CAS clinical applications
• Neurosurgery
• Orthopaedics
• Maxillofacial, craneofacial, and dental surgery
• Laparoscopic a...
Elements of CAS systems
Technical elements of CAS systems
1. Medical images
2. Medical image visualization
3. Segmentation and modeling
4. Virtual...
Key parameters for understanding and
comparing solutions
• How many procedures are performed yearly?
• What is the rate of...
1. Medical Images
Most common imaging modalities
• Film X-ray, Digital X-ray, Fluoroscopy, Digital
Substraction Angiography (DSA)
• Ultrasou...
Medical images: characteristics (1)
• Preoperative or intraoperative use
– depends on the size and location of imaging mac...
Medical images: characteristics (2)
• Field of view
• Radiation to patient and to surgeon
• Functional or anatomical imagi...
X-ray images
• Measure absorption of x-ray radiation from
source to set of receptors
• Film X-ray has very high resolution...
X-ray Fluoroscopy
Fluoroscopic images
X-ray image properties
• Traditional, cheap, widely available
• Two-dimensional projections (at least two
required)
• High...
Ultrasound imaging (US)
• Measure refraction properties of an ultrasound
wave as it hits tissue
• No radiation
• Poor reso...
Ultrasound imaging
Computed Tomography (CT)
Computed Tomography Images
cuts
d = 35mmd = 25mm
d = 15mmd = 5mm
Computed Tomography Principle
angle
intensity
X-rays
Computed Tomography Properties
• Sepcifications:
– 512x512 12bit gray level images; pixel size 0.5mm
– slice interval 1-10...
Magnetic Resonance Imaging
• Similar principle and construction than CT
machine, but works on magnetic properties of
matte...
Magnetic Resonance Images
Nuclear Medicine Imaging (NMI)
• Same slices principle
• Source of photons or positrons is injected in the
body. Shortly a...
Nuclear medicine images
Image Fusion: MRI and NMI
MRI (anatomy) NMI (functional)
Video images from within the body
• Used in laparoscopic and endoscopic surgery
Main medical imaging modalities
X-ray X-ray Fluoro US US Video CT MRI NMR Open
Film Digital (2D) (2.5D) MR
Pre/Intraop
2D/...
The imaging pipeline
2. Medical image visualization
• 3D visualization of complex structures
• image correlation and fusion
• quantitative meas...
Medical image visualization
Visualization: Technical needs
• image enhancing and noise reduction
• image interpolation: images from new viewpoints
• 3...
Medical image visualization
• Much activity! Radiologists are the experts
• Commercial packages
– 3DVIEWNIX, ANALYZE, IMIP...
3. Segmentation and modeling
• Isolation of relevant anatomical structures based
on pixel properties
• Model creation for ...
Segmentation and modeling
Segmentation and modeling:
technical needs
• Segmentation:
– landmark feature detection
– isosurface construction (Marchin...
Segmentation and modeling
• Medical images have very special needs!
• Commercial packages
– 3DVIEWNIX, ANALYZE, IMIPS
• Ma...
4. Virtual and augmented reality
• Create a virtual model for viewing during
surgery
• Project the model on the patient or...
Virtual and augmented reality
Virtual and augmented reality
• Part manipulation, visual and sensory feedback
• Interaction devices: goggles, gloves, etc...
5. Preoperative analysis and planning
• Task and procedure dependent
• Spatial and volume measurements
• Stress and fractu...
Preoperative analysis and planning
Preoperative analysis and planning
• About a dozen planners exist for different
procedures
• Main technical topics:
– plan...
6. Image and robot registration
• Define correspondance features
– point-to-point, point-to-line, surface-to-surface
• Est...
Multimodal registration problems
• Great differences depending on
– the type of data to be matched
– the anatomy that is b...
Registration chain example
3D surface model
X-rays
CT
Patient
Tracker
Instruments
Infrared tracker
Image and robot registration
• Rich topic of very great importance!
