Prototype of an online navigation system for laparoscopic radiofrequency ablation. 
Laparoscopic Radiofrequency-ablation is a safe and effective method for tumor destruction in patients with unresectable liver tumors.  However, accurate probe placement using laparoscopic ultrasound guidance is required to achieve complete tumor ablation.  After development and evaluation of laparoscopic navigation tools for radiofrequency ablation, we are now presenting a prototype of a navigation- and documentation-system for laparoscopic RFA.  An image-guided surgery system for laparoscopic liver treatments (LapAssistent) based on a 3D-navigation scene was developed.  A laparoscopic ultrasound probe and a RFA needle could be navigated using an electromagnetic tracking system.  The system was studied using a perfused tumour-mimic-model of a porcine liver.  The study showed that laparoscopic ultrasound-guided navigation is technically feasible.  The system enables the surgeon to intraoperatively update the three-dimensional planning data in case of new findings.  The RFA needle could be placed accurately in a targeted tumour with a targeting error ranging from 5 - 7 mm, even out of the ultrasound plane.  In case of multiple tumours lying in close spatial relationship, the documentation module helps to keep track of the already ablated tumours and those that still need to be treated.  Laparoscopic radiofrequency ablation requires advanced laparoscopic ultrasound skills for accurate placement of the RFA probe.  The system adds benefit to laparoscopic RFA enabling the surgeon to place the needle accurately inside the targeted tumours using the navigation scene.  The possibility to update the three-dimensional model with new intraoperative findings enables the surgeon to adapt to a new intraoperative situation.