Development of a QA phantom and automated analysis tool for geometric quality assurance of on-board MV and kV x-ray imaging systems
Development of a QA phantom and automated analysis tool for geometric quality assurance of on-board MV and kV x-ray imaging systems
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DOI：
10.1118/1.2885719
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发表时间：
2008-04-01
期刊：
影响因子：
3.8
通讯作者：
Xing, Lei
中科院分区：
文献类型：
--
作者：
Mao, Weihua;Lee, Louis;Xing, Lei
集成千伏平板成像仪的医用直线加速器（linac）已成为影像引导放射治疗的重要设备。由于安装x射线管和平板探测器的直线头的下垂和机械臂的弯曲，无论是二维投影图像还是三维锥束计算机断层扫描，在成像几何上普遍存在几何非理想性。通常，几何参数是在调试过程中建立的，并在各自的图像形成或重建中纳入校正软件。谨慎使用机载成像系统需要对系统的几何精度进行常规监控，如x射线源的位置、成像仪的位置和方向、等心、旋转轨迹以及源到成像仪的距离。在这里，我们描述了一个专门建造的幻影和一个数据分析软件，用于以有效和自动化的方式监测系统的这些重要参数。所开发的工具同样适用于兆伏（MV）电子传送门成像装置，因此允许我们测量直线加速器的MV和kV光束的等中心点的重合。该QA工具可以检测到0.1度的x射线源角不确定度。对于空间不确定性，如源位置、成像仪位置或kV/MV等心偏差，该工具的演示精度优于1.6 mm。开发的工具为我们提供了一种简单、可靠和客观的方法，可以在全自动过程中探测和监测成像系统的几何状态，并促进临床常规QA工作流程。(c) 2008年美国医学物理学家协会。
The medical linear accelerator (linac) integrated with a kilovoltage (kV) flat-panel imager has been emerging as an important piece of equipment for image-guided radiation therapy. Due to the sagging of the linac head and the flexing of the robotic arms that mount the x-ray tube and flat-panel detector, geometric nonidealities generally exist in the imaging geometry no matter whether it is for the two-dimensional projection image or three-dimensional cone-beam computed tomography. Normally, the geometric parameters are established during the commissioning and incorporated in correction software in respective image formation or reconstruction. A prudent use of an on-board imaging system necessitates a routine surveillance of the geometric accuracy of the system like the position of the x-ray source, imager position and orientation, isocenter, rotation trajectory, and source-to-imager distance. Here we describe a purposely built phantom and a data analysis software for monitoring these important parameters of the system in an efficient and automated way. The developed tool works equally well for the megavoltage (MV) electronic portal imaging device and hence allows us to measure the coincidence of the isocenters of the MV and kV beams of the linac. This QA tool can detect an angular uncertainty of 0.1 degrees of the x-ray source. For spatial uncertainties, such as the source position, the imager position, or the kV/MV isocenter misalignment, the demonstrated accuracy of this tool was better than 1.6 mm. The developed tool provides us with a simple, robust, and objective way to probe and monitor the geometric status of an imaging system in a fully automatic process and facilitate routine QA workflow in a clinic. (c) 2008 American Association of Physicists in Medicine.