In-field radiation contamination during intraoperative electron radiation therapy with a dedicated accelerator

The in-field radiation contamination including photons and neutrons originated from a dedicated intraoperative electron radiotherapy (IOERT) accelerator, LIAC12, at different electron energies (6-12 MeV) and applicator sizes (3, 5 and 10 cm diameter) were quantitatively evaluated in the current study. A validated MC model of LIAC12 head in conjunction with different applicator diameters was employed for this purpose. The results showed that the fluence of in-field photon contamination is highly dependent on the electron energy and field size so that it would be increased by the factors of about 3 and 10 with an increment of electron energy and decrement of field size, respectively. Neutron contamination was found only at 12 MeV electron energy and zero neutron fluence was obtained at lower electron energies. The same trend with the field size was observed for neutron contamination fluence that increased about 7 times by decreasing the applicator diameter from 10 cm to 3 cm. The maximum contaminant neutron dose and photon dose per one Gy delivered electron dose were obtained about 0.3 μSv and 7.24 mSv, respectively. The produced neutron contamination by this dedicated IOERT accelerator was approximately 10^-3 times lower than those originated from a conventional radiotherapy accelerator.