Advanced Radiochromic Film Based Dosimetry Techniques in Radiation Therapy and Diagnostic Radiology

胶片剂量学已发展成为放射治疗验证和质量保证的有力工具。放射变色胶片的推出具有胶片剂量测定的所有优点，而不需要湿处理机，使这种胶片类型成为重要的剂量测定工具。EBT薄膜模型已被引入，作为较早的MD-55模型的更敏感的替代。后续EBT2型号的有源层包含制造商添加的黄色标记染料，以校正有源层厚度的细微差异。在之前NSERC资助的赠款期间，我们大幅改善了最新EBT3辐射变色薄膜模型的能量响应，该模型也具有对称结构，并在保护聚酯层中嵌入了反牛顿环功能。 作为未来项目的一部分，我们将把各种辐射变色薄膜模型的使用扩展到目前正在出现的先进应用。XR-QA薄膜模型(具有高原子Z材料的敏感层)为最终的活体测量和用于诊断放射学的低KVP能量范围光子的参考剂量学提供了有希望的初步结果。最新的XR-QAA2胶片模型即使在诊断放射学中使用的相对较窄的光束质量范围内也显示出显著的能量依赖剂量响应。在我们成功地改善了EBT3薄膜模型的能量依赖剂量响应之后，我们将研究XR-QAA2薄膜模型敏感层的化学成分可能的变化，以降低其能量依赖性。 我们还将重点介绍使用放射变色胶片进行CTDI测量。与铅笔式电离室测量相比，该方法只需要一次曝光，不需要茎效应校正。此外，我们还将使基于放射变色胶片的CTDI测量成为该院放射治疗和诊断放射科质量保证计划的一部分。 第三个目标将集中于EBT3薄膜模型的开发和临床应用，用于机器和患者特定的QA在近距离治疗中的应用。在高剂量率近距离放射治疗中，缺乏临床测量和患者特定的QA程序(类似于调强放射治疗中的程序)，以便在近距离放射治疗过程中改善QA程序和患者的安全性。作为该项目的结果，我们希望得出可推荐用于近距离放射治疗质量保证的DD/DTA参数。 最后，我们将集中于建立低能质子束(使用HD-V2膜模型)中的辐射变色膜剂量测量方案，用于放射生物学实验(细胞和小动物照射)、术中质子放射治疗以及皮肤病(黑色素瘤、湿疹、感染性痤疮)的治疗。将使用参考剂量测量胶片测量(基于与石墨量热计的交叉校准)来测量辐射生物辐射的设置特定输出测量。

Film dosimetry was developed into a powerful tool for radiotherapy treatment verification and quality assurance. Introduction of radiochromic film having all advantages of film dosimetry without the need for wet processors make this film type an important dosimetric tool. The EBT film model has been introduced as a more sensitive alternative to the earlier MD-55 model. Active layer of subsequent EBT2 model contains a yellow marker dye added by manufacturer to correct for subtle differences in active layer thickness. During previously NSERC funded grant we have substantially improved the energy response of the latest EBT3 radiochromic film model, which also has a symmetric structure and embedded anti-Newton rings feature within protecting polyester layers. As part of future projects, we will extend the use of various radiochromic film models to currently emerging advanced applications. XR-QA film model (sensitive layer with high atomic Z materials) provided promising initial results for eventual in vivo and reference dosimetry at low kVp energy range photons used in diagnostic radiology. The latest XR-QA2 film model exhibits significant energy dependent dose response even in relatively narrow range of beam qualities used in diagnostic radiology. Following our success in improving energy dependent dose response of the EBT3 film model, we will investigate possible changes in chemical composition of the XR-QA2 film model sensitive layer to decrease its energy dependence. We will also focus on the use of radiochromic film strips for CTDI measurements. In contrast to pencil type ionization chamber measurements, proposed method requires only one exposure and does not need stem effect correction. Also, we will make radiochromic film based CTDI measurements part of QA program in both radiotherapy and diagnostic radiology departments in our hospital. Third objective will focus on the development and clinical applications of the EBT3 film model for both machine and patient-specific based QA in brachytherapy. Lack of clinical measurements and patient-specific QA procedures (similar to those in IMRT) in high dose rate brachytherapy are tempted to be developed in order to improve both the QA program and patient safety during brachytherapy procedures. As a result of this project, we are hoping to conclude on DD/DTA parameters that can be recommended for brachytherapy QA. Finally, we will concentrate on establishment of radiochromic film dosimetry protocols in low energy proton beams (using HD-V2 film model) for radio-biological experiments (cell and small animal irradiations), proton based intraoperative radiotherapy and for treatment of skin diseases (Melanomas, Eczema, Infectious Acne). Reference dosimetry film measurements (based on cross-calibration with graphite calorimeter) will be used to measure setup specific output measurements for radiobiological irradiations.