Introduction: Optical neuronavigation has been established as a reliable adjunct to many neurosurgical procedures. Procedures such as asleep deep brain stimulation (aDBS), and C2 pedicle screw placement benefit from the increased accuracy these systems offer. All systems have some degree of tolerated error in their design which may exceed that presumed by the surgeon, producing less accurate guidance, and suboptimal surgical outcomes.
Methods: A passive optical intraoperative navigation system was used to simulate an aDBS procedure with a “frameless” targeting system. Multiple configurations of the targeting system components were examined to determine sources of error. Virtual entry point and target variations were recorded and compared with points obtained using an electromagnetic navigation system and direct visual observation.
Results: The greatest source of error was the orientation of the targeting probe to the reference frame/ camera system. Virtual entry point errors ranged between 0.12mm and 1.4mm, while target errors ranged between 0.2mm and 2.4mm (mean 0.85mm, median 0.88mm, standard deviation 0.24mm). These errors produced a complex, reproducible pattern based on the orientation of the targeting probe. No orientation exceeded the acceptable tolerance programmed into the targeting software by the manufacturer. Representative configurations were tested for physical error using the electromagnetic system; physical errors between 1.2mm-1.4mm +/-0.4mm were measured and visually confirmed.
Conclusions: Use of optically guided neuronavigation is expected to expand in the future. Successful utilization of this technology depends on an understanding of the limits built into the systems. When high precision is critical, systems must be optimized beyond the manufacturer’s built-in tolerances. Optimal orientation of the optical markers into a plane roughly perpendicular to the line of sight from the tracking cameras is crucial to maximize accuracy.
Patient Care: Reduction of error in stereotactic procedures will reduce operative morbidity and improve patient outcomes
Learning Objectives: 1) Understand the limitations of optical navigations systems; 2) Appreciate the precision required for stereotactic procedures in the context of navigation systems; 3) Learn techniques to minimize error with optical navigation systems.