【作者】 孟伟；

【导师】 赵会娟；

【作者基本信息】 天津大学 ， 生物医学工程， 2014， 硕士

【摘要】 近红外光成像技术（Near-Infrared Imaging, NIRI）是目前国际公认的最有应用价值的生物检测分析技术之一，在生物医学领域有着广泛的应用。NIRI测量系统具有无创、便携、低功耗以及价格便宜等优势，作为现今主流脑功能成像方式如脑功能磁共振成像（fMRI）、脑电图（EEG）以及脑磁图（MEG）等的有效补充，其在脑认知科学相关研究、临床病理诊断和人体康复治疗等领域有着非常重要的意义。我们完善了一种用于脑功能光学成像的基于单光子计数的多通道数字锁相系统。向激光器施加可调幅的正弦波以调制输出光强的大小，不同的调制频率进行编码可实现多光源的并行输入检测；使用光电倍增管（Photomultiplier Tubes,PMTs）来接收漫射光，可大大改善系统的测量灵敏度以及信噪比；利用FPGA强大的逻辑资源对PMT产生的复合数字信号进行数字锁相解码，实现了对各出射光所含相关生理信息的分别提取。针对系统的完善所做的内容包括：系统各器件的配套整合与优化、上位机测量控制程序结构性的重构与优化、用于调制激光器的正弦波参数的选取与优化以及基于FPGA平台的数字锁相程序全局时序的约束与优化，进一步提升了系统的总体性能。此外，光源—探测器的分布对于检测效果以及成像质量有很大影响，而传统的方形分布并不能很好地满足脑功能在体实验方面的需求，有鉴于此，我们设计并评估了一种新型六边形源探分布方式，通过理论及实验验证，该分布相较于传统方形分布对成像结果在空间分辨率以及量化度方面均有所提升。最后，结合上述完善的测量系统以及新型六边形源探分布，进行了相关的双层仿体实验验证，同时设计了一种用于脑功能在体成像实验的简易头带，并利用工作记忆研究中的n-back任务进行了初步脑功能前额在体实验。结果表明，该方法能够在一定程度上反映出相关区域吸收系数的变化并进行有效分辨。更多还原

【Abstract】 Near-infrared imaging (NIRI) is internationally recognized as one of the mostvaluable biological detection&analysis technology, which has been widely applied inbiomedical field. NIRI measurement system possesses the advantages of portability,non-invasiveness, low power consumption and low price. As an effective supplementfor fMRI, EEG, MEG, etc., NIRI has played a very important role in cognitive scienceresearch, human clinical pathological diagnosis, rehabilitation treatment and otherrelated fields.In this paper, we perfected a multi-channel near-infrared functional brain imagingdetection system based on single photon counting digital lock-in technique. Sinewaves with different frequencies are generated so as to amplitude-modulate lasersources with different wavelengths, which enables parallel detection. The diffuse lightis detected by photomultiplier tubes (PMTs) which can greatly improve themeasurement sensitivity and signal-to-noise ratio of the system. The relevantphysiological information of different light can be extracted respectively by using thelogic resources of FPGA to decode the composite digital signal generated by PMT.The improvements of the existing system have been made, including the matching ofthe devices, the reconstruction of the data acquisition program, the selection ofparameters of sine wave used for laser modulation and the global timing constraintsand optimization of the digital lock-in program, which further enhance the overallperformance of the system.Besides, the source-detector distribution has a big effect on detection and imagingquality, and traditional square distribution can’t meet the needs of in vivo functionalbrain imaging well. To this end, a new type of source-detector distribution has beendesigned and evaluated; through the theoretical and experimental verification, boththe space resolution and the quantitative degree are improved compared with thetraditional square distribution.Finally, combined with the improved system and new source-detector distribution,the double-layer phantom experiments were performed, a simple optical bandage forfunctional brain imaging has been designed, and the in vivo experiments of forehead have been made by applying n-back task paradigm. Results show that this method canreflect the variation of relevant area’s absorption coefficient and distinguish iteffectively to a certain extent.更多还原