Using the 50 kVINTRABEAM® IORT systemafter breast-conserving surgery: Tumor recurrence and organs at risk (OARs), such as the lung and heart, long-term complications remain the challenging problems for breast cancer patients. So, the objective of this studywas to address these two problemswith thehelpof highatomicnumbernanoparticles (NPs).AMonteCarlo (MC) Simulation type EGSnrcC++ class library (egspp) with its Easy particle propagation (Epp) user code was used.The simulation was validated against themeasured depth dose data found in our previous study (Tegaw, et al 2020Dosimetric characteristics of theINTRABEAM® system with spherical applicators in the presence of air gaps and tissue heterogeneities, Radiat. Environ. Biophys. (10.1007/s00411-020-00835-0)) using thegammaindex andpassed2%/2mmacceptance criteria in thegamma analysis. Gold (Au)NPswere selected after comparingDose Enhancement Ratios (DERs) of bismuth (Bi),Au,andplatinum(Pt) NPswhich were calculated fromthe simulated results. As a result, 0.02, 0.2, 2, 10, and 20 mg-Au/g-breast tissue were used throughout this study. These particles were not distributed in discrete but in a uniform concentration. For 20mg-Au/g-breast tissue, theDERswere 3.6, 0.420, and 0.323 for breast tissue, lung, heart, respectively, using the 1.5 cm-diameter applicator (AP) and 3.61, 0.428, and 0.335 forbreast tissue, lung, and heart using the 5 cm-diameter applicator, respectively.DER increasedwith the decrease in the depth of tissues and increase in the effective atomicnumber (Zeff) and concentration ofAuNPs, however, there was no significant change asAPsizes increased.Therefore,AuNPs showed dual advantages such as dose enhancementwithin the tumor bed and reduction in theOARs (heart and lung).
