Journal of Intelligent and Robotic Systems 35: 193–202, 2002. © 2002 Kluwer Academic Publishers. Printed in the Netherlands. 193 Alternative Solution for a Robotic Stereotactic System V. MODRÁK, J. PAŠKO and S. PAVLENKO The Faculty of Production Technology of the Technical University in Košice, Prešov, Slovakia; e-mail: modrak.vladimir@fvt.sk (Received: 10 July 2001; in final form: 17 December 2001) Abstract. The development of robotic technology applications in the stereotactic neurosurgical method has reached the stage of high acceptation, which is the driving force for searching for other solutions. The article describes an alternative robotic system solution for stereotaxis and compares it with other known solutions. It is characterised by a minimal number of the controlled robot axes, while preserving required articulation possibilities. Since it is a non-traditional robotic architecture, the article outlines its kinematic analysis with the specification of transformation matrices for an inversion problem. At the same time, outputs from the robot computer animation, which is an indispensable aid in the development of kinematic mechanisms, are presented. Key words: computer animation, kinematic analysis, robotic architecture, stereotactic neurosurgery, 3D models. 1. Introduction Stereotactic neurosurgery is a technique that was developed more then 90 years ago. The first 3-D apparatus was invented by Horsley and Clarke [3]. The purpose of this surgical method is the guiding of a probe or other treatment instrument to a predetermined point in the nervous system without direct monitoring of the surgical site. There are two basic stereotactic methods: head stereotaxis and so- called body stereotaxis. This article deals with the first of them. Surgical operation is done in a stereotactic head frame, a brace, into which the patient’s head is placed. The utilisation of the conventional stereotactic head frame with manual adjustments caused certain problems, such as the transformation of scanned data and the setting of appropriate parameters on the moving part of the frame. Since the mentioned pioneering effort, many kinds of stereotactic device have been devised. Thanks to the integration of stereotaxis with computerized tomography (CT) scan, this technique has recorded significant progress. It is particularly visible in the development of robotic stereotactic systems, which are designed to replace the stereotactic moving frame for the positioning of the probe. Programmed robots, which are interconnected with CT, offer substantial flexibility, speed, and accuracy, allowing the surgeon to set the probe trajectory in an optimal direction.