ComputerAssisted Surgery

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Computer-Assisted Surgery

• November 20, 2001
• Jennifer Lyon

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What is CAS?

• Commonly known as Computer-Assisted,
  Computer-Aided or Computer-Enhanced Surgery
• Integration of Computer Science and Biomedical
  Engineering
• Permits more precise preoperative planning of
  surgical procedures, facilitates steps in surgery
• Specialization CAOS (Orthopedic Surgery) refines
  complex orthopedic procedures (osteotomy)

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The Osteotomy

• The drilling, cutting and realigning of bones to
  correct and improve alignment
• Traditional methods were error-prone
• Computers eliminate traditional physical
  constraints
• All bones are unique CT (computed tomography)
  scans build simulated models
• Imagining the invisible CT models allow us to
  see details
• 3D visualization importance of understanding the
  relative changes of bone pieces

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The Five Steps in CAOS

• CT Extraction
• Pre-operative Planning
• Optoelectronic Tracking
• Registration of Patient to Image
• Guidance in Osteotomy

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1. CT Extraction

• CT slices stacked into a volume

• Each slice (voxel) is an x-ray profile

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2. Pre-Operative Planning

• Prepare the models for surgery

• Simulate wedge extractions along planes and bone
  rotations about axes

• Orthopedic procedure is electronically simulated

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3. Optoelectronic Tracking

• Prepare the patient for surgery

• Calibrated cameras locate infra-red LEDs and
  reflective markers to set 3D locations

• Markers on patient and instruments determine
  relative positions of objects in the OR

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4. Registration

• Align the patient to computer images

• Begin with easily identifiable regions, then
  refine through algorithmic calculation

• Calculate precise transformation between CT
  co-ordinate plans and patients local co-ordinates

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Then the scary part . . .
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Guidance in the OR

• Surgical instruments are tracked

• Virtual instruments superimposed on computer
  images

• Distances and angles to planes calculated

• Surgeon uses computers to accurately drill, cut
  and realign bones

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Resulting Outcome

• Patients recovery process must be analyzed
• Procedures continually need enhancements
• Science and technology provide methods for
  improvement of CAS

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CAS at Queens

• CISC, Mechanical Engineering and KGH co-operation
• Development of Software and Mechanical Hardware
• Approximately 50 successful computer-aided
  osteotomies in the past three years
• A First in Canada

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Let us compare!
Error planned actual correction
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CAS at the drawing board

• Improve accuracy of pre-operative registration
• Effective assessment of outcomes
• Continue to improve biomechanics model of the
  human body
• Solve Visualization problems in 3D

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Visualization Problems
Rotate, rotate, rotate, translate

• Surgeons have trouble visualizing series of
  rotations and translations in 3D
• Chasles Theorem A series of rotations is
  equivalent to a single rotation by some angle
  about an axis and a translation parallel to that
  axis.

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A Solution The BVT
Bone Viewing Tool
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BVT Components

• VTK integration
• .vtk file format derived from CT

• Qt GUI
• Widget set

• C design
• OO ensures expandability

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So far, so good
toolbars
Import multiple bones
Widget control
Actor selection
Buttons change actor and coordinate states
Axis of rotation
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Whats next?
1. Complete 3rd coordinate system
2. Detailed help documentation
3. Finish Status Bar
4. Add axis model for relative comparisons
5. Testing and Implementation
6. Train the Surgeons!
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BVT Applications

• As a teaching tool
• For students, surgeons, patients.
• As a pre-operative planning tool
• For surgeons
• As a CISC undergrad project

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The Future of CAS

• Aiming for 100 accuracy in osteotomy
• Goals for widespread OR2010
• One step towards computerized surgery!

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Conclusions

• CAS and CAOS is a rapidly evolving field
• Step-by-step procedures are necessary to produce
  optimal outcome
• Problems in Orthopedic surgery can be minimized
  or eliminated with computers
• Computers are very effective tools to use in
  medicine
• We have seen only the beginning

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Questions?