Detection of Lung Cancer Using Optical Spectroscopy

Pre-neoplastic and malignant diseases are accompanied by local metabolic and architectural changes at cellular and subcellular level that are likely to affect the optical properties, i.e. the scattering, absorption and fluorescence properties of the tissue. Therefore, optical spectroscopy may be able to provide functional information to identify focal (pre-) cancerous lesions. In this thesis we studied the value of optical spectroscopy for the analysis of cancerous lesions of the bronchial mucosa. We developed a fiber-optic instrument allowing the measurement of autofluorescence (AFS), diffuse reflectance (DRS), and differential path length (DPS) spectroscopy during bronchoscopy. DPS is an original spectroscopic technique which was developed in our institution for the purpose of studying the optical properties of the most superficial layer of the bronchial mucosa, i.e. the epithelium. We demonstrated that optical spectroscopy can easily be used during bronchoscopy for the optical analysis of normal and of cancerous bronchial mucosa. We observed that the optical properties of the bronchial mucosa contain the most discriminative information for tissue classification and that the optical variations observed in bronchial tumors using DRS, DPS and AFS may be related to absorption of light by tissue blood. We observed that blood hypoxia is a common event in bronchial tumors especially in cases of aggressive tumors such as small cell lung carcinoma. Endobronchial tumors were also characterized by a higher blood content and larger microvessels in comparison with non-cancerous mucosa. Finally, we demonstrated that combination of optical spectroscopy with autofluorescence bronchoscopy (AFB) improves the specificity of AFB alone for the detection of endobronchial tumors.

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