一种用于超声成像的零相位滤波后处理方法*

针对超声成像中基于有限脉冲响应滤波器的零相位滤波处理效率低难以满足实时性要求高的系统需求的问题,提出采用无限冲激响应滤波器实现零相位滤波后处理的方法。首先,分别设计幅频特性相似的有限脉冲响应滤波器和无限冲激响应滤波器作为零相位滤波器的基础滤波器;然后,针对超声相控阵系统采集的超声波回波射频信号,采用两种不同的零相位滤波方法进行处理,对比分析二者的性能、成像效果和效率。结果表明,实现幅频特性近似的零相位滤波,无限冲激响应滤波器具有更低的阶数,可以达到前者的1/4,算法的运算量更低,仅约为前者的1/2。当无限冲激响应滤波器采用直接形式实现时,效率更高,系统的实时性更好。

A zero-phase filtering post-processing method for ultrasonic imaging

Zero-phase filtering processing based on finite impulse response (FIR) filter is inefficient and is difficult to meet the high real-time demand in ultrasonic system. We use infinite impulse response filter (IIR) based zero-phase filtering as an alternative. First of all, the FIR and IIR filter with similar amplitude-frequency response characterized by the same parameters are designed respectively. Then, analysis of the performance, imaging effectiveness and efficiency of both zero-phase filtering methods are made after the two different kinds of zero-phase filtering methods are applied to ultrasonic RF echoes collected by ultrasonic phased array system. The results show that zero-phase filtering based on IIR is less computationally intensive than that of FIR-based case even when amplitude-frequency characteristics of these two cases are almost the same. More specifically, the ratio of filter orders is about 1/4 and the ratio of the amount of computation is about 1/2. When IIR filter is realized in direct form (I), IIR based zero-phase filtering is more efficient, and can better meet the requirements of real-time ultrasonic system.