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Polarization sensitive optical coherence tomography (PS-OCT) for bronchoscopic airway imaging

Introduction: Bronchial thermoplasty (BT) is an endoscopic treatment for severe asthma that reduces airway smooth muscle (ASM) by radiofrequent energy. No diagnostic method is currently available to assess ASM, other than invasive, focal airway biopsies. Bronchoscopic standard optical coherence tomography (OCT) generates high resolution images of the airways. Polarization sensitive OCT (PS-OCT) provides tissue-specific contrast that might enable ASM detection and quantification. Aim: Use novel PS-OCT to detect ASM and determine changes in ASM before and after BT in severe asthma. Methods: Bronchoscopic PS-OCT was performed from distal to proximal airways in a severe asthma patient before and after BT. Standard OCT high resolution airway wall layer imaging was combined with PS-OCT birefringence and optical axis determination to detect, segment and quantify ASM as compared to histology (gold standard). Results: Standard OCT enabled airway wall layer detection. PS-OCT enables segmentation and quantification of ASM in volumetric airway segments over 5 cm. Circular structure of ASM within the airway was seen. Comparing before and after BT a reduction in ASM mass was detected in line with ASM reduction detected in airway biopsies. Conclusion: Bronchoscopic (PS-)OCT is a promising minimally-invasive imaging technique to assess airway wall layer and ASM mass in severe asthma patients.