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Feasibility of using O-18 for PET proton range verification

This study explores the feasibility of using O-18 for PET proton range verification in cancer therapy, highlighting its benefits such as Bragg Peak and challenges like range accuracy. The findings reveal O-18 as a promising candidate for this purpose. Detailed measurements, future research directions, and acknowledgements are included.

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Feasibility of using O-18 for PET proton range verification

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  1. Feasibility of using O-18 for PET proton range verification Cho JM1, Gillin M2, Ibbott GS2, Mawlawi O1. Dept. of Imaging Physics Dept. of Radiation Physics MD Anderson Cancer Center

  2. Proton Therapy • Pros • Bragg Peak (BP) • No distal dose • Cons • Range accuracy is critical • Range uncertainty up to 10%

  3. Proton range verification using PET Planned Dose Measured PET MC Dose MC PET Antje-Christin Knopf et al

  4. Proton range verification using PET Planned Dose Measured PET MC Dose MC PET Antje-Christin Knopf et al

  5. Proton range verification using PET Dose Dose Activity Activity Antje-Christin Knopf et al

  6. Interaction Cross Sections in Tissue Extremely rare isotope in the body Litzenberg et al

  7. O-18 enriched water • Biologically H2O18=H2O16 • Precursor for FDG • 18F half-life 110 min Extremely rare isotope in the body Litzenberg et al

  8. Measurements & Results (LLUMC)

  9. O16 water O18 water Heptane Empty Plastic water % Dose 160MeV Proton Depth (cm) Measurements & Results (MDACC) 4 different depths O18 O16 Empty C12

  10. O16 water O18 water Heptane Empty Plastic water PDD (%) 160MeV Proton Depth (cm) Measurements & Results (MDACC) 4 different depths dose at depth % O18 O16 Empty C12 96-70% 70-30% 30- 6% 15- 3%

  11. PDD (%) Depth (cm) Measurements & Results (MDACC) 18O 16O Empty 12C dose at depth % 99-87% 87-65% 65-20% 39- 8%

  12. PDD (%) Depth (cm) Measurements & Results (MDACC) 18O 16O Empty 12C dose at depth % 96-70% 70-30% 30- 6% 15- 3%

  13. Conclusion • O-18 : strong signal at distal end. • O-18 : candidate for proton range verification using PET.

  14. How to obtain O-18? From FDG precursor providers? $20 ~ $100 / gram

  15. How to obtain O-18? • From plants? • 4~10% enrichment Natural enrichment in plant

  16. Future Research Direction • Gel dosimetry study • Monte Carlo study • O-18 transport study • Animal study • Affordable O-18

  17. Acknowledgement Authors thank Dr. Schulte at Loma Linda University Medical Center and Dr. Gonzalez-Lepera at CABIR, MD Anderson Cancer Center. Author contact: jcho2@mdanderson.org

  18. 4 most abundant elements Total over 99% 6 most common interactions 16O(p,pn)15O (83.5%) 16O(p,3p4n)10C (4.2%) 16O(p,αpn)11C (2.4%) 12C(p,pn)11C (2.3%) 16O(p,p2n)14O (1.9%) 16O(p,α)13N (1.7%) 16O comprises 94 % Nuclear Interactions of Protons with Tissue Litzenberg et al

  19. Discussion At COM, 16O water initially gave high signal but after 20 minutes, 18O water signal was stronger. At Distal end, 18O water was strongest over the entire time. After 20 minutes, 16O water was at noise level. 18O water shows stronger PET signals in both COM and distal end. 16O signal was noise at distal end. Even diluted 10% 18O water gave more signal than 16O in both Gamma Camera and PET.

  20. In-vivo dosimetry using PET Proton beam Water in tissueDaughter product p ~> + 16O →15O + p + n decay 15N (stable) + e+ combine e-→ PET 0.511 MeV 0.511 MeV

  21. Proton range verification using PET Measured PET Planned Dose MC Dose MC PET Antje-Christin Knopf et al

  22. Bragg-Peak Review • Most protons < 10 MeV with max ~ 30 MeV • Proton at few MeV

  23. Overview • Proton Therapy • Proton Range Verification using PET • Purpose • Properties of O-18 • Method and Materials • Results • Conclusion • Future Direction

  24. O-18 enriched water • Biologically O-18 water = O-16 water • Precursor for FDG -18O(p,n)18F • Cross section threshold 2.6 MeV and maximum 5 MeV • 18F half-life 110 min

  25. Biologically O-18 water = O-16 water Precursor for FDG -18O(p,n)18F Cross section threshold 2.6 MeV and maximum 5 MeV 18F half-life 110 min O-18 enriched water Litzenberg et al

  26. Material and Methods

  27. Results – Gamma Camera at COM

  28. Results – Gamma Camera at distal end

  29. 98% O18 100% O16 100% O16 98% O18 10% O18 10% O18 Results – PET Axial COM PET axial images Distal end PET axial images Images taken over 60 minutes

  30. Method & Materials (LLUMC)

  31. 98% O18 100% O16 100% O16 98% O18 10% O18 10% O18 Results (LLUMC)

  32. Results (MDACC)

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