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Image Overlay System: Computer-generated Integral Photography

Image Overlay System: Computer-generated Integral Photography. Anand Viswanathan CIS II 600.446. Image Overlay. Picture taken from http://www.mrcas.ri.cmu.edu/projects/overlay/system.html. What is Image Overlay?.

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Image Overlay System: Computer-generated Integral Photography

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  1. Image Overlay System:Computer-generated Integral Photography Anand Viswanathan CIS II 600.446

  2. Image Overlay Picture taken from http://www.mrcas.ri.cmu.edu/projects/overlay/system.html

  3. What is Image Overlay? • The ability to see bone/tissue/target superimposed onto the patient during surgery. • Can be used for surgical planning. • Can be used for surgical navigation. • Using 3D marker information and creating an accurate 2D representation. • Superimposing this 2D representation with video input.

  4. Apparatus • Optical Tracking system (ie: Optotrak, POLARIS) • PC collecting data from tracking system • Lens array • LCD display • Half silvered mirror Picture taken from http://www.mrcas.ri.cmu.edu/projects/overlay/medical.html

  5. Requirements of a 3D navigational system • Surgeon should recognize 3D position and orientation of any surgery device. • High Image quality. • Minimal eyestrain and fatigue • 3D representation should include the area surrounding the target.

  6. Important Factors to Consider • Mechanical Accuracy/ Geometric Accuracy • Depth Perception • Distortion

  7. Necessary background • Three Dimensional Slice Image Overlay System with Accurate Depth Perception for Surgery. Ken Masamune, Yoshitaka Mautani, Susumu Nakajima, ichiro Sakuma, Takeyoshi Dohi, Hiroshi Iseki and Kintomo Takakura MICCAI pgs 395-402 • Surgical Navigation System with Intuitive Three-Dimensional Display Susumu Nakajima, Sumihisa Orita, Ken Masamune, Ichiro Sakuma Takeyoshi Dohi, and Kozo Nakamura MICCAI pgs 404-411

  8. Principle of Integral Photography (IP) • Captures and reproduces 3D objects using a lens array and film. • Computer generated IP: 3D info -> 2D coordinates replace film with LCD

  9. Computer IP Algorithm • Previous computer generated IP algorithm was too ‘costly’ and could not render medical objects in real time. • Novel approach: Consider each point in 3D space as a light source that will be reconstructed. • 3D object -> a group of reconstructed light sources

  10. Computer IP Algorithm • Main Calculation: • Computes the distance of the ith furthest point for the reference plane by intersection of 2 light rays.

  11. Registration Most Important Problem for display Manual Adjustment and then more precise Image Transformation to align coordinates of markers

  12. Geometric Accuracy • Most important consideration for medical imaging • Tested by trying to display a 100 mm square at a distance of 10 to 40 mm from the surface of the LCD • Mean differences were less than 3.8 mm

  13. Accuracy from the location of registered image to the object • 50mm vitamin capsule w/ 4 MRI markers used to test accuracy • Tried to superimpose 3D rendered version on the actual capsule • Magnitude of the errors = radius of the markers

  14. My Assessment • Image overlay is a very powerful tool for a surgery. • Significantly accurate within an error of 3-4 mm, but can be improved to let surgeon rely on the navigation system. • Computer-generated IP allows real-time integration of video and graphics.

  15. Possible next steps • Better, faster rendering algorithms • Better LCD screens: image resolution,pixel pitch. • Improved Accuracy • Multiple trackers • Network integration

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