Time Domian Electron Paramagnetic Resonance Imaging

项目摘要：a)人类应用的新脉冲序列：我们实验室开发的EPR成像系统用于临床前对小鼠肿瘤模型的肿瘤氧状态进行成像，无论是作为异种移植模型还是作为原位模型。放大共振结构，以便能够对更大的物体进行PO2成像。为了在人体研究中实施，有必要开发一种使用低RF电平的信号形成方法，以符合FDA的规定。开发了一种名为“Frank Pulse Sequence”的射频激励方案，利用该方案，可以产生毫瓦级的射频功率，而不是传统的50瓦功率。这是有可能的，因为开发了一种射频模块，它提供具有伪随机相位排序的激励脉冲，以及隔离激励和信号接收的谐振结构。我们目前正在集成无线植入式射频线圈/氧气传感探头组件的系统，以进行长期的氧气评估。一种微型无线射频线圈(直径4 mm)已经被开发出来，它在生物相容聚合物中嵌入了顺磁性固体，可以被植入体内以测试在植入点监测组织氧的可行性。植入的射频无线线圈没有引线，但可以用外部线圈进行探测，该外部线圈可以激励无线线圈和顺磁探头。因此，这种组件可以被长期植入到所需的部位，并且可以在数周/数月的时间内监测氧气的变化。初步研究表明，检测灵敏度提高了5~7倍。体内研究正在进行中。2)随着肿瘤氧动力学成像技术的提高，EPR成像有可能用于：a)监测肿瘤放疗后的复氧情况；b：肿瘤氧合与肿瘤移植瘤糖酵解的关系。

Project Summary: a) a) Novel Pulse sequences for human applications: The EPR imaging system developed in our lab is in routine use for pre-clinical imaging of tumor oxygen status in mouse models of cancer, both as xenografts and orthotopic models. Scaling up of resonant structures to enable imaging larger objects for pO2. For implementation in human studies, it is necessary to develop a signal formation method using low RF levels to comply with FDA regulations. An RF excitation scheme called "Frank Pulse Sequence" was developed whereby signals can be generated with RF power levels of milliwatt compared to the conventional power of 50 Watts. This was possible by the development of an RF module which delivers pulses of excitation with pseudo-random ordering of the phase and a resonant structure which isolates the excitation and signal reception. We are now in the process of integrating the system for Wireless implantable RF coil/oxygen sensing probe assembly for long term oxygen assessment. A miniature wireless RF coil (4 mm dia) with an embedded paramagnetic solid in a biocompatible polymer has been developed which can be implanted in vivo to test the feasibility of monitoring tissue oxygen at the point of implantation. The implanted RF wireless coil has no leads but can be probed with an external coil which can excite the wireless coil and the paramagnetic probe. Thus this assembly can be implanted chronically at desired sites and oxygen changes can be monitored over periods of weeks/months. Preliminary studies show that a 5-7 fold enhanced sensitivity of detection has been realized. In vivo studies are underway. b) With the improvements in imaging of tumor oxygen dynamics, it was possible to use EPR imaging to: a) monitor the post radiation tumor reoxygenation and b: relationship between tumor oxygenation and glycolysis in tumor xenografts.