A simulation based dosimetric study for electron therapy during breast surgery

Intraoperative electron radiotherapy (IOERT) is a relatively new method of direct ionizing radiation to the tumor or tumor bed during surgery. In order to properly treat the intended target, it is necessary to examine the radiation dose curves and the shield used to protect healthy tissues and organs. In particular, radiation therapy during breast surgery requires the protection of critical tissues within the field and underlying the target volume such as the heart and lungs. In this case, a thin layer of high-Z material is placed between the treated (breast) tissue and the underlying vital tissue. The breast, lung, and radiation shield were geometrically considered as three coaxial cylinders. Using the MCNPX code, breast tissue, shield, and lung were irradiated with 6, 9, and 12 MeV electrons. The flux and dose of electrons and secondary photons in different tissues were calculated. Investigations showed that for 6 MeV electrons, the use of shielding has a negligible effect on the amount of dose received by the tissues around the breast. At energies of 9 and 12 MeV, Al-Pb shielding and St-PMMA shielding have almost the same performance in reducing the amount of dose received by the tissues around the breast. At the energy of 18 MeV, the Al-Pb shielding has a better performance than the St-PMMA shielding in reducing the dose received by the organs adjacent to the breast tissue.