Papers by Cagatay Basdogan
International Congress Series, 2005
The lack of experimental data in current literature on material properties of soft tissues in liv... more The lack of experimental data in current literature on material properties of soft tissues in living condition has been a significant obstacle in the development of realistic soft tissue models for virtual reality based surgical simulators used in medical training. A robotic indenter was developed for minimally invasive measurement of soft tissue properties in abdominal region during a laparoscopic surgery. Using the robotic indenter, force versus displacement and force versus time responses of pig liver under static and dynamic loading conditions were successfully measured to characterize its material properties in three consecutive steps. First, the effective elastic modulus of pig liver was estimated as 10-15 kPa from the force versus displacement data of static indentations based on the small deformation assumption. Then, the stress relaxation function, relating the variation of stress with respect to time, was determined from the force versus time response data via curve fitting. Finally, an inverse finite element solution was developed using ANSYS finite element package to estimate the optimum values of viscoelastic and nonlinear hyperelastic material properties of pig liver through iterations. The initial estimates of the material properties for the iterations were extracted from the experimental data for faster convergence of the solutions.
Realistic simulation of tissue cutting and bleeding is important components of a surgical simulat... more Realistic simulation of tissue cutting and bleeding is important components of a surgical simulator that are addressed in this study. Surgeons use a number of instruments to perform incision and dissection of tissues during minimally invasive surgery. For example, a coagulating hook is used to tear and spread the tissue that surrounds organs and scissors are used to dissect the cystic duct during laparoscopic cholecystectomy. During the execution of these procedures, bleeding may occur and blood flows over the tissue surfaces. We have developed computationally fast algorithms to display (1) tissue cutting and (2) bleeding in virtual environments with applications to laparoscopic surgery. Cutting through soft tissue generates an infinitesimally thin slit until the sides of the surface are separated from each other. Simulation of an incision through tissue surface is modeled in three steps: first, the collisions between the instrument and the tissue surface are detected as the simulated cutting tool passes through. Then, the vertices along the cutting path are duplicated. Finally, a simple elastic tissue model is used to separate the vertices from each other to reveal the cut. Accurate simulation of bleeding is a challenging problem because of the complexities of the circulatory system and the physics of viscous fluid flow. There are several fluid flow models described in the literature, but most of them are computationally slow and do not specifically address the problem of blood flowing over soft tissues. We have reviewed the existing models, and have adapted them to our specific task. The key characteristics of our blood flow model are a visually realistic display and real-time computational performance. To display bleeding in virtual environments, we developed a surface flow algorithm. This method is based on a simplified form of the Navier-Stokes equations governing viscous fluid flow. The simplification of these partial differential equations results in a wave equation that can be solved efficiently, in real-time, with finite difference techniques. The solution describes the flow of blood over the polyhedral surfaces representing the anatomical structures and is displayed as a continuous polyhedral surface drawn over the anatomy.
IEEE Computer Graphics and Applications, 2007
ACM Transactions on Computer-human Interaction, 2000
Investigating virtual environments has become an increasingly interesting research topic for engi... more Investigating virtual environments has become an increasingly interesting research topic for engineers, computer and cognitive scientists, and psychologists. Although there have been several recent studies focused on the development of multimodal virtual environments (VEs) to study human-machine interactions, less attention has been paid to human-human and human-machine interactions in shared virtual environments (SVEs), and to our knowledge, no attention paid at all to what extent the addition of haptic communication between people would contribute to the shared experience. We have developed a multimodal shared virtual environment and performed a set of experiments with human subjects to study the role of haptic feedback in collaborative tasks and whether haptic communication through force feedback can facilitate a sense of being and collaborating with a remote partner. The study concerns a scenario where two participants at remote sites must cooperate to perform a joint task in an SVE. The goals of the study are (1) to assess the impact of force feedback on task performance, (2) to better understand the role of haptic communication in human-human interactions, (3) to study the impact of touch on the subjective sense of collaborating with a human as reported by the participants based on what they could see and feel, and (4) to investigate if gender, personality, or emotional experiences of users can affect haptic communication in SVEs. The outcomes of this research can have a powerful impact on the development of next-generation human-computer interfaces and network protocols that integrate touch and force feedback technology into the Internet, development of protocols and techniques for collaborative teleoperation such as hazardous material removal, space station Part of this research, including the development of the VE set-up, was supported by a grant from Office of Naval Research. Mel Slater's work in this research was part of his involvement in the European ACTS COVEN project (Collaborative Virtual Environments). repair, and remote surgery, and enhancement of virtual environments for performing collaborative tasks in shared virtual worlds on a daily basis such as cooperative teaching, training, planning and design, cybergames, and social gatherings. Our results suggest that haptic feedback significantly improves the task performance and contributes to the feeling of "sense of togetherness" in SVEs. In addition, the results show that the experience of visual feedback only at first, and then subsequently visual plus haptic feedback, elicits a better performance than presentation of visual plus haptic feedback first followed by visual feedback only.
