Applying tissue models in teleoperated robot-assisted surgery

Teleoperation allows surgeons to perform medical procedures that are remote in distance and/or different in scale. During a teleoperated surgical procedure, extracting information about the patient, in particular mechanical and geometrical models of tissues, may be useful for detecting tissue abnormalities, improving telemanipulator stability and fidelity of force feedback, and creating virtual boundaries to prevent the patient-side manipulators from entering unwanted regions in the workspace.;This dissertation consists of three studies involving the use of tissue models in robot-assisted surgery. First, we demonstrate a. real-time graphical overlay of stiffness information that is created using estimated tissue properties during teleoperation. A pseudo-stiffness parameter of a nonlinear Hunt-Crossley tissue model was chosen to describe tissue mechanical behavior, based on tests involving both self-validation and cross-validation of least-squares estimation. We used the hue-saturation-lightness color space to convert estimated stiffness information to graphical representation. The stiffness map was then overlaid on a. reconstructed three-dimensional surface model of the tissue acquired from a stereo camera. The overlaid image can help an operator detect a lump dining teleoperated palpation. With a custom version of the da Vinci Classic Surgical System. we conducted experiments using both artificial and biological tissues and quantified the accuracy of our technique. Second, we examine the impact of using a. mathematical environment model on the stability and transparency of a general bilateral teleoperation system. Considering an estimated environment model, we design a teleoperator controller that would provide high-fidelity force feedback to an operator. The stability conditions of our controller relax stability ma compared to a. previously proposed controller. Third, we present the development and evaluation of an open platform for augmented reality and haptic interfaces for robot-assisted surgery. Our goal is to create a system that enables interoperability between various kinds of telesurgical devices and enhances the surgeon's performance by providing haptic feedback and augmented reality. We demonstrate the feasibility of the interface for two augmentations, both of which are created using the detected geometry of the tissue surface: the real-time material property overlay described earlier, and forbidden-region virtual fixtures that prevent a patient-side manipulator from entering undesired regions of the workspace.