The application accuracy of the Pathfinder neurosurgical robot

TLDR: A new technique to measure the overall application accuracy of image-guided stereotactic systems has been used to measureThe Pathfinder neurosurgical robot, which uses a robot-mounted camera to triangulate fiducial skin markers, virtually eliminating line-of-sight problems experienced by other optical localisation methods.

Abstract: We have developed a new technique to measure the overall application accuracy of image-guided stereotactic systems. It has been used to measure the accuracy of the Pathfinder neurosurgical robot, which uses a robot-mounted camera to triangulate fiducial skin markers, virtually eliminating line-of-sight problems experienced by other optical localisation methods. A phantom consisting of plastic spheres on stalks was used. The targets are the centre of the spheres. Points on a sphere's surface were automatically selected on CT images, from which the centre of the sphere was calculated in image space to greater precision than the CT voxel dimensions. A depth gauge was attached to Pathfinder in place of a biopsy needle and driven to the target as defined on CT. Pathfinder then moved to several points over the sphere, moving perpendicular to the trajectory in a grid pattern. By considering the depth gauge reading, 3D points on the sphere's surface were measured in robot space and the centre of the sphere was found. The difference between the actual and planned targets yields the overall accuracy. Preliminary experiments show that the application accuracy of Pathfinder is 2.7 mm. Further calibrations of the robot are expected to improve this value significantly.