Teleoperators and Virtual Environments, 1999
Computer haptics, an emerging field of research that is analogous to computer graphics, is concer... more Computer haptics, an emerging field of research that is analogous to computer graphics, is concerned with the generation and rendering of haptic virtual objects. In this paper, we propose an efficient haptic rendering method for displaying the feel of 3-D polyhedral objects in virtual environments (VEs). Using this method and a haptic interface device, the users can manually explore and feel the shape and surface details of virtual objects. The main component of our rendering method is the ''neighborhood watch'' algorithm that takes advantage of precomputed connectivity information for detecting collisions between the end effector of a force-reflecting robot and polyhedral objects in VEs. We use a hierarchical database, multithreading techniques, and efficient search procedures to reduce the computational time such that the haptic servo rate after the first contact is essentially independent of the number of polygons that represent the object. We also propose efficient methods for displaying surface properties of objects such as haptic texture and friction. Our haptic-texturing techniques and friction model can add surface details onto convex or concave 3-D polygonal surfaces. These haptic-rendering techniques can be extended to display dynamics of rigid and deformable objects.
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... to rapidly load virtual objects into desired experimental scenarios, interactively manipulate... more ... to rapidly load virtual objects into desired experimental scenarios, interactively manipulate (translate, rotate ... During the simulations, the user manipulates the generic stylus of the force-feedback ... SVEs, (2) if so, what types of haptic communication/negotiation strategies they ...
IEEE Computer Graphics and Applications, 2004
M inimally invasive surgery has revolutionized many surgical procedures over the last few decades... more M inimally invasive surgery has revolutionized many surgical procedures over the last few decades. MIS is performed using a small video camera, a video display, and a few customized surgical tools. In procedures such as gall bladder removal (laparoscopic cholesystectomy), surgeons insert a camera and long slender tools into the abdomen through small skin incisions to explore the internal cavity and manipulate organs from outside the body as they view their actions on a video display. Because the development of minimally invasive techniques has reduced the sense of touch compared to open surgery, surgeons must rely more on the feeling of net forces resulting from tool-tissue interactions and need more training to successfully operate on patients. Although tissue color and texture convey important anatomical information visually, touch is still critical in identifying otherwise obscure tissue planes, blood vessels, and abnormal tissues, and gauging optimal forces to be applied for tissue manipulation. Much of the art of MIS and training for a particular procedure depend on the education and refinement of the trainee's haptic sensorimotor system.
International Journal of Robotic Research, 2000
IEEE Computer Graphics and Applications, 2004
M inimally invasive surgery has revolutionized many surgical procedures over the last few decades... more M inimally invasive surgery has revolutionized many surgical procedures over the last few decades. MIS is performed using a small video camera, a video display, and a few customized surgical tools. In procedures such as gall bladder removal (laparoscopic cholesystectomy), surgeons insert a camera and long slender tools into the abdomen through small skin incisions to explore the internal cavity and manipulate organs from outside the body as they view their actions on a video display. Because the development of minimally invasive techniques has reduced the sense of touch compared to open surgery, surgeons must rely more on the feeling of net forces resulting from tool-tissue interactions and need more training to successfully operate on patients. Although tissue color and texture convey important anatomical information visually, touch is still critical in identifying otherwise obscure tissue planes, blood vessels, and abnormal tissues, and gauging optimal forces to be applied for tissue manipulation. Much of the art of MIS and training for a particular procedure depend on the education and refinement of the trainee's haptic sensorimotor system.
Teleoperators and Virtual Environments, 1999
In this paper, we summarize our progress on two interaction techniques (point-based and ray-based... more In this paper, we summarize our progress on two interaction techniques (point-based and ray-based) for haptic rendering. First, we describe a new point-based rendering technique that i s computationally less expensive than previously proposed methods. We use a localized search procedure to reduce the number of computations and make it independent of the number polygons of the polyhedron. Second, we discuss the implementation details of a ray-based technique together with its advantages. We have utilized this rendering technique to display the haptic interactions between 3D objects and the stylus modeled as a line segment. In order to develop more effective multimodal VEs, we have experimented with multi-threading (on Windows NT platform) and multi-processing (on UNIX platform) techniques and have successfully separated the visual and haptic servo loops. Our experience is that both techniques are quite useful in achieving high haptic rendering rates and stable haptic interactions. Although creating a separate process for each modality requires more programming effort, it enables the user to display the graphics and/or haptics on any desired machine(s). On the other hand, programming with threads takes less effort, but t hey are not as flexible as processes. We have also developed a graphical interface that enables the user to construct virtual environments by means of user-defined text file, toggle stereo visualization, save the virtual environment and quit from the application. The user can load objects into the scene, assign simple visual and haptic properties to the objects using this text file. Following the c onstruction of the scene using the text file, the user can interactively translate, rotate, and scale objects and the interface will automatically update the visual and haptic models.
IEEE-ASME Transactions on Mechatronics, 2001
Computers & Graphics, 1997
... 61, Proceedings of the ASME Dynamic Systems and Control Division ASME 1997 A Ray-Based Haptic... more ... 61, Proceedings of the ASME Dynamic Systems and Control Division ASME 1997 A Ray-Based Haptic Rendering Technique for Displaying Shape and Texture of 3D ...
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Papers by Cagatay Basdogan