~ Ameri can Roentgen Ray Society Simplified CT-Guided

A stereotaxic frame worn during computed tomographic (CT) scanning of the head produces landmarks in each section that are used to relate section coordinates to frame coordinates. A small, commercially available, programmable calculator is used to interrelate frame and CT section geometry. The system can be used with any CT scanner that can specify (x,y) coordinates of a pixel, obviating the need for extensive modifications of the CT computer software. Representative clinical cases are pre-sented. Several investigators have desc ribed methods for using computed tomography (CT) to direct stereotaxic neurosurgical procedures [1-6]. These methods require patient fi xation to the CT scanner to insure that the CT sections obtained will be parallel to one another or parallel to the base of a stereotax ic fram e worn during scanning. An alternate technique is to incorporate a landmark-prod ucing appa-ratus into the stereotaxic frame. Then, when the frame is worn during scanning, landmarks will be produced in each CT section to spec ify the height and tilt of the section relative to the base of the stereotaxic frame, thus making it unnec