一种三源摆动螺旋安检CT成像方法研究

Triple-Source Swinging Spiral CT Imaging Method for Security Inspection

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。

Computed tomography(CT)is one of the important technical means in the field of security inspection.It is of great theoretical and practical value to study new CT imaging methods for security inspection.In this paper,a triple-source swinging spiral CT(TS-SCT)imaging method is proposed,which can be used for the safety inspection of passenger luggage and express parcels.Three groups of X-ray source-detector uniformly distributed in the circumference are used to swing around the rotation center in the range of 120°,the detected object moves along the axial direction in the scanning field of view,and the swing spiral scanning is realized.Compared with spiral CT,the proposed method does not need the whole rotation,and can use the rotating parts which are easier to manufacture,maintain,and are more wear-resistant than the slip-ring.Moreover,the cable is used to transmit data and power,breaking the limitation of a slip-ring on data and power transmission capacity.The imaging model of TS-SCT is established,the effects of scanning mode,scanning parameters,and ratio r between pitch h and projection height T of a cone-beam near the source in z-direction on imaging efficiency and results are analyzed,and the FDK reconstruction algorithm for TS-SCT is derived.The simulated and experimental results show that the TS-SCT FDK reconstruction algorithm is correct and effective,and the TS-SCT method can be used to realize the 3D imaging of detected objects.On the premise of ensuring imaging quality,r≤1/2 is suggested.