Zhonghua Lu

Wuhan University of Technology, Wu-han-shih, Hubei, China

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Publications (10)7.77 Total impact

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    ABSTRACT: High-frequency electricity is used in the majority of surgical interventions. However, modern computer-based training and simulation systems rely on physically unrealistic models that fail to capture the interplay of the electrical, mechanical and thermal properties of biological tissue. We present a real-time and physically realistic simulation of electrosurgery by modelling the electrical, thermal and mechanical properties as three iteratively solved finite element models. To provide subfinite-element graphical rendering of vaporized tissue, a dual-mesh dynamic triangulation algorithm based on isotherms is proposed. The block compressed row storage (BCRS) structure is shown to be critical in allowing computationally efficient changes in the tissue topology due to vaporization. We have demonstrated our physics-based electrosurgery cutting algorithm through various examples. Our matrix manipulation algorithms designed for topology changes have shown low computational cost. Our simulator offers substantially greater physical fidelity compared to previous simulators that use simple geometry-based heat characterization. Copyright © 2013 John Wiley & Sons, Ltd.
    International Journal of Medical Robotics and Computer Assisted Surgery 12/2013; · 1.49 Impact Factor
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    ABSTRACT: Surgical simulations require haptic interactions and collaboration in a shared virtual environment. A software framework for decoupled surgical simulation based on a multi-controller and multi-viewer model-view-controller (MVC) pattern was developed and tested. A software framework for multimodal virtual environments was designed, supporting both visual interactions and haptic feedback while providing developers with an integration tool for heterogeneous architectures maintaining high performance, simplicity of implementation, and straightforward extension. The framework uses decoupled simulation with updates of over 1,000 Hz for haptics and accommodates networked simulation with delays of over 1,000 ms without performance penalty. The simulation software framework was implemented and was used to support the design of virtual reality-based surgery simulation systems. The framework supports the high level of complexity of such applications and the fast response required for interaction with haptics. The efficacy of the framework was tested by implementation of a minimally invasive surgery simulator. A decoupled simulation approach can be implemented as a framework to handle simultaneous processes of the system at the various frame rates each process requires. The framework was successfully used to develop collaborative virtual environments (VEs) involving geographically distributed users connected through a network, with the results comparable to VEs for local users.
    International Journal of Computer Assisted Radiology and Surgery 07/2011; 6(4):457-71. · 1.36 Impact Factor
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    ABSTRACT: Morbid obesity accounts for more than 90,000 deaths per year in the United States. Laparoscopic adjustable gastric banding (LAGB) is the second most common weight loss procedure performed in the US and the most common in Europe and Australia. Simulation in surgical training is a rapidly advancing field that has been adopted by many to prepare surgeons for surgical techniques and procedures. The aim of our study was to determine face, construct, and content validity for a novel virtual reality laparoscopic adjustable gastric band simulator. Twenty-eight subjects were categorized into two groups (expert and novice), determined by their skill level in laparoscopic surgery. Experts consisted of subjects who had at least 4 years of laparoscopic training and operative experience. Novices consisted of subjects with medical training but with less than 4 years of laparoscopic training. The subjects used the virtual reality laparoscopic adjustable band surgery simulator. They were automatically scored according to various tasks. The subjects then completed a questionnaire to evaluate face and content validity. On a 5-point Likert scale (1 = lowest score, 5 = highest score), the mean score for visual realism was 4.00 ± 0.67 and the mean score for realism of the interface and tool movements was 4.07 ± 0.77 (face validity). There were significant differences in the performances of the two subject groups (expert and novice) based on total scores (p < 0.001) (construct validity). Mean score for utility of the simulator, as addressed by the expert group, was 4.50 ± 0.71 (content validity). We created a virtual reality laparoscopic adjustable gastric band simulator. Our initial results demonstrate excellent face, construct, and content validity findings. To our knowledge, this is the first virtual reality simulator with haptic feedback for training residents and surgeons in the laparoscopic adjustable gastric banding procedure.
    Surgical Endoscopy 04/2011; 25(4):1012-8. · 3.43 Impact Factor
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    ABSTRACT: We present a novel real-time technique for cutting during electrocautery procedures in surgical training. Our algorithm is based on cauterizing the part of the tissue that exceeds the critical vaporization temperature. The resulting topology changes due to cutting are accounted for in real-time. Results presented for the overall electrocautery cutting algorithm show that the real-time costs are minimal and thus allow interactive simulation.
    Studies in health technology and informatics 01/2011; 163:311-6.
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    ABSTRACT: The development of a multimodal interactive simulation is a very elaborate task due to the various complex software components involved, which run simultaneously at very high rates with maximum CPU load. In this work, we propose a multimodal parallel simulation framework called SoFMIS to create rapid interactive simulations such as surgical simulations. Our framework offers great flexibility and customization allowing simulation developers and researchers to concentrate on the simulation logic rather than component development.
    Studies in health technology and informatics 01/2011; 163:213-7.
