【作者】 王建伟；

【导师】 于清旭；

【作者基本信息】 大连理工大学 ， 光学工程， 2012， 博士

【摘要】 微量气体检测在大气环境和工业气体检测、医学临床诊断和生命科学领域扮演着重要角色。在众多的气体检测技术中,光声光谱技术因其灵敏度高、响应快和能够实时连续测量等优点受到人们的青睐。本文对近红外激光光声光谱微量气体检测技术及其在医学呼气检测中的应用进行了深入的研究。基于气体吸收光谱理论,深入讨论了波长调制光声光谱检测技术的基本原理,针对气体吸收谱线加宽的Lorentzian线型函数推导了波长调制的谐波表达式,作为确定调制振幅的依据着重分析了2次谐波的强度与线宽。在分析气体光声光谱检测技术经典理论的基础上,给出了多组分气体光声光谱检测的一般方法,为光声光谱多组分气体检测技术研究提供了理论依据。在理论研究的基础上,本论文设计和研制了基于近红外可调谐光纤激光器和共振光声池的光声光谱多组分气体检测系统,并进行了多组分混合气体检测的实验研究,实现了C2H2、CO、CO2和H20四种组分混合气体的同时检测,极限检测灵敏度分别达到2ppb、4ppm、4ppm和70ppm,并具有良好的线性度。在多组分气体光声光谱分析研究的基础上,开展了针对终末期肾病(ESRD)患者血液透析过程中呼出氨气监测的理论及临床实验研究。通过对呼出氨气的医学诊断病理学分析及呼气样品采集的特殊要求,设计了一种专用的采气口鼻面罩和全聚四氟乙烯材料光声池,对气路系统进行了恒温控制,针对呼气中高浓度C02和H20背景对超低浓度NH3测量的干扰问题,提出了呼出氨气高灵敏度检测的多组分气体测量算法,实现了高浓度C02和H20背景下的NH3气体的高灵敏度测量,极限检测灵敏度达到16ppb。利用研制的光声光谱呼气分析系统,测量了多名健康志愿者和6名ESRD患者的呼出氨气。检测结果表明,健康志愿者的呼出氨气浓度在300ppb左右；ESRD患者透析前的呼出氨气浓度在2000ppb左右。在透析过程中呼出氨气浓度随透析时间的延长逐渐降低,透析结束时呼出氨气浓度降至200～600ppb,接近健康者的水平,其呼出氨气浓度的下降率均超过65%,这与临床常用的BUN检测透析治疗充分性标准很好的符合。基于近红外可调谐光纤激光器的光声光谱呼气分析系统具有高灵敏度,多种气体同时测量,可实时、连续监测和适合临床应用等优点。本论文的研究工作将为进一步研制开发医用呼气分析仪和血液透析监测仪奠定理论和实验基础。更多还原

【Abstract】 Trace gas detection plays an important role in the fields of atmospheric environment, industrial applications, medical diagnosis and life sciences. Among many detection techniques of trace gases, photoacoustic spectroscopy (PAS) has attracted a lot of interests as they enable high detection sensitivity, real time and continuous measurements. In this thesis, the near-IR laser photoacoustic spectroscopy for multi-component gas detection and its medical application of breath detection are deeply studied.Based on the theory of gas molecular absorption spectrum, the principle of wavelength modulation photoacoustic spectroscopy is discussed in detail. General harmonic expressions of wavelength modulation are given for the absorption line shapes of Lorentzian signals broadened by modulation. The linewidths and the signal intensities of second-harmonic have been calculated analytically as a function of the modulation amplitude. The general method of multi-component gas detection is given by analyzing the classic theory of photoacoustic spectroscopy. The method provides theories basis for detecting multi-component gas with photoacoustic spectroscopy.On the foundation of theoretical research, the photoacoustic multi-component gas detection system based on a near-IR tunable fiber laser and a resonant PA cell is designed and developed. The experimental investigation of multi-component gas mixture detection is conducted. Simultaneous and continuous measurement of trace water vapor, acetylene, carbon dioxide, and carbon monoxide (H2O, C2H2, CO and CO2) in gas mixtures are achieved. The detection limits (signal-to-noise ratio=l) of70ppm for H2O,2ppb for C2H2,4ppm for CO and4ppm for CO2were demonstrated with the detection system. The detection system has advantages of high level of linearity.The theoretical and clinical experimental studies of the breath ammonia monitoring in patients with end-stage renal disease (ESRD) undergoing hemodialysis are done on the basis of photoacoustic spectroscopy for multi-component gas detection. The breath ammonia pathological diagnosis and the specific requirement of sampling are analyzed. The dedicated mask of sampling and a teflon photoacoustic cell are designed. The gas path system are carried out constant temperature control. Aiming at the problem of high concentration of CO2and H2O interference with breath ammonia, the algorithm of multi-component gas measurement is proposed. The high sensitive ammonia measurements in high concentration of CO2and H2O is realized using the algorithm at atmospheric pressure. The minimum detection limit of16ppb (signal to noise ratio=1) in simulated breath samples (5.3%CO2and6.2%H2O (100%relative humidity at37℃)) is achieved.The breath ammonia levels of many healthy volunteers and six patients with ESRD were measured by means of photoacoustic spectroscopy breath analysis system. Experimental results indicated that, the breath ammonia levels of healthy volunteers are about300ppb. The initial concentration levels of breath ammonia are about2000ppb before dialysis treatment. These preliminary data indicate that breath ammonia levels decreased gradually as the treatment proceeded. Breath ammonia concentrations decreased to200～600ppb in the end stage of dialysis, which are close to the levels of healthy persons. The breath ammonia concentrations concentrations have decreased by more than65%. It is consistent with the current standard of the BUN.The breath analysis system of photoacoustic spectroscopy based on a near-IR tunable fiber laser has high sensitivity, multi-component gas simultaneous measurement, real time, continuous monitoring and suitable for clinical application. These works of the thesis will make some theoretical and experimental preparations for developing the medical breath analyser and the hemodialysis monitor.更多还原