Force interactions in laparoscopic simulations: haptic rendering of soft tissues.

Research in the area of computer assisted surgery and surgical simulation has mainly focused on developing 3D geometrical models of the human body from 2D medical images, visualization of internal structures for educational and preoperative surgical planning purposes, and graphical display of soft tissue behavior in real time. Conveying to the surgeon the touch and force sensations with the use of haptic interfaces has not been investigated in detail. We have developed a set of haptic rendering algorithms for simulating "surgical instrument--soft tissue" interactions. Although the focus of the study is the development of algorithms for simulation of laparoscopic procedures, the developed techniques are also useful in simulating other medical procedures involving touch and feel of soft tissues. The proposed force-reflecting soft tissue models are in various fidelities and have been developed to simulate the behavior of elastically deformable objects in virtual environments. The developed algorithms deal directly with geometry of anatomical organs, surface and compliance characteristics of tissues, and the estimation of appropriate reaction forces to convey to the user a feeling of touch and force sensations.