[Laser-based endoscopic measurement of airway dimensions]

Bronchoscopy is the technique of choice for the evaluation of a stenosis in the large airways. However, no system has been successfully employed for the bronchoscopic measurement of airway stenosis. The purpose of these study was the development and validation of a method for measuring the cross-sectional areas in the large airways. Furthermore, this application should be used for the 3D-reconstruction and visualisation of airway stenosis. A laser probe inserted into the operating channel of the bronchoscope enabled assessment of the distance between the images and the tip of the bronchoscope by means of projecting a ring of light on to the endoluminal wall. Image distortion due to the wide-angle lens was corrected by a computer program developed by us. Plastic tubes with known diameters were used for validation. Additionally, distortion-corrected bronchoscopic images were compared with distortion-free videoscopic image analysis of tracheal slices taken from pigs. When plastic tubes were used, the correlation coefficient (r) was slightly higher (r = 0,99, p < 0,01) than the correlation of cross-sectional areas between bronchoscopic and videoscopic images of tracheal slices (r = 0,88, p < 0,01). Furthermore the system could be used in a few patients for 2D and 3D measurement and visualisation of airway stenosis. Application of the present method offer quantitative assessment of airway stenosis located in the large airways.