Laser based method for real-time three-dimensional monitoring of chest wall movement

摘要

Novel method for monitoring the entire three-dimensional shape of the chest wall in real time is presented. The system is based on the multiple-line laser triangulation principle. The laser projector generates a light pattern of 33 equally inclined light planes directed toward the measured surface. The camera records the illuminated surface from a different viewpoint, and consequently, the light pattern is distorted by the shape of the surface. The acquired images are transferred in the personal computer, where contour detection, three-dimensional surface reconstruction, shape analysis, and displaying are performed in real time. Surface displacements are calculated by subtraction of the current measured surface from the reference one. Differences are displayed with color palette, where the blue represent the inward (negative) and the red represent the outward (positive) movement. The accuracy of the calibrated apparatus is ±0.5 mm, which is calculated as a standard deviation between points of the measured and nominal reference surface. The measuring range is approximately 400×600×500 mm in width, height and depth. The intention of this study was to evaluate the system by means of its ability to distinguish between different breathing patterns and to verify the accuracy of measuring chest wall deformation volumes during breathing. The results demonstrate that the presented 3-d measuring system has a great potential as a diagnostic and training tool in case of monitoring the breathing pattern. We believe that exact graphical communication with the patient is much more simple and easy to understand than verbal and/or numerical.