电流注入式磁声成像中样本电导率边界的提取

Boundary extraction of electric conductivity sample in current exciting magneto-acoustic imaging

目的借助步进电机对电流注入式磁声成像进行实验研究,同时对电导率边界重建算法进行探讨与比较。方法实验研究中,选用正弦脉冲信号作为实验研究的激励信号。选用铜丝环作为实验对象,通过步进电机旋转探头沿圆周运动扫描样本采集声信号,用声信号重建样本边界信息。在电导率边界重建算法设计中,利用了"最值-两侧单调"方法检测信号的峰值,使用"跟踪峰值确定边界走向"的方法查找峰值边界。结果实验结果表明,利用步进电机采集到的超声信号及新的电导率边界重建算法,在声信号数据不太理想的情况下寻找到良好的边界,算法适应性较好。所寻找到的边界中包含95%(190/200)以上角度中的边界信息。结论找到了铜丝环中铜丝中心线对应的峰值边界,同时找到了铜丝环外边界的上限和内边界的下限。

Objective To study current exciting magneto-acoustic imaging by step motor, and discuss the algorithm for reconstructing conductivity boundary. Methods Sinusoidal pulse signal was chosen as the excitation signal and copper loop as the experimental sample. Ultrasound detector was driven by step motor and moved in a circle to collect signals, which were used for reconstructing conductivity boundary of sample. In algorithm design, signal peaks were detected by means of ＂extreme valuemonotonous in two sides＂ and sample conductivity boundary was extracted by means of ＂tracking trend of peaks＂. Results Precise conductivity boundary could still be found even when the signal was not ideal and the boundary included boundary information from more than 95 % of angles, indicated the feasibility of the algorithm. Conclusion It is demonstrated that the peak boundary corresponding to the center line of copper wire in copper loop are found. The superior limit of outer boundary of copper loop and inferior limit of inner boundary of copper loop are also established.