基于聚焦换能器的超声透射CT技术*

超声透射CT技术能够重建物体横断面的图像,为了重建高质量图像,分别从换能器和图像重建算法两个方面展开研究。分析了弧形线聚焦换能器焦域处聚焦切片尺寸与换能器几何尺寸的关系及其对CT检测的影响。搭建了超声透射CT检测系统,以等角扇形束的扫描方式获取投影数据,并利用滤波反投影和最小二乘正交分解两种算法重建图像,对比发现最小二乘正交分解算法通用性更强,成像质量更佳。实验结果表明,利用聚焦换能器并结合最小二乘正交分解算法对物体进行CT检测,能够取得较好的成像结果,检测分辨力可达毫米量级。

Ultrasonic transmission CT technology based on the focused transducer

The ultrasonic transmission CT technique can be used to reconstruct the image of the cross section. In order to reconstruct a high-quality image, the research was carried out from two aspects: transducer and image reconstruction algorithm. The relationship between the focused slice size of the arc line-focus transducer and its geometric size, and the influence of the focus slice size on the CT detection were analyzed. The ultrasonic transmission CT detection system was set up. The projection data were obtained by the scanning mode of equiangular fan beam. Algorithms of filter back projection (FBP) and least squares QR-factorization (LSQR) were used to reconstruct the image. By comparison, the LSQR algorithm is more universal and the imaging quality is better. The experimental results show that, using the focused transducer and the LSQR algorithm to detect objects, good imaging results with detection resolution reaching millimeter scale can be obtained.