摘要
目的:通过电子射野影像系统(Electron PortalImaging Device,EPID)测定和分析三维适形及调强放疗中的摆位误差,并依此计算CTV外扩PTV边界的大小,定期分析误差原因,不断提高科室的质量控制水平。方法:对2007年10月份开始连续四个月月份各12、11、17、16例头颈部肿实行适形或调强放疗的肿瘤患者进行摆位误差测定,体位固定采用头颈肩膜固定,每例患者每周一次于治疗前在加速器上拍摄正、侧位等中心验证片各一张,与治疗计划系统中的DRR(Digital Reconstructed Radiograph)片比较,计算出摆位误差。CTV到PTV外扩边界的大小由公式2.0Σ+0.7σ计算得出,其中Σ为系统误差,σ为随机误差,于每月底计算本月度的CTV到PTV外扩边界数值,分析误差原因,并提出具体质控措施。结果:由公式得出我科头颈部肿瘤外扩PTV的理论边界前1、2、3月份数值呈不断下降,自4月份开始,数值呈稳定状态。结论:通过对摆位误差的分析为我科外扩CTV边界提供了理论依据,确定了CTV到PTV外扩边界的大小,通过不断的改进,使边界外扩数值不断减少,减少患者照射区域,提高治疗水平。
Objective： This study was to investigate the set-up error using electronic portal imaging device （EPID） for intensity modulated radiation （IMRT）, assess of the CTV-to-PTV margins, analyze the factors on causing the error periodically, and to improve the quality control level. Methods： From October 2007 to January 2008, twelve, eleven, seventeen; and sixteen patients with head and neck carcinoma were enrolled in this study. The patients were immobilized with the head/neck shoulder immobilization system on margins. The set-up errors were analyzed by comparing the films of digitally reconstructed radiographs （DRR） with EPID. Electronic portal imaging was performed for twice each week before each treatment at the position AP （gantry angle 0°） and LT （gantry angle 90°）, respectively. CTV-to-PTV margins were calculated by the equation 2.0Σ＋0.7σ （Σ is the systematic error, and σ- is the random error） in the end of each month, the factors which might be the causes were analyzed and some quality control methods were proposed. Results- The theoretical CTV-to-PTV margins calculating by the equation was declined gradually during the previous three months and stable in the fourth month. Conclusions： This study supplied theoretical evidences and validated CTV-to-PTV margins for our department of radiotherapy by analyzing the set-up errors. This strategy may diminish the unnecessary irradiation fields and enhance the treatment outcome through the technique improvement.
出处
《中国医学物理学杂志》
CSCD
2009年第3期1154-1155,1183,共3页
Chinese Journal of Medical Physics
基金
淮安市科技支撑项目(No.HAS08005)
关键词
放射治疗
摆位误差
边界
电子射野影像系统
质量保证
radiotherapy
, set-up erors
margin
Electron Portal Imaging Device （EPID）
quality assurance
