer/imager can address objects up to the size of a whole mouse, and well resolved 2-D and 3-D images could be obtained using narrow line spin probes based on triarylmethyl radicals, using volume excitations in presence of static gradients and filtered back-projection techniques. The imaging modalities are outlined and representative examples from phantoms and in vivo studies are presented. The use of local relaxation time differences brought about by changes in the tissue pO2to provide contrasts in the images is also described. Time domain RF FT-EPR method may turn out to be an important imaging tool to provide valuable information on tumor hypoxia, vascular perfusion profiles and the assessment of in vivo pO2and will act as an useful adjunct to CT, BOLD-MRI and PET.