• Types of registration methods vary widely
• Main tec...
7. Medical robotics devices
• Task and procedure dependent
• Accurate, steady, and repeatable 3D positioning
• Navigation ...
Medical robotics devices
Medical robotics devices
• Mostly passive and semiactive devices
• Rich topic of very great importance!
• Main technical t...
8. Real-Time tracking devices
• Ideally, an accurate Global Positioning System!
• Current technologies offer only partial ...
Optical and video tracking devices
camera
instrument
Passive markers
Instrument has infrared
LEDs attached to it Active ma...
What kind of accuracy?
9. Safety, man-machine interfaces
• Medical systems have very stringent safety
requirements
• Reported cases of radiation ...
10. Systems integration
• Complete systems that address specific clinical
problems in domains
• Use available technology t...
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  1. 1. CAS clinical applications • Neurosurgery • Orthopaedics • Maxillofacial, craneofacial, and dental surgery • Laparoscopic and endoscopic surgeries • Radiotherapy • Specific procedures in ophtalmology, othorhinolaringology, etc.
  2. 2. Elements of CAS systems
  3. 3. Technical elements of CAS systems 1. Medical images 2. Medical image visualization 3. Segmentation and modeling 4. Virtual and augmented reality, tele-surgery 5. Preoperative analysis and planning 6. Image and robot registration 7. Medical mechanical and robotics systems 8. Real-time tracking 9. Safety, man-machine interface, human factors
  4. 4. Key parameters for understanding and comparing solutions • How many procedures are performed yearly? • What is the rate of complications? What are their causes? • In what aspects can a CAS system help? • Does it address part of a clinically important problem? • What stage is the system in: in-vitro, cadaver, clinical trials?
  5. 5. 1. Medical Images
  6. 6. Most common imaging modalities • Film X-ray, Digital X-ray, Fluoroscopy, Digital Substraction Angiography (DSA) • Ultrasound -- 2D and 2.5D (stack of slices) • Computed Tomography (CT) • Magnetic Resonance Imaging (MRI) • Nuclear Medicine (NM) – PET -- Positron Emission Tomography – SPECT -- Single Photon Emission Tomography
  7. 7. Medical images: characteristics (1) • Preoperative or intraoperative use – depends on the size and location of imaging machine • Dimensionality: 2D, 2.5D, 2D+time – projection, cross section, stack of projections, time sequence • Image quality – pixel intensity and spatial resolution – amount of noise; signal/noise ratio – spatial distortions and intensity bias
  8. 8. Medical images: characteristics (2) • Field of view • Radiation to patient and to surgeon • Functional or anatomical imaging – neurological activity, blood flow, cardiac activity • What it’s best at for – bone, soft tissue, fetus, surface/deep tumors, etc • Clinical use – diagnosis, surgical, navigation,
  9. 9. X-ray images • Measure absorption of x-ray radiation from source to set of receptors • Film X-ray has very high resolution Gray value proportional to radiation energy
  10. 10. X-ray Fluoroscopy
  11. 11. Fluoroscopic images
  12. 12. X-ray image properties • Traditional, cheap, widely available • Two-dimensional projections (at least two required) • High resolution, low noise (more fluoroscope) – film size, 64K gray levels – fluoroscopic images: TV quality, 20cm field of view • Relatively low radiation • Bone and metal images very well • Fluoroscopy used for intraoperative navigation
  13. 13. Ultrasound imaging (US) • Measure refraction properties of an ultrasound wave as it hits tissue • No radiation • Poor resolution, distortion, noise • Low penetration properties • One 2D slice or several slices (2.5D) • Relatively cheap and easy to use • Preoperative and intraoperative use
  14. 14. Ultrasound imaging
  15. 15. Computed Tomography (CT)
  16. 16. Computed Tomography Images cuts d = 35mmd = 25mm d = 15mmd = 5mm
  17. 17. Computed Tomography Principle angle intensity X-rays
  18. 18. Computed Tomography Properties • Sepcifications: – 512x512 12bit gray level images; pixel size 0.5mm – slice interval 1-10mm depending on anatomy – 50-200 slices per study – noise in the presence of metal (blooming) • All digital, printed on X-ray film • Acquisition 1sec/slice (spiral models) • 15mins for image reconstruction • Costs about $250-750K, each study $500
