ULTIMATE SIGNAL TO NOISE IN LOW FREQUENCY EPR

描述：(申请者摘要)监测生理状况的能力 用低频电子顺磁共振(EPR)研究体内过程 光谱学将对生物医学研究做出重大贡献。几个 实验室已经进行了初步实验，但尚未实现 足够的信噪比(SNR)以执行有用的成像。更好 身体的穿透和较低的能量沉积导致低放射性 有利于生物医学EPR的频率(RF)。所获得的低信噪比 这些研究人员和文献中的陈述加强了一种 假设信噪比对频率的高阶依赖关系。我们最近的计算 预测在低频下的信噪比损失比通常假设的要小，因此我们 预测一个比目前达到的更好的固有信噪比。我们还有 开发了一种新的谐振器，即交叉环谐振器(CLR)，它具有 在微波频率(约3 GHz)显示出很强的优势。从基础 考虑因素，我们也希望CLR在低射频下具有这些优势 频率。我们建议对这些新的预测进行实验测试 信噪比的频率依赖性和CLR的低频性能。 我们将测试传统的环隙谐振器(LGR)，频率从9 GHz至200 MHz。我们还将在相同条件下测试LGR和CLR 200 MHz，以确定每种方法的相对优势。组合 存在我们预测的噪声源、样本大小和射频功率 通过使用CLR，显著提高了SNR。信号和噪声 拟议工作所获得的信息将为 预测低频成像在各种测量中的应用 目标。

DESCRIPTION: (applicant's abstract) The ability to monitor physiological processes in vivo with low frequency electron paramagnetic resonance (EPR) spectroscopy would contribute significantly to biomedical research. Several labs have performed preliminary experiments but have not achieved an adequate signal-to-noise ratio (SNR) for performing useful imaging. Better penetration of the body and lower energy deposition makes low radio frequencies (RF) advantageous for biomedical EPR. The low SNRs obtained by these researchers and statements made in the literature have reinforced an assumed high order dependence of SNR on frequency. Our recent calculations predict less SNR penalty at low frequency than generally assumed, thus we predict a better inherent SNR than that achieved so far. We have also developed a new kind of resonator, a crossed-loop resonator (CLR), that has shown strong advantages at microwave frequencies (ca. 3 GHz). From basic considerations, we also expect the CLR to have these advantages at low RF frequencies. We propose to experimentally test these new predictions for frequency dependency of SNR and the low frequency performance of the CLR. We will test the traditional loop-gap resonator (LGR) at frequencies from 9 GHz to 200 MHZ. We will also test the LGR and CLR under the same conditions at 200 MHZ to determine the relative benefits of each. Combinations of noise source, sample size, and rf power exist for which we predict significant SNR increase by use of the CLR. The signal and noise information obtained by the proposed work will provide a solid basis for predicting the utility of low frequency imaging for various measurement goals.