Intraoperatively, the surgeon will interrogate the liver with ultrasound. The time spent by the surgeon using the ultrasound is recorded. If all lesions seen on pre-op imaging were found, the patient does not have the Pathfinder Explorer system applied. If one or more lesions cannot be found, then the Pathfinder Explorer system is calibrated and a tracking device is attached to the ultrasound probe, which the surgeon will use to reattempt localization of the missing tumor. The Pathfinder Explorer system operates in real-time in conjunction with the ultrasound.