Major Difficulties of Stereotaxy
One of the major difficulties of stereotactic surgery is graphic conceptualization of the location of surgical instruments inserted into deep brain structures. Not only are such instruments out of the surgeon's site, but they may be tilted, rotated, and extended in many different directions. These factors make maintaining a mental picture of the instruments almost impossible. The surgeon must imagine its location while taking into account many other angular variables. An additional difficulty is that the coordinate system of the stereotactic frame or localizer used by the surgeon seldom corresponds to the patient's "brain coordinate system." This lack of correspondence introduces more room for error in placing surgical instruments. Furthermore, stereotactic surgery is essentially a blind surgical procedure with many complex geometric variables. The surgeon must have a method for accurately and rapidly calculating coordinates for a given target operative site located within the depths of the brain. These coordinates must be translated from "brain coordinates" to three-dimensional reference coordinates for accurate positioning of instruments.