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。辐射变色胶片的引入具有胶片剂量测定的所有优点，而不需要湿处理器，使得这种胶片类型成为重要的剂量测定工具。EBT胶片模型已被引入作为早期MD-55模型的更敏感的替代品。后续EBT 2型号的活性层包含制造商添加的黄色标记染料，以校正活性层厚度的细微差异。在之前的NSERC资助期间，我们大幅改善了最新EBT 3辐射变色胶片模型的能量响应，该模型也具有对称结构，并在保护聚酯层内嵌入了防牛顿环功能。作为未来项目的一部分，我们将把各种辐射变色胶片模型的使用扩展到目前新兴的先进应用中。XR-QA薄膜模型（具有高原子Z材料的敏感层）为诊断放射学中使用的低kVp能量范围光子的最终体内和参考剂量测定提供了有希望的初步结果。最新的XR-QA 2胶片模型即使在诊断放射学中使用的相对较窄的射束质量范围内也表现出显著的能量依赖剂量响应。在我们成功改善EBT 3薄膜模型的能量依赖剂量响应之后，我们将研究XR-QA 2薄膜模型敏感层的化学成分的可能变化，以降低其能量依赖性。* 我们还将重点关注使用辐射变色胶片条进行CTDI测量。与铅笔型电离室测量相比，该方法只需要一次曝光，不需要茎效应校正。此外，我们将使基于辐射变色胶片的CTDI测量成为我院放射治疗和诊断放射科QA计划的一部分。* 第三个目标将侧重于EBT 3胶片模型的开发和临床应用，用于近距离放射治疗中基于机器和患者特定的QA。在高剂量率近距离放射治疗中缺乏临床测量和患者特异性QA程序（类似于IMRT中的QA程序），这是为了改善近距离放射治疗程序期间的QA程序和患者安全性。作为该项目的结果，我们希望总结可推荐用于近距离放射治疗QA的DD/DTA参数。* 最后，我们将专注于建立低能量质子束（使用HD-V2薄膜模型）中的辐射变色薄膜剂量测定方案，用于放射生物学实验（细胞和小动物辐照）、基于质子的术中放疗和皮肤病（黑色素瘤、湿疹、传染性痤疮）的治疗。参考剂量测定胶片测量值（基于石墨量热计的交叉校准）将用于测量放射生物学辐照的装置特定输出测量值。**

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.**