Document Type : Original Research

Authors

1 MSc, Ocular Oncology service, Farabi Eye Hospital, Tehran University of Medical Sciences, Tehran, Iran

2 MD, Retina & Vitreous Service- Ocular Oncology service, Farabi Eye Hospital, Tehran University of Medical Sciences, Tehran, Iran

3 MSc, Department of Nuclear Engineering, Shiraz University of Medical Sciences, Shiraz, Iran

4 MSc, Department of Medical Physics, Tabriz University of Medical Science, Tabriz, Iran

5 MD, Ocular Oncology service, Farabi Eye Hospital, Tehran University of Medical Sciences, Tehran, Iran

6 MD, Retina service, Farabi Eye Hospital, Tehran University of Medical Sciences, Tehran, Iran

7 PhD, Radiation Medicine Program, Princess Margaret Cancer Centre, University Health Network, Toronto, Ontario, Canada

Abstract

Background: Ophthalmic brachytherapy using radioactive plaques is an effective technique for the treatment of uveal melanoma. Ru-106 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-106 eye plaques (CCA, CCB, CGD, CIB, COB and COD) using radiochromic EBT3 film, Geant4 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 EBT3 films. Also, Geant4.10.5 scoring mesh was implemented to obtain the 2D dose distribution of the plaques. The results were compared with Plaque Simulator software and the manufacturer’s (BEBIG) data. The gamma index criterion (3%/3 mm) was used to evaluate dose distributions obtained by the film measurements and Geant4 simulation.
Results: A good agreement was achieved between simulation and experimental results. Gamma index passing rate was 94.2%, 89.3%, 88.2%, 82.2%, 92.2% and 90.1% for CCA, CCB, CGD, CIB, COB and COD plaques, respectively. Absolute dose rate (mGy/min) obtained by EBT3 film at the depth of 2 mm was 79.4 mGy/min, 81.0 mGy/min, 78.6 mGy/min, 62.2 mGy/min, 75.2 mGy/min and 81.2 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.

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