Development and implementation of a Monte Carlo frame work for evaluation of patient specific out- of - field organ equivalent dose

Background: The aim of this study was to develop and implement a Monte Carlo framework for evalua on of pa ent specific out-of-field organ equivalent dose (OED). Materials and Methods: Dose calcula ons were performed using a Monte Carlo-based model of Oncor linac and tomographic phantoms. Monte Carlo simula ons were performed using EGSnrc user codes. Dose measurements were performed using radiochromic films. Furthermore, the applicability of this framework was examined for a 3D conformal radiotherapy of breast. Results: Commissioning of the beam model was done by comparing the measured and calculated out-of-field dose values of several points in the physical and tomographic phantoms, respec vely. The maximum percentage difference was 17%, which was smaller than 30% acceptance criteria for Monte Carlo modeling. The maximum sta s cal uncertainty in out -of-field dose calcula on was 23%. Organ equivalent doses for out of field organs in 3D conformal radiotherapy of le1 breast varied from 2.4 cGy for right kidney to 134.6 cGy for the le1 humeral head. Conclusion: The framework developed in this research is a valuable tool for calcula ng peripheral dose and out-of field pa ent specific OEDs, the quan es needed for calcula ng risk of secondary cancer induc on as a result of radiotherapy. This code can be used as a pa ent specific treatment plan op miza on tool in order to select a treatment plan with the lowest risk of secondary cancer induc on.