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Assessment of dosimetric leaf gap correction factor in Mobius3D commissioning affected by couch top

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This study assesses the dosimetric leaf gap (DLG) correction factor in Mobius3D commissioning affected by a couch top platform and calculates the optimal DLG value according to the point dose difference function. DLG optimizations were performed for 3 LINAC machines and a total of 30 patient volumetric modulated arc therapy plans (i.e., 10 plans per each LINAC). Point dose calculations were performed using an automatic dose calculation system in Mobius3D as well as Mobis3D calculation using a Mobius Verification Phantom (MVP)-based quality assurance plan with a carbon fiber couch top. Subsequently, the results were compared with measurement data. The averaged point dose measured for the MVP with a couch top decreased by approximately 2% relative to that without the couch top. The average of the optimal DLG factors increased by 1.153 mm due to the couch top effect for a dose decrease of 2% at the measured point. In the procedure of Mobius beam commissioning, users should adjust the DLG correction factor using a specific phantom (including MVP) with a couch top structure. If the DLG optimization were performed by using MVP automatic dose calculation system, the factor should be increased by approximately 1.2 mm per 2% dose difference considering user’s couch top effect.

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Data availability

The datasets analyzed during the current study are available from the corresponding author on reasonable request.

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This work was supported by Radiation Technology R&D program through the National Research Foundation of Korea funded by the Ministry of Science and ICT (MSIT) (Project No.: NRF-2015M3A9E2067001, NRF-2020R1A4A1016619, NRF-2020R1C1C1005713).

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Conception, design, and drafting the manuscript were performed by M.C. Han, J. Kim, C-S. Hong, K. H. Chang, S. C. Han, K. Park, D. W. Kim, and J. S. Kim Data collection and interpretation were performed by M. C. Han, M. K. Park, and Y. Y. Noh, C-S. Hong, and J. S. Kim. All authors read and approved the final version of the manuscript.

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Correspondence to Chae-Seon Hong or Jin Sung Kim.

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Han, M.C., Kim, J., Hong, CS. et al. Assessment of dosimetric leaf gap correction factor in Mobius3D commissioning affected by couch top. Phys Eng Sci Med 43, 1069–1075 (2020).

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