任意扫描轨迹的CT成像方法研究

Research on CT Imaging Method Along a General Scanning Trajectory

在工业CT成像应用中,由于复杂结构件形状、结构、组分等特征的限制,使得射线能量与有效厚度不匹配,常规的扫描方式易使投影数据缺失,投影数据完备性较差。为此,本文通过改变轨迹来弥补投影数据缺失,推导任意轨迹的成像模式。首先,在任意轨迹的基础上进行投影几何关系建模,结合空间几何知识完成投影矩阵的刻画;其次,基于迭代重建算法对轨迹的无约束化,进行任意轨迹成像模式下的迭代重建;最后通过小锥角、大锥角以及厚度差异比较大的构件成像仿真实验,验证算法的正确性和可行性。对于厚度差异比较大的工件,该方法相对于传统的圆轨迹扫描,投影数据更完备,CT重建质量高。

In the application of industrial CT imaging, The X-ray energy mismatch to the effective thickness and traditional scanning is difficult to preserve the data integrity of projection due to the limit of complex-structure＇s shape, structure and so on. Therefore, changing the general scanning trajectory to make up for the deficiency of projection data, and then deriving the iterative reconstruction algorittun along a general scanning trajectory. First of all, in the base of general scanning trajectory, we combine the knowledge of analytic geometry with the projection to obtain the projection matrix. The second, the iterative reconstruction algorithm is no binding trajectory, so we study the iterative reconstruction algorithm along a general scanning trajectory. Finally, according to the numerical simulation of small cone-beam angle, lager cone-beam angle scanning and different thickness of structure testing to verify the correctness and feasibility of the algorithm. For the different thickness of structure, compared to the traditional circle scanning, this method is better for preserving the data integrity of projection and improving the quality of reconstructed image.