mechatronics lab workshop i visualisering presentation haptic and visual simulation of a material...
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Mechatronics Lab
Workshop i Visualisering Presentation
Haptic and Visual Simulationof a Material Cutting Process
Using Patient Specific High Resolution CT-datafor Haptic- and Graphic rendering
Magnus G. Eriksson
Supervisor: Professor Jan WikanderCo-supervisor: Professor Hans von Holst
CTV (Center for Technology and Health Care)The Mechatronics Lab/Machine Design, KTH, StockholmDepartment of Neuronic Engineering KTH-STH, Huddinge
Mechatronics Lab
Background
Since 1980s
Since 1990
Since 1990s
Mechatronics Lab
Temporal Bone Surgery Simulator
Mechatronics Lab
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
Mechatronics Lab
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 <-> Simulator training (Ahlberg et al.)
Mechatronics Lab
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)
Mechatronics Lab
Pos.
Pos.
ForceFeedback.
Pos.
”Real Force”
DrillingOperation
Anatomical Model
”Calc.Force”
VisualFeedback
VisualFeedback
surgeon
3D graphic
slave
master
The Temporal Bone Surgery System
patient
Mechatronics Lab
Research Goal and Focus
Goal:
• To develop a haptic and VR system for training and educating surgeons who practice bone milling
Focus:
1. To develop a VR system for realistic 3D representation of the human skull, including the changes resulting from the milling process
2. 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
Mechatronics Lab
System Design
SenseGraphics H3DAPI
Initialization
Graphic Thread 30 Hz
•3D Visualization•Material Removal
Haptic Thread 1000 Hz
•Collision Detection•Calculate Force
Mechatronics Lab
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
Mechatronics Lab
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
Mechatronics Lab
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
Mechatronics Lab
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.
Mechatronics Lab
Graphic Rendering
• Update rate > 30Hz and a latency of less than 300ms
Graphic thread, 30 Hz
Check for milling
Marching cubes algorithm on updated
tree nodes
OpenGL to create the shape of the object
Update density and gradient values
X_max
Y_max
r
d
Y_min
X_min
Film, skull bone milling
Mechatronics Lab
Haptic thread, 1000 Hz
Haptic Rendering
Collision detection
A force based on a proxy-probe method
Send force to the haptic device
If milling, add vibration force
proxyp
probep
1n̂
2n̂
2n
a1a
2a
tngproxyp _
)( _ probesurfaceproxy ppkF
Mechatronics Lab
Verification of the Haptic Algorithm
A Stiff Surface A Soft Surface