本课题的主要目的是分析不同扫描光源下 EBT2 胶片的剂量响应特性，将由 EBT2 胶片、Uniscan C880 平板扫描仪和 FilmQA 剂量分析软件组建的 IMRT 剂 量验证系统应用于临床。 课题研究首先将 EBT2 胶片被放置于固体水模体中，使用 6MV 光子线照射 胶片，照射的剂量范围为 0—280cGy，通过将扫描后的胶片影像分离成红光、绿 光和蓝光影像，来分析不同扫描光源下胶片的剂量响应特性；然后通过对扫描 仪的扫描不确定性和扫描方向对扫描仪读数的影响进行测试以评估由 EBT2 胶 片、Uniscan C880 平板扫描仪和 FilmQA 剂量分析软件组成的 IMRT 剂量验证系 统的性能，并将该系统应用于一例鼻咽癌病例的剂量验证，来认识和掌握该系 统的使用方法；最后使用该系统和 mapcheck 半导体探测器阵列对 10 组 IMRT 照射野进行剂量验证，通过观察不同参数设置下 DTA 指数和 Gamma 指数的变 化，来分析 EBT2 胶片在 IMRT 剂量学验证上的优点。 通过研究我们发现，EBT2 胶片在红光扫描光源下的剂量响应灵敏度最高且 其响应曲线是非线性的，使用三次多项式可以满足该剂量响应曲线的拟合要求。 扫描仪的单次扫描不确定性和多次扫描不确定性分别是 0.22%和 1.12%，胶片放 置方位对扫描仪读数影响很大。通过对一组鼻咽癌 IMRT 照射野的剂量验证，发 现该系统使用方法简单，测量结果与计划计算数据基本一致。通过对比 mapcheck 获取的 IMRT 验证结果，发现 EBT2 胶片比 mapcheck 具有更高的空间分辨率， 能够测量到更多剂量检验点上的剂量变化。 研究说明，基于辐射自显影胶片 EBT2 的 IMRT 剂量验证系统操作简单、结 果准确，具有很高的空间分辨率，非常适合射野内剂量梯度变化大、准确性要 求高的 IMRT 的剂量验证，值得在临床中推广应用。 关键词：辐射自显影胶片 调强放疗 剂量验证II Abstract The purpose of this study is to investigate the dose response characteristic of EBT2 film which is scanned with different light sources. Then the IMRT dosimetric verification system which was composed by EBT2 film, Uniscan C880 scanner and FilmQA dosimetry analysis software was applied in clinical. The EBT2 film was placed in solid water phantom, radiated with 6MV photon beam whose delivered dose are span from 0 to 280 cGy. Then the film was scanned with flatbed color scanner, and the scanned images were separated into red, green and blue images. The characteristic of image’s dose response was analyzed respectively. The scanner’s scanning uncertainty and film orientation effect were tested to evaluate the IMRT dosimetric verification system which was composed by EBT2 film, Uniscan C880 flatbed scanner and FilmQA dosimetry software. Then the system was applied in a NPC case in experimental trial as well. 10 cases were tested by this system and mapcheck, the results were analyzed with DTA and Gamma index. The advancement of EBT2 film in IMRT dosimetric verification was investigated by setting various parameters to DTA and Gamma index. The results showed that sequence of dose response sensitivity of the EBT2 film is red, green and blue when scanned in different lights. Cubic polynomial fitting method can satisfy the requirement of dose response curve. The Uniscan C880 scanner’s single and multiple scanning uncertainties were 0.22% and 1.12% respectively. Film orientation had a big effect on scanner’s readout. The IMRT dosimetric verification system composed by EBT2 film, Uniscan C880 flatbed scanner and FilmQA dosimetry software was easy to use, and the results got from this system were accurate. Compared with mapcheck, EBT2 have a higher spatial resolution; can check out more spatial point’s dose difference. The IMRT dosimetric verification system based on radiochromic film EBT2 is easy to use and can acquire an accurate result. Due to the advantages of high spatial resolution, it is suitable to use in IMRT dose verification and is valuable for clinical application.III Keywords ： radiochromic film intensity modulated radiotherapy dosimetric verificationIV 目 录 第 1 章 绪论 ........................................................1 1.1 研究背景与意义 .............................................1 1.1.1 研究背景 .............................................1 1.1.2 研究现状 .............................................2 1.1.3 研究意义 .............................................4 1.2 研究目的 ...................................................4 1.3 研究流程 ...................................................5 第 2 章 辐射自显影胶片的特性及其在 IMRT 剂量验证中的应用 .............6 2.1 引言 .......................................................6 2.2 辐射自显影胶片的应用原理 ...................................6 2.3 几种辐射自显影胶片 .........................................7 2.3.1 B3 WINdose 辐射自显影胶片.............................7 2.3.2 FWT-60-00 辐射自显影胶片..............................7 2.3.3 GAFCHROMIC(R)系列辐射自显影胶片 ........................7 2.4 EBT2 辐射自显影剂量胶片的物理特性...........................8 2.4.1 EBT2 剂量胶片的结构组成...............................8 2.4.2 EBT2 剂量胶片的有效原子序数与能量依赖性...............9 2.4.3 EBT2 剂量胶片的感光响应..............................10 2.4.4 EBT2 剂量胶片响应均匀性..............................11 2.4.5 EBT2 胶片黑度的变化..................................11 2.4.6 EBT2 胶片的处理与存档................................12 2.5 辐射自显影胶片应用于 IMRT 的剂量验证 .......................12 2.6 小结 ......................................................13 第 3 章 基于辐射自显影胶片 EBT2 的 IMRT 剂量验证系统 .................14 3.1 引言 ......................................................14 3.2 剂量验证系统构成 ..........................................14 3.2.1 辐射自显影剂量胶片 ..................................14V 3.2.2 扫描仪 ..............................................14 3.2.3 剂量分析软件 ........................................14 3.3 胶片剂量验证系统的建立 ....................................15 3.3.1 胶片剂量的校准 ......................................15 3.3.2 胶片剂量响应曲线的建立 ..............................17 3.4 胶片剂量测量系统的特性 ....................................18 3.4.1 扫描分辨率的选择 ....................................18 3.4.2 扫描仪响应的重复性 ..................................19 3.4.3 EBT2 胶片放置对扫描仪读数的影响......................21 3.5 调强放疗剂量验证流程 ......................................23 3.6 小结 ......................................................24 第 4 章 基于辐射自显影胶片 EBT2 的 IMRT 剂量验证系统的临床应用 .......26 4.1 引言 ......................................................26 4.2 材料与方法 ................................................26 4.2.1 设备材料 ............................................26 4.2.2 实验方法 ............................................26 4. 3 结果分析 .................................................27 4.3.1 离轴剂量曲线的比较 ..................................28 4.3.2 平面剂量分布对比 ....................................30 4.3.3 DTA 指数分析.........................................33 4.3.4 Gamma 指数分析.......................................34 4.4 小结 ......................................................36 第 5 章 不同剂量验证系统 IMRT 剂量验证结果比较 ......................38 5.1 引言 ......................................................38 5.2 材料与方法 ................................................38 5.2.1 设备材料 ............................................38 5.2.2 实验方法 ............................................38 5.3 结果分析 ..................................................39 5.3.1 DTA 指数分析.........................................39 5.3.2 Gamma 指数分析.......................................43VI 5.4 讨论 ......................................................47 第 6 章 结论与展望 .................................................49 6.1 结论 ......................................................49 6.2 展望 ......................................................50