基于FPGA的数字滤波器在超声诊断设备中的应用进展

在超声诊断系统中,一个重要的环节就是实时处理庞大的超声信号,尤其是用数字硬件电路实时进行信号处理.信号处理的关键部分就是滤波器的设计,数字滤波器的设计会直接影响超声诊断设备的性能.简要介绍数字滤波器的分类,着重介绍近年来基于现场可编程门阵列（FPGA）的多种数字滤波器的硬件实现方法,尤其是经典数字滤波器中基于分布式算法实现有限脉冲响应（FIR）滤波器;分析了每种数字滤波器的优点及存在的问题;展望了超声诊断设备中现代数字滤波器的发展趋势.     

基于FPGA的眼科超声数字化成像中内插变频技术与实现

眼科高频超声数字化成像中使用内插滤波器可等效地提高采样率以节约资源。在研究分析了有限脉冲响应（FIR）内插滤波器的两种常见结构以及半带滤波器、级联积分梳状（CIC）滤波器两种特殊结构等四种内插滤波器的基础上,设计了四种高效结构。通过Verilog硬件描述语言描述以上四种高效结构,并在现场可编程门阵列（FPGA）中实现,最后通过实验仿真验证各内插变频算法的有效性。以有限脉冲响应（FIR）内插滤波器的两种常见结构以及半带滤波器为基础改进的高效结构均能达到变频的效果,同时可节约资源且效率更高。而CIC滤波器高效结构在效率和资源节约方面虽更具优势,但未能达到眼科超声变频信号处理所要求的性能,尚不适用。     

一种新型自适应动态滤波器在超声成像中的应用

目的 为使动态滤波器的中心频率可实时匹配回波信号中心频率,本文设计了一种新型的自适应动态滤波器.方法 本文自适应机制是以快速傅里叶变换（fast Fourier transform,FFT）算法实时分析真实回波信号的频率特性,根据频率编号自适应匹配动态滤波器的系数.该滤波器的所有模块基于现场可编程门阵列（field programmable gate array,FPGA）硬件实现,最后将加入白噪声的正弦信号使用Modelsim时序仿真工具进行仿真.结果 仿真结果表明,这种滤波器能良好匹配回波信号中心频率,消除噪声.结论 本文提出的自适应动态滤波器满足高速实时系统的要求,为超声系统中滤波器的设计提供了可靠依据.     

一种基于水平集的前列腺超声图像自动分割算法

由于超声图像存在着斑点噪声和较低的信噪比,使得传统的分割算法很难应用于超声图像的自动分割,而手工分割方法非常耗时且重复性差.因此提出了一种基于水平集和改进径向浅浮槽算法(RBR,radical bas-relief)的前列腺直肠超声(TRUS)图像全自动分割算法.首先使用Sticks滤波器来去除斑点噪声,并且增强图像的对比度.然后使用径向浅浮槽算法来对图像进一步增强,通过使用形态学算法和边界填充得到前列腺的初始轮廓,使用该轮廓来初始化水平集算法,从而实现全自动分割.实验结果表明,该方法能有效地去除斑点噪声的影响,并且能够对前列腺超声图像实现较好的分割效果.     

眼科高频环阵超声波数字化成像技术的研究

目的设计眼科高频环阵B超平台,实现超声波全程数字化处理。方法设计环阵换能器发射接收电路,将高频的超声回波信号经过前级放大后直接引出进行高分辨率、高速的模拟数字采样。信号数字化后,通过高速的现场可编程门阵列（field-programmable gatearray,FPGA）完成波束形成、动态聚焦、滤波、检波及对数放大等一系列信号处理。结果通过临床验证,眼科高频环阵B超平台图像横向分辨率0．2mm,侧向分辨率0．4mm,满足临床要求。结论环阵超声波数字化成像技术可提高图像分辨率和疾病检出率。     

基于FPGA的全数字眼科超声诊断仪信号处理设计与实现

目的研制基于FPGA(field programming gate array,可编程逻辑门陈列)的全数字眼科超声回波信号处理系统.方法信号处理技术主要采用内插、动态滤波、TGC、包络检波和对数放大.在FPGA中采用以原理图设计为顶层模块.硬件描述语言VHDL作为底层模块的设计方法.结果通过构建实验模型验证了系统各阶段信号处理的有效性.对正常人体眼球和眼眶进行检测,获得了很好的回波信号.结论本设计对眼科高频超声回波信号具有良好的实时处理能力,达到了设计要求,具有良好的应用前景.     

