Image guided surgery of paranasal sinuses and anterior skull base--five years experience with the InstaTrak-System.

We report on our experience with navigational tools in paranasal sinus and anterior skull base surgery, especially with electromagnetic guidance systems. During the last five years we operated over 80 selected cases with the InstaTrak system from VTI (Lawrence, MS, USA). Applicability and user friendliness were explored. The InstaTrak 3500 employs a Sun Workstation and is a frameless and free-arm and navigation system. Two different suction devices, used as sensors (receivers), and one transmitter are interconnected to this workstation. The position of the tip of the aspirator is displayed as a pair of crosshairs on the screen in axial, coronal and sagittal planes of the patient's CT-scan on the computerscreen online. Our results showed high accuracy-level, usually better than one millimeter and a setup-time less than ten minutes, on average. No additional personnel is required in the OR. We believe that the system enhances efficacy in selected cases like revision surgery, tumor surgery or difficult anterior skull base surgery. However, one should consider that medicolegal responsibility stays always with the surgeon and not with any navigation system.