IN VIVO EPR SPECTROMETRY VIA 200 MHZ FIELD SWITCHING

由于它的非侵入性/非破坏性，磁共振 技术代表了一系列基础和临床的强大方法 生物医学研究问题。核磁共振(核磁共振) 尤其是在活体系统中的应用出现了爆炸性增长 从小动物模型到人类。尽管如此，核磁共振应用 受到极差的信噪比灵敏度的严重限制。 对于许多应用，电子顺磁共振(EPR)提供了 极大地改善了SIN，如果存在与 可以解决导电样品的问题。例如，体内EPR实验 在标准的微波频率下，遭受极端的微波样本-- 穿透限制和天线灵敏度衰减。在此，我们 提出了一种利用快场的非常规EPR光谱仪设计方案 切换(FFS)，如果成功，将启用常规低场(70 Gauss/200 MHz)EPR活体实验。在无线电频率上操作 大大降低了导电样品相关的技术难度。这 通过避免微波询问脉冲，设计允许极大地 光谱仪死区时间小于10 ns的快速接收器恢复 预期中。这将允许广泛的电子自旋标记被 使用。电子自旋的短自旋晶格弛豫时间将 允许非常有效的时间平均进一步增加S/N。 设计利用了最近才有的大电流快速开关 晶体管。据我们所知，目前没有其他实验室正在进行这方面的研究 设计策略。如果成功，这种体内EPR方法将使 磁共振技术可以获得的一种全新的 生物医学研究问题。

Because of its non-invasive/non-destructive nature, magnetic resonance techniques represent powerful approaches to a host of basic and clinical biomedical research problems. Nuclear magnetic resonance (NMR) in particular has seen an explosion in applications to in vivo systems ranging from small animal models to man. Nevertheless, NMR applications are severely restricted by extremely poor signal-to-noise sensitivity. For many applications, electron paramagnetic resonance (EPR) offers greatly improved SIN if major technical problems associated with large conductive samples can be solved. For example, in vivo EPR experiments at standard microwave frequencies suffer extreme microwave sample-- penetration limitations and antenna sensitivity damping. Herein we propose an unorthodox EPR spectrometer design utilizing fast field switching (FFS) that if successful will enable routine low field (70 Gauss/200 MHz) EPR experiments in vivo. Operation at radio frequencies greatly reduces conductive sample related technical difficulties. This design, by avoiding microwave interrogation pulses, allows for extremely fast receiver recovery with spectrometer dead times less than 10 ns expected. This will allow a wide range of electron spin labels to be used. The short spin lattice relaxation times of electron spins will allow very efficient time averaging further increasing S/N. The FFS-EPR design makes use of only recently available high current fast switching transistors. We know of no other laboratory currently pursuing this design strategy. If successful this approach to in vivo EPR will make accessible to magnetic resonance techniques an entirely new regime of biomedical research problems.