A method for bronchoscope tracking using position sensor without fiducial markers

Abstract

This paper proposes a method for tracking a bronchoscope using a position sensor without fiducial markers. Recently, a very small electromagnetic position sensor has become available that can be inserted into the bronchoscope's working channel to obtain bronchoscope camera motion. In most tracking methods using position sensors, registration is performed using the positions of fiducial markers attached to a patient's body. However, these methods need to measure the positions of fiducial markers on both the actual patient's body and the reference image, such as a CT image of the patient. Therefore, we propose a method for bronchoscope tracking without fiducial markers that estimates a transformation matrix between the actual patient's body and the CT image taken prior to bronchoscope examination. This estimation is performed by computing the correspondences between the outputs of the position sensor and the bronchi regions extracted from the CT image. We applied the proposed method to a rubber bronchial model. Experimental results showed that average target registration error of the five bronchial branches was a minimum of about 3.0mm, and the proposed method tracked a bronchoscope camera in real time.