Background: Lung cancer is one of the most common malignant tumors worldwide. Currently, effective screening methods for early lung cancer are still scarce. Breath analysis provides a promising method for the pre-screening or early screening of lung cancer. Isoprene is a potential and important breath biomarker of lung cancer. Material and Methods: To investigate the clinical value of isoprene for diagnosing lung cancer patients, a cavity ringdown spectroscopy (CRDS) based near-real time, sensitive analysis method of breath isoprene is developed in our lab. In this paper, 92 breath samples from lung cancer patients, 17 breath samples from patients with benign lesions, and 107 breath samples from healthy people were collected. Results: Research indicates that breath isoprene concentration is significantly higher in healthy individuals (221.3±122.2ppbv) than in patients with lung cancer (112.0±36.6ppbv) and benign lung lesions (127.9±41.2ppbv). The result of Receiver Operating Characteristic (ROC) curve suggests that the concentration of isoprene is meaningful for the diagnosis of lung cancer (AUC=0.822, sensitivity=63.6%, specificity=90.2%, P<0.01). Conclusion: This study demonstrates that the CRDS breath isoprene analysis system can effectively analyze a large sample of human breath isoprene, and preliminarily confirms the use of breath isoprene as a biomarker for lung diseases.Background: Lung cancer is one of the most common malignant tumors worldwide. Currently, effective screening methods for early lung cancer are still scarce. Breath analysis provides a promising method for the pre-screening or early screening of lung cancer. Isoprene is a potential and important breath biomarker of lung cancer. Material and Methods: To investigate the clinical value of isoprene for diagnosing lung cancer patients, a cavity ringdown spectroscopy (CRDS) based near-real time, sensitive analysis method of breath isoprene is developed in our lab. In this paper, 92 breath samples from lung cancer patients, 17 breath samples from patients with benign lesions, and 107 breath samples from healthy people were collected. Results: Research indicates that breath isoprene concentration is significantly higher in healthy individuals (221.3±122.2ppbv) than in patients with lung cancer (112.0±36.6ppbv) and benign lung lesions (127.9±41.2ppbv). The result of Receiver Operating Characteristic (ROC) curve suggests that the concentration of isoprene is meaningful for the diagnosis of lung cancer (AUC=0.822, sensitivity=63.6%, specificity=90.2%, P<0.01). Conclusion: This study demonstrates that the CRDS breath isoprene analysis system can effectively analyze a large sample of human breath isoprene, and preliminarily confirms the use of breath isoprene as a biomarker for lung diseases.

为了分析青藏高原地区甲烷浓度的垂直分布, 本文采用腔衰荡光谱技术(CRDS)设计了一套高灵敏度的球载甲烷浓度实时测量系统, 该测量系统在基于DSP的单板电路上实现腔模锁定、衰荡信号采集、光谱扫描、数据存储等功能并在DSP上实时处理衰荡信号、光谱信号和浓度等数据。本文首先介绍了CRDS测量原理与采用的光谱处理算法, 通过固定高斯线宽的方式改进光谱拟合算法, 使得浓度计算结果得到明显提升。然后, 分析了电路系统采集的衰荡信号与光谱信号, 采集的衰荡信号信噪比达62 dB, 并在实验室使用标准气体进行了标定试验, 标准气体的测量值标准差σ最大为2.2×10-9, 测量值的均方值RMS和标准气体标称值之间的校正可决系数为0.998 7。最后, 系统进行了实际试验, 在西藏鲁朗地区成功实现了从海拔3 340 m到海拔6 000 m的上升和下降过程中甲烷浓度的测量。该系统可以通过改变激光波长与光腔反射镜测量其他大气痕量气体, 进一步改进与优化的系统可以应用到大气同位素丰度的测量中。

呼吸气体分析技术在疾病诊断和代谢监测方面无创性、实时性的优势使其成为一个颇具前途的研究领域，也是未来新型诊断仪器的发展方向。目前大多呼吸生物标志物的检测和定量分析均采用气相色谱-质谱联用技术。近几年来，激光光谱技术和激光光源的发展加速推进了呼吸气体分析研究的进展。与质谱技术相比，激光光谱技术不但具有高灵敏度、高选择性的优点，而且具有低成本、实时性及即时检测（POCT）的功能特点。目前，在已确定的35种呼吸生物标记物中，研究人员采用可调谐半导体激光吸收光谱、光腔衰荡光谱以及光声光谱技术进行了多种呼吸生物标记物人体呼吸气体实验，其相应生物标记物的光谱“指纹”涵盖了从紫外到中红外的光谱范围。

理论分析了腔内电磁诱导透明效应(EIT)对腔衰荡光谱(CRDS)的影响，提出了利用V型三能级EIT中的光泵效应提高探测光透过率从而改善CRDS性能的方案。实验中采用铷87原子的D2线构建了V型三能级EIT，在适当的控制光强度下实现了CRDS衰荡时间及其灵敏度的改善，使灵敏度增强至原有灵敏度的1.45倍。

搭建了基于近红外连续激光器的高灵敏度快速扫描光腔衰荡光谱仪(SC-CRDS)。通过压电陶瓷(PZT)快速扫描腔长，并用跟踪电路使腔长自动跟踪激光波长变化，实现衰荡光谱的快速测量。利用CH4在1653.73 nm (6046.95 cm-1)附近的光谱吸收峰，用该装置对CH4气体含量进行测量。通过测量多个光谱点确定吸收线中心吸收峰值和激光波长，并反馈补偿激光中心波长使其稳定在吸收线，成功解决了由于激光器波长/频率严重漂移导致的不能持续准确测量问题。利用标准浓度的CH4样品校准其1653.73 nm 吸收峰谱线强度。该光腔衰荡光谱仪装置结构简单，性能稳定，CH4浓度检测限达到1.0×10-9，可用于长时间监测室外空气中的CH4浓度。