6 MV photon beam modeling for Varian Clinac iX using GEANT4 virtual jaw

TL;DR

This paper introduces a virtual jaw method in GEANT4-based beam modeling for 6 MV photon beams, significantly improving simulation efficiency while maintaining accuracy within clinical tolerances.

Contribution

A novel virtual jaw approach in GEANT4 modeling reduces photon absorption, enhancing computational efficiency by about 67% without compromising accuracy.

Findings

Agreement within 2% for depth dose and profiles

Penumbra width within 0.6 mm of measurements

Efficiency increased by approximately 67%

Abstract

Most virtual source models (VSM) use beam modeling, with the exception of the patient-dependent secondary collimator (jaw). Unlike other components of the treatment head, the jaw absorbs many photons generated by the bremsstrahlung, which decreases the efficiency of the simulation. In the present study, a new method of beam modeling using a virtual jaw was applied to improve the calculation efficiency of VSM. The results for the percentage depth dose and profile of the virtual jaw VSM calculated in a homogeneous water phantom agreed with the measurement results for the CC13 cylinder type ion chamber within an error rate of 2%, and the 80 to 20% penumbra width agreed with the measurement results within an error of 0.6 mm. Compared with the existing VSM, in which a great number of photons are absorbed, the calculation efficiency of the VSM using the virtual jaw was expected to increase by approximately 67%.