工业CT半扫描成像技术

Half-scan mode for industrial CT

工业CT即ICT(Industrial Computed Tomography)采用三代扫描方式对构件进行快速检测.但受探测器长度的限制,三代的扫描视场小,可检构件的尺寸受到限制.为解决较大尺寸构件ICT快速检测问题,讨论了一种工业CT半扫描成像技术,推导了其滤波反投影FBP(Filter Back-Projection)重构算法.该算法首先利用扇束三代CT重排原理,将半扫描形成的扇束投影数据修正为360°内不完备的平行束数据;然后利用平行束对称性,生成180°内完备的平行束数据;最后利用平行束重建算法实施重建.计算机模拟和实验结果证明了该技术的正确性.分析表明,其有效扫描视野比三代提高0.8倍以上.

Industrial computed tomography （ICT） adopts generation Ⅲ scan mode to execute the rapid test of objects. However, generation Ⅲ has the small filed of view limited by the length of the detector. It is difficult to test the large objects rapidly. In order to realize the rapid ICT test of large objects, a scan mode called half-scan was discussed and its filter back-projection （FBP） reconstruction algorithm was deduced. This algorithm firstly modified the fan-beam projection data acquired by half-scan into the in-completed parallel-beam data at 0° ～ 360° with the rebin reconstruction principle of fan-beam generation Ⅲ CT. Then the completed parallel-beam data at 0°～180° was created with the symmetry of parallel-beam. Finally CT reconstruction was executed with parallel-beam reconstruction algorithm. The validity of half-scan mode was verified by the results of computer simulation and experiments. Analysis shows that the effective scan field of view can be improved more than 80% compared with that of generation Ⅲ.