探讨热释光在螺旋断层放射治疗系统和直线加速器中剂量标定  

Dosimeteric calibration of thermoluminescence in helical tomotherapy system and linear accelerator

作　　者：王为[1] 沈奕晨[1] 蒋马伟[1] WANG Wei;SHEN Yichen;JIANG Mawei(Department of Oncology,Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine,Shanghai 200092,China)

机构地区：[1]上海交通大学医学院附属新华医院肿瘤科

出　　处：《中国医学物理学杂志》2019年第11期1261-1266,共6页Chinese Journal of Medical Physics

基　　金：上海促进市级医院临床技能与临床创新3年行动计划项目（16CR2014A）

摘　　要：目的:比对热释光剂量计(TLD)在普通直线加速器(LINAC)和螺旋断层放射治疗系统(TOMO)中的剂量刻度差异,探讨TLD特性,为后续临床实测应用提供依据。方法:在6 MV光子束下,通过LINAC和TOMO对同批次TLD分别刻度。LINAC出束跳数30、50、100、150、200、300 MU;TOMO出束时间为3、5、10、15、20、30、40 s。在TLD测量位置,应用电离室交叉校准。每组测量数据为3个TLD片平均值。计算相应剂量为TLD读数的函数。将LINAC和TOMO下的TLD剂量校准曲线分别进行最小二乘法的线性模型和二次模型拟合比较,统计分析和配对t检验计算校准因子。验证相应TLD灵敏度、重复性、分散性和剂量响应等特性。结果:LINAC中,TLD发光读数y与照射剂量x关系式:y=94.754x+0.001x^2,R^2=0.9971;TOMO中:y=93.835x+0.0003x2,R^2=0.9982。在0.30~3.74 Gy剂量范围内,对6 MV光子束,TLD计数值与剂量呈近似线性关系。cGy剂量级同批次TLD各重复测量5次,读出平均值变化为1.48%。结论:同等能量下TOMO和LINAC的TLD刻度结果差异小于3%,符合要求。TLD线性相关性强、重复测量精度高、性能稳定,可应用于相关临床放疗剂量测量。Objective To compare the differences in scale factors of thermoluminescent dosimeters(TLD)between a linear accelerator(LINAC)and a helical tomotherapy system(TOMO)and to investigate the characteristics of TLD for providing basis for follow-up clinical applications.Methods The same batch of TLD was calibrated at 6 MV photon beams via LINAC and TOMO.The machine units of LINAC were 30,50,100,150,200 and 300 MU,respectively,while the delivery time of TOMO was 3,5,10,15,20,30 and 40 s,respectively.Cross-calibration of an ionization chamber was applied at TLD measurement positions.Each set of measurement data was defined as the average of 3 TLD chips,and the dose as a function of TLD reading was calculated.The TLD dose calibration curves under LINAC and TOMO were compared with the linear model and the quadratic model fitting with least square method,respectively.Statistic analysis and paired t test were performed to calculate calibration factors.Meanwhile,the corresponding TLD characteristics such as sensitivity,repeatability,dispersibility and dose response performance were also verified.Results The correlation between TLD reading y and irradiation dose x in LINAC was y=94.754x+0.001x2,R^2=0.9971.In TOMO,the correlation was y=93.835x+0.0003x2,R^2=0.9982.In the dose range of 0.30-3.74 Gy,the TLD dose-response curve of 6MV photon beams was approximately linear.The measurement for the same batch was repeated 5 times at each cGy dose level,and the average change in reading was 1.48%.Conclusion The difference in TLD calibrated with LINAC and TOMO at the same energy was less than 3%.With the advantages of strong linear correlation of dose response,precise measurements,high repeatability,and stable performance,the proposed TLD system is appropriate for relevant clinical irradiation dose measurements.

关 键 词：热释光剂量测量系统 螺旋断层放射治疗系统 兆伏级剂量校准 刻度因子 

分 类 号：R815[医药卫生—放射医学]