基于虚拟仪器平台的新型超声辐射热疗仪软件设计

介绍了基于虚拟仪器工程平台的超声热疗治癌仪的工作原理及人机界面设计.阐述了组织温度控制算法、治疗头水温控制以及脉宽调制信号产生三个系统核心子模块的设计.根据系统特殊要求,在癌变组织温度控制子程序中,改进了比例积分微分(PID)算法,实现了对靶区组织温度的严格控制.通过对内嵌于数据采集卡的8254芯片编程产生了HD控制的脉宽调制信号,同时设计了水温控制算法.实验验证,软件设计可靠,满足了超声热疗仪的要求.     

一种基于多agent系统的生化系统分布式随机仿真算法

系统生物学关注于对生化反应网络进行定量的数学建模和计算机仿真,这是理解生化网络的拓扑结构和动态行为的主要手段.Gillespie的随机仿真算法(SSA)是仿真均匀生化反应系统的一种标准的算法,而SSA算法最大的问题在于计算代价过高.基于并行思想提出一种基于多agent系统实现的分布式随机仿真算法(DSSA),利用分布式计算来提高SSA算法的计算性能,为建模与仿真大规模生化反应系统提供了一种有效的方式.实验显示DSSA算法在时间性能上带来显著的提升.     

数字助听器算法开发平台pDHA的构建和测试

数字助听器是目前广大聋人康复的唯一有效手段,因此数字助听算法的研究日益重要.为便于进行助听算法的开发测试,本论文设计实现了一款基于可编程DSP的全数字助听算法开发平台pDHA.该平台具有计算功能强大、实时便携、扩展能力丰富等特点.本论文还针对此类平台的独特应用需求和相关标准,制定了一套完整的测试流程.参数测试结果表明,该系统具备足够的能力进行高级数字助听算法的开发和测试.     

一种适合于生物医学信号实时处理的零相移递归数字滤波方法

生物医学信号处理经常需要应用实时零相移数字滤波器,以避免波形失真。FIR滤波器具有线性相位,但其计算量太大,难于实时实现。ⅡR滤波器在满足同样的幅频特性要求时,其计算量比FIR少得多。但它的相频特性是非线性的,为了实现线性相位,需将具有相同参数的因果性ⅡR与非因果性ⅡR系统并联,这又不能实时实现。本文提出了一种能使零相移ⅡR滤波器实时实现的算法,可实现连续处理。其计算量虽然比传统ⅡR滤波器要大些,但比FIR滤波器要小得多。适用于生物医学信号作实时无相位失真滤波。本文得出听觉诱发响应信号处理的结果。     

Optimal digital filters for long-latency components of the event-related brain potential

A fundamentally important problem for cognitive psychophysiologists is selection of the appropriate off-line digital filter to extract signal from noise in the event-related brain potential (ERP) recorded at the scalp. Investigators in the field typically use a type of finite impulse response (FIR) filter known as moving average or boxcar filter to achieve this end. However, this type of filter can produce significant amplitude diminution and distortion of the shape of the ERP waveform. Thus, there is a need to identify more appropriate filters. In this paper, we compare the performance of another type of FIR filter that, unlike the boxcar filler, is designed with an optimizing algorithm that reduces signal distortion and maximizes signal extraction (referred to here as an optimal FIR filter). We applied several different filters of both types to ERP data containing the P300 component. This comparison revealed that boxcar filters reduced the contribution of high-frequency noise to the ERP but in so doing produced a substantial attenuation of P300 amplitude and, in some cases, substantial distortions of the shape of the waveform, resulting in significant errors in latency estimation. In contrast, the optimal FIR filters preserved P300 amplitude, morphology, and latency and also eliminated high-frequency noise more effectively than did the boxcar filters. The implications of these results for data acquisition and analysis are discussed.     

A unified design algorithm of two-dimensional digital filters for radioisotope image processing

A unified design algorithm of two-dimensional digital filters for radioisotope image processing based on the Fourier-Bessel transform and the weighted least-squares method is described. The algorithm presented here can treat the various kinds of two-dimensional digital filters in a unified approach. Design examples are presented and several graphs are included to show the relationships between the design parameters as an aid in practical applications. The application of the method in radioisotope image processing is also presented. Several low-pass, Wiener and band-pass filters were designed using the method and applied to some clinical data in nuclear medicine including SPECT images. The digital filter design technique proposed here is considered to provide a powerful tool for extraction of additional qualitative information and improvement of the quality of nuclear medicine images both in research and in routine clinical work.     