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    ABSTRACT: In the real world, tools used for manipulation are pivoted with specialized tips for specific functions including grasping and cutting. Manipulating deformable virtual objects with them involves maintaining extended contact, which is difficult due to the variations in applied force. Our method consists in selecting a fixed set of points on the jaws of a pivoted tool, and placing them either equidistant or according to the geometry of the tool. Vertex and triangle proximities are calculated for each of the interacting deformable objects for collision detection. This method was successfully tested in a surgical simulation scenario where a deformable omental fat model was grasped and retracted while maintaining full contact with the pivoted tool tip at all times.
    Studies in health technology and informatics 01/2011; 163:555-9.
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    ABSTRACT: Haptic enabled virtual reality surgical simulators are increasingly replacing more traditional training tools in teaching hospitals. Development of these simulators may be greatly facilitated using physics libraries such as NVIDIA's PhysX. While volumetric models of soft bodies may be easily generated and simulated using such engines, it is not straightforward to develop complex surgical tasks such as surgical cutting and hence novel algorithms are necessary. Electrocautery is a tissue cutting process used in surgery to burn away soft tissues by localized heating using a specialized probe. Unlike typical surgical cutting with sharp instruments, the electrocautery process depends upon the duration of the tool tissue contact and the rate of heat conduction. The simulation of electrocautery depends on understanding the physics of heat conduction as well as empirical measurements of temperature in the tissue. In this paper we report a physics-based paradigm for the simulation of electrocautery procedures that can directly work on volumetric objects. Based on the solution characteristics of the conduction equation and empirical observations using a thermal imaging camera, we manipulate only the tetrahedral mesh vertices that are inside a sphere of influence whose centre is located at the tip of the electrocautery tool and which expands as a function of time. A 3D orthogonal plane is used to split the tetrahedral mesh vertices along the three Cartesian directions. Examples are provided from a realistic surgical simulation environment.
    Haptics Symposium, 2010 IEEE; 04/2010
  • Zhonghua Lu, Dingfang Chen
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    ABSTRACT: A finite element method is used to simulate the deformation of soft body. The crucial procedure of cutting simulation is the geometry remeshing. During remeshing, the inner topologie consistence need be considered. Previously, a large number sub-tetrahedral is used to avoid the consistence problem or an additional algorithm is used to check and adjust the geometry to keep its consistence. In this paper we present a novel method with minimal elements to guarantee the geometry consistence during tetrahedralization. And when the edge cut is close to an existing node, then just split the node instead of cutting the edge, which avoids small tetrahedra generated and significantly improves the stability of numeric solution.
    01/2010;
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    ABSTRACT: The development of modern surgical simulators is highly challenging, as they must support complex simulation environments. The demand for higher realism in such simulators has driven researchers to adopt physics-based models, which are computationally very demanding. This poses a major problem, since real-time interactions must permit graphical updates of 30 Hz and a much higher rate of 1 kHz for force feedback (haptics). Recently several physics engines have been developed which offer multi-physics simulation capabilities, including rigid and deformable bodies, cloth and fluids. While such physics engines provide unique opportunities for the development of surgical simulators, their higher latencies, compared to what is necessary for real-time graphics and haptics, offer significant barriers to their use in interactive simulation environments. In this work, we propose solutions to this problem and demonstrate how a multimodal surgical simulation environment may be developed based on NVIDIA's PhysX physics library. Hence, models that are undergoing relatively low-frequency updates in PhysX can exist in an environment that demands much higher frequency updates for haptics. We use a collision handling layer to interface between the physical response provided by PhysX and the haptic rendering device to provide both real-time tissue response and force feedback. Our simulator integrates a bimanual haptic interface for force feedback and per-pixel shaders for graphics realism in real time. To demonstrate the effectiveness of our approach, we present the simulation of the laparoscopic adjustable gastric banding (LAGB) procedure as a case study. To develop complex and realistic surgical trainers with realistic organ geometries and tissue properties demands stable physics-based deformation methods, which are not always compatible with the interaction level required for such trainers. We have shown that combining different modelling strategies for behaviour, collision and graphics is possible and desirable. Such multimodal environments enable suitable rates to simulate the major steps of the LAGB procedure.
    International Journal of Medical Robotics and Computer Assisted Surgery 06/2009; 5(3):341-53. · 1.49 Impact Factor
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    ABSTRACT: This paper describes the development of an overhead crane simulator system targeted to operator training and examine. The virtual overhead crane model were made by 3DMAX with its real dimensions, and be export as IVE data Format which can be used OSG (OpenSceneGraph) 3D engine to control its inner relative mechanism motion. And distributed Multi-Screen display technique of visual system is used to afford high quality video with wide angle of view. Using hardware and software to realize the interactive response between operator and virtual scene. And these response simulations can optionally be stored as animations, and can later be played back, modified, filmed from different viewpoints. An overhead crane simulator is implemented successfully and is used to train new motormen who can be easier to control real cranes after training.
    Pervasive Computing and Applications, 2008. ICPCA 2008. Third International Conference on; 11/2008

Publication Stats

40 Citations
7.77 Total Impact Points

Institutions

  • 2013
    • Wuhan University of Technology
      Wu-han-shih, Hubei, China
  • 2009–2011
    • Rensselaer Polytechnic Institute
      • Department of Mechanical, Aerospace and Nuclear Engineering
      Troy, NY, United States
    • Universidade Federal do Rio Grande do Sul
      • Instituto de Informática
      Porto Alegre, Estado do Rio Grande do Sul, Brazil