中国癌症杂志 ›› 2020, Vol. 30 ›› Issue (9): 689-693.doi: 10.19401/j.cnki.1007-3639.2020.09.008

• 论著 • 上一篇    下一篇

基于患者出射EPID剂量验证的在体调强放疗质控技术研究

吴志强,陈元华,王佳舟,胡伟刚   

  1. 复旦大学附属肿瘤医院放疗科,复旦大学上海医学院肿瘤学系,上海 200032
  • 出版日期:2020-09-30 发布日期:2020-10-12
  • 通信作者: 胡伟刚 E-mail: jackhuwg@gmail.com
  • 基金资助:
    国家自然科学基金(11675042)。

A study of in vivo dosimetry verification based on EPID transit dose

WU Zhiqiang, CHEN Yuanhua, WANG Jiazhou, HU Weigang   

  1. Department of Radiation Oncology, Fudan University Shanghai Cancer Center; Department of Oncology, Shanghai Medical College, Fudan University, Shanghai 200032, China
  • Published:2020-09-30 Online:2020-10-12
  • Contact: HU Weigang E-mail: jackhuwg@gmail.com

摘要: 背景与目的:调强放疗(intensity-modulated radiation therapy,IMRT)中剂量投照失误可导致严重后果,而目前常用的治疗前计划验证方法并不能反映患者真实投照剂量。实现一种评估患者在体剂量执行准确度的方法,能够在分次治疗中及时发现较大剂量错误,避免发生患者投照剂量过高或不足。方法:复旦大学附属肿瘤医院收治的患者首次实施治疗前行锥形束计算机断层成像(cone beam computed tomography,CBCT)扫描,与定位CT图像进行配准保证治疗体位与模拟定位时一致,实时治疗中使用电子射野影像装置(electronic portal imaging device,EPID)获取患者出射剂量影像,并把首次出射EPID影像作为剩余分次治疗的基准值,后续分次实时治疗野结束后快速将其出射EPID影像与对应基准影像进行γ分析比较,以验证治疗计划是否准确执行于患者身上。设计模体实验对治疗部位错误和摆位误差情况进行分析,来评估本方法识别放疗差错的准确性。结果:本方法可有效地识别出IMRT放疗中患者治疗部位错误和非平行于射野角度方向的摆位误差,但对平行于射野角度方向的摆位误差并不敏感,30例鼻咽癌患者临床应用结果中能够直观显示分次治疗间摆位重复性情况。结论:基于EPID实现的一种在体剂量验证方法能够对调强放疗中患者实时剂量的准确性进行评估,在单个治疗野结束后可快速检测出较大治疗错误。

关键词: 在体剂量验证, 电子射野影像装置, 治疗部位错误, 摆位误差

Abstract: Background and purpose: Mistreatment in intensity-modulated radiation therapy (IMRT) may cause major harms. However, pre-treatment plan verification approaches are not able to detect on-treatment errors. The aim of this study was to develop an in vivo dose verification method to quickly identify gross errors during radiation delivery and prevent larger or smaller delivered dose from adversely affecting patient. Methods: For each patient who was treated in Fudan University Shanghai Cancer Center, a cone beam computed tomography (CBCT) scan was acquired before the start of the first fraction treatment. The CBCT scans were implemented image registration with the planning CT. The electronic portal imaging device (EPID) images were captured during the first treatment delivery and used as the baseline measurement for the rest of the treatment. Dose comparisons were made using gamma analysis to verify whether the dose delivered to the patient as planned. Tests were developed to simulate incorrect site and setup error to evaluate the accuracy of this method. Results: This study showed that our method successfully detected simulated gross errors due to incorrect site and non-parallel beam direction shifts, however, it was insensitive to the translational shifts at the parallel beam direction. The inter-fraction setup was easily observed in clinical application for 30 nasopharyngeal carcinoma patients. Conclusion: Real-time error detection method for online IMRT treatment has been developed, and could detect gross errors immediately after an individual field is delivered.

Key words: In vivo dosimetry, Electronic portal imaging device, Incorrect site, Setup error