Dosimetric Comparison of Passive Scattering and Active Scanning Proton Therapy Techniques Using GATE Simulation

TL;DR

This study used GATE Monte Carlo simulations to compare passive scattering and pencil beam scanning proton therapy techniques, revealing PBS's superior dose conformity and lower out-of-field dose in clinical scenarios.

Contribution

The paper provides a comprehensive dosimetric comparison of PSPT and PBS using GATE simulation, including clinical case analysis, which is novel in quantifying their differences.

Findings

PBS shows better dose conformity and target coverage.

PBS has significantly lower out-of-field dose.

PSPT has a higher peak-to-entrance dose ratio.

Abstract

In this study, two proton beam delivery designs, passive scattering proton therapy (PSPT) and pencil beam scanning (PBS), were quantitatively compared in terms of dosimetric indices. The GATE Monte Carlo code was used to simulate the proton beam system; and the developed simulation engines were benchmarked with respect to the experimental measurements. A water phantom was used to simulate system energy parameters using a set of depth-dose data in the energy range of 120-235 MeV. To compare the performance of PSPT against PBS, multiple dosimetric parameters including FWHM, peak position, range, peak-to-entrance dose ratio, and dose volume histogram have been analyzed under the same conditions. Furthermore, the clinical test cases introduced by AAPM TG-119 were simulated in both beam delivery modes to compare the relevant clinical values obtained from DVH analysis. The parametric comparison in the water phantom between the two techniques revealed that the value of peak-to-entrance dose ratio in PSPT is considerably higher than that from PBS by a factor of 8%. In addition, the FWHM of the lateral beam profile in PSPT was increased by a factor of 7% compared to the corresponding value obtained from PBS model. TG-119 phantom simulations showed that the difference of PTV mean dose between PBS and PSPT techniques are up to 2.9% while the difference of max dose to organ at risks (OARs) exceeds 33%. The results demonstrated that the PBS proton therapy systems was superior in adapting to the target volume, better dose painting, and lower out-of-field dose compared to PSPT design.