Study And Application Of Proton Dose Calculation Of Pencil-Beam Algorithms For The DeepPlan Treatment Planning System

Taking advantages of the Bragg Peak,proton therapy can deliver more conformal dose distributions to the target than that of the photon therapy while reducing the normal tissues radiation injuries.Comparing to the double scattering proton therapy,the active scanning proton therapy can provide a more highly conformal dose distributions in the tumor area but requiring a higher accuracy of dose calculations.Although the proton therapy is growing rapidly in China,the research and development of its own TPS(Treatment Planning System)in China is clearly in need of improvement.The aim of this study is to develop a PBA(Pencil-Beam Algorithm)proton dose-calculation software for active scanning proton therapy.Four research tasks are included:(1)To review the existing proton dose-calculation algorithms;(2)To develop a PBA dose-calculation software based on PBA;(3)To correct PBA to improve dose calculation accuracy;(4)To integrate this PBA dose-calculation software into the DeepPlan TPS and verify its accuracy.In order to complete the above tasks,this study adopted the algorithms by Gottschalk and Soukup to calculate the lateral dose distribution caused by Multiple Coulomb Scattering and Nuclear Scattering.Based on the Integrated Depth Dose database simulated by Monte Carlo method,a PBA proton dose-calculation software for active scanning proton therapy was developed in the C#programming language.The algorithm was corrected by taking into account the impacts of energy spread,range shifter and air gap,and by dividing the scanning beam into several sub-beams in heterogeneous materials.Then,this software was integrated into DeepPlan TPS as a proton dose-calculation module.The following results were obtained:(1)Finished the review of proton dose-calculation algorithms and compared their charateristcs in details as well as the availability under clinical environment.(2)Developed a PBA proton dose-calculation software for the active scanning proton therapy.To verify the accuracy of PBA software,the in-water dose distributions calculated by PBA software and Monte Carlo method were compared.(3)The results calculated by corrected PBA software were compared with those of Monte Carlo simulations.The differences between them were less than 2%for different energies and spot sizes.The maxijmum difference was less than 5%for proton beams with 1 MeV and 5 MeV energy spread.The maximum difference between them was also less than 5%for proton beams with different range shifter thicknesses and air gaps.(4)A prostate case was performed by both Monte Carlo method and DeepPlan.The 2 mm/2%gamma pass rate of DeepPlan dose computation was 97%compared with TOPAS dose computation.The innovations of this work:the pencil beam proton dose-calculation algorithm was improved to be better suited for clinical active scanning proton therapy.Based on this pencil beam algorithm,a proton dose-calculation software has been developed and integrated into DeepPlan TPS as proton dose-calculation module.This work focuses on proton PBA algothrim and meets the urgent need for domestic research and development in the field of proton TPS.