Feasibility Study of Neutron Dose for Real Time Image Guided Proton Therapy: A Monte Carlo Study

TL;DR

This study uses Monte Carlo simulations to evaluate neutron dose equivalents to x-ray imaging equipment during proton therapy, revealing dose levels and reduction strategies for safer treatment practices.

Contribution

It provides detailed neutron dose assessments for various proton therapy configurations and identifies effective dose reduction methods, advancing safety protocols in proton therapy.

Findings

Neutron dose at imaging equipment ranges from 0.07 to 0.19 mSv/Gy.

Multi-leaf collimator reduces neutron dose by approximately 50%.

Neutron dose varies with treatment setup and distance from isocenter.

Abstract

Two full rotating gantry with different nozzles (Multipurpose nozzle with MLC, Scanning Dedicated nozzle) with conventional cyclotron system is installed and under commissioning for various proton treatment options at Samsung Medical Center in Korea. The purpose of this study is to investigate neutron dose equivalent per therapeutic dose, H/D, to x-ray imaging equipment under various treatment conditions with monte carlo simulation. At first, we investigated H/D with the various modifications of the beam line devices (Scattering, Scanning, Multi-leaf collimator, Aperture, Compensator) at isocenter, 20, 40, 60 cm distance from isocenter and compared with other research groups. Next, we investigated the neutron dose at x-ray equipments used for real time imaging with various treatment conditions. Our investigation showed the 0.07 ~ 0.19 mSv/Gy at x-ray imaging equipments according to various treatment options and intestingly 50% neutron dose reduction effect of flat panel detector was observed due to multi- leaf collimator during proton scanning treatment with multipurpose nozzle. In future studies, we plan to investigate experimental measurement of neutron dose and validation of simulation data for x-ray imaging equipment with additional neutron dose reduction method.