A flexible multichannel FPGA and PC-Based ultrasound system for medical imaging research: initial phantom experiments

IntroductionIn this paper, we present the initial results of a fully programmable 128-channel FPGA and PC-based system that has been developed for medical ultrasound (US) imaging research in our University laboratory (Federal University of Technology - Paraná, Brazil).MethodsIn order to demonstrate the feasibility of the US research system, two applications involving unfocused plane wave transmission and conventional B-mode beamforming were evaluated using a commercial tissue-mimicking phantom and a 3.2 MHz 128-element convex array transducer.ResultsTesting results show that the hardware platform is able to synthesize arbitrary pulses up to 100 Vpp with second order harmonic distortion below 80 dB. For the first application, a 41-tap digital FIR bandpass filter was applied to the acquired RF echoes, sampled at 40 MHz with 12-bit resolution, to improve the noise suppression. In the second application, after offline apodization weighting, filtering, delay-and-sum processing, envelope detection, log compression and scan conversion, the reconstructed B-mode image is displayed over a 50 dB range.DiscussionThe presented results indicate that the open US imaging system can be used to support different ultrasonic transmission and reception strategies, which typically cannot be implemented in conventional data flow architectures that are mainly based on hardware.

引言
本文介绍了巴西巴拉那联邦理工大学实验室开发的一款完全可编程128通道现场可编程门阵列（FPGA）与个人计算机（PC）联用系统的初步研究成果，该系统面向医学超声（US）成像研究应用。
方法
为验证该超声研究系统的可行性，我们采用商用组织仿体与一款3.2 MHz、128元凸阵换能器，对非聚焦平面波发射与常规B型波束成形两类应用开展了性能评估。
结果
测试结果表明，该硬件平台可生成峰峰值电压最高达100 Vpp的任意脉冲，其二阶谐波失真低于80 dB。在第一项应用中，我们对采样率40 MHz、分辨率12位的采集射频（RF）回波应用了41抽头数字有限长单位冲激响应（FIR）带通滤波器，以优化噪声抑制效果。在第二项应用中，经离线切趾加权、滤波、延迟求和处理、包络检测、对数压缩与扫描转换后，重建的B型超声图像以50 dB的动态范围进行显示。
讨论
本次展示的研究结果表明，该开放式超声成像系统可用于支撑多样化的超声发射与接收策略——这类策略通常难以在以硬件为核心的常规数据流架构中落地实现。