Abstract:
The photoneutron production from three Varian linear accelerators ranging in energies from 6 MV to 23 MV has been investigated. Photoneutrons are produced during (γ, n) interactions with materials located within the treatment head. These unwanted neutrons not only increase patient dose, but may also lead to the requirement of additional shielding for the treatment room. All neutron measurements were made using BD-PND dosimeters manufactured by Bubble Technology Industries. A series of neutron measurements were completed for various geometries and for three IMRT prostate plans. The IMRT plans revealed neutron dose equivalents of 8.92±0.62 uSv/cGy for a 23 MV beam. IMRT was also found to increase the neutron dose to patients by a factor of 1.8 when compared to more conventional radiation therapy plans.
