Adaptive Aperture Commissioning Presentation at 57th PTCOG
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Adaptive Aperture Commissioning Presentation at 57th PTCOG
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Adaptive Aperture Commissioning Presentation at 57th PTCOG
- 1. Commissioning of a unique penumbra sharpening adaptive aperture of HYPERSCAN Minglei Kang, PhD, Assistant Professor Dalong Pang, PhD, Professor Georgetown University Hospital, Washington, DC 1
- 2. Outline • Adaptive aperture(AA) – Main components of AA – How does AA work • Commissioning – Leaf leakage test – Leaf position accuracy test – Penumbra reduction with AA • Conclusion 2
- 3. Adaptive aperture(AA) • Why AA? 3 (a) scanning magnets (b) (b) IC1 & IC2 (c) energy degrader (ED) (d) adaptive aperture (AA) Cross view of ED Spot size evolution in air
- 6. Outline • Adaptive aperture(AA) – Main Components of AA – How does AA work • Commissioning – Leaf leakage test – Leaf position accuracy test – Penumbra reduction with AA • Conclusion 6
- 7. Leaf leakage test 7 • 10 spots pattern • EBT3 film and solidwater phantom Open AA Block spots
- 8. Leaf leakage test • Before AA upgrade 8 0% 1% 2% 3% 4% 5% 6% 7% 0.0 0.5 1.0 1.5 2.0 2.5 Leakage(%) Depeth in phantom(cm) Old_big_leaf Old_small_leaf
- 9. Leaf leakage test 9 • AA upgrade to reduced the leakage ≤ 1.5% • Increase the depth of Toungue and Groove • Increase TG pairs from 2 to 3 0% 1% 2% 3% 4% 5% 6% 7% 0.0 0.5 1.0 1.5 2.0 2.5 Leakage(%) Depeth in phantom(cm) Old_big_leaf Old_small_leaf New_big_leaf New_small_leaf
- 10. Outline • Adaptive aperture(AA) – Main Components of AA – How does AA work • Commissioning – Leaf leakage test – Leaf position accuracy test – Penumbra reduction with AA • Conclusion 10
- 11. Leaf position accuracy test • Transparency alignment fixture, deviation ≤ ±1mm 11 Courtesy of Jimmy from Mevion
- 12. 12 Leaf position accuracy test • Transparency alignment fixture, deviation ≤ ±1mm
- 13. Outline • Adaptive aperture(AA) – Main Components of AA – How does AA work • Commissioning – Leaf leakage test – Leaf position accuracy test – Penumbra reduction with AA • Conclusion 13
- 14. • Spot size changes with energy and distance 14 Dosimetry performance with AA
- 15. Penumbra reduction with AA • Energy, field size and air gap – 227, 110 and 64MeV, the ranges in water are 32.2, 9.1 and 3.6cm. – Field size 3x3,10x10 and 15x15 – Air gap 5, 10 and 15cm 15 E(MeV) Air Gap (cm) FS(cm2) Pen. AA(cm) Pen. nAA(cm) Reduction(cm) 227 5 3x3 0.64 0.87 0.23 10x10 0.66 0.88 0.22 15x15 0.65 0.88 0.24 10 3x3 0.64 0.87 0.23 10x10 0.66 0.87 0.21 15x15 0.65 0.88 0.23 15 3x3 0.61 0.87 0.26 10x10 0.64 0.88 0.24 15x15 0.62 0.88 0.26 110.23 5 3x3 0.81 1.50 0.69 10x10 1.06 1.74 0.68 15x15 1.13 1.81 0.69 10 3x3 0.90 1.65 0.75 10x10 1.20 2.03 0.83 15x15 1.25 2.03 0.78 15 3x3 1.00 1.88 0.88 10x10 1.38 2.22 0.85 15x15 1.50 2.33 0.83 64.49 5 3x3 0.88 1.88 1.00 10x10 1.31 2.38 1.06 15x15 1.44 2.44 1.00 10 3x3 0.91 2.04 1.13 10x10 1.63 2.66 1.04 15x15 1.64 2.69 1.05 15 3x3 1.13 2.25 1.13 10x10 1.81 2.94 1.13 15x15 1.94 3.06 1.13
- 16. Penumbra reduction with AA • 227MeV penumbra reduced by 2mm. 16 0.00 0.20 0.40 0.60 0.80 1.00 0.5 1 1.5 2 2.5 3 3.5 Penumbra(cm) Field size E227_AG5cm_AA E227_AG5cm_noAA E227_AG10cm_AA E227_AG10_nAA E227_AG15cm_AA E227_AG15cm_nAA No AA AA
- 17. 0.0 0.5 1.0 1.5 2.0 2.5 0.5 1 1.5 2 2.5 3 3.5 Penumbra(cm) Field size E110_AG5cm_AA E110_AG5cm_noAA E110_AG10cm_AA E110_AG10_noAA E110_AG15cm_AA E110_AG15cm_noAA Penumbra reduction with AA • E110MeV penumbra reduced by 7~8mm 17 AG15cm AG10cm AG5cm
- 18. Penumbra reduction with AA • E64MeV penumbra reduced by 10~13mm 18 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 0.5 1 1.5 2 2.5 3 3.5 Penumbra(cm) Field size E64_AG5cm_AA E64_AG5cm_noAA E64_AG10cm_AA E64_AG10_noAA E64_AG15cm_AA E64_AG15cm_noAA AG15cm AG10cm AG5cm
- 19. Outline • Adaptive aperture(AA) – Main Components of AA – How does AA work • Commissioning – Leaf leakage test – Leaf position accuracy test – Penumbra reduction with AA – Conclusion 19
- 20. Conclusion • New design of AA can maintain a small leaf leakage • Position accuracy within 1mm • AA can reduce penumbras compared without AA, and the appropriate air gap is critical to determine the penumbra. 20
- 21. Acknowledgments • Rob Cessac • James Cooley • Adam Molzahn • Kately Milkowski • Stanley Rosenthal • Mike Maginn • Caroline Cole 21
- 22. Thank you! 22
Editor's Notes
- The hyperscan is the first gantry mounted pbs delivery system. Higher energy protons exit the accelerator are directly going through scanning magnets, ion chamber I and ii, energy degrader and adaptive aperture. Compared to conventional beam transportation line, hyper scan doesn't have any quadruple focusing or energy selection system.
- • The aperture is composed of the alloy Nickel 200. • The aperture is 10 cm in height along the beamline. • The aperture is non-divergent. • The aperture does not exceed the 20 cm x 20 cm treatment field at isocenter. • No spot has a centroid outside of the aperture curve.
- No spot has a centroid outside of the aperture curve. The two big leaves will completely close to trim peripheral spots.
- Scatter protons pass through the small gap
- Leakage has been reduced to less 1.5% for both large and small leaves.
- 3 basic patterns + 2 complex patterns
- The smaller of the air gap the sharper dose falloff the AA can achieve. Quantify the penumbra reduction at depth 3cm of solidwater phantom