A Multi-view Opto-Xray Imaging System

The success of minimally invasive trauma and orthopedic surgery procedures has resulted in an increase of the use of fluoroscopic imaging. A system aiming to reduce the amount of radiation has been introduced by Navab et al. [1]. It uses an optical imaging system rigidly attached to the gantry such that the optical and X-ray imaging geometry is identical. As an extension to their solution, we developed a multi-view system which offers 3D navigation during trauma surgery and orthopedic procedures. We use an additional video camera in an orthogonal arrangement to the first video camera and a minimum of two X-ray images. Furthermore, tools such as a surgical drill are extended by optical markers and tracked with the same optical cameras. Exploiting that the cross ratio is invariant in projective geometry, we can estimate the tip of the instrument in the X-ray image without external tracking systems. This paper thus introduces the first multi-view Opto- Xray system for computer aided surgery. First tests have proven the accuracy of the calibration and the instrument tracking. Phantom and cadaver experiments were conducted for pedicle screw placement in spinal surgery. Using a postoperative CT, we evaluate the quality of the placement of the pedicle screws in 3D.