Effects of strong magnetic fields on electron path in MRI-LINAC radiotherapy: analytic and Monte Carlo approaches.

AMIEL GAYOL; JOSÉ VEDELAGO; MAURO VALENTE

León - Guanajuato

Congreso; Congreso de Ingeniería y Física Aplicada a la Biomedicina (CIFAB) 2021; 2021

Universidad de Guanajuato - León

MRI guided radiotherapy system, MRI-LINAC, is based on the use of strong magnetic fields that may affect the radiation field. Trajectory of secondary electrons, and charged particles in general, are influenced by the Lorentz force, causing potential local dose variations. The aim of the present study is to investigate the feasibility and reliability of the Monte Carlo FLUKA and PENELOPE main codes to assess electron trajectory in the presence of a strong magnetic field, and to compare these results against theoretical formulations for the curvature of the electrons path.In-vacuum electron paths were studied by means of both Monte Carlo codes in presence of a uniform magnetic field considering typical values of kinetic energy and magnetic field intensity used in MRI-LINAC treatments. The curvature radius was calculated from the simulations? output and further compared with analytical approaches. Results show an excellent agreement between FLUKA and PENELOPE codes, as well as noticeable agreements with the theoretical-analytical models, thus confirming the ability of the codes to model the alterations in the electron trajectories due to external magnetic fields.Since electrons strongly affect the dose deposition in radiotherapy, the information provided by this work about their path under the influence of strong magnetic fields, like the ones used in the MRI-LINAC technique, remarks the relevance of the potential significant dosimetry effects due to the presence of strong magnetic fields, as required for the implementation of this new IGRT technology.