Technical aspects and feasibility of laparoscopic ultrasound navigation in radiofrequency ablation of unresectable hepatic malignancies

Purpose: Laparoscopic radiofrequency ablation is safe, practicable, and combines minimally invasive surgery with the advantages of laparotomy. However, application of the laparoscopic freehand puncture is restricted because of capnoperitoneum and the consequent fixation of the needle on two different points. The use of a laparoscopic ultrasound probe with a canal for puncture can solve this problem and improve precision. However, a stiff needle limits the necessary angulation that is needed to reach right-lateral and cranial liver metastases. Therefore we present a new navigation tool for laparoscopic interventions. Materials and Methods: The US Guide 2000 (Ultra Guide, Tirât Hacarmel, Israel) is an independent navigation system compatible with all ultrasound machines and has six degrees of freedom. After proper evaluation of this system under operating room conditions during transcutaneous radiofrequency ablation, we used this technique in laparoscopic radiofrequency ablation. A special adapter was developed to attach the ultrasound-based navigation system to a laparoscopic ultrasound probe. After calibrating the system with an ultrasound phantom, laparoscopic navigation in a liver organ model was studied. Results: Even in cases of angulation of the ultrasound probe no disturbances of the navigation system could be detected. Anatomic landmarks in the liver could be safely reached. No interaction between the navigation system and the laparoscopic ultrasound probe or operating instruments was observed. Conclusion: Our preliminary results show the feasibility of this technique in laparoscopic radiofrequency ablation. The use of an ultrasound-based laparoscopic inline navigation system offers the possibility of out-of-plane needle placement and could combine the flexibility of freehand puncture with the accuracy of a canal for puncture. This could increase the safety and accuracy of punctures.