Hossein Pourbeygi - Assistant Professor, Nuclear Science Research School, Nuclear Science and Technology Research Institute,Tehran, Iran
Habibeh Ghasemi - Radiation Technologist, Department of Radiation Medicine Engineering, Science and Research Branch, IslamicAzad University, Tehran, Iran
Parivash Mohammadi - MSc Student, Physics Department, Faculty of sciences, University of Sistan and Baluchestan, Zahedan, Iran
Akbar Sarabiasl - MSc Student, Department of Radiation Medicine, Faculty of Advanced Sciences and Technologies,Isfahan University, Isfahan, Iran

Introduction: The AccuBoost system is a novel technology to employs a conventional mammography unit, a computed radiography )CR) system, and a 192Ir-HDR brachytherapy source remote afterloading system to deliver noninvasive image-guided breast brachytherapy (NIIGBB). In this study, for the first time, the dose enhancement to the early-stage breast tumors due to gold nanoparticles (AuNPs) during noninvasive imageguidedbreast brachytherapy have been investigated. The objective was to determine whether AuNPs were appropriate for macroscopic dose enhancement (MDE) in AccuBoost system. In order to make this distinction, The MCNP5 Monte Carlo code was used to simulate this system with AuNPs. Materials/Methods: The 192Ir-HDR brachytherapy source and a pair of non-invasive round tungsten applicators was positioned on opposite sides of a compressed breast phantom to simulate a clinical geometry. A tumor region for a range of depths with a size of 1×1×1 cm3 loaded with AuNPs were simulated inside of ICRU 44 breast phantom. The dose enhancement factor (DEF) defined as the ratio of the dose with and without AuNPs was calculated in the presence of AuNPs with 10, 20 and 30 mg/ml concentrations, separately with sizes of 50,100 and 200 nm inside the tumor volume. Then, DEF was averaged over various cubic cells in the tumor on the central axis of the beam and the average value was reported. Among the three mentioned concentrations, the dose enhancement related to 30 mg/ml is higher.Results: In this study, possible tumor dose enhancement by the use of gold nanoparticleswas estimated by Monte Carlo calculations. Our preliminary results indicate that major dose enhancement to breast tumors can be achieved using AuNPs. We found a DEF of from 1.3 to 2.79 for 36 number of 192Ir-HDR source beams.The effect of AuNP size was not considerable, but the AuNP concentration had a substantial impact on achieved DEF in AuNP-based brachytherapy.Conclusion: The data demonstrate that the biological effect when irradiating in the presence of 30 mg/ml concentration of AuNP is about 30%–180% greater than without AuNP. Meanwhile, without radiation, the AuNP showed minimal effect on the cancer cells. These findings provide evidence that AuNP may be employed as radiosensitizers during noninvasive image-guided breast brachytherapy also highlight a potential newapproach for radiation boosting to breast tumors using AuNPs.

AccuBoost brachytherapy, 192Ir-HDR, Breast cancer, AuNPs