(Sunday, 7/12/2020) [Eastern Time (GMT-4)]
Room: AAPM ePoster Library
Purpose: investigate the effects of lung tumor size on photon and proton planning comparison, and to evaluate the robustness of 3D and 4D optimization for proton pencil beam scanning plans.
Methods: Three categories of ten lung tumor patients were evaluated: A) Prescription 50Gy(1250cGyx4) early stage SBRT, with peripheral lung tumor diameter 2cm-4.5cm; B) Prescription 60Gy(750cGyx8) hypo fractionated treatment(HIGRT), with central lung tumor 2.5-6cm; C) Prescription >60Gy(200cGyx30) advanced stage lung tumors.
Previously treated photon IMRT/VMAT plans covers Rx>95%PTV. For category A) and B), all planning target volumes (PTV) included 5mm expansion to the internal target volume (ITV). Proton planning IGTVs (union of 10 phases) were the same as photon ITVs. For C) PTV included the CTV plus 5mm margin expansion.
Results: planning strategies were implemented to generate proton plans based on Monte Carlo calculation with RayStation(V8bSP1) proton planning pencil beam scanning system (PronovaSC360), with/without Robustness Optimization (RO). The 3D optimization was done on ITV for average CT, and 4D optimization (4% range uncertainty, 5mm setup uncertainty) was implemented for GTV (or CTV) on each individual breathing phase. Each phase-GTV and all plans were examined by physicians to ensure optimal target coverage and OAR constrains. The comparison among photon and proton plans for three tumor types were evaluated, the proton plans (no-RO/3D-RO/4D-RO) were compared. Selected results were presented in supporting material. Higher target coverage was achieved with the 4D optimization proton planning method. Above 4cm, the 3D Robustness proton plans for SBRT, HIGRT and IMRT patients benefits more over photon IMRT plans.
Conclusion: tumor size larger than 4cm diameter, the optimized proton plans demonstrated the superior OAR sparing compared to photon plans; higher target coverage was achieved with the 4D robust optimization proton planning method over 3D robustness optimization.
Keywords
Not Applicable / None Entered.
Taxonomy
TH- External Beam- Particle/high LET therapy: Proton therapy – dose optimization
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