非晶硅平板电子射野影像用于放射治疗剂量学质量控制检验的应用  

Application of Amorphous Silicon Electronic Portal Imaging Device (a-Si EPID) to Dosimetry Quality Assurance of Radiation Therapy

作　　者：陈明伟[1] 邓小武[1] 黄劭敏[1] 陈利[1] 康德华[1] 

机构地区：[1]华南肿瘤学国家重点实验室

出　　处：《癌症》2007年第11期1272-1275,共4页Chinese Journal of Cancer

基　　金：广东省科技计划项目(No.2002C30302);吴阶平医学基金项目(No.WKJ2005-3-006-7)~~

摘　　要：背景与目的:非晶硅平板型电子射野影像系统(amorphous silicon electronic portal imaging device,a-SiEPID)具有良好的剂量学品质,作为一种快速的二维剂量测量系统,在常规质量控制、调强照射野验证及实时患者剂量监测等方面具有广阔的应用前景。为将非晶硅平板电子射野影像用于放射治疗的剂量学检验,本研究针对其射野影像建立了修正模型,并应用于加速器照射野的常规质量保证工作。方法:对a-SiEPID常用的图像刻度模式进行剂量刻度改进以用于照射剂量测量:通过一种由若干个小野组合形成"泛野"的方式来克服传统的泛野获取方式的缺陷,从而较准确地修正a-Si EPID各像素单元之间的灵敏度差异;并建立离轴剂量的响应曲线和修正数学模型。以修正后的a-SiEPID射野影像测量照射野的剂量分布并与三维水箱中电离室扫描的结果进行比较验证。结果:经所建立的模型进行剂量刻度和修正后,高剂量区,a-Si EPID与电离室测量结果偏差<2%,在半影区,a-Si EPID测量的剂量分布曲线比电离室测量结果略为陡峭。结论:非晶硅平板型电子射野影像(a-Si EPID)系统具有良好的物理剂量学品质,可以用作照射野常规质控检验和调强放射治疗射野剂量能量分布的快速工具。BACKGROUND ＆ OBJECTIVE： Due to its good dosimetric properties, amorphous silicon electronic portal imaging device （a-Si EPID）, as a rapid two-dimensional dosimetric measurement device, presents an attractive prospect in routine quality assurance （QA） test, dosimetric verification of intensity-modulated radiotherapy treatment （IMRT） and in vivo dose monitoring. This study was to explore the application of a-Si EPID as a detector for dosimetric QA of linear accelerator radiotherapy, and setup the calibration module. METHODS： The imaging calibration procedure of conventional a-Si EPID was modified for dosimetric measurement by acquiring the traditional ＂flush field＂ from integrated subfields to correct the dosimetric responding difference in pixel sensitivity. The energy dependence of the a-Si EPID detectors was analyzed through off-axis dose response curves. Calibrated dose profile obtained with a-Si EPID was compared with the measuring results of ion chamber in a 3-D water phantom. RESULTS： The calibrated dose profiles measured with a-Si EPID showed a deviation within 2% in high dose regions, but dropped much steeply in the penumbra region, as compared with that scanned using ion chamber in water. CONCLUSION： With the modeling management set up in this research, a-Si EPID can be applied for dosimetric QA of linear accelerator in radiotherapy.

关 键 词：非晶硅平板 EPID 射野剂量 质量控制 

分 类 号：R815[医药卫生—放射医学]