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VIRTUAL ARTHROSCOPIC KNEE SURGERY TRANING SYSTEM

VIRTUAL ARTHROSCOPIC KNEE SURGERY TRANING SYSTEM. Yang Xiaosong The Chinese University of Hong Kong Tsinghua University. VIRTUAL ARTHROSCOPIC KNEE SURGERY TRANING SYSTEM. A joint project between the Chinese University of Hong Kong Tsinghua University, sponsored by

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VIRTUAL ARTHROSCOPIC KNEE SURGERY TRANING SYSTEM

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  1. VIRTUAL ARTHROSCOPIC KNEE SURGERY TRANING SYSTEM Yang Xiaosong The Chinese University of Hong Kong Tsinghua University

  2. VIRTUAL ARTHROSCOPIC KNEE SURGERY TRANING SYSTEM A joint project between the Chinese University of Hong Kong Tsinghua University, sponsored by The National Natural Science Foundation of China RGC of Hong Kong

  3. Minimally Invasive Microsurgical Technique • Less trauma • Reduced pain • Quicker convalescence

  4. Restrictions of Arthroscopy • Restricted vision • Poor hand-eye coordination • Limited mobility of surgical instruments

  5. Surgical Skill Training • Animals • Cadavers • Virtual reality based simulation systems

  6. Arthroscopy Surgery

  7. Virtual Arthroscopic Knee Surgery Training System • Modeling using data from Visible Human Project • Simulation of the deformation of soft tissue with topological change by FEA • User interaction • Force feedback

  8. Hardware System Architecture Central Computer (PIV 1.5G, Nivdia Geforce 3, Windows 2000) Input Device Display Screen

  9. Preprocess Stage CT, MRI Volume Data Segmented Volume Data 3D Segmentation Geometry Modeling Physical Attributes • Surface and Tetrahedral mesh On the FLY Stage Set Force Force Feedback Device • Real-time simulation of non-linear deformation with cutting • Force feedback calculation of soft tissues Manipulation of Operation Facilities Contacted Collision Detection 3D Tetrahedral mesh Surface mesh Surface mesh • Realistic Rendering • View from outside • Arthroscopy Simplify & Smooth Local Remesh in Operation Area Software System Architecture

  10. Mesh Generation of Human Organs • Segmentation • Surface boundary meshes creation • Tetrahedral mesh generation • Mesh smoothing

  11. Collision Detection • Prevent the arthroscope and operation facility from entering a solid object • Get the initial intersection point for cutting simulation • Collision detection for deformable objects, different from that of rigid objects • AABB tree

  12. Simulation of Soft Tissue Deformation With Flexible Cutting • Physically reality • Real-time interaction Hybrid Finite Element Method

  13. Hybrid FEM • Non-linear deformation and topology changing model in operating region (Region 1). • The local small region, fast to compute • Linear deformation and topology constant model in non-operating region (Region 2) • The remaining large region, accelerated by pre-processing

  14. 2-Dimension Sample

  15. Cutting of a single element Degeneration cases Normal Cases

  16. 3-Dimension Example • A simplified model of thigh • Tetrahedral meshes simplification

  17. Input Device • Four DOFs for arthroscope and instruments • Pitch • Yaw • Insertion • Rotation • Force feedback • Three DC motors attached for the first three DOF • The fourth DOF need no force feedback

  18. Input Device Picture

  19. System Interface

  20. Sample

  21. Work to do • More effective interactive 3-D segmentation system • Realistic Rendering • Simulation of complicated operation facilities

  22. Tetrahedral Mesh Generation of Human Organs on Segmented Volume

  23. Tetrahedralization Algorithm on Segmented Volume • Voxel-Split tetrahedralization • 3D conforming Delaunay tetrahedralization algorithm • Feature point based tetrahedralization

  24. Voxel-Split tetrahedralization

  25. Voxel-Split tetrahedralization

  26. Voxel-Split tetrahedralization

  27. Voxel-Split tetrahedralization

  28. Voxel-Split tetrahedralization • Simplification of Segmentation Volume

  29. Voxel-Split tetrahedralization • Global Simplification of Segmentation Volume • Boundary voxel decomposition • The order of voxel merge

  30. 3D conforming Delaunay tetrahedralization algorithm

  31. Tissue boundaryextraction

  32. 3D conforming Delaunay tetrahedralization algorithm

  33. Feature point based tetrahedralization • Accurate. • Small scale. • Well-shaped.

  34. Feature point based tetrahedralization • Placement of the mesh vertices • Delaunay Triangulation • Restore the tissue boundary and set element’s tissue type

  35. Feature point based tetrahedralization • Point Displacement • feature point, steiner point and structured mesh point

  36. Feature point based tetrahedralization • Feature Point

  37. Feature point based tetrahedralization • Feature Point • Gradient computation of the mid point of each voxel edge • Compare of the gradient in the local neighbors • Error bounded simplification of feature point

  38. Feature point based tetrahedralization • Steiner point displacement

  39. Feature point based tetrahedralization

  40. Feature point based tetrahedralization • Cross Tissue Boundary Detection • Criterion for crossing boundary • Boundary Points (BP) • Voxel Points (VP) • Edge: VP-VP BP-VP BP-BP

  41. Feature point based tetrahedralization Remesh to restore the tissue boundary • No=3, flip32 to delete the crossing edge. • No=4, Flip4Diagonal to swap the diagonal crossing edge. • No>4

  42. Feature point based tetrahedralization • Remesh to restore the tissue boundary

  43. Feature point based tetrahedralization Volume 297 x 341 x 180= 18,229,860 Tetehedral Mesh 94,953 nodes, 490,409 elements

  44. Thanks

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