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KMID : 1164220190310010017
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Journal of Korean Society for Radiotherapeutic Technology
2019 Volume.31 No. 1 p.17 ~ p.24
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Assessment on Accuracy of Stereotactic Body Radiation therapy (SBRT) using VERO
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Lee Wi-Yong
Kim Hyun-Jin
Yun Na-Ri
Hong Hyo-Ji
Kim Hong-Il
Baek Seung-Wan
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Abstract
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Purpose : The present study aims to assess the level of coherency and the accuracy of Point dose of the Isocenter of VERO, a linear accelerator developed for the purpose of the Stereotactic Body Radiation Therapy(SBRT).
Materials and Method : The study was conducted randomly with 10 treatment plans among SBRT patients in Kyungpook National University Chilgok Hospital, using VERO, a linear accelerator between June and December, 2018. In order to assess the equipment’s power stability level, we measured the output constancy by using PTWLinaCheck, an output detector. We also attempted to measure the level of accuracy of the equipment’s Laser, kV(Kilo Voltage) imaging System, and MV(Mega Voltage) Beam by using Tofu Phantom(BrainLab, Germany) to assess the accuracy level of geometrical Isocenter. We conducted a comparative analysis to assess the accuracy level of the dose by using an acrylic Phantom(30×30×20 cm), a calibrated ion chamber CC-01(IBA Dosimetry), and an Electrometer(IBA, Dosimetry).
Results : The output uniformity of VERO was calculated to be 0.66 %. As for geometrical Isocenter accuracy, we analyzed the error values of ball Isocenter of inner Phantom, and the results showed a maximum of 0.4 mm, a minimum of 0.0 mm, and an average of 0.28 mm on X-axis, and a maximum of -0.4 mm, a minimum of 0.0 mm, and an average of -0.24 mm on Y-axis. A comparison and evaluation of the treatment plan dose with the actual measured dose resulted in a maximum of 0.97 % and a minimum of 0.08 %.
Conclusion : The equipment’s average output dose was calculated to be 0.66 %, meeting the ±3 % tolerance, which was considered as a much uniform fashion. As for the accuracy assessment of the geometric Isocenter, the results met the recommended criteria of ±1 mm tolerance, affirming a high level of reproducibility of the patient’s posture. The difference between the treatment plan dose and the actual measurement dose was calculated to be 0.52 % on average, significantly less than the 3 % tolerance, confirming that it obtained predicted does. The current study suggested that VERO equipment is suitable for SBRT, and would result in notable therapeutic effect.
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KEYWORD
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VERO, SBRT, Isocenter, Point dose, Accuracy
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