摘要
目的:研究磁共振图像引导质子治疗中边缘场存在时束流轨迹的校正和校正前后机体中剂量变化。方法:使用开源的治疗计划软件mat Rad对脑肿瘤、肝脏肿瘤、前列腺癌病例进行计划设计,并在蒙特卡罗模拟工具包TOPAS中进行模拟研究,计算质子剂量分布。建立一种适用于三维磁场的质子束轨迹校正模型,并基于此开发一个束流轨迹校正算法。分析边缘场存在时,质子布拉格峰的偏转情况。对边缘场存在时的3种肿瘤治疗计划模拟并进行剂量校正,使用γ分析法评估校正效果,定量分析校正后靶区和危及器官中的剂量变化情况。结果:磁场的扰动会使质子束轨迹发生横向偏转,而边缘场的存在会显著地增加这一影响,且随束流能量的增加而增加。边缘场存在时,对脑肿瘤、肝脏肿瘤和前列腺癌治疗计划进行校正,在3%/3 mm标准下靶区γ通过率分别为94.844%、92.054%、97.863%,校正后体内的总剂量分别增加2.8%、2.5%和1.5%,增加的剂量主要由入射质子贡献。结论:在磁共振图像引导质子治疗中,应该考虑边缘场带来的影响。校正后入射质子束能量的增加会导致体内总剂量的增加,由于束流轨迹仍然存在曲率,在不同危及器官中剂量的变化不同。
Objective To explore the correction of beam trajectories in the presence of fringe fields in magnetic resonance imagingguided proton therapy and dose changes in the body before and after correction.Methods The open-source treatment planning software matRad was used to design plans for brain tumor,liver tumor,and prostate cancer cases,and simulation studies were conducted in the Monte Carlo simulation toolkit TOPAS to calculate proton dose distribution.Aproton beam trajectory correction model suitable for three-dimensional magnetic fields was established,and a beam trajectory correction algorithm was developed.The deflection of the proton Bragg peak in the presence of fringe fields was analyzed.Furthermore,3 treatment plans were simulated and dose correction was carried out when the fringe field existed.Gamma analysis method is used to evaluate the correction effect;and the dose changes in the target area and organs-at-risk after correction were quantitatively analyzed.Results The perturbation of the magnetic field would cause lateral deflection of the proton beam trajectory,and the presence of fringe fields would significantly increase this effect,which increased with the increasing of beam energy.When the fringe field existed,the treatment plans for brain tumor,liver tumor,and prostate cancer were corrected.Under the 3%/3 mm criterion,the gamma passing rates for target area were 94.844%,92.054%,and 97.863%,respectively,and after correction,the total dose in the body was increased by 2.8%,2.5%,and 1.5%,respectively.The increased dose was mainly contributed by incident protons.Conclusion In magnetic resonance imaging-guided proton therapy,the effects of fringe fields should be considered.The increase in incident proton beam energy after correction will lead to an increase in the total dose in the body.Since the beam trajectory still has curvature,the dose changes differently in different organs-at-risk.
作者
李国栋
王明
薛景硕
董浪
孙甜甜
代伟
张磊
LI Guodong;WANG Ming;XUE Jingshuo;DONG Lang;SUN Tiantian;DAI Wei;ZHANG Lei(College of Nuclear Technology and Automation Engineering,Chengdu University of Technology,Chengdu 610059,China;Department of Radiation Physics,Zhejiang Cancer Hospital/Hangzhou Institute of Medicine,Chinese Academy of Sciences,Hangzhou 310022,China)
出处
《中国医学物理学杂志》
CSCD
2024年第6期661-666,共6页
Chinese Journal of Medical Physics
基金
国家自然科学基金(12105030)
四川省教育厅科研基金(2022NSFSC1185)。
关键词
质子治疗
磁共振图像引导
边缘场
束流轨迹校正
proton therapy
magnetic resonance imaging-guided
fringe field
beam trajectory correction
