Daily QA of linear accelerators using only EPID and OBI
Daily QA of linear accelerators using only EPID and OBI
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DOI：
10.1118/1.4929550
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发表时间：
2015-10-01
期刊：
影响因子：
3.8
通讯作者：
Mutic, Sasa
中科院分区：
文献类型：
--
作者：
Sun, Baozhou;Goddu, S. Murty;Mutic, Sasa
目的：随着治疗交付变得越来越复杂，迫切需要强大的质量保证（QA）工具来提高效率和全面性，同时保持高准确性和灵敏度。本工作旨在介绍仅使用电子射野成像设备（EPID）和kV平板探测器的直线加速器（LINAC）的综合QA开发的硬件和软件工具。每日QA体模，包括两个正交定位的体模，用于MV射束的QA和kV机载成像（OBI）悬挂在机架附件保持器上，以测试LINAC和OBI的几何和剂量测定组件。MV组件由0.5 cm水当量塑料片组成，其中包含11个圆形钢塞，用于通过多种厚度进行透射测量，以及一个用于MV图像质量测试的分辨率塞。KV体模由利兹体模（Varian提供的TOR-18 FG体模）组成，用于测试低和高对比度分辨率。在开发的过程中，现有的LINAC工具被用来自动化MV和kV图像的日常采集和软件工具的开发，这些图像的同时分析。开发了一种方法，用于从这些图像中导出和评价传统QA参数[输出、平整度、对称性、均匀性、TPR 20/10以及钳口和多叶准直器（MLC）的位置精度]。通过对失谐的6 MV射束进行测量来验证基于EPID的日常QA工具，以测试其在检测输出、对称性、能量和MLC位置误差方面的有效性。开发的QA过程是临床委托，实施，并在一个瓦里安TrueBeam LINAC（瓦里安医疗系统，帕洛阿尔托，加利福尼亚州）超过三个months.Results的评价：机器输出恒定测量与EPID（与校准的离子室相比）被证明是在+/-0.5%。使用EPID和2D离子室阵列测量的射束对称性和平坦度偏差分别在+/- 0.5%和+/- 1.2%的交叉线和内联轮廓内一致。MLC位置误差为0.5 mm，可使用栅栏测试检测。射野大小和体模定位精度可确定在0.5 mm以内。整个日常QA过程大约需要15分钟，用于进行5个光子束的测试、MLC测试和成像检查。独家使用基于EPID的QA工具，包括QA体模和同步分析软件工具，已被证明是一种可行、高效，和LINAC性能的日常评估的综合过程。(C)2015年美国医学物理学家协会。
Purpose: As treatment delivery becomes more complex, there is a pressing need for robust quality assurance (QA) tools to improve efficiency and comprehensiveness while simultaneously maintaining high accuracy and sensitivity. This work aims to present the hardware and software tools developed for comprehensive QA of linear accelerator (LINAC) using only electronic portal imaging devices (EPIDs) and kV flat panel detectors.Methods: A daily QA phantom, which includes two orthogonally positioned phantoms for QA of MV-beams and kV onboard imaging (OBI) is suspended from the gantry accessory holder to test both geometric and dosimetric components of a LINAC and an OBI. The MV component consists of a 0.5 cm water-equivalent plastic sheet incorporating 11 circular steel plugs for transmission measurements through multiple thicknesses and one resolution plug for MV-image quality testing. The kV-phantom consists of a Leeds phantom (TOR-18 FG phantom supplied by Varian) for testing low and high contrast resolutions. In the developed process, the existing LINAC tools were used to automate daily acquisition of MV and kV images and software tools were developed for simultaneous analysis of these images. A method was developed to derive and evaluate traditional QA parameters from these images [output, flatness, symmetry, uniformity, TPR20/10, and positional accuracy of the jaws and multileaf collimators (MLCs)]. The EPID-based daily QA tools were validated by performing measurements on a detuned 6 MV beam to test its effectiveness in detecting errors in output, symmetry, energy, and MLC positions. The developed QA process was clinically commissioned, implemented, and evaluated on a Varian TrueBeam LINAC (Varian Medical System, Palo Alto, CA) over a period of three months.Results: Machine output constancy measured with an EPID (as compared against a calibrated ion-chamber) is shown to be within +/- 0.5%. Beam symmetry and flatness deviations measured using an EPID and a 2D ion-chamber array agree within +/- 0.5% and +/- 1.2% for crossline and inline profiles, respectively. MLC position errors of 0.5 mm can be detected using a picket fence test. The field size and phantom positioning accuracy can be determined within 0.5 mm. The entire daily QA process takes similar to 15 min to perform tests for 5 photon beams, MLC tests, and imaging checks.Conclusions: The exclusive use of EPID-based QA tools, including a QA phantom and simultaneous analysis software tools, has been demonstrated as a viable, efficient, and comprehensive process for daily evaluation of LINAC performance. (C) 2015 American Association of Physicists in Medicine.