Comparison of the performance of different tools for fast simulation of ultrasound data

Simulation of ultrasound data is often performed for developing new ultrasound data processing techniques. The spatial impulse response method (as implemented in FieldII) has typically been used as the gold standard due to its excellent accuracy in the linear domain. When scatterer numbers become significant and when 3D volumetric data sets need to be computed, calculation time can become an issue however. In order to solve this problem, two alternative methods have recently been proposed both of which are based on the principle of convolving a set of point scatterers with a point spread function. “FUSK” operates in the frequency domain while “COLE” runs in the spatio-temporal domain. The aim of this study was to directly contrast both methodologies in terms of accuracy and processing speed using FieldII as a reference.     

Research interface on a programmable ultrasound scanner

Motivation

Commercial ultrasound machines in the past did not provide the ultrasound researchers access to raw ultrasound data. Lack of this ability has impeded evaluation and clinical testing of novel ultrasound algorithms and applications.

Objectives

Recently, we developed a flexible ultrasound back-end where all the processing for the conventional ultrasound modes, such as B, M, color flow and spectral Doppler, was performed in software. The back-end has been incorporated into a commercial ultrasound machine, the Hitachi HiVision 5500. The goal of this work is to develop an ultrasound research interface on the back-end for acquiring raw ultrasound data from the machine.

Methods

The research interface has been designed as a software module on the ultrasound back-end. To increase the amount of raw ultrasound data that can be spooled in the limited memory available on the back-end, we have developed a method that can losslessly compress the ultrasound data in real time.

Results and discussion

The raw ultrasound data could be obtained in any conventional ultrasound mode, including duplex and triplex modes. Furthermore, use of the research interface does not decrease the frame rate or otherwise affect the clinical usability of the machine. The lossless compression of the ultrasound data in real time can increase the amount of data spooled by ∼2.3 times, thus allowing more than 6 s of raw ultrasound data to be acquired in all the modes. The interface has been used not only for early testing of new ideas with in vitro data from phantoms, but also for acquiring in vivo data for fine-tuning ultrasound applications and conducting clinical studies. We present several examples of how newer ultrasound applications, such as elastography, vibration imaging and 3D imaging, have benefited from this research interface. Since the research interface is entirely implemented in software, it can be deployed on existing HiVision 5500 ultrasound machines and may be easily upgraded in the future.

Conclusions

The developed research interface can aid researchers in the rapid testing and clinical evaluation of new ultrasound algorithms and applications. Additionally, we believe that our approach would be applicable to designing research interfaces on other ultrasound machines.     

Strategies for reliable automatic onset time picking of acoustic emissions and of ultrasound signals in concrete

Determining the onset of transient signals like seismograms, acoustic emissions or ultrasound signals is very time consuming if the onset is picked manually. Therefore, different approaches exist, especially in seismology. The concepts of the most popular approaches are summarized. An own approach adapted to ultrasound signals and acoustic emissions, based on the Akaike Information Criterion (AIC), is presented. The AIC-picker is compared to an automatic onset detection algorithm based on the Hinkley criterion and also adapted to acoustic emissions. Manual picks performed by an analyst are used as reference values. Both automatic onset detection algorithms are applied to ultrasound signals which are used to monitor the setting and hardening of concrete. They are also applied to acoustic emissions recorded during a pull-out test. The AIC-picker produces sufficient reliable results for ultrasound signals where the deviation from the manual picks varies between 2% and 4%. Concerning acoustic emissions, only 10% of the events result in a mislocation vector greater than 5mm. It can be shown that our AIC-picker is a reliable tool for automatic onset detection for ultrasound signals and acoustic emissions of varying signal to noise ratio.     

