上海市质子重离子医院临床实践中放射治疗师的职业照射水平评估

Assessment of occupational exposure doses to physicians in clinical practice at Shanghai Proton and Heavy Ion Center

目的评估上海市质子重离子医院质子重离子临床实践过程中，放射治疗师的职业照射水平。方法通过简单随机抽样方法选取2016年9-11月治疗的40例患者，其中接受质子和重离子治疗各20例。记录每个患者的粒子类型、粒子总数、处方剂量。利用光子／中子辐射剂量仪分别测量出束过程中控制室内剂量率、出束结束1min后距肿瘤最近的皮肤处剂量率、距肿瘤约30cm处（治疗师立位处）的剂量率；最后测量固定装置、床、机械臂、束流应用及监测系统（BAMS）窗口处的剂量率。分析影响治疗师的职业照射水平的因素，评估该院治疗师的年平均剂量。结果治疗结束约1min后，距肿瘤最近的皮肤处剂量率为（20．68±21．91）μSv／h，此处是各测量点位中剂量率最大的点位，且与治疗用的粒子总数呈显著正相关（r=0．828，P＜0．05），受质子或重离子照射后的肿瘤是本研究中治疗师职业照射的辐射源；距肿瘤约30cm处（治疗师立位处）的平均剂量率为（2．03±2．84）μSv／h；控制室内剂量率为（0．08±0．01）μSv／h，患者的固定装置、床、机械臂、BAMS窗口处的剂量率为（0．09±0．01）μSv／h；未检测到中子，放疗师受到的年平均剂量为0．508 mSv。结论上海市质子重离子医院放射治疗师受到的年平均剂量处于较低水平。

Objective To assess the occupational exposure doses received by the physicians in clinical practice at Shanghai Proton and Heavy Ion Center （SPHIC）. Methods A total of 40 patients treated from September to November in 2016, including 20 proton cases and 20 carbon cases at SPHIC, were selected using simple random sampling method. Particle type, total particle number and prescribed doses were recorded for all the cases. The dose rates in the eontrol room were measured by using a photon and neutron personal radiation detector during patient treatment. The dose rates around the surface of the patient＇s tumor 1 rain after completion of beam delivery and the dose rates about 30 cm to the tumor surface （where a physician stands） were also measured during unfixing and assisting the patients. Finally, the dose rates surrounding the fixtures, couch, robotic arm and window of BAMS were measured. The factors affecting the oecupational exposure of physician were analyzed and the annual dose equivalent was assessed for physicians in SPHIC. Results Proton and heavy ion released nearly all energy in the tumor for Bragg peak advantage, so there was no induced radioactivity in the treatment room. However, the tumor became the main induced radioactivity source to the occupational exposure dose to physicians in clinical practices. The dose rate around the surface of the patient＇s tumor 1 rain after completion of beam delivery was （20.68±21.91） μSv/h, which was the highest in the working places of physicians, thus regarded as the main source. A significant positive correlation （ r = 0. 828, P 〈0.05 ） was shown between dose rates andtotal number of particles delivered for the treatment. The dose rate measured in the control room was （0.08±0.01 ）μSv/h, and the dose rate measured surrounding the fixtures, couch, robotic arm and BAMS window was （0.09 ± 0.01 ）μSv/h. No neutron was detected. The dose rate about 30 cm to the tumor surface （where physicians stand） was （2.03 ＋ 2.84） tzSv/h during unfixing and assisting the patients. The average annual dose to physicians was about 0. 508 mSv. Conclusions The average annual dose to physicians was at a low level in SPHIC