Technical considerations regarding accuracy of the MKM (TM) navigation system. An experimental study on impact factors

The purpose of this study was to investigate experimentally, factors determ ining the navigation accuracy of the MKM(TM) navigation system by Zeiss. Th e MKM(TM) consists of an operating microscope mounted to a six-axis motor-d riven robot arm and an alpha-workstation, The image-guided surgery device p rovides navigation information based on calculation of the cartesian coordi nates of the robot arm, and coordinates of the focus point assessed by lase r assisted measurement Navigation information (current position, direction and distance to a previously selected target) is optically projected into t he microscopic field. Following factors were examined in an experimental se tting for their impact on accuracy of the MKM(TM). optical system, mechanic al precision of the robot arm, and registration procedure. The robot arm an d the optical system of the microscope allow high precision measurements of any focus point (error < 2 mm if the following aspects are considered: the use of auto-focus function instead of manual focusing, positioning of the registration points as a square or a triangle focus point should be selecte d on a surface that is perpendicular to the optical axis.