Open AccessDevelopment of a Geant4‐based independent patient dose validation system with an elaborate multileaf collimator simulation model
Author(s) -
Choi Hyun Joon,
Park Hyojun,
Shin WookGeun,
Kim Jungin,
Min Chul Hee
Publication year - 2019
Publication title -
journal of applied clinical medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.83
H-Index - 48
ISSN - 1526-9914
DOI - 10.1002/acm2.12530
Subject(s) - multileaf collimator , imaging phantom , monte carlo method , collimator , nuclear medicine , radiation treatment planning , ionization chamber , biomedical engineering , computer science , mathematics , physics , radiation therapy , medicine , optics , statistics , radiology , ion , quantum mechanics , ionization
Despite the improvements in the dose calculation models of the commercial treatment planning systems ( TPS ), their ability to accurately predict patient dose is still limited. One of the limitations is caused by the simplified model of the multileaf collimator ( MLC ). The aim of this study was to develop a Monte Carlo ( MC ) method‐based independent patient dose validation system with an elaborate MLC model for more accurate dose evaluation. Varian Clinac 2300 IX was simulated using Geant4 toolkits, after which MC commissioning with measurements was performed to validate the simulation model. A DICOM ‐ RT interface was developed to obtain the beam delivery conditions including the hundreds of MLC motions. Finally, the TPS dose distributions were compared with the MC dose distributions for water phantom cases and a patient case. Our results show that the TPS overestimated the absolute abutting leakage dose in the closed MLC field, with about 20% more of the maximum dose than that of the MC calculation. For water phantom cases, the dose distributions inside the target region were almost identical with the dose difference of less than 2%, while the dose near the edge of the target shows difference about 10% between Geant4 and TPS due to geometrical differences in MLC model. For the patient analysis, the Geant4 and TPS doses of all organs were matched well within 1.4% of the prescribed dose. However, for organs located in areas with high ratio of leaf pairs with distances less than 10 mm leaf pair ( LP (<10mm) ), the maximum dose of TPS was overestimated by about 3% of the prescribed dose. These dose comparison results demonstrate that our system for calculating the patient dose is quite accurate. Furthermore, if the MLC sequences in treatment plan have a large ratio of LP (short) , more than 3% dose difference in normal tissue could be seen.