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本文提出一种基于图像对比度分析的自适应声速优化技术,从而实时得到对比度增强、组织结构清晰可见的超声影像。论文首先描述超声系统动态延迟聚焦的波束形成过程,并引入系统声速以及组织真实声速等概念,进而讨论其两者不匹配对图像品质的影响。介绍图像灰度值表示的对比度之后,论文阐述了准确估计与组织声速一致的系统声速的基本原理。最后,论文通过已知声速的仿人体组织体模和真实人体组织超声影像来验证,并与已有声速优化方法进行比较。实验结果不仅表明本研究所估计的声速是准确的,而且算法运算速度亦适用于超声系统的实时应用。
In this paper, an adaptive speed optimization technique based on image contrast analysis is proposed to obtain real-time ultrasound images with enhanced contrast and clear structure. The thesis first describes the beamforming process of dynamic delayed focusing in the ultrasonic system, introduces the concept of the sound speed of the system and the real sound velocity of the tissue, and then discusses the influence of the mismatch between them on the image quality. After introducing the contrast represented by the gray value of the image, the paper presents the rationale for accurately estimating the sound velocity of a system that is consistent with the tissue sound velocity. Finally, the paper verifies the ultrasound images of simulated human body tissue and real human tissue with known sound velocity and compares them with the existing method of sound velocity optimization. The experimental results not only show that the velocity of sound estimated in this study is accurate, but also the algorithm speed is also suitable for the real-time application of ultrasound system.