Towards hybrid bronchoscope tracking under respiratory motion: evaluation on a dynamic motion phantom

This paper presents a hybrid camera tracking method that uses electromagnetic (EM) tracking and intensity-based image registration and its evaluation on a dynamic motion phantom. As respiratory motion can significantly affect rigid registration of the EM tracking and CT coordinate systems, a standard tracking approach that initializes intensity-based image registration with absolute pose data acquired by EM tracking will fail when the initial camera pose is too far from the actual pose. We here propose two new schemes to address this problem. Both of these schemes intelligently combine absolute pose data from EM tracking with relative motion data combined from EM tracking and intensity-based image registration. These schemes significantly improve the overall camera tracking performance. We constructed a dynamic phantom simulating the respiratory motion of the airways to evaluate these schemes. Our experimental results demonstrate that these schemes can track a bronchoscope more accurately and robustly than our previously proposed method even when maximum simulated respiratory motion reaches 24 mm.