With our medical technology, surgeons can see and operate within the body. This surgical technique is possible because the surgeon navigates by advanced three-dimensional maps that show him the way around the inside of the body. 3D ultrasonic images enable the surgeon to see changes in the tissue during the operation itself. The system has been developed by research groups in Trondheim. Thanks to close collaboration with clinicians at St. Olav's Hospital and NTNU, we in SINTEF have succeeded in combining real-time 2D ultrasonics with 3D images made with ultrasonics, MR (magnetic resonance) and x-rays.