Augmented Reality guided radio-frequency tumor ablation

Introduction The treatment of liver tumors by radio-frequency ablation (RFA) is an evolving technology using coagulative necrosis to treat patients with unresectable primary or metastatic hepatic cancers [McGa]. However, the guidance procedure to reach the tumors with the needle is usually performed visually using intraoperative two dimensional (2D) cross-sections of the patient obtained with either ultrasound (US) or computed tomography (CT) studies. Because of the difficulty to locate the tumor's center in three dimensions (3D), it usually requires many trials to put the tip of the needle in the proper position to perform tumor coagulation. Then, the targeting procedure is often very time consuming. Real-time superimposition of images reconstructed in 3D from CT studies onto a real patient, socalled Augmented Reality (AR), may improve the accuracy and decrease complications in interventions such as RFA needle placement. One purpose of this project was to build an AR system that could superimpose 3D reconstructions of the liver and its tumors onto a video image associated with a real-time tracking system of the needle. In such a system, the overall margin of error has to be less than 5 mm to provide a meaningful and safe result. We present in this paper our preliminary experiments made on a human abdomen phantom.