Korean J Med Phys.
2012 Mar;23(1):33-41.
Quality Assurance of Volumetric Modulated Arc Therapy for Elekta Synergy
- Affiliations
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- 1Department of Radiation Oncology, College of Medicine, Eulji University, Daejeon, Korea.
- 2Department of Radiation Oncology, College of Medicine, Korea University, Seoul, Korea.
- 3Department of Radiation Oncology, Cheil General Hospital & Women's Healthcare Center, Kwandong University College of Medicine, Seoul, Korea.
- 4Department of Radiation Oncology, Soonchunhyang University College of Medicine, Asan, Korea.
- 5Department of Radiation Oncology, College of Medicine, Kyung Hee University, Suwon, Korea.
- 6Department of Radiation Oncology, College of Medicine, Gachon University Gil Hospital, Incheon, Korea.
- 7Department of Medical Physics, Graduate School of Science, Kyonggi University, Suwon, Korea.
- 8Department of Radiological Science, College of Health Science, Eulji University, Seongnam, Korea. voku98@eulji.ac.kr
Abstract
- For applying the quality assurance (QA) of volumetric modulated arc therapy (VMAT) introduced in Eulji Hospital, we classify it into three different QA steps, treatment planning QA, pretreatment delivering QA, and treatment verifying QA. These steps are based on the existing intensity modulated radiation therapy (IMRT) QA that is currently used in our hospital. In each QA step, the evaluated items that are from QA program are configured and documented. In this study, QA program is not only applied to actual patient treatment, but also evaluated to establish a reference of clinical acceptance in pretreatment delivering QA. As a result, the confidence limits (CLs) in the measurements for the high-dose and low-dose regions are similar to the conventional IMRT level, and the clinical acceptance references in our hospital are determined to be 3 to 5% for the high-dose and the low-dose regions, respectively. Due to the characteristics of VMAT, evaluation of the intensity map was carried out using an ArcCheck device that was able to measure the intensity map in all directions, 360degrees. With a couple of dosimetric devices, the gamma index was evaluated and analyzed. The results were similar to the result of individual intensity maps in IMRT. Mapcheck, which is a 2-dimensional (2D) array device, was used to display the isodose distributions and gave very excellent local CL results. Thus, in our hospital, the acceptance references used in practical clinical application for the intensity maps of 360degrees directions and the coronal isodose distributions were determined to be 93% and 95%, respectively. To reduce arbitrary uncertainties and system errors, we had to evaluate the local CLs by using a phantom and to cooperate with multiple organizations to participate in this evaluation. In addition, we had to evaluate the local CLs by dividing them into different sections about the patient treatment points in practical clinics.
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