Dose calculation from photoneutrons emitted in radiotherapy treatments by means of MCNP6 simulation and unstructured mesh

摘要

Medical Linear Accelerators (LINAC) often make use of high energies that are able to generate photoneutrons. Most 3D conformed radiotherapy treatments use LINAC emitting photons or electrons to provide the needed dose to the patient's tumor. When the LINAC operates with energies higher than 8-10 MeV, undesirable neutrons are generated by means of photonuclear reactions (γ, n) with collimators, flattening filters, target, multi leaf collimators (MLC) and remainder of shielding, which are composed of high atomic number materials such as lead and tungsten. Thus, external therapeutic beams from LINAC are contaminated by neutrons. This work, uses the last version of Monte Carlo code MCNP6.1.1 to determinate neutron dose received by a patient. The Monte Carlo model of the anthropomorphic RANDO phantom is generated with finite element modeler software Abaqus/CAE using unstructured meshes to simulate a real patient. The purpose of this work is to reveal the non-negligible dose received by a patient during his treatment due to induced neutrons and not considered by most current radiotherapy treatment planners.