一种基于延时交错时钟采样的超声生物显微镜成像方法

An imaging method of ultrasound biomicroscopy based on delayed interlaced clock sampling mode

目的超声生物显微镜通常采用频率为35 MHz及以上超声波,用于人体浅表组织精细成像,其系统的模数转换器(analog-to-digital converter,ADC)的采样率通常需要高于200 MHz。因此,传统超声诊断设备中的数据采集硬件方案,难以实现超声生物显微镜的数字化成像。本文提出一种交错时钟采样方法,通过单路ADC采集电路,可实现4倍频数据采样率的高频超声实时成像系统,其性能指标达到临床诊断的需要。方法基于可编程逻辑器件,通过构建相位相差90°的4组80 MHz采样时钟,分别对相邻的4条扫描线进行采样。设计分时采样控制模块和4通道数据缓存器,将回波数据逐一插点拼接,达到与采样频率320 MHz相当的图像效果。结果通过钨丝测试线靶测试,轴向、侧向分辨力达到50μm,并采用体外猪眼球进行体外成像,图像的信噪比和显示范围符合诊断要求。结论该方法是设计高频超声诊断系统数据采集模块的一种可行性方案,可有效降低硬件需求,实现了超声生物显微镜实时数字化成像的目标,有较好的临床应用前景。

Objective Ultrasound biomicroscopy usually uses ultrasonic waves at a frequency of 35 MHz and above for fine imaging of human superficial tissues.The sampling rate of its system’s analog-to-digital converter is usually higher than 200 MHz.Therefore,it is difficult to realize the digital imaging by ultrasound biomicroscopy with the hardware scheme of data acquisition in traditional ultrasound diagnostic equipment.In this paper,a interlaced clock sampling method is proposed.Through a acquisition circuit with a single analog-to-digital converter(ADC),a high-frequency ultrasound real-time imaging system with 4 times of frequency data sampling rate can be realized,and its performance can meet the needs of clinical diagnosis.Methods Based on a field programmable gate array(FPGA),four sets of 80 MHz sampling clocks with a phase difference of 90°were constructed to sample four adjacent scan lines.A time-sharing sampling control module and a four-channel data cache were designed to splice echo data one by one to achieve an imaging effect equivalent to the sampling frequency of 320 MHz.Results The axial and lateral resolution reached 50μm by tungsten wire test.In vitro imaging was carried out using a porcine eyeball,and the signal-to-noise ratio and the detection depth of the image both met the diagnostic requirements.Conclusions This method is a feasible scheme for the design of data acquisition module of high-frequency ultrasound diagnosis system,which can effectively reduce the hardware requirements and achieve the goal of real-time digital imaging of ultrasound biomicroscopy,and has a good clinical application prospect.