Tele-immersive Cranial Implant Design

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Tele-immersive Cranial Implant Design

• Chris ScharverSeptember 12, 2001scharver_at_evl.uic
  .edu
• In collaboration withRay Evenhouse, Virtual
  Reality Medicine Laboratory

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Cranial Prosthetics

• Images from the current process
• Before image
• Magnetic resonance imaging-based model
• Stereo lithography model,
• After image

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Problem Statement
Tele-immersive tools will allow cheaper and more
rapid prototyping and evaluation of cranial
prosthetic implants than clay and polymer
modeling techniques.
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Current Surgical Method

• Magnetic resonance scan of patient
• Stereo lithography model of defect
• Defect sculpted with clay
• Defect cast
• Implant modeled with dental wax
• Implant cast
• Surgery and implantation
• Very expensive!

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Jim Foleys Top Ten (2000)

• Top ten problems in computer graphics
• Updated list at Vision 2000
• 9 User interfaces for creativity

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Immersive Modeling

• CHIMP Chapel Hill Immersive Modeling Program
  (UNC)
• Architecture
• http//www.cs.unc.edu/mine/chimp.html
• Samuel (Fraunhofer-Gesellschaft)
• General use
• http//vr.iao.fhg.de/imodeling/samuel.en.html

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Skull Model

• Theoretically obtained from MRI data, then
  converted into geometry for loading into scene
  graph
• Manually made from the Visible Human data set

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Hardware Setup

• PHANToM haptic device
• 6DOF position and rotation
• 3DOF force feedback
• Tracking system
• Display device
• Immersive display?
• Would a monitor suffice?

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PARIS

• Prototyped using the CAVE
• Hands are visiblethrough the displayscreen
  throughthe use of ahalf-silveredmirror screen
• Tracking issimilar to anImmersaDesk

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Software

• PHANToM
• GHOST API, NT driver only
• Interface with trackd SDK?
• Display and scene graph
• GHOST provides geometry and properties
• OpenSG, Open Inventor, TGS Inventor 3.0,
  Performer?
• Additional libraries
• VTK, geolib, NURBS, CAVERNsoft

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e-Touch 3D

• Open module API and building tool
• NT and Solaris
• OpenGL
• GHOST SDK support
• CAVELib, trackd, and support for other platforms?

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Defect Specification

• Outline with connect the dots
• Intersection testing
• Performer provides the ray casting
• Draping algorithms
• Volumetric collision detection

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Modeling Method?

• Parametric surfaces
• Non-Uniform Rational B-Splines (NURBS)
• These are surfaces, not volumes
• Constructive solid geometry
• Most algorithm implement only primitives
• Implementation with polygons more difficult
• Metaballs
• Blobby modeling
• Already used for haptic clay applications

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Input from Artists

• Constraints
• Implant must be separate piece
• Cannot simply copy and paste the other side
• Minute refinement is required
• What kinds of tools would you use?
• How would you apply 2D modeling tools to a
  tele-immersive environment?

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Collaborative Modeling?

• Mutual exclusions in interaction
• Communication between the participants
• Likely only one haptic user
• Audio conferencing
• Evaluation methods
• Photographs of patient
• Side by side comparisons
• Overlays
• Teacher-student paradigm

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Thesis Concentration

• Not trying to create the ultimate modeling
  package!
• What aspects of tele-immersion are important to
  this usage?
• Is it worth using these technologies in this
  manner?
• What are the benefits and pitfalls?

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General Time Frame

• September-October
• Install libraries, hook up hardware
• Determine incompatibilities
• October-February
• Interaction and modeling programming
• February-May
• Testing, evaluation, refinement
• Retesting

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Possible Consequences

• Patient is not required to travel hundreds of
  miles until the surgury is planned
• Cost of production is significantly lower than
  the current process
• Tangible and quantifiablecontribution of virtual
  realitytechnology to medicine.

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Credits

• http//www.bvis.uic.edu/VRML/Research/CranialImpla
  nts/CranialImplants01.htm
• http//www.evl.uic.edu/images/research/PARIS2.jpg
• http//www.sensable.com/
• http//www.etouch3d.org/etouch.htm