Continuous Wave Electron Paramagnetic Resonance Imaging

连续波电子顺磁共振成像

• 批准号: 7292186
• 负责人: murali cherukuri
• 金额: --
• 依托单位: DIVISION OF BASIC SCIENCES - NCI
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/7292186
• 关键词: Continuous; Wave; Electron; Paramagnetic; Resonance

Project 3: Continuous Wave Electron Paramagnetic Resonance Imaging.Summary: Since nitroxides are used as therapeutic agents in vivo in animal models as well as in human applications, monitoring the distribution, metabolism, and elimination, non-invasively is an important goal. This project's main motivation is develop instrumentation and image data collection strategies to provide the capabilities of imaging paramagnetic probes such as the nitroxide radicals, which are not amenable by other means. To accomplish the goals, we have undertaken development of instrumentation as well as novel data acquisition strategies, and the progress on these aspects is given below.Instrumentation:Digital Signal processing in CW EPR imaging: The CW EPR Imaging spectrometer in our laboratory and other labs implements the capability of detecting the paramagnetic species using analog devices. This has been the only option until the advent of digital signal processing (DSP) technology. We have initiated efforts to develop an EPR Spectrometer using DSP technology with hope of realizing significant enhancements in sensitivity of detecting the species of interest. By eliminating analog components, which contribute to noise in general, we have designed, tested and implemented successfully the first EPR spectrometer based on DSP concepts. We are now optimizing the spectrometer and have it ready for routine operation.Rapid-scan EPR imaging: The CW EPR imaging method is an intrinsically slow modality for imaging and therefore is prone to artifacts in in vivo imaging where animal motion such as heart beat, breathing can contribute to noise and image artifacts. We have borrowed concepts developed in NMR Spectroscopy and developed instrumentation for rapid scan capabilities where the scan times have been reduced from several minutes to a few seconds for image. In this mode of image data collection, individual projections which make the image take less than millisecond minimizing motional artifacts. The first version of the scanner is complete and we also introduced an efficient way of image data collection by rotating the gradients. Initial feasibility studies are complete and currently, we are optimizing the scanner for automated operation.Co-axial coil for EPR Imaging: Current studies in animals in EPR Imaging require us to have the animal placed in a resonator coil which is perpendicular to the magnet axis for signal detection. However, this makes causes difficulty in monitoring the vital signs, maintain core body temperature, maintain anesthesia and have i.v lines in the animal for contrast agent delivery. A resonator coil co-axial with the magnet axis avoids these difficulties. We have tested a resonator coil which satisfies this need and compared with the previous versions. We have found that we are able to carry out in vivo experiments with great ease and also realized enhanced sensitivity in detection.T1-weighted imaging for pO2 mapping: EPR spectra of paramagnetic species are prone to an artifact called "power saturation" where signal intensity is lost at higher RF powers, especially in regions where the oxygen-dependent line width is significantly lower than when in the presence of normoxic conditions. Utilizing this artifact, we have developed a novel image data collection/image reconstruction procedure where it was possible to collect image data rapidly compared to currently used methods and obtain quantitative maps of pO2.

项目三：连续波电子顺磁共振成像.摘要：由于氮氧化物在动物模型和人体应用中被用作体内治疗剂，因此非侵入性地监测其分布、代谢和消除是一个重要目标。该项目的主要动机是开发仪器和图像数据收集策略，以提供成像顺磁探针的能力，如氮氧自由基，这是不服从其他手段。为了实现这一目标，我们进行了仪器的开发以及新的数据采集策略，在这些方面的进展如下：仪器：CW EPR成像的数字信号处理：我们实验室和其他实验室的CW EPR成像光谱仪实现了使用模拟设备检测顺磁物质的能力。这一直是唯一的选择，直到数字信号处理（DSP）技术的出现。我们已经开始努力开发一种使用DSP技术的EPR光谱仪，希望能够显著提高检测感兴趣物质的灵敏度。通过消除模拟组件，这有助于噪声一般，我们已经成功地设计，测试和实施的第一个EPR光谱仪基于DSP的概念。快速扫描EPR成像：CW EPR成像方法本身是一种成像速度较慢的成像方式，因此在体内成像中容易产生伪影，因为动物的运动（如心跳、呼吸）会导致噪声和图像伪影。我们借用了NMR光谱学中开发的概念，并开发了用于快速扫描功能的仪器，其中扫描时间已从几分钟减少到几秒钟。在这种图像数据收集模式下，使图像花费少于毫秒的单个投影最小化运动伪影。扫描仪的第一个版本已经完成，我们还引入了一种通过旋转梯度来收集图像数据的有效方法。初步的可行性研究已经完成，目前我们正在优化扫描仪的自动化操作。EPR成像的同轴线圈：目前在EPR成像的动物研究中，我们需要将动物放置在垂直于磁轴的谐振线圈中进行信号检测。然而，这使得难以监测生命体征、维持核心体温、维持麻醉以及在动物中具有用于造影剂递送的静脉注射线。与磁体轴线同轴的谐振器线圈避免了这些困难。我们已经测试了一个谐振器线圈，满足这一需要，并与以前的版本相比。我们已经发现，我们能够很容易地进行体内实验，也实现了更高的灵敏度检测。T1加权成像的pO 2映射：顺磁物质的EPR谱容易出现一个伪影，称为“功率饱和”，信号强度在较高的RF功率下丢失，特别是在氧依赖性线宽明显低于常氧条件下的区域。利用该伪影，我们开发了一种新的图像数据收集/图像重建程序，与目前使用的方法相比，该程序可以快速收集图像数据并获得pO 2的定量图。