Visualization tool for improved accuracy in needle placement during percutaneous radio-frequency ablation of liver tumors Thomas Stüdeli *a , Denis Kalkofen b, Petter Risholm c , Wajid Ali c , Adinda Freudenthal a , Eigil Samset c a Faculty of Industrial Design Engineering, Delft University of Technology, Landbergstraat 15, NL-2628 CE Delft, the Netherlands b Institute for Computer Graphics and Vision, Graz University of Technology, Inffeldgasse 16, A-8010 Graz, Austria c The Interventional Centre, Rikshospitalet University Hospital, Sognsvannsveien 20, N-0027 Oslo, Norway ABSTRACT The European research network “Augmented reality in Surgery” (ARIS*ER) developed a system that supports percutaneous radio frequency ablation of liver tumors. The system provides interventionists, during placement and insertion of the RFA needle, with information from pre-operative CT images and real-time tracking data. A visualization tool has been designed that aims to support (1) exploration of the abdomen, (2) planning of needle trajectory and (3) insertion of the needle in the most efficient way. This work describes a first evaluation of the system, where user performances and feedback of two visualization concepts of the tool – needle view and user view – are compared. After being introduced to the system, ten subjects performed three needle placements with both concepts. Task fulfillment rate, time for completion of task, special incidences, accuracy of needle placement recorded and analyzed. The results show ambiguous results with beneficial and less favorable effects on user performance and workload of both concepts. Effects depend on characteristics of intra-operative tasks as well as on task complexities depending on tumor location. The results give valuable input for the next design steps. Keywords: Visualization, Technology assessment, Intra-operative Imaging, Image-Guided Therapy, Abdominal procedure 1. INTRODUCTION In the percutaneous radiofrequency ablation the surgeon or the intervention radiologist (both will be called interventionist or user) punctures a needle with an electrode (RFA device) through the skin, into the abdomen, into the liver and hits a predefined place in the tumor. After the needle is placed in the tumor, the electrode in the needle is set to dissipate radio-frequency waves and heats up and coagulates the tissue in the neighborhood of the electrode. That means that the tumor is locally destroyed by radiofrequency waves dissipating from the electrode. In most cases the interventionists actually do not use more than a simple needle holder (RFA device) as well as the US image to support the placement of the needle (manual tasks), the final check before the ablation is sometimes done with CT. Poon and colleges [13] report a significant learning curve in their first 100 RFA procedures, although the direct percutaneous approach with local destruction of the tumor is widely seen as a simple and effective way. The accuracy of the needle placement is seen as an important factor for a successful ablation. It might be also one of the reasons for the reported training effect. Many interventionist expressed their wish to be supported by newest technological possibilities during RFA procedures [2], e.g. recently McGahan [10] an experienced interventionist who in 1990, 18 years ago, performed the first RFA of a liver tumor. 1.1. First design loop The European research training network ARIS*ER - “Augmented Reality in Surgery” [3,1] aims to support interventionists with “super vision” (e.g. combined US-CT) and “super sense” (e.g. haptic support for the needle insertion). A result of a first design loop 2005-2006 was an augmented reality system running on a liver phantom, see * T.P.Studeli@tudelft.nl, phone: +31 15 278 30 20, http://www.io.tudelft.nl/medisign Medical Imaging 2008: Visualization, Image-guided Procedures, and Modeling, edited by Michael I. Miga, Kevin Robert Cleary, Proc. of SPIE Vol. 6918, 69180B, (2008) 1605-7422/08/$18 · doi: 10.1117/12.769399 Proc. of SPIE Vol. 6918 69180B-1 Downloaded from SPIE Digital Library on 22 Jan 2010 to 131.180.130.114. Terms of Use: http://spiedl.org/terms