15 MV医用直线加速器光中子蒙特卡罗模拟  

Monte Carlo simulation of photoneutron for a 15 MV medical linear accelerator

作　　者：邓磊 瞿述根[3] 王哲 陈以水 涂彧 张陆兵[1] Deng Lei;Qu Shugen;Wang Zhe;Chen Yishui;Tu Yu;Zhang Lubing(Institute of Occupational Medicine of Jiangxi,Nanchang 330006,China;State Key Laboratory of Radiation Medicine and Protection,School of Radiation Medicine and Protection of Soochow University,Suzhou 215123,China;School of Public Health and Management,Wenzhou Medical University,Wenzhou 325035,China)

机构地区：[1]江西省职业病防治研究院,南昌330006 [2]苏州大学放射医学与防护学院,放射医学与辐射防护国家重点实验室,苏州215123 [3]温州医科大学公共卫生与管理学院,温州325035

出　　处：《中华放射医学与防护杂志》2023年第12期1010-1015,共6页Chinese Journal of Radiological Medicine and Protection

基　　金：放射医学与辐射防护国家重点实验室资助项目(GZK1202019)。

摘　　要：目的研究高能医用直线加速器运行过程中因光核反应所形成的光中子辐射场。方法利用蒙特卡罗(MC)程序模拟Clinic 2300CD型医用电子加速器15 MV X射线模式下光中子污染,掌握机头内不同位置光中子能谱和不同照射野下等中心处中子周围剂量当量变化,分析光中子在等中心平面内剂量分布和水模体中剂量衰减。结果准直器关闭时,加速器机头内靶、主准直器、均整器和多叶准直器下表面的光中子平均能量分别为1.08、1.20、0.35、0.30 MeV;等中心处中子周围剂量当量随着照射野的增大先增大后减少,在30 cm×30 cm照射野下达到最大;随着测点在水模体中的深度增加,中子通量先增加后减小,而中子剂量却在逐渐减小;不同照射野下,光中子剂量率在水模体深度20 cm处,基本都接近本底。结论探究高能医用直线加速器机头光中子谱和剂量分布特点,以及光中子在水模体内剂量沉积规律,能为进一步研究高能医用直线加速器光中子污染对患者产生的附加剂量提供支持。Objective To study the photoneutron radiation field caused by photonuclear reaction during the operation of high energy medical linac.Methods Monte Carlo was used to simulate the photoneutron pollution of Clinic 2300CD medical electron accelerator in 15 MV X-ray mode.The photoneutron spectrum at different positions of the head and the variation in neutron ambient dose equivalent in different irradiation fields were investigated,and the dose distribution of photoneutron on the isocenter plane and the dose attenuation in the water model were analyzed.Results When the collimator was closed,the average photoneutron energy at the lower surface of target,primary collimator,flattening filter and multi-leaf collimator was 1.08,1.20,0.35 and 0.30 MeV,respectively.The neutron ambient dose equivalent at the isocenter first increased and then decreased with the irradiation field expanding,reaching the maximum in about 30 cm×30 cm irradiation field.With the increase in the depth of the measuring point in water phantom,the neutron fluent first increased and then decreased,while the neutron dose gradually decreased.In different irradiation fields,the photoneutron dose rate was almost close to the background when the depth of the water was 20 cm.Conclusions By exploring the photoneutron spectrum and dose distribution characteristics of the high energy medical linac head,as well as the dose deposition mechanism of photoneutron in water phantom,this study provides data support for further research on the additional dose and secondary cancer effects on patients caused by photoneutron pollution from the high energy medical linac.

关 键 词：医用直线加速器 光核反应 中子周围剂量当量 蒙特卡罗 

分 类 号：TL53[核科学技术—核技术及应用] R14[医药卫生—公共卫生与预防医学]