Dosimetric study of the 15mm ROPES eye plaque

The main aim of this paper is to make a study of dose‐rate distributions obtained around the 15mm, radiation oncology physics and engineering services, Australia (ROPES) eye plaque loaded with I125 model 6711 radioactive seeds. In this study, we have carried out a comparison of the dose‐rate distributions obtained by the algorithm used by the Plaque Simulator (PS) (BEBIG GmbH, Berlin, Germany) treatment planning system with those obtained by means of the Monte Carlo method for the ROPES eye plaque. A simple method to obtain the dose‐rate distributions in a treatment planning system via the superposition of the dose‐rate distributions of a seed placed in the eye plaque has been developed. The method uses eye plaque located in a simplified geometry of the head anatomy and distributions obtained by means of the Monte Carlo code GEANT4. The favorable results obtained in the development of this method suggest that it could be implemented on a treatment planning system to improve dose‐rate calculations. We have also found that the dose‐rate falls sharply along the eye and that outside the eye the dose‐rate is very low. Furthermore, the lack of backscatter photons from the air located outside the eye‐head phantom produces a dose reduction negligible for distances from the eye‐plaque r