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

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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.