中文摘要：

网像引导系统由于能帮助对肿瘤靶区进行精确定位，在直线加速器放疗设备上得到了成功应用。考虑到γ射线立体定向放疗设备的机械结构的特殊性，本文拟开发基于Co-60的图像引导装置。为此本文设计并安装了以Co-60为放射源的锥束CT成像系统。在该系统上成功地实现了多种轨迹（包括圆、螺旋、马鞍、圆线等）锥束CT扫描。采用一般轨迹下的基于弦线段和感兴趣区的BPF重建算法和圆轨迹下的FDK算法进行了图像重建。本文分别用头部和胸部体模研究了该系统的成像质量，最后采用Min／Max曲率流方法对重建后图像进行了去噪处理。结果表明采用该系统可以清晰地确定被扫描物体轮廓和骨性边界，为实现γ射线立体定向放疗设备在影像引导下进行病人自动摆位打下了基础。

英文摘要：

Image guidance system, helping to target tumor precisely, was successfully used in linear accelerator radiotherapy instrument. Considering the specialty of mechanical structure of gamma-ray stereotatic radiotherapy instrument, we planned to develop a Co-60 based image guidance system. We designed and installed a cone beam CT imaging system with Co-60 as the radiation source. Various CT scanning trajectories （including circle, spiral, saddle, and circle-line） was successfully implemented on this system. The chord-line and VOI based BPF algorithm with a general trajectory and FDK algorithm were used for image reconstruction. We studied the imaging quality of this sys- tem using head and chest phantom respectively, and finally use of the Min/Max curvature flow method to eliminate the noise of the reconstructed image. The result showed that the contour and bone boundaries of scanned object can be clearly determined, which supplied the basis of further patient auto-positioning for cobah-60 gamma-ray stereotatic radiotherapy device.