基于调强放疗射野下的二维电离室矩阵探测器的方向性响应研究  

Angular dependence study on two-dimensional ionization chamber matrix detector in IMRT fields

作　　者：李立芳 翟贺争[2,3] 王永志 明鑫 韩宝林 Lifang;Zhai Hezheng;Wang Yongzhi;Ming Xin;Han Baolin(Department of Radiation Oncology,Tianjin Baodi Hospital,Baodi Clinical College of Tianjin Medical University,Tianjin 301800,China;Center of Radiation Detection and Evaluation,Institute of Radiation Medicine,Chinese Academy of Medical Sciences,Tianjin 300192,China;School of Precision Instruments and OPTO-Electronics Engineering,Tianjin University,Tianjin 300072,China;School of Biomedical Engineering,Tianjin Medical University,Tianjin 300070,China)

机构地区：[1]天津市宝坻区人民医院放疗科,天津医科大学宝坻临床学院放疗科,301800 [2]中国医学科学院放射医学研究所,辐射检测与评价中心,天津300192 [3]天津大学精密仪器与光电子工程学院,300072 [4]天津医科大学生物医学工程与技术学院,300070

出　　处：《国际生物医学工程杂志》2020年第4期297-303,共7页International Journal of Biomedical Engineering

基　　金：国家自然科学基金(11805144);天津市教委科研计划项目(2017KJ231)。

摘　　要：目的研究调强放疗(IMRT)下,二维电离室矩阵探测器在不同照射方向(0°、45°、90°和135°)和医用加速器机架角度(0°、15°、30°、45°、60°、-15°、-30°、-45°和-60°)下的方向性响应,初步建立对其方向性的测试方法。方法对医用加速器、二维电离室矩阵探测器分别进行刻度及校准后,采用固体水模体覆盖二维电离室矩阵探测器上部,通过调整固体水模的厚度,使二维电离室矩阵探测器探头的有效测量中心到模体表面射线中心轴入射点的等效水距离为5 cm。选取探测器相对于治疗床长轴0°、45°、90°和135°共4个位置,于每个位置分别在医用加速器机架角度为60°、45°、30°、15°、0°、-15°、-30°、-45°和-60°时对选取的13个电离室探头进行测试。结果医用加速器在不同机架角度下,输出的剂量偏差≤0.18%;在相同照射野、不同入射角度下,二维电离室矩阵探测器电离室探头的方向性响应偏差≤0.63%;二维电离室矩阵探测器各探头对于其中心探头的测量偏差均<0.50%。结论二维电离室矩阵探测器具有良好的方向性响应,是开展IMRT质量控制的有效工具。本研究中初步建立的测试方法可为相关医用加速器计量部门制定相应的质量控制检测规范提供基础性依据。Objective To study the dose response of two-dimensional ionization chamber matrix detectors under IMRT fields irradiation at different gantry angles and different directions.Methods After the dose calibration of the medical accelerator and the two-dimensional ionization chamber matrix detector respectively,the solid water phantom was used to cover the upper part of the two-dimensional ionization chamber matrix detector.Adjusting the thickness of the solid water,the effective distances between the effective measuring center of the two-dimensional ionization chamber matrix detector and the incident point of the central axis of the radiation on the surface of the phantom was always controlled at 5 cm.Four locations with 0、45、90 and 135 degrees of the long axis of the treatment bed were selected,and each location was irradiated by IMRT fields at different frame angle of 60°,45°,30°,15°,0°,-15°,-30°,-45°and-60°,respectively.Results The dose deviation of the medical accelerator was less than 0.18%in the range of different rack angles.The directional response deviation of the two-dimensional ionization chamber matrix detector was less than 0.63%,and the measurement deviation of each probe of the two-dimensional ionization chamber matrix detector to its center probe was less than 0.50%.Conclusions The two-dimensional ionization chamber matrix detector has good directional response and it is a useful tool for developing intensity-modulated radiotherapy technology.The method proposed in this study can provide a basic basis for the relevant medical accelerator metrology departments to formulate corresponding quality control test specifications.

关 键 词：二维电离室矩阵 方向性响应 调强放射治疗 

分 类 号：R730.55[医药卫生—肿瘤]