BJ-6B加速器剂量监测系统校准10年回顾  

Review of Dose Monitoring System Calibration in BJ-6B Accelerator

作　　者：李贤富[1,2] 谢力[1,2] 郭飞[1,2] 周进伟[1,2] 柳弥[1,2] 谭榜宪[1,2] 

机构地区：[1]医学影像四川省重点实验室四川省肿瘤学重点学科,四川南充637000 [2]川北医学院附属医院放疗科,四川南充637000

出　　处：《中国医学物理学杂志》2013年第4期4232-4234,共3页Chinese Journal of Medical Physics

基　　金：四川省卫生厅科研课题(100158);川北医学院重点培育项目(CBY11-A-ZP04)

摘　　要：目的:明确按时对加速器剂量监测系统校准的必要性。方法:查阅国产BJ-6B 6Mv加速器剂量监测系统结构,以便结合电路分析剂量校准出现偏差的原因。按照IAEA提出的规程校准吸收剂量。对加速器剂量监测系统校准系数K随时间变化的情况进行回顾,选择连续的201周数据,做出校准系数和时间关系曲线。查阅维修记录,寻找系数变化大的原因。结果:系数变化大时,经过仔细排查,发现了以下比较严重的机器故障:1.电离室信号电缆因破损、漏电,校准系数由1.103变化为1.173,剂量偏低约6.3%。2.电离室击穿,输出剂量偏低约7.7%。3.防漏射铅板滑动,遮挡校准点,剂量偏低约9.9%。4.更换加速管,剂量偏低约4.7%。5.均整位置有偏移,中心轴剂量偏差7.7%。6.调制器稳压器坏,输出电压偏低,剂量偏低3.5%。较小的校准系数变化,与温度、湿度、气压等有关,有以年为周期的变化趋势。结论:元件老化,磨损,一些不容易发现的机器故障有可能影响剂量传递准确;由于加速器所处环境温度、湿度、气压等变化,也会影响加速器剂量监测系统监测准确性,一定要按国家标准GBZ126-2011规定的频次校准加速器剂量。Objective： Emphasize the necessity of calibrating dose monitoring system of accelerator on time. Methods： Research the construction of dose monitoring system in BJ-6B accelerator to find the factors of dose deviation. Calibrate dose according to IAEA regulations. Review the calibration coefficient K of dose monitoring system of accelerator within the past 10 years.Draw the relation curve between calibration coefficient K and time in the past continuous 201 weeks.Look for the cause of the greater change of K by looking up the maintenance record. Results： Some serious machine trouble were found when the coefficient K change was great. 1. Ionization chamber signal cable damaged, dose lower 6.3%. 2.Ionization chamber broke, dose lower 7.7%. 3. Fastened lead board shed and block beam axis, dose lower 9.9%. 4. Change accelerator tube, dose change 4.7%.5. Flatten filter position deviated, dose changed 7.7%. 6） Voltage stabilizer for modulator output lower, dose lower 3.5%.The little fluctuation of K concerns with environment temperature,humidity and airpressure,etc, which has the tendency of change in cycle time of year. Conclusions： The machine element aging,wearing and other trouble probably affect dose dilivery;the change such as tempera- ture, air-pressure and humiditY can affect dose monitoring system.So,we should calibrate dose on time according to national stan- dard GBZ126-2011.

关 键 词：加速器 剂量 校准 

分 类 号：R730.55[医药卫生—肿瘤] R815.6[医药卫生—临床医学]