针对变电流投影融合中的阈值选择问题, 提出了一种基于动态时间弯曲的变电流投影融合方法.该方法首先计算不同电流下投影的灰度值-有效边缘梯度序列, 然后利用动态时间弯曲距离对预处理后的序列进行相似匹配, 自动判断最佳融合阈值, 最后根据阈值确定不同电流投影的子区域并对其进行融合, 实现了探测器动态范围的扩展.本文方法计算的各角度下融合阈值的平均误差仅为2.26%, 能够避免人工选择融合阈值的主观性, 基于融合后重建图像的信噪比与几何尺寸测量准确度均优于固定融合阈值的方法.

Aiming at this threshold selection problem for multi-current projection fusion, a method based on dynamic time warping was proposed. Firstly, the sequences of gray value-effective edge gradient is calculated from the projections with different currents. Secondly the dynamic time warping distance is used to match the similarity of the above sequences, and the optimal fusion threshold is automatically determined. Finally the sub regions are extracted for fusion based on the threshold, achieving a higher dynamic range of the detector. The average error of fusion threshold at each angle is only 2.26% calculated by the proposed method, which could avoid subjectivity in the fusion threshold selection. Simulation and experimental results show that both the SNR and the measurement accuracy of geometric dimensions based on the fused computed tomography image are better than those with a fixed threshold.