超声平面波两种数据压缩方法初步比较

Preliminary Comparison of Two Compression Methods for Ultrasonic Plane Wave Data

超声平面波成像是超声成像研究的热点之一,超声平面波带来超高帧频的同时也带来了超大数据量。如果将这些数据量直接通过硬件传输,势必对硬件带来极大的负担,也对硬件处理数据的能力提出了极高的要求。为了减少大数据量高帧频所带来的问题,该文通过数据压缩的方式来降低采集数据的传输量。分别从有损压缩和无损压缩方向进行了研究,选择了LZW压缩算法来尝试无损压缩的效果,而根据平面波特点,提出频域切割压缩算法作为有损压缩方法。将LZW算法在FGPA进行了实施,通过对超声仿真数据进行测试,可以达到一定的压缩比。在已知分数带宽的条件下,可以求出频谱中需要保留的带宽,而其余部分频率信号对图像影响的意义不大。通过对超声仿真数据的测试,频域切割压缩算法可以达到较高的压缩比,而比较原始图像和压缩重建图像,其差异是微小的。所以从压缩比角度,频域切割压缩算法是进行超声数据压缩的优先选择。

Ultrasonic plane wave imaging is one of the hot topics in the study of ultrasound imaging, but the plane wave ultrahigh frequency ultrasound has brought a large amount of data. If these data are transmitted directly through the hardware, it will not only bring a great burden on the hardware, but also put a requirement for the ability of the hardware processing data. In order to reduce the problem caused by the high frame frequency and large amount of data, the data compression methods are used to reduce the amount of data acquisition and transmission. In this paper both lossy compression and lossless compression are studied, where LZW compression algorithm is chosen to test lossless compression effect, and based on the plane wave characteristics, the frequency domain cutting compression algorithm is developed as a lossy compression method. In this paper, the LZW algorithm is implemented in FGPA, and it can achieve a certain compression ratio after testing the ultra sonic simulation data. Under the condition of known fractional bandwidth, it is found that the main bandwidth can be preserved in the spectrum, while the rest of the frequency signal has little effect on the image. By testing the ultrasonic simulation data, the frequency domain cutting algorithm can achieve high compression ratio, and the difference between the original image and the reconstructed image is relatively small. So from the point of the compression ratio, the frequency domain cutting algorithm is the primary choice of the ultrasonic data compression algorithm.