Fig. 5.

Approximate left (red) and right (green) camera positions are marked on the endoscope surface in the CT scan using the segmented endoscope rendering (bottom left). The left camera position is fixed in subsequent manual alignment and a target point is identified roughly in the direction of the relevant anatomy. The resulting axes of this 30${}^{\circ }$ endoscope are shown in yellow, with the Z axis pointing towards the target point. This provides an initial alignment from CT to endoscope, which can be subsequently refined manually.