Robust intraoperative US probe tracking using a monocular endoscopic camera.

In the context of minimally-invasive procedures involving both endoscopic video and ultrasound, we present a vision-based method to track the ultrasound probe using a standard monocular video laparoscopic instrument. This approach requires only cosmetic modification to the ultrasound probe and obviates the need for magnetic tracking of either instrument. We describe an Extended Kalman Filter framework that solves for both the feature correspondence and pose estimation, and is able to track a 3D pattern on the surface of the ultrasound probe in near real-time. The tracking capability is demonstrated by performing an ultrasound calibration of a visually-tracked ultrasound probe, using a standard endoscopic video camera. Ultrasound calibration resulted in a mean TRE of 2.3 mm, and comparison with an external optical tracker demonstrated a mean FRE of 4.4 mm between the two tracking systems.