应用网格堆叠结构展宽粒子束流布拉格峰的初步研究  

A preliminary study of Bragg peak broadening by using mesh-stacked porous structure in scanningparticlebeam

作　　者：董思学 王佳舟[1] 盛尹祥子 胡伟刚[1] Dong Sixue;Wang Jiazhou;Sheng Yinxiangzi;Hu Weigang(Department of Radiation Oncology,Fudan University Shanghai Cancer Center/Department of Oncology,Shanghai Medical College,Fudan University/Shanghai Key Laboratory of Radiation Oncology/Shanghai Clinical Research Center for Radiation Oncology,Shanghai 200032,China;Department of Medical Physics,Shanghai Proton and Heavy lon Center/Shanghai Key Laboratory of Radiation Oncology(20dz2261000)/Shanghai Engineering Research Center of Proton and Heavy lon Radiation Therapy,Shanghai201321,China)

机构地区：[1]复旦大学附属肿瘤医院放射治疗中心,复旦大学上海医学院肿瘤学系,上海市放射肿瘤学重点实验室,上海市放射治疗临床医学研究中心,上海200032 [2]上海市质子重离子医院放射物理科,上海市放射肿瘤学重点实验室(20dz2261000),上海质子重离子放射治疗工程技术研究中心,上海201321

出　　处：《中华放射肿瘤学杂志》2024年第9期833-839,共7页Chinese Journal of Radiation Oncology

摘　　要：目的开发并验证一种用于展宽布拉格峰的结构体,以提高粒子放疗的效率与适形性.方法通过随机堆叠与规律堆叠两种方式来制作具有多孔性的网格堆叠结构(MPS),每一层网格中,网格厚度、线宽与线间距分别为0.1、0.1、0.5mm,总尺寸为10cm×10cm.使用蒙特卡罗程序FLUKA模拟196 MeV/u的碳离子束流与105 MeV的质子束流穿过MPS后的输运过程,评估调制后束流的剂量分布、束流不均匀性以及MPS的调制能力稳定性,并评估MPS在鼻咽癌(63 Gy分21次)、肺癌(77 Gy分22次)与前列腺癌(70.4 Gy分16次)各1例临床计划中的调制效果.结果MPS最多能够将质子束流和碳离子束流的布拉格峰宽度分别增加1.73 mm和2.95 mm,对于不同入射位置,10层以上的规律堆叠能够将MPS的调制能力差异降至5%之内.堆叠30层的MPS调制后的束流输运18 cm后可使不均匀性降至3%之内,与临床使用的波纹滤波器相比,MPS能够将质子等中心束斑减小0.91 mm.在鼻咽癌计划调制中,使用MPS能够将治疗时间缩短213s(37%)且脑干所受的最大剂量减小了3.28 Gy(7.5%).结论使用MPS能够有效地展宽粒子束流的布拉格峰,提高临床放疗效率,规律堆叠的MPS调制能力稳定性较强.调制后的束流能够实现相对良好的均匀性,具有贴近患者而减小横向散射并提高适形性的临床应用潜力.Objective To develop and validate a structure for broadening the Bragg peak to improve the efficiency and conformality of particle radiotherapy.Methods Techniques of random stacking and regular stacking were employed to fabricate the mesh-stacked porous structure(MPS).In each layer of the grid,the thickness,line width and spacing were set at 0.1 mm,0.1 mm and 0.5 mm,respectively,resulting in a total size of 10 cm x10 cm.Monte Carlo code FLUKA was performed to simulate the transportation of 196 MeV/u carbon ion beam and a 105 MeV proton beam through the MPS.Dose distribution,fluence homogeneity,and modulation stability of the modulated beams were evaluated.Moreover,the modulation effect of MPS in clinical radiotherapy plans for nasopharyngeal carcinoma(63 Gy in 21 fractions),lung cancer(77 Gy in 22 fractions)and prostate cancer(70.4 Gy in 16 fractions)was also evaluated,respectively.Results The MPS was capable of broadening the Bragg peak width by 1.73 mm for proton beams and 2.95 mm for carbon ion beams.For different entrance positions,regular stacking of more than 10 layers could reduce the modulation power difference of MPS to within 5%.For MPS with 30 layers of regular stacking,the modulated fluence homogeneity could achieve a value of less than 3%by transporting 18 cm distance in air.When comparing to the clinically used ripple filters,MPS reduced the isocenter spot size of proton beams by 0.91 mm.In the comparison study of the treatment plan for nasopharyngeal carcinoma,the use of MPS could shorten the treatment time by 213 s(37%)and reduce the maximum dose to the brainstem by 3.28 Gy(7.5%).Conclusions MPS effectively broadens the Bragg peak of particle beams and improves the efficiency of clinical radiotherapy.Regularly stacked MPS demonstrates robust modulation stability,and the modulated beam achieves relatively well fluence homogeneity,making it a promising clinical application for closer to the patients and reducing lateral scattering.

关 键 词：放射疗法 粒子 波纹滤波器 布拉格峰展宽 蒙特卡罗模拟 

分 类 号：R312[医药卫生—基础医学]