Accuracy of Out of Field Photon Dose Calculations by a Treatment Planning System Kumar Silpa Ajay1, Musthafa MM2, Tripathy JayaPrasad3, Duraisamy Karthickeyan4, Bharathan Resmi K1, Ayyappan Suja Cheruliyil1, Muttath Geetha1 1Lecturer, Department of Radiation Oncology, Malabar Cancer Centre, Thalassery, Kannur, Kerala, India 2Professor, Department of Physics, Calicut University, Kerala, India 3Operational Research Fellow, International Union Against Tuberculosis and Lung Disease, The Union South East Asia Office, New Delhi, India 4Founder and Chair, Academy for Public Health, Kozhikode, Kerala, India Online published on 19 August, 2019. Abstract Introduction Present study was conducted to compare 2D array detector and Eclipse Treatment Planning System for out-of-field photon dose measurement among patients with pharyngeal cancers treated with Volumetric Modulated Arc Therapy. Aim To compare 2Darray Detector and Eclipse treatment planning system for the out of field photon dose measurement among Head and Neck cancer patients treated with Volumetric Modulated Arc Therapy. Method Verification plan was created for each treatment plan in Eclipse treatment planning system using the analytical anisotropic algorithm [AAA] with the 2-D array ionization chamber. All the plans were done using 6MV photon energy. Doses were measured along the +X and +Y axes at 5, 8, 10 and 12 cm distance away from the isocenter. All measurements were performed on a Varian Clinac iX linear accelerator and the results were cross-compared with the fluence measurements obtained at the same points using 2D 729 array detector combined with Octavius 4D phantom. Evaluation of the 2-D array measurements was done using PTW Verisoft software Result Good agreement observed between the calculated and measured doses. The deviation increases as the distance increases. A maximum deviation of 28.6% along the Y-axis and 5.1% along X-axis. Out of field dose found to be slightly higher in Nasopharyngeal cancers compared to other pharyngeal cancers due to its large volume. Conclusion Study shows good agreement between the measured and calculated Out of field dose. Top Keywords VMAT, 2D array, SORT IT, out-of-field photon dose. Top |