Evaluation of a novel reference chamber “stealth chamber” through Monte Carlo simulations and experimental data

Abstract

Purpose: To evaluate a novel reference chamber (Stealth Chamber by IBA) through experimental data and Monte Carlo simulations for 6 and 15 MV photon energies.

Methods: Monte Carlo simulations in a water phantom for field sizes ranging from 3×3 and 25×25 cm² were performed for both energies with and without the Monte Carlo model of the Stealth Chamber in the beam path, and compared to commissioning beam data. Percent depth doses (PDDs), profiles, and gamma analysis of the simulations were performed along with an energy spectrum analysis of the phase-space files generated during the simulation. Experimental data were acquired in water with IBA three-dimensional (3D) blue phantom in a set-up identical to the one used in the Monte Carlo simulations. PDD comparisons for fields ranging from 1×1 to 25×25 cm² were performed for photon energies. Profile comparison for fields ranging from 1×1 to 25×25 cm² were executed for the depths of dmax, 5, 10 and 20 cm. Criteria of 1%, 1 mm to compare PDDs and profiles were used. Transmission measurements with the Stealth Chamber and a Matrixx detector from IBA were investigated. Measurements for 6 and 15 MV with fields ranging from 3×3 to 25×25 cm² dimensions were acquired in an open field with and without the Stealth Chamber in the path of the beam. Profiles and gamma analysis with a 1%, 1 mm gamma analysis criterion were performed.

Results: Monte Carlo simulations of the PDDs and profiles demonstrate the agreement between both simulations. Furthermore, the gamma analysis (1%, 1 mm) result of the comparison of both planes has 100% of the points passing the criteria. The spectral distribution analysis of the phase spaces for an open field with and without the chamber reveals the agreement between both simulations. Experimental measurements of PDDs and profiles have been conducted and reveal the comparability of relative dosimetric data acquired with the Stealth Chamber and our gold standard the CC13 chamber. Transmission data measured with an ion chamber array (Matrixx) showed the small attenuation caused by the use of the Stealth Chamber.

Conclusion: Simulations and experimental results from this investigation indicate the benefits associated with chamber positioning and time expended during the acquisition of the relative measurements of PDDs and profiles for the beam commissioning of photon beams when the Stealth Chamber is used as a reference chamber to perform these tasks. The results demonstrate that relative profiles and PDDs scanned with the Stealth Chamber in place are consistent with those made using a CC13 chamber within a 1% and 1 mm criterion.