Fig. 3.

Illustrations describing the process of calibrating the tracker to the C-arm X-ray source using hand–eye calibration and an external optical navigation system. a An infrared reflective marker is attached to the gantry and calibrated to the X-ray source using a second marker that is imaged by the navigation system and the C-arm simultaneously (Fig. 2). b The C-arm gantry, and therefore, the tracker and the optical marker are moved and corresponding pose pairs in the respective frames of reference are collected that are then used for hand–eye calibration following Tsai et al. [38]