【作者】 朱苹苹；

【导师】 高峰；

【作者基本信息】 天津大学 ， 生物医学工程， 2012， 硕士

【摘要】 光学拓扑成像方法源自于近红外组织光谱测量技术(Near-Infrared Spectroscopy,NIRS),可实现高阶脑功能动态成像。作为现有高阶脑功能成像模态如功能核磁共振成像(Functional Magnetic Resonance Imaging, fMRI)等的有效补充,它对脑科学研究、神经系统诊断和临床康复治疗有着重要的应用价值。目前已经推出的光学拓扑成像系统价格昂贵,较难推广,因此设计出一种结构简便、性价比高的光学拓扑成像系统一直是目前该领域研究者努力的方向之一。本文设计了一种基于数字锁相检测技术的光学拓扑成像系统,该系统利用数字锁相检测技术缩短信道带宽、改善测量信噪比和动态性能、实现微弱双波长反射信息的有效分离并提取出每个波长下调制信号的幅值信息。此外,本文优化了调制信号源以及数据采集程序,并设计出符合要求的源-探测光纤排布以及数据处理程序。在此基础上,系统利用光开关实现了5个源位置处耦合信号顺序入射、并实现了4通道同步数据采集及处理。本文详细介绍了系统的各个组成部分,并利用输入调制信号的幅值变化与输出反射信号的幅值变化成正比的关系,证明了系统的可用性以及系统所测得的幅值信息的有效性。本文设计的光学拓扑成像系统旨在以血红蛋白的浓度变化为指标,实现脑功能成像研究。考虑到系统处在验证阶段,选择以吸收系数的变化反映血红蛋白浓度的变化情况,在此基础上对40×40mm~2区域内不同吸收目标的液态仿体进行了双波长成像实验。以修正的Lambert-Beer定理为理论模型,重建出吸收系数的变化图像。该成像结果准确反映出吸收系数的变化趋势,初步验证了系统和方法的可行性和有效性。更多还原

【Abstract】 As an extension to tissue near-infrared spectroscopy (NIRS) technique, optical topography has the ability to realize the mapping of the high-order functions in the brains. Now it has been one of the most beneficial supplements to the other established methods used for the functional imaging of the cerebral cortex, such as functional magnetic resonance imaging, and can play great roles in the brain research, diagnosis of the neurological system, clinical rehabilitation.This paper presents a dual-wavelength optical topography system, based on digital lock-in technique that can effectively compress channel bandwidth, ameliorate the signal-to-noise ratio and the dynamic performance, realize the effective segregation of the weak dual-wavelength signal and extract the amplitude information of every modulation signals. Also, we have optimized the modulation signals and the data acquisition procedure, completed the design of the optode array and the processing program. In the system, a photo switch is used to accomplish the orderly import of coupling signal at the 5 source places, and then the 4-channel data is synchronously collected by a Data Acquisition Card and processed in the computer. We introduce every components of the system, and verify the availability of the system and its measured amplitude information by the proportional relationship between the input amplitude changes and the output ones.Through monitoring the variation of hemoglobin concentration, this optical topography system can apply in the study of the brain functional imaging. In validation experiments of the system, we utilize changes of the absorption coefficient to represent the variation of hemoglobin concentration. A dual-wavelength pilot validation was performed using liquid phantom with targets of different absorption coefficient in an area of 40×40 mm2. Then we use the modified Lambert-Beer‘s Law to reconstruct the distribution of the absorption coefficient‘s variation. The experimental results clearly show the variation tendency of the absorption coefficient with a reasonable accuracy, and validate the feasibility and availability of the system and method.更多还原