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KMID : 1164220210330010009
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Journal of Korean Society for Radiotherapeutic Technology
2021 Volume.33 No. 1 p.9 ~ p.14
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Examination of Dose Change at the Junction at the Time of Treatment Using Multi-Isocenter Volumetric Modulated Arc Therapy
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Jung Dong-Min
Park Kwang-Soon
Ahn Hyuk-Jin
Choi Yoon-Won
Park Byul-Nim
Kwon Yong-Jae
Moon Sung-Gong
Lee Jong-Oon
Jeong Tae-Sik
Park Ryeong-Hwang
Kim Se-Young
Kim Mi-Jung
Baek Jong-Geol
Cho Jeong-Hee
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Abstract
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This study examined dose change depending on the reposition error of the junction at the time of treatment with multi-isocenter volumetric modulated arc therapy. This study selected a random treatment region in the Arccheck Phantom and established the treatment plan for multi-isocenter volumetric modulated arc therapy. Then, after setting the error of the junction at 0 ~ 4 mm in the X (left), Y (upper), and Z (inner and outer) directions, the area was irradiated using a linear accelerator; the point doses and gamma indexes obtained through the Phantom were subsequently analyzed. It was found that when errors of 2 and 4 mm took place in the X and Y directions, the gamma pass rates (point doses) were 99.3% (2.085) and 98% (2.079 Gy) in the former direction and 98.5% (2.088) and 95.5% (2.093 Gy) in the latter direction, respectively. In addition, when errors of 1, 2, and 4 mm occurred in the inner and outer parts of the Z direction, the gamma pass rates (point doses) were found to be 94.8% (2.131), 82.6% (2.164), and 72.8% (2.22 Gy) in the former part and 93.4% (2.069), 90.6% (2.047), and 79.7% (1.962 Gy) in the latter part, respectively. In the X and Y directions, errors up to 4 mm were tolerable; however, in the Z direction, error values exceeding 1 mm were beyond the tolerance level. This suggests that for high and low dose areas, errors in the direction same as the progress direction in the treatment region have a more sensitive dose distribution. If the guidelines for set-up errors are established at the institutional level through continuous research in the future, it will be possible to provide good quality treatment using junctions.
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KEYWORD
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VMAT, Multi-Isocenter, Junction, Dose distribution change
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