基于FPGA的智能建筑湿度检测控制系统设计

在信息化社会,智能建筑越来越多的被提及,智能建筑是指对建筑内外信息交换、舒适性、便利性和节能性的要求;建筑物室内湿度是人们在其中生活、工作、生产的重要考量因素;而随着技术发展,以高效稳定的FPGA芯片为核心的控制系统开始向智能建筑领域应用部署;因此文章提出并设计了基于FPGA的智能建筑湿度检测控制系统方案;文中采用硬件分析和软件设计相结合的方法;硬件分析需要对系统做一个整体把握并寻找经济实惠、稳定可靠的芯片,硬件的可靠是系统稳定工作的前提;软件设计需要将系统的工作方式和实际可能遇到的问题考虑进去,提高系统的容错能力;最后软硬结合并实验实践操作验证系统的可靠性;在实验结果中,该系统可以有效的调节室内的湿度并根据遇到的问题发出警告提示;得出结论,以FPGA控制器为核心的系统,可以担起智能建筑的湿度检测控制任务,并稳定工作。     

成像光谱技术中机上实时数据压缩方法研究

根据成像光谱仪的特点用一系列串行的一维压缩实现二维图像压缩.提出了在机上对原始数据从光谱方向进行实时压缩的“二真值线性预测方法”.该法可做到压缩/复原后光谱特征信息不丢失.实验表明,对大多数光谱数据在1%的重建精度下,至少可获得2:1的压缩比.从总体而言,压缩后原始数据率可降低3～4倍.文中还对压缩数据的编码和误差进行了讨论.     

大数据预处理中属性约简的特性保持分析

伴随着工业及社会信息化程度的增强,各个领域的自动化程度越来越高,大规模及超大规模海量数据应运而生,呈现出大数据特征。这些海量数据在提升行业发展动力的同时,也带来了巨大的挑战性问题—数据可用性。为了从海量数据中甄别出无用信息、挖掘有利于相关领域发展的有价值信息,就需要对其进行数据分析。数据预处理技术可以极大地减少数据分析时的处理量,提高数据分析处理的效率,而属性约简在数据预处理中是一个比较重要的环节。在分析大数据属性特征的基础上,较系统地分析了目前几种主流的属性约简算法,对各类算法的性能进行了剖析,并展望了今后大数据预处理的研究工作思路。     

Application of passive quadrature phase demodulation for the detection of laser ultrasound

In this paper we describe a laser ultrasound detection scheme based on a new passive phase demodulation technique. Typical laser interferometers suffer from the loss of sensitivity because of phase drifts resulting from the mechanical movements of optical components and normally require closed loop stabilisation control. Through the use of a custom-designed grating mask, the present design completely eliminates the need for any feedback control by simultaneously sampling the interferometer output in the four quadrants of the optical phase circle. The signals are then processed to reproduce the actual waveform of the ultrasound pulse. The operation of the proposed technique is demonstrated through the detection of laser-generated ultrasound waves propagating inside an aluminium block.     

The combined effect of spatial compounding and nonlinear filtering on the speckle reduction in ultrasound images

Recently, a spatial compounding ultrasound imaging method was presented that utilizes a conventional 64-element phased array transducer with two unfocused pistons, each placed at one of the sides of the phased array transducer. This method is augmented here by inclusion of nonlinear filtering of the compounded images. The combined effects of the specific spatial compounding and nonlinear filtering on speckle reduction in the generated ultrasound images are studied and evaluated in two stages: First, the image quality is studied when nonlinear filtering is used as part of the spatial compounding. The study is performed by simulations using the Field II program, by processing several B-mode images of a kidney. The second stage compares the results obtained by the simulations to those obtained by in vitro laboratory experiments. Five different compounding strategies and two nonlinear filters, Gaussian and anisotropic diffusion, are investigated and evaluated in terms of image quality parameters-contrast and signal-to-noise ratio. It is shown that the combination of "averaging+nonlinear Gaussian filtering" produces the greatest improvement of image quality. When compared to a conventional phased array imaging system, the spatial compounding method that includes the conventional 64-element phased array transducer with two unfocused pistons, and employs the "averaging+nonlinear Gaussian filtering" strategy, obtains improvement in SNR that has reached 334%. Thus, though this method necessitates a somewhat wider probe, it produces significantly improved images.     

