Saw Cheng B, Yang Yong, Li Fang, Yue Ning J, Ding ChuXiong, Komanduri Krishna, Huq Saiful, Heron Dwight E
Department of Radiation Oncology, University of Pittsburgh Cancer Institute, Pittsburgh, PA, USA.
Med Dosim. 2007 Summer;32(2):80-5. doi: 10.1016/j.meddos.2007.01.003.
A medical linear accelerator equipped with optical position tracking, ultrasound imaging, portal imaging, and radiographic imaging systems was installed at University of Pittsburgh Cancer Institute for the purpose of performing image-guided radiation therapy (IGRT) and image-guided radiosurgery (IGRS) in October 2005. We report the performance characteristics and quality assurance aspects of the kilovoltage cone-beam computed tomography (kV-CBCT) technique. This radiographic imaging system consists of a kilovoltage source and a large-area flat panel amorphous silicon detector mounted on the gantry of the medical linear accelerator via controlled arms. The performance characteristics and quality assurance aspects of this kV-CBCT technique involves alignment of the kilovoltage imaging system to the isocenter of the medical linear accelerator and assessment of (a) image contrast, (b) spatial accuracy of the images, (c) image uniformity, and (d) computed tomography (CT)-to-electron density conversion relationship were investigated. Using the image-guided tools, the alignment of the radiographic imaging system was assessed to be within a millimeter. The low-contrast resolution was found to be a 6-mm diameter hole at 1% contrast level and high-contrast resolution at 9 line pairs per centimeter. The spatial accuracy (50 mm +/- 1%), slice thickness (2.5 mm and 5.0 mm +/- 5%), and image uniformity (+/- 20 HU) were found to be within the manufacturer's specifications. The CT-to-electron density relationship was also determined. By using well-designed procedures and phantom, the number of parameter checks for quality assurance of the IGRT system can be carried out in a relatively short time.
2005年10月，匹兹堡大学癌症研究所安装了一台配备光学位置跟踪、超声成像、射野成像和放射成像系统的医用直线加速器，用于开展图像引导放射治疗（IGRT）和图像引导放射外科（IGRS）。我们报告千伏锥束计算机断层扫描（kV-CBCT）技术的性能特征和质量保证方面的情况。该放射成像系统由一个千伏源和一个通过可控臂安装在医用直线加速器机架上的大面积平板非晶硅探测器组成。研究了该kV-CBCT技术的性能特征和质量保证方面，包括千伏成像系统与医用直线加速器等中心的对准，以及对（a）图像对比度、（b）图像的空间准确性、（c）图像均匀性和（d）计算机断层扫描（CT）与电子密度转换关系的评估。使用图像引导工具评估放射成像系统的对准误差在一毫米以内。发现低对比度分辨率为在1%对比度水平下直径6毫米的孔洞，高对比度分辨率为每厘米9线对。空间准确性（50毫米±1%）、层厚（2.5毫米和5.0毫米±5%）和图像均匀性（±20HU）均在制造商规定范围内。还确定了CT与电子密度的关系。通过使用精心设计的程序和体模，IGRT系统质量保证的参数检查数量可以在相对较短的时间内完成。