基于FPGA的眼科超声数字化中CIC内插滤波器的改进与实现

目的眼科高频超声数字化成像中使用内插滤波器可等效地提高采样率以节约资源。方法在研究分析了级联积分梳状（CIC）滤波器的基础上,结合运用余弦（COSINE）滤波器和内插二阶多项式（1SOP）滤波器对其进行改进。结果通过硬件描述语言描述改进后的高效结构,并在现场可编程门阵列（FPGA）中实现,最后通过实验仿真验证该内插变频算法的有效性。结论改进后的CIC滤波器基本保留了效率和资源节约方面的优势,同时也改善了其通带宽度和阻带衰减特性,能够适用于10MHz的高频眼科超声信号处理的要求。     

Use of finite wordlength FIR digital filter structures with improved magnitude and phase characteristics for reduction of muscle noise in EEG signals

One of the main disturbances in EEG signals is EMG artefacts generated by muscle movements. In the paper, the use of a linear phase FIR digital low-pass filter with finite wordlength precision coefficients is proposed, designed using the compensation procedure, to minimise EMG artefacts in contaminated EEG signals. To make the filtering more effective, different structures are used, i.e. cascading, twicing and sharpening (apart from simple low-pass filtering) of the designed FIR filter. Modifications are proposed to twicing and sharpening structures to regain the linear phase characteristics that are lost in conventional twicing and sharpening operations. The efficacy of all these transformed filters in minimising EMG artefacts is studied, using SNR improvements as a performance measure for simulated signals. Time plots of the signals are also compared. Studies show that the modified sharpening structure is superior in performance to all other proposed methods. These algorithms have also been applied to real or recorded EMG-contaminated EEG signal. Comparison of time plots, and also the output SNR, show that the proposed modified sharpened structure works better in minimising EMG artefacts compared with other methods considered.     

1024点高速FFT处理器的FPGA设计与实现

目的 设计满足高速实时信号处理需要的快速傅里叶变换(FFT)处理器。方法采取基-2按频率抽取( DIF)FFT算法,蝶形运算单元采用流水线方式,接收数据采用乒乓操作的方法设计基于现场可编程门阵列(FPGA)的1 024点、32位字长、定点复数FFT处理器。结果在时钟100 MHz下,计算1次1 024点定点FFT耗时约...     

一种DICOM文件并行查找算法的设计与实现

目的为提高DICOM文件查找的速度和效率。方法在分析DICOM文件查找的基本原理基础上,设计一种基于任务等分策略的文件并行查找算法,并基于．NETF ramework 4和Leadtools DICOM开发包实现该算法。该算法特点是采用多线程并行技术,通过任务等分和多核并行实现DICOM文件并行查找。在HPDL380G5服务器上对并行算法进行性能测试,获得并行加速比曲线图。结果测试表明该算法具有良好的并行性能,可显著提高DICOM文件查找效率。结论采用任务等分策略和多线程并行模型,能够有效提高DICOM文件查找的速度和效率。     

基于对数域连续小波变换电路的心电图QRS波检测

为满足植入式心脏起搏器之类的医疗设备低功耗、实时处理等应用要求的需要,提出了基于低电压、低功耗对数域连续小波变换电路的心电图QRS波检测方法。为便于用模拟VLSI实现小波变换,用混合粒子群算法构造了类高斯一阶导数小波。以平衡式对数域积分器为积木块,设计了用于QRS波检测的连续小波变换电路,该电路由冲激响应为类高斯一阶导数小波函数的反褶及其伸缩的滤波器组构成。由该电路实现心电信号的小波变换,进行QRS波检测。仿真结果表明了该方法的可行性。     

Filtering techniques for the removal of ventilator artefact in oesophageal pulse oximetry

The oesophagus has been shown to be a reliable site for monitoring blood oxygen saturation (SpO₂). However, the photoplethysmographic (PPG) signals from the lower oesophagus are frequently contaminated by a ventilator artefact making the estimation of SpO₂ impossible. A 776th order finite impulse response (FIR) filter and a 695th order interpolated finite impulse response (IFIR) filter were implemented to suppress the artefact. Both filters attenuated the ventilator artefact satisfactorily without distorting the morphology of the PPG when processing recorded data from ten cardiopulmonary bypass patients. The IFIR filter was the better since it conformed more closely to the desired filter specifications and allowed real-time processing. The average improvements in signal-to-noise ratio (SNR) achieved by the FIR and IFIR filters for the fundamental component of the red PPG signals with respect to the fundamental component of the artefact were 57.96 and 60.60 dB, respectively. The corresponding average improvements achieved by the FIR and IFIR filters for the infrared PPG signals were 54.83 and 60.96 dB, respectively. Both filters were also compared with their equivalent tenth order Butterworth filters. The average SNR improvements for the FIR and IFIR filters were significantly higher than those for the Butterworth filters.