Tracked ultrasound for laparoscopic surgery

We calibrate a tracked laparoscopic ultrasound probe for application in image-guided surgery and 3-D volume reconstruction. With a plane-mapping technique, the spatial relationship between the ultrasound beam emitted from the tip of the probe to the local coordinate system of the probe was determined by mapping it with an optically tracked pointer. A cross-wire calibration technique was also performed for comparison. The accuracy and precision of the calibrated probe was evaluated by measuring its ability to localize targets in a water bath. Target registration error depended upon probe position, varying from an average 0.88 mm for the fixed probes to 6.09 mm for a moving probe. This error can be reduced to 4.54 mm by accounting for target localization error which is the error determining the position of the probe itself. These results validate the plane-mapping calibration technique for this type of ultrasound probe, and better probe tracking is expected to reduce the overall registration error.