  19. 19. Magnetic Resonance Imaging • Similar principle and construction than CT machine, but works on magnetic properties of matter – magnetic fields of 0.1 to 4 Teslas • Similar image quality characteristics as CT • Excellent resolution for soft tissue • Costs $1-2M, each study $1,000 • Open MR: intraoperative device (only 15 to date)
  20. 20. Magnetic Resonance Images
  21. 21. Nuclear Medicine Imaging (NMI) • Same slices principle • Source of photons or positrons is injected in the body. Shortly after, radiation of metabolism is measured • Poor spatial resolution • Expensive machine AND installation ($4-5M) • Expensive and time-consuming • Provides functional info no other source does
  22. 22. Nuclear medicine images
  23. 23. Image Fusion: MRI and NMI MRI (anatomy) NMI (functional)
  24. 24. Video images from within the body • Used in laparoscopic and endoscopic surgery
  25. 25. Main medical imaging modalities X-ray X-ray Fluoro US US Video CT MRI NMR Open Film Digital (2D) (2.5D) MR Pre/Intraop 2D/2.5D Resolution Radiation Anatomy Procedure Establish a comparative table of modality properties
  26. 26. The imaging pipeline
  27. 27. 2. Medical image visualization • 3D visualization of complex structures • image correlation and fusion • quantitative measurements and comparisons • visualization of medical and CAD data Enhance diagnosis by improving the visual interpretation of medical data
  28. 28. Medical image visualization
  29. 29. Visualization: Technical needs • image enhancing and noise reduction • image interpolation: images from new viewpoints • 3D visualization from 2.5D data – volume rendering: display voxels and opacity values – surface rendering: explicit reconstruction of surface • 3D modeling from 2.5D data • 2D and 3D segmentation • 3D+T visualization (beating heart)
  30. 30. Medical image visualization • Much activity! Radiologists are the experts • Commercial packages – 3DVIEWNIX, ANALYZE, IMIPS • Main technical topics: – 3D volume rendering techniques – 3D image filtering and enhancement – surface construction algorithms: Marching cubes, etc. • Sources: chapters 3,9, and 10 in textbook • Related fields: computer graphics, image processing
  31. 31. 3. Segmentation and modeling • Isolation of relevant anatomical structures based on pixel properties • Model creation for the next computational task – real-time interaction and visualization – simulation – registration, matching, – morphing Extract clinically useful information for a given task or procedure
  32. 32. Segmentation and modeling
  33. 33. Segmentation and modeling: technical needs • Segmentation: – landmark feature detection – isosurface construction (Marching cubes) – contour extraction, region identification • Modeling: – points, anatomical landmarks, surface ridges – surfaces as polygon meshes, surface splines – model simplification methods (Alligator, Wrapper)
  34. 34. Segmentation and modeling • Medical images have very special needs! • Commercial packages – 3DVIEWNIX, ANALYZE, IMIPS • Main technical topics: – Volumetric segmentation techniques for CT, MRI – 2D and 3D segmentation with deformable elements – surface and model simplification algorithms • Sources: chapters 4 and 8 in textbook • Related fields: image processing, computer vision
  35. 35. 4. Virtual and augmented reality • Create a virtual model for viewing during surgery • Project the model on the patient or integrate with surgeon’s view • Useful for intraoperative anatomy exploration and manipulation • Telesurgery systems Use images to create or enhance a surgical situation
  36. 36. Virtual and augmented reality
  37. 37. Virtual and augmented reality • Part manipulation, visual and sensory feedback • Interaction devices: goggles, gloves, etc • Only a handful of systems exist • Main technical topics: – a couple of the working systems; simulators – telesurgery systems • Sources: chapters 14 and 15 in textbook • Related fields: computer graphics