LiDAR data reduction assisted by optical image for 3D building reconstruction

The focus of LiDAR data compression and reduction has been raised in recent years due to the dramatically huge amount of points cloud. To improve the disposal efficiency of LiDAR data, a data reduction method assisted by optical image for 3D reconstruction of building facade is proposed in this article. The method involves a series of procedures of “2D feature line extraction – 3D feature line converting – buffer area of LiDAR points”. The main issue here is finding out a LiDAR point dataset around the 3D feature segment converted from 2D feature lines, which benefits to improving the efficiency of post-processing based on LiDAR data. The reduced LiDAR data can be obtained with reliable structures and accurate geometric position. Furthermore, the experiment of the LiDAR data reduction was conducted over the Xingyuan Building in Nanjing Normal University. The reduction method in this paper proved to be suit for the regular objects modeling, on the basis of the reliable and rigorous mathematical models and computer algorithms, and was a fundamental and useful approach to improve the efficiency of 3D reconstruction of building with the higher modeling accuracy.     

A new method of ultrasound color flow mapping

Conventional ultrasound color flow mapping systems estimate and visualize only the axial velocity component. To obtain the transverse velocity component a modification of a multiple-beam method is proposed. The new two-dimensional color flow mapping system has a small size and consists of three transducers. The central transducer is an appodized and focused phased array. The other transducers are unfocused probes. Three transducers act as receivers and the central transducer operates as a transmitter. All receivers acquire rf scan lines that are then processed to estimate three axial velocity components using an autocorrelation method. These estimates are then combined to estimate the transverse velocity component, taking into account the geometric relationships among three transducers. Two algorithms for transverse velocity estimation are proposed. The first uses the Doppler angle estimate for calculation of the transverse velocity component. The other algorithm calculates the transverse velocity component directly from the axial components. The accuracy of the flow velocity estimators is estimated by simulations. Analysis of accuracy allows choosing the more effective algorithm for two-dimensional velocity estimation, which is insensitive to variations of the Doppler angle.     

Long distance real-time measurement of multi-points micro-vibration in region by digital holography

Many applications require micro-vibration measurement, especially multi-points detection at long distance in real-time. In this paper, a micro-vibration measurement approach based on digital holographic interferometry is proposed for middle-low frequency detection. It can be used to monitor irregular frequency/amplitude vibration in selected region over 10 m away simultaneously and synchronously. A series of experiments were conducted including real-time measurement of 300 Hz, 1 kHz, 2 kHz and 3 kHz constant frequency/amplitude periodic vibration, precision and frequency response tests with calibration of LDV, 1 kHz irregular amplitude vibration, irregular frequency/amplitude vibration as well as the real-time measurement and simultaneous display of multi-points vibration. The experimental results demonstrate the feasibility of the proposed method and reveal its unique advantages.     

超声波在食品技术中的应用

强超声在媒质中传播时产生力学效应、空化效应和热效应,产匝此增强质量传输和热传递,对介质产生强的切向力。本文对超声波在辅助或强化提取,冷冻、乳化、结晶和干燥等食品的加工技术中应用加以综述。     

A comparative analysis of multi-pulse techniques in contrast-enhanced ultrasound medical imaging

One of the important issues in the field of ultrasound medical imaging using contrast agents is the development of techniques able to separate the response of the contrast media from that of the biological tissues. In the literature, one can find various solutions involving the use of multiple transmitted signals and the combination of related echoes. However, the quality of these techniques may be reduced due to some undesired effects that are seldom considered, despite the fact that they are always present in real systems. These effects are the signal distortions introduced by the hardware equipment, the thermal noise in the electronic circuitry, and body motion between successive pulses. In this paper we propose a simulation tool that will allow the calculation of the backscattered echo from a population of contrast agents immersed in a biological tissue, considering all the mentioned effects. With this tool, an assessment of the comparative robustness of three well-known multi-pulse techniques has been carried out under realistic working conditions and the performance of the three techniques has been evaluated in terms of contrast-to-tissue ratio and signal-to-noise ratio. The results show that the undesired effects have a strong impact on these techniques and that there are notable differences in their robustness. Finally, some suggestions on the choice of the particular technique to be applied are provided on the basis of the specific work conditions.     

