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https://doi.org/10.3938/NPSM.69.421
Quality Assurance of the Dosimetric Characteristics of the Multileaf Collimator for the VERO 4D-IGRT System
New Phys.: Sae Mulli 2019; 69: 421~428
Published online April 30, 2019;  https://doi.org/10.3938/NPSM.69.421
© 2019 New Physics: Sae Mulli.

Su-ho MOON1, Seoung-Jun LEE1, Sung-Joon KIM2,  Byoung-Soo KO2, Jeong-Eun LEE*3

1Department of Radiation Oncology, Kyungpook National University Hospital, Daegu, 41944, Korea
2Department of Radiation Oncology, Kyungpook National University Chilgok Hospital, Daegu, 41404, Korea
3Department of Radiation Oncology, School of Medicine, Kyungpook National University, Daegu, 41944, Korea

Correspondence to: dream2201@naver.com
Received December 12, 2018; Revised January 27, 2019; Accepted February 1, 2019.
cc This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract
To qualify the dosimetric characterization of the multileaf collimator (MLC) for the VERO 4D IGRT System, we performed quality assurance (QA), including the field characteristics, leaf position accuracy, leakage, and picket fence test, using a 6-MV photon beam, an electronic portal imaging device (EPID), Gafchromic EBT2 films and a water phantom. The leaf leakage was up to 0.47\%, and the tolerance ($T$) was up to 0.63 for the picket fence test. The dose profile exhibited regions of underdose due to the tongue and groove effect. The mean value of the underdose was 12.3\%. Regarding the deviation between the actual and the ideal MLC leaf positions at the end of each segment, the maximum deviation was 0.2~mm in plan 1 and 0.1~mm in plan 2. Regarding the irradiated dose and the gantry movement, the maximum deviations were 3.35\% in plan 1 and 0.23\% in plan 2. Regarding the deviation between the actual and the plan irradiated dose per unit angle, the maximum deviation was 0.02\% in plan 1 and 0.01\% in plan 2. Despite the fact that independent jaws not exist in the VERO system due to insufficient space and, therefore, only the MLC represents a specific field shape, QA revealed a dosimetric characterization of high accuracy.
PACS numbers: 87.15.La, 87.85.gp, 81.40.Wx, 87.55.N-, 87.56.-v
Keywords: MLC, dosimetry, VERO, Leakage, Radiation


April 2019, 69 (4)
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