Radiotherapy dosimetry parameters intercomparison among eight gel dosimeters by Monte Carlo simulation

Abstract

Dosimetry in radiotherapy is extremely important to guarantee effectiveness of the treatment, as described by quality assurance procedures. The main dosimeter framework proposed by International Protocols is commonly based on determinations of in-water absorbed dose. Gel dosimetry, mainly based on liquid water, offers the unique characteristic that the phantom constitutes itself the radiosensitive material. This study reports on the suitability of gel dosimetry formulations, typically implemented for clinical purposes, evaluating dosimetry outputs by means of PENELOPE and FLUKA Monte Carlo simulations, along with experimental data. The effects on the absorbed dose distributions due to variation in the mass density and the mean excitation energy are calculated for BANG®, Fricke, ITABIS, MAGIC, NBT-Pluronic, NIPAM, PAGAT, and PRESAGE formulations at irradiations with 6 and 15 MV photon and 6 MeV electron beams. Dosimetry parameters for photon and electron beams are calculated, and effects due to variations in mass density and mean excitation energy are carefully investigated. According to the results obtained from Monte Carlo simulations, along with dose profile comparisons with simulations of in-water irradiations, and comparisons with experimental data, all studied gel dosimetry formulations are capable of assessing reliable dosimetry outputs extracted from 3D dose distributions, even with uncertainties in their mass density or mean excitation energy of ±10%.