A Feasibility Study of IMRT of Lung Cancer Using Gafchromic EBT۳ Film

Background: Intensity modulated radiation therapy (IMRT) is an advanced method for delivery of three dimensional therapies, which provides optimal dose distribution with giving multiple nonuniform fluency to the patient. The complex dose distribution of IMRT should be checked to ensure that the accurate dose is delivered. Today, film dosimetry is a powerful tool for radiotherapy treatment Quality Assurance (QA) and a good method to verify dose distribution in phantoms. Objective: This study aimed to evaluate the accuracy of IMRT treatment planning system, Prowess Panther® software, with Gafchromic EBT۳ films in a inhomogeneity phantom. Material and Methods: The IMRT plan was generated by Prowess Panther® treatment planning system (TPS) version ۵.۲ on a inhomogeneity phantom, then it was irradiated by ONCOR linear accelerator (Linac) with ۶ (MV) photon beam energy. The Gafchromic EBT۳ film located between the phantom has measured the dose distribution.To compare between TPS calculated doses and film measured doses, Gamma criteria ۳%/۳ mm, ۴%/۴ mm, ۵%/۵ mm, ۶%/۶ mm and ۷%/۷ mm Dose Difference (DD) and Distance to Agreement (DTA), respectively were used. Results: Gammas passing rates for PTV are obtained ۶۷.۵% for ۳%/۳mm, ۷۸.۸% for ۴%/۴mm, ۸۶.۳% for ۵%/۵mm, ۹۱.۲% for ۶%/۶mm and ۹۴.۳% for ۷%/۷mm and for organs at risk is ۷۲.۴% for ۳%/۳mm, ۸۲.۸% for ۴%/۴mm, ۸۹.۸% for ۵%/۵mm, ۹۳.۳% for ۶%/۶mm and ۹۵.۴% for ۷%/۷mm (respectively DD/DTA). By increasing the range of criteria the capability increased. Conclusion: The results show that the use of EBT۳ film in a inhomogeneity phantoms allows us to evaluate the dose differences between the EBT۳ measured dose distribution and TPS calculated dose distribution .Hence, a result Prowess Panther® TPS can be used for IMRT technique treatment.

کلیدواژه ها:

Radiotherapy ، IMRT QA ، Prowess Panther® ، Inhomogeneity Phantom ، Lung Cancer ، Gafchromic EBT۳ Film ، Gamma Analysis