超声内窥数字成像技术

Technology of Digital Endoscopic Ultrasonic Imaging

超声内窥镜系统将微型超声探头通过电子内窥镜的活检通道插入消化道器官,既可通过内窥镜直接观察粘膜表面的病变形态,又可进行超声扫描成像,获得消化器官管壁各个断层的组织学特征。利用编码激励技术,以4位Barker编码的方式激励换能器,在不增加峰值负声压的前提下,显著提高超声换能器的发射功率,增大系统探测深度以及成像的信噪比;用数字下变频技术实现超声回波的中频采样、编码信号的脉冲压缩以及信号包络的提取;采用装有超声耦合液的玻璃烧杯作为实验样品,对其进行旋转扫描,得到256级灰度的超声图像,轴向分辨率达0.4 mm,验证了系统原理的正确性。

By sending a micro-ultrasonic probe into coelom through biopsy channel of electronic endoscope,ultrasonic endoscope system can not only acquire pictures of the alimentary canal mucosal surface by direct observing,but also get images of the full histology of the digestive organs by ultrasonic scanning. In this paper,we introduced the coded excitation technique into the ultrasonic imaging system,which uses a 4-bit Barker coded pulse to excite the ultrasonic transducer resulting that the detecting depth and imaging quality of the medical ultrasonic endoscope be increased greatly with the peak negative acoustic pressure unchanged. Then we utilized the digital down conversion technique to realize medium frequency sampling,pulse compression and envelope extraction of the ultrasonic echo. Finally,using a glass beaker with ultrasonic coupling liquid as experimental sample,achieved a 256 gray-scale ultrasound image with the axial resolution of 0.4 mm,so the results proved the validity of system principle.