An algorithm for the empirical determination of intracranial stereotactic targets

The determination of empirical targets for functional brain lesions is usually made with graphical techniques using CT or MR software. Geometrical errors occur in the method when the intercommissural line and plane of the third ventricle are not parallel and orthogonal to transaxial images. A mathematical algorithm can be used to calculate target coordinates from the coordinates of the anterior commissure, the posterior commissure, and the position of a third point within the inferior, third ventricle. These coordinates may be determined in any image plane in stereotactic space. By supplying the distance of the target from the mid-point of the intercommissural line, the distance lateral and inferior to the line, target coordinates are computed. This overcomes geometrical errors of previous graphical methods.