Workshop i Visualisering Presentation

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Workshop i Visualisering Presentation
Haptic and Visual Simulation of a Material
Cutting Process Using Patient Specific High
Resolution CT-data for Haptic- and Graphic
rendering
Magnus G. Eriksson Supervisor Professor Jan
Wikander Co-supervisor Professor Hans von
Holst CTV (Center for Technology and Health
Care) The Mechatronics Lab/Machine Design, KTH,
Stockholm Department of Neuronic Engineering
KTH-STH, Huddinge
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Background
Since 1980s
Since 1990
Since 1990s
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Temporal Bone Surgery Simulator
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Education of Surgeons

• See one, do one, teach one
• Patients risky situation
• Ethically and economically unacceptable
• Cadavers, plastic models or animals (high cost,
  ethical problems, difficulties of training
  results)

Exampel
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Training in VR Simulators

• Avoid patients and cadavers
• Performance feedback
• Not time related
• Pre-operation planning
• Older, experienced surgeons
• Rare pathologies
• Reduce expensive costs
• First 60 patients lt-gt Simulator training (Ahlberg
  et al.)

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VR and Haptic Simulators Used Today

• Film example from Simulatorcentrum
• AccuTouch Endoscopy Simulator
• LapSim Laparoscopy Simulator

Metrics and Certified by US Food and Drug
Administration (FDA)
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The Temporal Bone Surgery System
3D graphic
patient
Anatomical Model
Visual Feedback
Visual Feedback
Calc. Force
Drilling Operation
Pos.
Pos.
Force Feedback.
surgeon
Real Force
Pos.
master
slave
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Research Goal and Focus

• Goal
• To develop a haptic and VR system for training
  and educating surgeons who practice bone milling
• Focus
• To develop a VR system for realistic 3D
  representation of the human skull, including the
  changes resulting from the milling process
• To develop an efficient algorithm for realistic
  haptic feedback to mimic the milling procedure
  using CT-data of the skull
• Real time demands, without artifacts or delays
  when removal of material

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System Design
SenseGraphics H3DAPI
Initialization

• Haptic Thread 1000 Hz
• Collision Detection
• Calculate Force

• Graphic Thread 30 Hz
• 3D Visualization
• Material Removal

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Possible VR Haptic and Milling Applications

• Temporal bone surgery
• Craniofacial surgery
• Dental tooth milling
• Vertebral operating procedures
• Freeform design

Research Goal To develop a haptic and VR system
for training and educating surgeons who practice
bone milling
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Conclusion

• A haptic and VR surgical milling simulator
  prototype
• Patient specific DICOM data
• Efficient graphical rendering
• Haptic rendering to avoid fall-through problems
• Real time requirements when removing material

Film, tooth milling
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Future Work

• Investigate various force models (3-DOF vs 6-DOF,
  mill is turned on-off, material removal rate) and
  benchmark
• Other applications, bone fractures, sculpting
  etc
• User interface and virtual environments /
  visualisation
• Validate the simulator together with
  Simulatorcentrum
• Re-Design the haptik device and API
  (Matlab/Simulink)
• Investigate the economical and ethical benefits
  of using simulators

Film, skull bone milling
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Initialization

• Initialization
• Volumetric data from a DICOM-file
• Density and gradient 3D matrices
• Octree node structure containing the voxel data

• Range of x, y, and z coordinates.
• Max/min density values.

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Graphic Rendering

• Update rate gt 30Hz and a latency of less than
  300ms

Graphic thread, 30 Hz
Check for milling
Update density and gradient values
Marching cubes algorithm on updated tree nodes
OpenGL to create the shape of the object
Film, skull bone milling
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Haptic Rendering
Haptic thread, 1000 Hz
Collision detection

A force based on a proxy-probe method

If milling, add vibration force
Send force to the haptic device
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Verification of the Haptic Algorithm
A Stiff Surface
A Soft Surface