Virtual probe for a stereotactic digitizer for use in surgery

Abstract

This invention relates to a three-dimensional digitizer and a probe means associated with said digitizer that enables a virtual target point to be visualized and depth and range measurements to that target to be determined. In one embodiment, a mechanical articulated arm or other type of 3-D digitizer is used in conjunction with a graphics workstation which displays images from CT, MR, or other scanning means of the anatomy. By registration of the digitizer to the patient's physical anatomy, a representation of the digitizer on the display means of the graphics workstation is possible. The position of the digitizer will be displayed in its quantitative relationship to the patient's anatomy, including internal pathologies such as tumors. The end means of the 3-D digitizer could be a holder or fixation device which can accept a sliding probe. The probe, for example, could be a shaft which slides in a spring-loaded or non-spring-loaded fashion within the fixation means of the digitizer. The degree of extension of the probe from the fixation means can be read out by a scale, which might be engraved on the shaft of the sliding probe. The digitizer, when calibrated to the anatomy, would register a target point and also a direction of the probe as it would approach that point, as seen on the graphics workstation. There may be a pre-determined relationship of the virtual tip of a probe relative to the fixation means as it scans the anatomy with the probe moving in space. The physical probe might be the sliding rod, which will be retractile within the fixation means. Thus, by knowing the degree of retraction, one can gauge the distance from the tip of the sliding probe to the virtual target, as calculated in the 3-D graphic workstation.