Feasibility of Image-Guided SRS for Trigeminal Neuralgia with Novalis

1. Feasibility of Image-Guided SRS for Trigeminal Neuralgia with Novalis

2. Feasibility of Image-Guided SRS for Trigeminal Neuralgia with Novalis Physicists (University of Arizona) RJ Hamilton CJ Watchman J Gordon NJ Stanley Radiation Oncologist (University of Arizona) B Stea Neurosurgeon (Center for Neurosciences, Tucson, AZ) A Sanan

3. Accuracy of Frame-Based Novalis SRS for TGN • Rahimian et al (J. Neurosurg S3 101:351-55, 2004) • Image Fusion 0.4 mm • MR 0.2 mm • Gantry 0.3 mm • Couch 0.6 mm • Overall 0.9 mm (0.6 mm w/o couch) • Target position 0.2 mm • Laser 0.2 mm • Phantom Radiographic Test 0.7 ± 0.1 mm

4. Frame-Based SRS for TGN Human Issues Pins fix frame to skull Uncomfortable during treatment delivery too Patient remains in department for several hours waiting for treatment Difficult to abort procedure (machine problems) Scheduling: patient, neurosurgeon, radiation oncologist, physicist, treatment time, etc…

5. Frame-Based SRS for TGN • Technical Issues • Frame-based systems require that the position of a patient in the frame is unchanged from application of the pins through treatment completion • The stereotactic frame (not the patient) is aligned with the machine isocenter for treatment • Differential torque on the head ring deforms it • Head ring is bolted to the table assembly, patient may be displaced relative to it.

6. Image-Based SRS for TGN • Human Issues • Plastic mask (BrainLab U-PLAST mask fixation system)helps patient remain still • Scheduling: specialists (neurosurgeon, radiation oncologist) may work at their convenience, treatment time set for patient

7. Image-Based SRS for TGN • Technical Issues • Positioning accuracy • Depends on the accuracy of the registration of images between the planning system (DRRs) and imaging system (ExacTrac) • Depends on the calibration of the imaging system with the mechanical isocenter • Variations of the position of the patient in the mask (stereotactic coordinate space) are not important provided that the imaging system can correct for it (ExacTrac X-Ray 6D and Robotics) • Once positioned for treatment, the patient must remain fixed.

8. Feasibility of Image-Based SRS for TGN • Demonstrate System Accuracy • Anthropomorphic Phantom Experiment • Demonstrate that variations of the patient position in the mask are not important • Anthropomorphic Phantom Experiment • Confirm for each patient that deviations of their head within the mask may be corrected by the ExacTrac X-ray 6D and robotics • Perform planning CT scan plus two addition CT scans. The final scan is performed 1 hour prior to the scheduled treatment time. • Confirm that the patient does not move during treatment • Repeat the ExacTrac X-ray positioning 3-4 times (every 3rd couch position) during treatment delivery

9. Demonstrate System Accuracy • Anthropomorphic Phantom • 0.25” BB embedded in head • BrainLab U-PLAST mask constructed • Axial CT scan (35 cm FOV 1.5mm slice) with BrainLab Head & Neck Localizer • BrainScan Plan • ExacTrac 6D X-Ray and Robotics

10. Anthropomorphic Phantom CT

11. Anthropomorphic Phantom CT

12. Anthropomorphic Phantom CT

13. Anthropomorphic Phantom Plan

14. Accuracy of Isocenter Determination • Two planners contoured the BB in the planning system and then placed the isocenter at the center. Repeated the procedure 10 times each.

15. Pixel Size Pixel Size = 0.5 mm

16. Pixel Size Pixel Size = 0.5 mm

17. Pixel Size Pixel Size = 0.5 mm

18. Pixel Size Pixel Size = 0.5 mm 0.5 mm

19. ExacTrac Calibration

20. ExacTrac Calibration

21. ExacTrac Calibration

22. ExacTrac Calibration

23. ExacTrac Calibration

24. ExacTrac Calibration

25. ExacTrac Calibration

26. ExacTrac Calibration

27. ExacTrac Calibration

28. ExacTrac Calibration

29. ExacTrac Calibration

30. Anthropomorphic Phantom Treatment Head Holder

31. Anthropomorphic Phantom Treatment

32. Anthropomorphic Phantom Treatment Select Isocenter

33. Anthropomorphic Phantom Treatment Automatic Preposition

34. Anthropomorphic Phantom Treatment

35. Anthropomorphic Phantom Treatment Automatic Preposition Film Verification Difference = ( 0.3, -0.2 ) = 0.4 mm 10 mm cone BB shadow

36. Anthropomorphic Phantom Treatment

37. Anthropomorphic Phantom Treatment

38. Anthropomorphic Phantom Treatment

39. Anthropomorphic Phantom Treatment

40. 10 mm cone BB shadow Anthropomorphic Phantom Treatment Film Verification Difference = ( 0.1, 0.1 ) = 0.1 mm

41. Phantom Displacement Experiment • Phantom moved by exactly 2.0 cm in all three directions as determined by a ruler • Perform X-ray Alignment with ExacTrac • Shifts Found by ExacTrac • AP 19.85 mm • Lateral 20.05 mm • Vertical 20.40 mm

42. Phantom Moved: Not in Mask !!! Head Rotated

43. Head Holder Removed Phantom Moved: Not in Mask !!! No Head Holder  Head Lower and Rotated

44. Phantom Moved: Not in Mask !!! Position using standard procedures with array

45. Phantom Moved: Not in Mask !!!

46. Phantom Moved: Not in Mask !!!

47. Phantom Moved: Not in Mask !!!

48. 10 mm cone BB shadow Phantom Moved: Not in Mask !!! Film Verification Difference = ( 0.1, 0.1 ) = 0.1 mm

49. Phantom Moved: Not in Mask !!! Rotation too large for robotics

50. Phantom Moved: Not in Mask !!!