A preliminary in vitro assessment of polymer-shelled microbubbles in contrast-enhanced ultrasound imaging

This paper focuses on the use of poly (vinyl alcohol)-shelled microbubbles as a contrast agent in ultrasound medical imaging. The objective was an in vitro assessment of the different working conditions and signal processing methods for the visual detection (especially in small vessels) of such microbubbles, while avoiding their destruction. Polymer-shelled microbubbles have recently been proposed as ultrasound contrast agents with some important advantages. The major drawback is a shell that is less elastic than that of the traditional lipidic microbubbles. Weaker echoes are expected, and their detection at low concentrations may be critical. In vitro experiments were performed with a commercial ultrasound scanner equipped with a dedicated acquisition board. A concentration of 100 bubbles/mm³, excitation pressure amplitudes from 120 kPa to 320 kPa, and a central frequency of 3 MHz or 4.5 MHz were used. Three multi-pulse techniques (i.e., pulse inversion, contrast pulse sequence based on three transmitted signals, and contrast pulse sequence in combination with the chirp pulse) were compared. The results confirmed that these microbubbles produce a weaker ultrasound response than lipidic bubbles with a reduced second-order nonlinear component. Nevertheless, these microbubbles can be detected by the contrast pulse sequence technique, especially when the chirp pulse is adopted. The best value of the contrast-to-tissue ratio was obtained at an excitation pressure amplitude of 230 kPa: although this pressure amplitude is higher than what is typically used for lipidic microbubbles, it does not cause the rupture of the polymeric contrast agent.     

Design of data acquisition system and algorithm research for omnidirectional gamma-ray positioning equipment

This article introduces the design and performance of the data acquisition system used in an omnidi- rectional gamma-ray positioning system, along with a new method used in this system to obtain the position of radiation sources in a large field. This data acquisition system has various built-in interfaces collecting, in real time, information from the radiation detector, the video camera and the GPS positioning module. Experiments show that the data acquisition system is capable of carrying out the proposed quantitative analysis to derive the position of radioactive sources, which also satisfies the requirements of high stability and reliability.     

Cellular processing for edge detection in an optical shadow casted architecture

The principles of two-dimensional cellular processing are utilized to obtain the edges of a binary image in an optical shadow casted architecture. The processing steps, based on image logic algebra are introduced where operation kernels are set by the on/off states of four light sources. The input binary image is shifted, superimposed, then logically operated and finally decoded to obtain the edges. The whole process is controlled by a microcomputer. Experimentally simulated results are presented.     

浅析用图像法处理实验数据

指出了图像法在解决物理问题中的优势及应注意的问题,并对用图像法处理实验数据的考题进行了归类．     

基于OTSU多阈值分割算法的激光线扫点云数据表达及精简方法研究

激光线扫方式获取的点云数据量庞大,不利于点云数据的存储、处理与分析。为了对激光线扫点云数据进行有效精简,提出了一种基于OTSU多阈值分割算法的激光线扫点云数据表达及精简方法。基于点云数据坐标与图像灰度值的映射,采用OTSU多阈值分割算法进行区域分割,并将分割后的各区域进行边缘提取及细化处理。根据原映射关系将细化的二值图像重新以点云方式表示,即得到精简的点云数据。在保持原有点云数据关键信息完整度的基础上,可有效地精简点云数据。实验结果表明:基于OTSU多阈值分割算法可有效地精简点云数据,同时能够有效地去除扫描过程中的背景干扰数据,具有较大的适用性和实际应用参考价值。     

J-TEXT 偏振仪信号相位差实时计算方法研究

介绍了常用的相位差算法过零检测法、数字相关法和FFT 算法,对这三种算法的测试表明,三者均能在几十微秒量级的延时内较准确地获得计算结果,但所需的资源和时间开销有所不同。过零检测法占用的资源较多,但平均计算延时较小;FFT 资源占用率和延时均较大;而数字相关法资源占用率和延时均较小,但相位翻转的判断存在困难。