  38. 38. 5. Preoperative analysis and planning • Task and procedure dependent • Spatial and volume measurements • Stress and fracture analysis • Implant and tool selection and positioning • Surgical approach planning: bone rearrangement, angle evaluation, radiation dose planning, etc Use images and models to assist surgeons in planning a surgery and evaluate options
  39. 39. Preoperative analysis and planning
  40. 40. Preoperative analysis and planning • About a dozen planners exist for different procedures • Main technical topics: – planning systems for orthopaedics, neurosurgery – application of engineering analysis techniques: finite- element methods, stress analysis, etc • Sources: chapters 11, 25, 33, 41, 52--56in textbook • Related fields: CAD, computational geometry, engineering analysis
  41. 41. 6. Image and robot registration • Define correspondance features – point-to-point, point-to-line, surface-to-surface • Establish correspondances between features • Establish a similarity measure • Formulate and solve dissimilarity reduction problem • Related tasks: image fusion, morphing, atlas matching Establish a quantitative relation between different refererence frames
  42. 42. Multimodal registration problems • Great differences depending on – the type of data to be matched – the anatomy that is being imaged – the specific clinical requirements of procedures • Feature selection and extraction: stereotactic frame, implanted fiducials, anatomical landmarks and surfaces, contours and surfaces in • Manual vs. automatic feature selection, pairing • Rigid vs. deformable registration • Nearly similar vs. dissimilar images • Noiseless vs. noisy images (outlier removal)
  43. 43. Registration chain example 3D surface model X-rays CT Patient Tracker Instruments Infrared tracker
  44. 44. Image and robot registration • Rich topic of very great importance! • Types of registration methods vary widely • Main technical topics: • rigid registration methods: three points and more – deformable registration: local and global methods – intensity-based registration • Sources: chapters 5-7 in textbook, many papers Book on Medical Image Registration • Related fields: vision, robotics
  45. 45. 7. Medical robotics devices • Task and procedure dependent • Accurate, steady, and repeatable 3D positioning • Navigation and localization aids • Cutting and milling, biopsies • Key issues are: – kinematic design, trajectory planner – controller, safety provisions Semi-active and active mechanical devices for improving surgical outcome
  46. 46. Medical robotics devices
  47. 47. Medical robotics devices • Mostly passive and semiactive devices • Rich topic of very great importance! • Main technical topics: – compare features and functionalities of systems – discuss and compare design considerations – devices for specific surgeries laparoscopy) • Sources: chapters 16-18, 22, 29, 34, 39, 45, 47, and 48 in textbook • Related fields: robotics, mechatronics
  48. 48. 8. Real-Time tracking devices • Ideally, an accurate Global Positioning System! • Current technologies offer only partial solution • Based on different principles – video: follow known objects – optical: follow light-emitting diodes – magnetic: measure the variation of – acoustic: works like a radar Hardware to follow in real time the precise position and orientation of anatomy and instruments during surgery
  49. 49. Optical and video tracking devices camera instrument Passive markers Instrument has infrared LEDs attached to it Active markers
  50. 50. What kind of accuracy?
  51. 51. 9. Safety, man-machine interfaces • Medical systems have very stringent safety requirements • Reported cases of radiation overdose due to faulty system design • Important issues in man-machine interfaces • Ideas for presentations – the radiotherapy accident – chapters 12-15 and 19 in textbook
  52. 52. 10. Systems integration • Complete systems that address specific clinical problems in domains • Use available technology to develop the system • The hard part: make it all work! • Main technical topics: – systems in orthopaedics, neurosurgery, etc • Sources: chapters in each section of • Related fields: all!

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