基于数字锁相检测技术的光学拓扑成像系统研究

发布时间：2018-12-16 06:16

【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。
[Abstract]:Optical topological imaging is derived from near infrared tissue spectroscopy (Near-Infrared Spectroscopy,NIRS), which can realize high order dynamic imaging of brain function. As an effective supplement to the existing high-order brain functional imaging modes such as (Functional Magnetic Resonance Imaging, fMRI), it has important application value in the research of brain science, the diagnosis of nervous system and the clinical rehabilitation therapy. The optical topological imaging system which has been developed is expensive and difficult to popularize, so it is one of the directions that the researchers in this field have been working hard to design a simple and cost-effective optical topological imaging system. In this paper, an optical topological imaging system based on digital phase-locked detection technology is designed. The digital phase-locked detection technique is used to shorten the channel bandwidth and improve the measurement of SNR and dynamic performance. The weak double wavelength reflection information can be separated effectively and the amplitude information of the modulation signal at each wavelength can be extracted. In addition, the modulation signal source and data acquisition program are optimized, and the source-detection fiber layout and data processing program are designed. On this basis, the system uses the optical switch to realize the sequential incidence of the coupled signals at five source positions, and realizes the synchronous data acquisition and processing of the four channels. In this paper, the components of the system are introduced in detail, and the relationship between the amplitude variation of the input modulation signal and the amplitude change of the output reflection signal is used to prove the availability of the system and the validity of the amplitude information measured by the system. The optical topological imaging system designed in this paper aims to realize the study of brain function imaging based on the change of hemoglobin concentration. Considering that the system is in the verification stage, the change of absorption coefficient is selected to reflect the change of hemoglobin concentration, and the dual-wavelength imaging experiments are carried out for different absorption targets in the region of 40 脳 40mm~2. The modified Lambert-Beer theorem is used as the theoretical model to reconstruct the changing image of absorption coefficient. The imaging results accurately reflect the changing trend of absorption coefficient, and the feasibility and effectiveness of the system and method are preliminarily verified.
【学位授予单位】：天津大学
【学位级别】：硕士
【学位授予年份】：2012
【分类号】：R318.51

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