Dosimetric Investigation of Six Ru-۱۰۶ Eye Plaques by EBT۳ Radiochromic Films and Monte Carlo Simulation

Background: Ophthalmic brachytherapy using radioactive plaques is an effective technique for the treatment of uveal melanoma. Ru-۱۰۶ eye plaques are considered as interesting issue due to their steep gradient dose. The pre-planning evaluation of dosimetric parameters is essential for the treatment planning system.Objective: The current study aims at providing dose distributions of six Ru-۱۰۶ eye plaques (CCA, CCB, CGD, CIB, COB and COD) using radiochromic EBT۳ film, Geant۴ Monte Carlo toolkit and the treatment planning software (Plaque Simulator).Material and Methods: In this experimental study, an in-house phantom was employed for depth dose measurements with EBT۳ films. Also, Geant۴.۱۰.۵ scoring mesh was implemented to obtain the ۲D dose distribution of the plaques. The results were compared with Plaque Simulator software and the manufacturer’s (BEBIG) data. The gamma index criterion (۳%/۳ mm) was used to evaluate dose distributions obtained by the film measurements and Geant۴ simulation.Results: A good agreement was achieved between simulation and experimental results. Gamma index passing rate was ۹۴.۲%, ۸۹.۳%, ۸۸.۲%, ۸۲.۲%, ۹۲.۲% and ۹۰.۱% for CCA, CCB, CGD, CIB, COB and COD plaques, respectively. Absolute dose rate (mGy/min) obtained by EBT۳ film at the depth of ۲ mm was ۷۹.۴ mGy/min, ۸۱.۰ mGy/min, ۷۸.۶ mGy/min, ۶۲.۲ mGy/min, ۷۵.۲ mGy/min and ۸۱.۲ mGy/min for CCA, CCB, CGD, CIB, COB and COD plaques, respectively.  Conclusion: The measured dose distributions and lateral dose profiles may be utilized in the treatment planning system to cover clinical volumes such as the clinical target volume and the gross tumor volume.

Keywords:

Uveal melanoma , Ru-۱۰۶ Plaque , Dosimetry , Brachytherapy , EBT۳ Film , Monte Carlo Method