Making image guidance work: understanding control of accuracy.

Use of image-guided surgery is becoming increasingly common in both sinus surgery and neuro-otologic applications. The purpose of this study was to determine the effect of fiducial distribution and mean fiducial error on point accuracy. Using a plastic model, we determined that optimal navigation accuracy was achieved by surrounding the operative target with a widespread field of fiducials. True accuracy was always highest when we targeted a surface point. Accuracy was decreased at points removed from the center of the registration target zone created by the fiducials. Inaccurate registration resulted in increased mean fiducial error and lower accuracy at the target point. Understanding the registration process will enhance the utility of image-guided surgery in otolaryngoloey and skull base surgery.