Accuracy evaluation of a 3D ultrasound-based neuronavigation system

We have investigated the 3D navigation accuracy of ail ultrasound-based neuronavigation system for surgical planning and intraoperative image guidance. In addition, we present a detailed description and review of the error sources associated with conventional MRI-based and ultrasound-based surgical neuronavigation. A phantom with 27 precisely defined points was scanned with ultrasound by various translation and tilt movements of the ultrasound probe (180 3D scans), and the 27 image points in each volume were located using ail automatic detection algorithm. These locations were compared to the physically measured locations of the same 27 points. The accuracy of the neuronavigation system and the effect of varying acquisition conditions, were found through a thorough statistical analysis of the differences between the two point sets. The accuracy was found to be 1.40 +/- 0.45 mm (arithmetic mean) for the system in our laboratory setting. Improper probe calibration is the major contribution to this number. Based on our extensive data set and evaluation, we expect the accuracy found in the laboratory setting to be close to the overall clinical setting in ultrasound-based neuronavigation. Our analysis indicates that the overall clinical accuracy may be as low as 2 mm when using intraoperative imaging to eliminate the brain shift.