The purpose of this study is to evaluate the dosimetric impact of the margin on the multileaf collimator-based dynamic tumor tracking plan. Furthermore, an equivalent setup margin (EM) of the tracking plan was determined according to the gated plan. A 4-dimensional extended cardiac-torso was used to create 9 digital phantom datasets of different tumor diameters (TDs) of 1, 3, and 5 cm and motion ranges (MRs) of 1, 2, and 3 cm. For each dataset, respiratory gating (30% to 70% phase) and tumor tracking treatment plans were prepared using 8-field 3-dimensional conformal radiation therapy by 4-dimensional dose calculation. The total lung V20 was calculated to evaluate the dosimetric impact for each case and to estimate the EM with the same impact on lung V20 obtained with the gating plan with a setup margin of 5 mm. The EMs for {TD = 1 cm, MR = 1 cm}, {TD = 1 cm, MR = 2 cm}, and {TD = 1 cm, MR = 3 cm} were estimated as 5.00, 4.16, and 4.24 mm, respectively. The EMs for {TD = 5 cm, MR = 1 cm}, {TD = 5 cm, MR = 2 cm}, and {TD = 5 cm, MR = 3 cm} were estimated as 4.24 mm, 6.35 mm, and 7.49 mm, respectively. This result showed that with a larger MR, the EM was found to be increased. In addition, with a larger TD, the EM became smaller. Our result showing the EMs provided the desired accuracy for multileaf collimator-based dynamic tumor tracking radiotherapy.

Department of Electrical Engineering Graduate School of Engineering Tohoku University Sendai Japan

Department of Radiation Oncology Southern Tohoku BNCT Research Center Koriyama Japan

Department of Radiation Oncology Tohoku University Graduate School of Medicine Sendai Japan

Department of Radiation Oncology Tohoku University Graduate School of Medicine Sendai Japan; Department of Radiotherapy Tokyo Metropolitan Cancer and Infectious Diseases Center Komagome Hospital Tokyo Japan

Department of Radiological Imaging and Informatics Tohoku University Graduate School of Medicine Sendai Japan

Department of Radiological Imaging and Informatics Tohoku University Graduate School of Medicine Sendai Japan; Department of Instrumentation and Control Engineering Faculty of Mechanical Engineering Czech Technical University Prague Prague Czech Republic

Department of Therapeutic Radiology Tohoku University Graduate School of Medicine Sendai Japan

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