基于EPID和EBT3胶片剂量计对动态MLC叶片到位精度检测研究  

Measurement of leaf position accuracy of dynamic multi-leaf collimator using electronic portal imaging device and EBT3 film dosimeter

作　　者：李盈辉[1] 陈立新[2] 庄永东 王彬[2] 朱金汉[2] 刘小伟[1] 

机构地区：[1]中山大学物理学院,广州510275 [2]华南肿瘤学国家重点实验室中山大学肿瘤防治中心放疗科,广州510060

出　　处：《中华放射肿瘤学杂志》2016年第9期989-993,共5页Chinese Journal of Radiation Oncology

基　　金：广东省教育部产学研重点项目（20128091000144）;广东省自然科学基金（2014A030310188）

摘　　要：目的建立一种使用EPID和EBT3胶片剂量计进行动态MLC叶片到位精度的快速准确检测方法。方法美国瓦里安6MV加速器的固定机架角和准直器角度为0°。共设计11个MLC以滑窗方式运行的射野，每个射野由一组相同宽度的窄条野组成，窄条野的宽度为1-10mm，窄条野之间的间距为2cm。使用EPID、EBT3胶片剂量计作为测量工具，刻度设计窄条野宽度（带宽）与测量带宽的半高宽的关系。以同样方式设计一带宽为5mm射野，并在不同位置设计几处MLC叶片偏差，通过EPID、EBT3分析MLC叶片到位精度。结果当设计带宽〉4mm时，可很好地线性拟合设计带宽与实测带宽的半高宽。EPID检测带宽、峰值间距、MLC叶片位置的精度分别为±0．2、±0．1、±0．1mm，EBT3检测的分别为±0．3、±0．2、±0．2mm。结论提供了一种使用EPID或EBT3胶片剂量计快速检测MLC实际到位精度的方法，为MLC的QA提供帮助。Objective To establish a fast and accurate method for measurement of leaf position accuracy of dynamic multi-leaf collimator （MLC） using electronic portal imaging device （EPID） and EBT3 film dosimeter. Methods A Varian 6 MV accelerator was used with the gantry angle and the collimator angle fixed at zero degree. A total of 11 sliding window MLC fields were designed. Each field contained a group of strip fields with the same width. The width of a strip field ranged from 1 mm to 10 mm and the distance between two adjacent strip fields was 20 mm. The relationship between the width of the strip field （band width） and the full width at half maximum （FWHM） was calibrated using EPID and EBT3 as measurement tools. A field with a band width of 5 mm was designed in the same way and several MLC leaf deviations were made in different positions. EPID and EBT3 film dosimeter were used to analyze the leaf position accuracy. Results A good linear relationship between band width and FWHM was achieved when the band width was larger than 4 mm. The accuracy of band width, distance between peaks, and MLC leaf position were determined as ±0. 2 mm, ±0. 1 mm, and ±0. 1 mm by EPID and ±0. 3 mm, ±0. 2 mm, and ± 0. 2 mm by EBT3 film dosimeter, respectively. Conclusions This study provides a fast and accurate method for the measurement of MLC leaf position accuracy using EPID or EBT3 film dosimeter, which is helpful for quality assurance of MLC.

关 键 词：电子射野影像装置 EBT3胶片剂量计 多叶准直器 质量保证 

分 类 号：R730.55[医药卫生—肿瘤]