A model for estimating initial transform matrix for using inertial sensors in surgical navigation

Because targets attached to surgical instruments can be obscured from view, surgical instruments should be tracked in the case of vision-based navigation system failure. To this end, we present a model capable of translating the orientation data from an inertial measurement unit (IMU), rigidly fixed to the surgical instrument, to the camera coordinate system. The model works by calculating the fixed rotation matrix between the IMU and the surgical instrument. Here, we use the direction of gravity measured using the IMU and surgical instrument coordinates in the algorithm for calculating the rotation matrix between the different coordinates. We then compare the orientation data of surgical instruments obtained from the IMU and a vision-based navigation system.