The Effect of Breast Phantom Material on the Dose Distribution in AccuBoost Brachytherapy

Introduction: Long-term teletherapy program is not suitable for old and working patients and those living in areas where little access to primary health care is available. Accelerated partial breast irradiation (APBI) using high dose rate (HDR) brachytherapy is an appropriate alternative for these patients due to its limited number of fractions. The AccuBoost is a system for delivering APBI. The brachytherapy dose is delivered from parallel-opposed beams from 192Ir sources in circle applicators. This study was conducted to investigate the effects of breast phantom material on the dose distribution in AccuBoost brachytherapy using Monte Carlo N-Particle method. Material and Methods: In this study,different inhomogeneous breast phantoms composed of various materials were simulated. Dosimetric evaluations including a comparison of dose distribution between different breast phantom materials and water phantom was performed. Results: There was no significant difference between the breast and water phantoms in terms of mean dose values in different positions of each phantom. The most significant differences between the doses of different compositions and water were found to be about 6% near the skin. Conclusion: No significant differences were observed between the breast phantoms composed of diverse materials and water phantoms considering the dose distributions.  Therefore, it is not necessary to replace the current treatment planning systems using Task Group No. 43 formalism with combined model-based and patient-specific dosimetry methods.