计算机断层成像(CT)技术是安全检查领域重要的技术手段之一,研究新型安检CT成像方法具有重要的意义。提出一种可用于旅客行李、快递邮包安全检查的三源摆动螺旋CT(Triple-Source Swinging Spiral CT, TS-SCT)成像方法,呈圆周均布的三组射线源-探测器围绕旋转中心在120°范围内往复摆动,检测物体在扫描视场内沿轴向移动,从而实现摆动螺旋扫描。相对于螺旋CT,该方法不需要整周旋转,选用比滑环耐磨损且易于制造、维护的转动部件,采用线缆传输数据和电力,避免滑环对传输能力的限制。建立了TS-SCT成像模型,分析了扫描方式、扫描参数及螺距h与锥束靠近射线源端在视场z方向的投影高度的比值r对成像效率和成像结果的影响,初步设计了一种TS-SCT结构,推导了用于TS-SCT的FDK算法。仿真实验和模拟实验结果表明,TS-SCT FDK算法正确有效,TS-SCT方法能实现检测对象的三维成像,在保证成像质量的前提下建议r≤1/2。

In order to improve the diagnosis and analysis ability of 3D spiral CT and to reconstruct the contour of 3D spiral CT damage image, a contour reconstruction method based on sharpening template enhancement for 3D spiral CT damage image is proposed. This method uses the active contour LasSO model to extract the contour feature of the 3D spiral CT damage image and enhances the information by sharpening the template enhancement technique and makes the noise separation of the 3D spiral CT damage image. The spiral CT image was processed with ENT, and the statistical shape model of 3D spiral CT damage image was established. The gradient algorithm is used to decompose the feature to realize the analysis and reconstruction of the contour feature of the 3D spiral CT damage image, so as to improve the adaptive feature matching ability and the ability to locate the abnormal feature points. The simulation results show that in the 3D spiral CT damage image contour reconstruction, the proposed method performs well in the feature matching of the output pixels, shortens the contour reconstruction time by 20/ms, and provides a strong ability to express the image information. The normalized reconstruction error of CES is 30%, which improves the recognition ability of 3D spiral CT damage image, and increases the signal-to-noise ratio of peak output by 40 dB over other methods.

研究了锥束螺旋Katsevich和FDK重建算法，并对这两种算法进行比较。实验结果表明: 当投影数据没有噪声的时候，FDK算法和Katsevich算法均能取得较好的效果，当对实际物体进行重建的时候，投影数据含有噪声， Katsevich算法需要对投影数据求导，而它对投影数据的噪声较敏感，重建质量有所下降。