Document Type : Original Paper
M.Sc. student in Medical Physics, Medical Physics and Engineering Dept., Tehran University of Medical Sciences, Tehran, Iran.
Associate Professor, Medical Physics and Engineering Dept., Tehran University of Medical Sciences, Tehran, Iran.
Assistant Professor, Biochemistry and Biophysics Dept., Mazandaran University of Medical Sciences, Sari, Iran.
Introduction: GafChromic EBT films are one of the self-developing and modern films commercially available for dosimetric verification of treatment planning systems (TPSs). Their high spatial resolution, low energy dependence and near-tissue equivalence make them suitable for verification of dose distributions in radiation therapy. This study was designed to evaluate the dosimetric parameters of the RtDosePlan TPS such as PDD curves, lateral beam profiles, and isodose curves measured in a water phantom using EBT Radiochromic film and EGSnrc Monte Carlo (MC) simulation.
Methods and Materials: A Microtek color scanner was used as the film scanning system, where the response in the red color channel was extracted and used for the analyses. A calibration curve was measured using pieces of irradiated films to specific doses. The film was mounted inside the phantom parallel to the beam's central axis and was irradiated in a standard setup (SSD = 80 cm, FS = 10×10 cm2) with a 60Co machine. The BEAMnrc and the DOSXYZnrc codes were used to simulate the Co-60 machine and extracting the voxel-based phantom. The phantom's acquired CT data were transferred to the TPS using DICOM files.
Results: Distance-To-Agreement (DTA) and Dose Difference (DD) among the TPS predictions, measurements and MC calculations were all within the acceptance criteria (DD=3%, DTA=3 mm).
Conclusion: This study shows that EBT film is an appropriate tool for verification of 2D dose distribution predicted by a TPS system. In addition, it is concluded that MC simulation with the BEAMnrc code has a suitable potential for verifying dose distributions.