Delaware Valley 2010

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2009 Delaware Valley Young Investigators Symposium

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Delaware Valley 2010

  1. 1. Treatment time reduction for proton modulated scanning beams James Durgin, Derek Dolney, James McDonough University of Pennsylvania December 9, 2009 Delaware Valley AAPM Young Investigator Symposium
  2. 2. Treatment Options Double Scattering Uniform Scanning Modulated Scanning Distal Conformity ~Equal ~Equal ~Equal Proximal Conformity Poor Poor Good Lateral Conformity Depth dependent Depth dependent Depth dependent Dose Uniformity Target dependent Target dependent Best Time Fastest Intermediate Slowest
  3. 3. Bragg Peak Stacking Achieving a uniform dose requires many Bragg peaks At lower energies, range straggling decreases resulting in sharper Bragg peaks
  4. 4. Beamline Transmission Reducing proton energy in beam line reduces the rate of protons in nozzle ~1% at 100MeV
  5. 5. Range Shifters, Ridge Filters Current solution is a Ridge filters could be range shifter used in conjunction Pulls back distal Spreads out Bragg peak peak Increases range Minimal degradation straggling of penumbra Neutron production possible
  6. 6. Designing a Ridge Filter Goals Flat ~1cm area at 100MeV Preserve distal falloff Conserve penumbra Considerations Focused beam MLC, bolus exchanger Dedicated nozzle
  7. 7. Geant4 Simulations Commonly used for proton modeling Saves on development costs No beam time issues Code used for Eclipse commissioning available
  8. 8. Ridge Filter Shape
  9. 9. Depth Doses
  10. 10. Ridge Filter Penumbra
  11. 11. 1-Dimensional Stacking A simple algorithm was used to test stacking in 1 dimension Spacing increased Number of energy levels decreased
  12. 12. Eclipse Commissioning Real test is how Eclipse uses beam data Commissioning requires depth dose in water, penumbra in air, other machine parameters
  13. 13. Preliminary Results Tested a sphere target, d=1.5 cm, in Rando phantom at ~100MeV Similar dose distrubtions with and without RF
  14. 14. Preliminary Results Energy levels from 14 to 5 Ridge filter Beam spots from 150 to 122 MUs reduced by ~45% Unobstructed
  15. 15. Summary Modulated scanning is slow at shallow depths A range shifter is required A ridge filter can be constructed to decrease delivery time while preserving much of the beam quality Eclipse commissioning shows fewer energy levels, beam spots, and MUs with similar coverage
  16. 16. Future Work Combine range shifter and ridge filter Site specific devices Refine machine parameters for planning Validate Monte Carlo models
  17. 17. Acknowledgements James McDonough Derek Dolney This work was supported by the US Army Medical Research and Material Command under Contract Agreement No. DAMD17-W81XWH-04-2-0022. Opinions, interpretations, conclusions and recommendations are those of the author and are not necessarily endorsed by the US Army.
  18. 18. Additional Slides
  19. 19. Ridge Filter Material
  20. 20. Penumbra v. Distance of RF
  21. 21. Penumbra v. Thickness of RF
  22. 22. Depth Dose at Several Energies
  23. 23. Penumbra v. Depth
  24. 24. MLCs with Modulated Scanning
  25. 25. Penumbra v. Depth

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