A simple sensor calibration technique for estimating the 3D pose of endoscopic instruments.

Background: The aim of this study was to describe a simple and easy-to-use calibration method that is able to estimate the pose (tip position and orientation) of a rigid endoscopic instrument with respect to an electromagnetic tracking device attached to the handle.

Methods: A two-step calibration protocol was developed. First, the orientation of the instrument shaft is derived by performing a 360° rotation of the instrument around its shaft using a firmly positioned surgical trocar. Second, the 3D position of the instrument tip is obtained by allowing the tip to come in contact with a planar surface.

Results: The results indicate submillimeter accuracy in the estimation of the tooltip position, and subdegree accuracy in the estimation of the shaft orientation, both with respect to a known reference frame. The assets of the proposed method are also highlighted by illustrating an indicative application in the field of augmented reality simulation.

Conclusions: The proposed method is simple, inexpensive, does not require employment of special calibration frames, and has potential applications not only in training systems but also in the operating room.