Gafchromic® EBT2 film dosimetry in an anthropomorphic head and neck phantom measuring Intensity Modulated Radiation Therapy (IMRT) dose distributions

Cancer is one of the leading causes of death in Australia. Radiation therapy is one of the main options for the treatment of cancer. Intensity modulated radiation therapy (IMRT) is a new implementation of existing radiation therapy techniques which spares critical structures e.g. parotid glands. The checking of the accuracy of IMRT treatment delivery is important as any errors may result in further complications for the patient. Hence a level III dosimetry survey of departments in Australia is currently underway. This is called the ICARIS (a dosimetric Inter- Comparison of Australian Radiotherapy Systems) project. This thesis describes precursor equipment testing and analysis procedures undertaken to establish relevant limits for the accuracy of dose delivery during the ICARIS project. This thesis describes some of the precursor dosimetry tests which assisted with the ICARIS implementation. This thesis does not describe actual ICARIS inter centre survey results. In this thesis, a procedure for the irradiation and analysis of Gafchromic® EBT2 film was established. The film was calibrated and irradiated with a conventional 10x10cm2 field and a basic IMRT plan in solid water in order to establish these procedures. To test the procedures, EBT2 film contained within a custom built CIRS™ head and neck anthropomorphic phantom was irradiated with a four field box. Applying a gamma analysis criterion of 3mm5% resulted in 5.47% of pixels with y>1. Finally, EBT2 film was irradiated with three different head and neck intensity modulated radiation therapy treatment plans using the CIRS™ anthropomorphic phantom. All three irradiations were analysed using the gamma analysis criterion of 3mm5%. When using this criterion, a 90% agreement between the planned treatment and the measured values was obtained.