Room: Exhibit Hall
Purpose: This work investigated the quality of external photon beam dosimetry based on different beam properties (e.g. symmetry, flatness and penumbra) for linear accelerator (linac) quality assurance (QA) using the Gafchromic EBT3 film. Contemporary radiation dose delivery techniques such as intensity modulated radiotherapy or volumetric modulated arc therapy provide the superlative treatment to cancer patients. All aspects in a radiotherapy procedure need strict QA to maintain an acceptable quality level.
Methods: The 6 and 15 MV photon beams produced by a Varian linac equipped with a 120-leaf multileaf collimator were used in this study. The reference photon beam data such as symmetry, flatness and penumbra were measured using the PTW ionization chamber and big scanning water tank at different depths and field sizes, and compared with the Gafchromic film dosimetry. The irradiated Gafchromic EBT3 films were analyzed using the film QA Pro software 2016.
Results: Dosimetric comparison on the photon beam symmetry, flatness and penumbra between the measured and calculated values was analyzed at different channels of the film (green, blue, red) processor with both phases (i.e. one and two sides). The difference between measured and calculated results was not significant within the acceptable level according to the ICRU guideline.
Conclusion: The EBT3 film measurement compared to those from the ionization chamber implied that the EBT3 film dosimetry is a reliable and cost effective method for linac QA. The results provide support to physicists to choose the best method for the quality control purpose.