Monte Carlo modeling of electron beams from a NEPTUN 10PC medical linear accelerator

The Monte Carlo (MC) simulation of radiation transport is considered to be one of the most accurate methods
of radiation therapy dose calculation. With the rapid development of computer technology, MC-based treatment planning
for radiation therapy is becoming practical. A basic requirement for MC treatment planning is a detailed knowledge of
radiation beams of medical linear accelerators (linacs). A practical approach to acquire this knowledge is to perform
MC simulation of radiation transport for linacs. The aims of this study were: modeling of the electron beams from the
NEPTUN 10PC linear accelerator (linac) with the MC method, obtaining of the energy spectra of electron beams, and
providing the phase-space files for the electron beams of this linac at different field sizes. Electron beams produced by
the linac were modeled using the BEAMnrc MC system. Central axis depth-dose curves and dose profiles of the electron
beams were measured experimentally and also calculated with the MC system for different field sizes and energies. In
order to benchmark the simulated models, the percent depth dose (PDD) and dose-profile curves calculated with the
MC system were compared with those measured experimentally with diode detectors in an RFA 300 water phantom. The
results of this study showed that the PDD and dose-profile curves calculated by the MC system using the phase-space
data files matched well with the measured values. This study demonstrates that the MC phase-space data files can be
used to generate accurate MC dose distributions for electron beams from NEPTUN 10PC medical linac.