Use of MOSFET dosimeters to validate Monte Carlo radiation treatment calculation in an anthropomorphic phantom

Abstract

Radiation therapy treatment planning based on Monte Carlo simulation provide a very accurate dose calculation compared to deterministic systems. Nowadays, Metal-OxideSemiconductor Field Effect Transistor (MOSFET) dosimeters are increasingly utilized in radiation therapy to verify the received dose by patients.In the present work, we have used the MCNP6 (Monte Carlo N-Particle transport code) to simulate the irradiation of an anthropomorphic phantom (RANDO) with a medical linear accelerator. The detailed model of the Elekta Precise multileaf collimator using a 6 MeV photon beam was designed and validated by means of different beam sizes and shapes in previous works.To include in the simulation the RANDO phantom geometry a set of Computer Tomography images of the phantom was obtained and formatted. The slices are input in PLUNC software, which performs the segmentation by defining anatomical structures and a Matlab algorithm writes the phantom information in MCNP6 input deck format.The simulation was verified and therefore the phantom model and irradiation was validated throughout the comparison of High-Sensitivity MOSFET dosimeter (Best medical Canada) measurements in different points inside the phantom with simulation results. On-line Wireless MOSFET provide dose estimation in the extremely thin sensitive volume, so a meticulous and accurate validation has been performed.The comparison show good agreement between the MOSFET measurements and the Monte Carlo calculations, confirming the validity of the developed procedure to include patients CT in simulations and approving the use of Monte Carlo simulations as an accurate therapy treatment plan.

Semiconductor dosimetry in modern external-beam radiation therapy

“…At present however, the literature (Francescon et al 1998, Sauer andWilbert 2007) does not generally support the use of commercial MOSFETs for small-field dosimetry in megavoltage photon beams because of the high spread of their data (IAEA 2017). MOSFETs have also been used to verify dose in IMRT dose verification (Chuang et al 2002), and to validate a Monte Carlo-based TPS (Juste et al 2015).…”

VARIAN CLINAC 6 MeV Photon Spectra Unfolding using a Monte Carlo Meshed Model

“…The second simulation corresponds to the water phantom and starts from the previous surface source generated with more than 10 7 collected particles. [8] To speed up the calculations without compromising the accuracy of the results, the MCNP6 (version 6.1.1) code has been parallelized in SENUBIO ISIRYM research group´s cluster Quasar using the MPI protocol with 26 processors. Finally, the computational real time real time was about 48 hours.…”