数字超声成像关键技术的优化设计与实现

【作者】 彭龙飞；

【导师】 李辉；

【作者基本信息】 电子科技大学 ， 机械制造及其自动化， 2010， 硕士

【摘要】 B超诊断仪在医疗诊断设备中有着非常重要的地位,研制全数字化的B超诊断仪已成为当前技术发展的主流。实现全数字化B超诊断仪的关键是数字扫描超声成像技术(DSC),它直接决定了B超诊断仪的各项性能指标。在数字化超声成像技术领域,我国与国外先进水平尚有较大的差距,因此对数字超声成像关键技术开展研究具有重要的意义。设计了以FPGA(EP2C35F484C8)为主控器,以发射放大、接收放大、模数转换、USB2.0接口和其它电路为辅的数字B超采集卡硬件电路;对基于FPGA的超声成像数字化方法进行了研究,重点对数字超声成像的核心部分:波束形成、动态滤波、坐标变换、时间增益补偿进行了优化设计,且对它们的设计结果进行了仿真和分析。在波束形成方面,细化延时基准时钟,提高了延时叠加的精度;采用分段动态聚焦,提高了成像的分辨率和对比度;采用窗函数实现的幅度变迹,有效的抑制了旁瓣的幅度、提高了图像的对比度;通过在不同聚焦深度采用不同的孔径,达到了减少最大延时量、增加近场区的焦区深度和减少时间增益的控制范围的目的。在动态滤波方面,针对回波信号的频率随探测深度增加而变小的状况,通过改变FIR滤波器系数的方法和采用分布式算法的设计方法,达到了高速、有效的滤除杂波的功能。在坐标变换方面,通过采用双时钟控制坐标旋转数字计算机算法和定时输出的方法,使坐标变换达到了实时性好、速度快、精度高、节约资源的效果。在时间增益补偿方面,采用了在B超采集卡上使用定曲线补偿与在上位机上使用可变、可控数字增益放大相结合的二级补偿方法,实现了高增益、可控性好、实时性好的时间增益补偿。以本文设计的数字B超采集卡硬件和超声成像软件系统为核心的数字B超诊断仪,在医院试用中表现稳定,成像效果较好,图像内容丰富,证明本文的总体设计正确,采用的优化方法有效。更多还原

【Abstract】 B-mode ultrasonic apparatus is playing a very important role in the modern clinic. And now, research and manufacturing full-digital B-mode ultrasonic apparatus is becoming the inevitable trend. The key to realize full-digital is DSC, which directly determines the parameters of the apparatus. At present, the level of our country has great disparities compared to the international advanced technology in the field of digital medical imaging technology. Therefore, the research of the digital B-mode ultrasonic imaging has great significance.A high reliability and signal noise ratio (SNR) digital B-mode ultrasonic gather card based on FPGA (EP2C35F484C8) was designed in this paper, combined with USB2.0 interface and other circuits. The methods of digital ultrasonic imaging were well researched based on FPGA, focusing on the optimized design and implementation of the key technology of the ultrasonic imaging, such as beam forming, dynamic filter, coordinate transformation and time gain compensation (TGC), and the results of their programs were simulated and verified.In the design of beam forming, the accuracy of delay superposition was improved by refining delay reference clock, the imaging resolution and contrast were improved by segmented dynamic focusing, the side lobe peak was suppressed effectively and the imaging contrast was improved by variable magnitude using window function, and the maximum time delay and the TGC range were decreased, as the same time the focus depth of the near-field was increased by changing the aperture with different focusing depth. During the design of filter, the frequency of the echo signal becomes smaller when the depth of the focus increased, so an effective dynamic filter with changing coefficients was designed and realized by the distributed arithmetic (DA). In the realization of coordinate transformation, the design with better real-time, faster response, higher precision and less source was realized by using dual-clock control of Coordinate Rotation Digital Computer (CORDIC) algorithm and timing output. In the design of TGC, the method of fixed curve compensation on the full-digital B-mode ultrasonic gather card and veriable, controllable compensation on the host computer was designed for TGC, which led to a high gain, easy control and good real-time compensation effect.During the trial period in hospital, the full-digital B-mode ultrasonic apparatus, which is mainly composed by the hardware of full-digital B-mode ultrasonic gather card and the soft system of the digital ultrasonic image, has showed its superiorities, stability, well imaging effect, rich image content. Therefore, the design of the full-digital B-mode ultrasonic gather card in this paper is correct. The optimized methods of the imaging, which were used in this full-digital B-mode ultrasonic apparatus, are efficient.更多还原