Department of Medical Physics, Memorial Sloan Kettering Cancer Center, 500 Westchester Avenue, West Harrison, NY 10604, United States of America. Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, 55 Fruit Street, Boston, MA 02114, United States of America. Department of Radiation Oncology, Brigham and Women's Hospital and Harvard Medical School, 75 Francis Street, Boston, MA 02115, United States of America. These authors have contributed equally to this paper.
Phys Med Biol. 2019 Apr 5;64(8):085004. doi: 10.1088/1361-6560/ab056d.
To promote accurate image-guided radiotherapy (IGRT) for a proton pencil beam scanning (PBS) system, a new quality assurance (QA) procedure employing a cone-shaped scintillator detector has been developed for multiple QA tasks in a semi-automatic manner. The cone-shaped scintillator detector (XRV-124, Logos Systems, CA) is sensitive to both x-ray and proton beams. It records scintillation on the cone surface as a 2D image, from which the geometry of the radiation field that enters and exits the cone can be extracted. Utilizing this feature, QA parameters that are essential to PBS IGRT treatment were measured and analyzed. The first applications provided coincidence checks of laser, imaging and radiation isocenters, and dependencies on gantry angle and beam energies. The analysis of the Winston-Lutz test was made available by combining the centricity measurements of the x-ray beam and the pencil beam. The accuracy of the gantry angle was validated against console readings provided by the digital encoder and an agreement of less than 0.2° was found. The accuracy of the position measurement was assessed with a robotic patient positioning system (PPS) and an agreement of less than 0.5 mm was obtained. The centricity of the two onboard x-ray imaging systems agreed well with that from the routinely used Digital Imaging Positioning System (DIPS), up to a consistent small shift of (-0.5 mm, 0.0 mm, -0.3 mm). The pencil beam spot size, in terms of σ of Gaussian fitting, agreed within 0.2 mm for most energies when compared to the conventional measurements by a 2D ion-chamber array (MatriXX-PT, IBA Dosimetry, Belgium). The cone-shaped scintillator system showed advantages in making multi-purpose measurements with a single setup. The in-house algorithms were successfully implemented to measure and analyze key QA parameters in a semi-automatic manner. This study presents an alternative and more efficient approach for IGRT QA for PBS and potentially for linear accelerators.
为了促进质子笔形扫描（PBS）系统的精确图像引导放射治疗（IGRT），我们开发了一种新的质量保证（QA）程序，该程序使用锥形闪烁探测器以半自动方式进行多项 QA 任务。锥形闪烁探测器（XRV-124，Logos Systems，CA）对 X 射线和质子束均敏感。它记录进入和离开圆锥体的辐射场的几何形状，从而在圆锥体表面上记录闪烁。利用此功能，测量和分析了 PBS IGRT 治疗必不可少的 QA 参数。首次应用提供了激光，成像和辐射等中心的符合检查，并依赖于龙门架角度和射束能量。通过结合 X 射线束和铅笔束的同心度测量，可以进行 Winston-Lutz 测试的分析。与数字编码器提供的控制台读数相比，验证了龙门架角度的准确性，发现两者相差小于 0.2°。使用机器人患者定位系统（PPS）评估了位置测量的准确性，得到的结果相差小于 0.5 mm。两个机载 X 射线成像系统的同心度与常规使用的数字成像定位系统（DIPS）吻合良好，一致的小偏移为（-0.5 mm，0.0 mm，-0.3 mm）。与传统的二维离子室阵列（MatriXX-PT，IBA 剂量学，比利时）相比，大多数能量下的铅笔束光斑尺寸（高斯拟合的 σ）的测量结果相差在 0.2 mm 以内。锥形闪烁体系统在单次设置下进行多种用途的测量具有优势。成功实施了内部算法以半自动方式测量和分析关键 QA 参数。这项研究为 PBS 和潜在的线性加速器的 IGRT QA 提供了一种替代且更有效的方法。
