Measurement of the photon and thermal neutron doses of contralateral breast surface in breast cancer radiotherapy

Introduction and purpose: During the radiation therapy of tumoral breast, the contralateral breast (CB) will receive scattered doses. In the present study, the photon and thermal neutron dose values received by CB surface during breast cancer radiation therapy were measured. Materials and methods: The right breast region of RANDO phantom was considered as CB, and the measurements of photon and thermal neutron dose values were carried out on this region surface. The phantom was irradiated with 18 MV photon beams, and the dose values were measured with thermoluminescent dosimeter (TLD-600 and TLD-700) chips for 11 x 13, 11 x 17 and 11 x 21 cm(2) field sizes in the presence of physical and dynamic wedges. Results: The total dose values (photon thorn thermal neutron) received by the CB surface in the presence of physical wedge were 12.06%, 15.75% and 33.40% of the prescribed dose, respectively, for 11 x 13, 11 x 17 and 11 x 21 cm(2) field sizes. The corresponding dose values for dynamic wedge were 9.18%, 12.92% and 29.26% of the prescribed dose, respectively. Moreover, the results showed that treatment field size and wedge type affect the received photon and thermal neutron doses at CB surface. Conclusion: According to our results, the total dose values received at CB surface during breast cancer radiotherapy with high-energy photon beams are remarkable. In addition, the dose values received at CB surface when using a physical wedge were greater than when using a dynamic wedge, especially for medial tangential fields.