Anatomic and Functional Guidance of Neurosurgery.

1. Anatomic and FunctionalGuidance of Neurosurgery. Robert L. Galloway Jr. Associate Professor of Biomedical Engineering and Neurosurgery Director, Center for Technology-Guided Therapy TGT

2. Technology-Guided Therapy The use of technology to improve the spatial and temporal specificity of the delivery of therapy TGT

3. Technology -Guided Therapy • Pre-therapeutic data (images, population data, therapy plan…) • Registration methodology (matching pre-therapeutic data to specific patient in specific position) • Intraoperative guidance and data collection. • Display of position, plan, anatomy, function and disease.

4. History of Image-Guided Therapy • 1896 J.H. Clayton. X-Ray use in surgery • 1904 Horsley and Clarke. Stereotactic frame • 1946 Spiegel and Wycis. Stereotactic frame using xrays. • 1940’s~1950s: Leksell, Riechert-Mundinger, Talairach, Cooper... TGT

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7. Problems with X-Ray film Stereotaxy • Target must be clearly visible in both images • Lack of apparent relationship between arc settings and position. • Best for electrophysiology-based ablation TGT

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12. Problems with Frame-Based Stereotaxy • Still point-based • Frame obstructs surgical field • Arc-based approach obscures relationship between target points and arc settings. TGT

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15. Registration When the mathematical relationship between a point in one space and the homologous point in another space is known, the spaces are considered registered. If that relationship can be reduced to a single common translation and rotation, the registration is considered rigid, TGT

16. Rigid Registration Rotate Translate TGT

17. Point Based Registration • Fiducial point (landmarks) • Intrinsic Fiducials (anatomic landmarks) • Extrinsic Fiducials (markers) TGT

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21. Marker -Based Registration

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23. New Methods of Registration Surface-Based Registration

24. Surface-based registration of physical space with CT images using A-mode ultrasound localization of the skull • Image to Physical Space Registration • Use the outer surface of the skull • Segmentation in CT forms a surface • Measure points on the outer surface of the skull with ultrasound

25. Comparison with Fiducial Markers • Advantages • No separate surgical procedure • No additional imaging scans • Disadvantages • Residual Error is less predictive of actual error • More time consuming in the OR

30. Tomographic Images • Can show anatomy • Can show function (PET and functional MR) • Can show extent of disease. All of the above are qualified statements

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35. Surface Normal Uncertainty Surface TGT

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38. Tomographic Angiography TGT

39. Surgically Appropriate MIPs 1) Threshold image, make binary image 2) Calculate center of mass from binary image 3) Fit center of mass points from each slice to a line 4) Extend plane from the line perpendicular to MIP trajectory

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41. Depth-Buffer Based Targeting

42. Depth-Buffer Based Targeting

43. Originals Global transformation Local transformation TGT

44. Implantation of Thalamic Stimulators TGT

45. Population Data • Goal - to provide information from multiple subjects during surgery • Create a functional Atlas (MR or CT)

46. Tglobal Tlocal Tlocal+ Tglobal

47. Optical Flow • Differences between images considered as motion from one time frame to the next • This motion is observed as a change in intensity, represented as a field of velocity vectors called the optical flow

48. Atlas Atlas  Patient Patient

50. 3D Visualization Display