Transposition of image-defined trajectories into arc-quadrant centered stereotactic systems.

A methodology and computer program used for transposition of image-defined trajectories into stereotactic space is presented. Arc-quadrant centered stereotactic frames (Leksell, modified by us Komai) are based on the principle of aiming a target point from any entry of a formed sphere of known radius. Frames adapted isocentrically to CT gantry and parallel to the scanning plane allow interactive selection of targets and trajectories based on multiplanar reformatted images. The mathematical fundaments to calculate angle A in the coronal plane and angle B in the saggital plane based on the geometrical configuration of arc-quadrant centered stereotactic devices are presented.