Combined endoscopic video tracking and virtual 3D CT registration for surgical guidance

Bronchoscopic needle biopsy is a common step for early lung-cancer detection. This procedure uses two steps: (1) 3D computed-tomography (CT) chest image analysis, to choose a biopsy site; (2) live bronchoscopy, to perform the biopsy. CT-based virtual endoscopic analysis can improve the results of biopsies, yet errors can still occur. We describe a procedure to combine the endoscopic video tracking (the "real" world) and CT-based virtual endoscopic registration (the "virtual" world). By bringing both sources of information together, a more robust surgical guidance system is realizable. Both the endoscope's video and the thoracic CT scan are used as data sources in the tracking. An optical flow algorithm estimates the endoscope motion between successive video frames. The virtual CT rendering creates a range map for the optical flow equation. This simplifies the endoscope movement calculation into a straightforward linear system. We demonstrate this method for a phantom human airway-tree example.