KOPFHAUBE VERSEHEN MIT MARKEN ZUR ORTUNG

摘要

A detachable cap for use in determining the location of the center of the imageable portion of a fiducial marker is disclosed. The lower portion of the cap has three arms and a boss for providing a detachable connection with an implanted base portion to which an imaging marker can be attached. The upper portion of the cap includes a divot - like depression that is configured to mate with a ball whose center can be determined. The ball, marker, and divot are configured so that the center of the ball, when mated to the divot, is coincident with the center of the marker when it is attached to the base in place of the cap. Knowledge of the location of the center of the ball when it is brought into engagement with the divot of the cap can be used to determine the location of the center of the marker when it is attached to the base.