Computer analysis of ultrasonic signals in diffuse liver disease

A minicomputer based digital processing system has been assembled for the on-line analysis of ultrasonic signals from a standard B-scanner in daily clinical use. The radio-frequency signals from the transducer are digitized to a precision of eight bits at a rate of 20 MHz/word and the data is stored in raw form on floppy disks. The system has been applied to the study of alcohol induced diffuse liver disease using a combination of simple statistical and texture analyses on the recorded signals. The accuracy of these analyses in the detection of such disease has been found to be substantially higher than that achieved by experienced observers using grey-scale B-scans. Additionally, pattern recognition procedures using the parameters of echo amplitude and texture have been designed in an attempt to classify the state of disease present. This has met encouraging success particularly for patients with alcoholic hepatitis and cirrhosis.     

Quantitative arthroscopic ultrasound evaluation of living human cartilage

OBJECTIVE: To investigate whether living human articular cartilage can be evaluated quantitatively by means of a new diagnostic technique that introduces an ultrasonic probe into the knee joint under arthroscopy and then analyzes the A-mode echogram by means of wavelet transformation. DESIGN: Intact and injured sites of living human articular cartilage were evaluated under arthroscopy. The maximum magnitude and the echo duration (defined as the length of time that included 95% of echo signal) were selected as the quantitative indices on the wavelet map. BACKGROUND: Quantitative evaluation of articular cartilage in situ has the potential to contribute to our understanding of cartilage breakdown and to the effectiveness of cartilage regeneration. However, a reliable method of quantitative cartilage evaluation has yet to be developed for clinical use. METHODS: Living human articular cartilage was analyzed using an ultrasonic probe under arthroscopy and the cartilage characteristics on the echo duration-maximum magnitude graph were examined. RESULTS: Unlike the L-shape distribution of human cadaver cartilage data, the distribution of the living human articular cartilage data showed a smooth curve with a steep initial gradient that flattens gradually at the highest value of echo duration on the echo duration-maximum magnitude graph. CONCLUSIONS: The present study suggests a new quantitative evaluation system for articular cartilage with clinical potential.     

An ASIC design for versatile receive front-end electronics of an ultrasonic medical imaging system--16 channel analog inputs and 4 dynamically focused beam outputs

An ultra large-scale ASIC is designed for the receive front-end electronics of an ultrasonic medical imaging system. The chip receives 16 channel analog rf signals and outputs 4 sets of sample-point-wise dynamically focused partial beam data. Four complete beam data sets are obtained in parallel by simply cascading as many chips as needed in an array system. High resolution of the focusing delay is obtained by nonuniformly selecting each channel data from a quadruply-interpolated rf data stream. The proposed ASIC can be applied to most practical array transducers in the frequency range of 2 to 10 MHz. The digital part of the designed ASIC can be implemented on a chip area of 17.9 microm2 with 0.18 mm CMOS technology, leaving sufficient room for 16 ADCs of 8 bits, 50 MHz on the 5.7 mm x 5.7 mm chip with a 208 pin package.     

Study of ultrasonic contrast agents using a dual-frequency band technique

We have developed a dual-frequency band technique to study frequency-dependent phenomena associated with ultrasonic contrast agents. Our technique uses a superimposed high-frequency (10 MHz) broad-band ultrasound (US) pulse to investigate contrast agent interaction with a low-frequency (e.g., 0.5 MHz) ultrasonic field. Our digitally controlled system has the ability to produce two colinear, confocal US pulses at different center frequencies, to adjust the relative phasing and pulse repetition frequency of each pulse, and to acquire digital backscatter data. A series of experimental studies demonstrated that the high-frequency backscatter signal responded to several phenomena induced in contrast agent particles by the low-frequency beam. These phenomena included radial pulsations, nonlinear oscillations and depletion. Initial results also demonstrated a relative phase shift between the high- and low-frequency signals; this shift is due to a difference in sound velocity at these frequencies, and it may convey information about the contrast agent concentration.     

Measurement of the mechanical condition of articular cartilage with an ultrasonic probe: quantitative evaluation using wavelet transformation

OBJECTIVE: To develop a new diagnostic technology to evaluate articular cartilage quantitatively by introducing an ultrasonic probe into the knee joint under arthroscopy and analyzing the A-mode echogram by means of wavelet transformation. DESIGN: Quantitative evaluation using comparison of two indices on the wavelet map and macroscopic evaluation using the Outerbridge classification. As the quantitative indices on the wavelet map, the maximum magnitude and the echo duration which was defined as the length of time that included 95% of echo signal were selected. BACKGROUND: Quantitative evaluation of articular cartilage in situ is required for new tissue-engineered cartilage but an evaluation system that fully meets this requirement has yet to be established for clinical use. METHODS: Human articular cartilage specimens were analyzed using an ultrasonic probe after macroscopic evaluation and the cartilage characteristics on the echo duration-maximum magnitude graph were examined. RESULTS: There were significant differences between grade 1 and 3, and grade 2 and 3 in the echo duration and maximum magnitude. The cartilage specimens had a L-shaped distribution in echo duration-maximum magnitude graph. CONCLUSIONS: The present study is the new quantitative evaluation system of the articular cartilage in situ and a clinical trial under arthroscopy is presently underway. The ultrasonic measurement is highly reproducible, so we can expect this system to be suitable for in situ reliable examination under arthroscopy. RELEVANCE: Precise evaluation of articular cartilage is of particular importance for longitudinal clinical trials for determination of best surgical option or effect of new chondroprotective drugs in arthritic disease and rheumatoid arthritis.     

High frequency ultrasonic imaging of skin: experimental results

Experimental results are presented demonstrating the application of pulse echo ultrasound to imaging the skin. A laboratory prototype B-mode mechanical scanner was employed to obtain images of human skin, both in vitro and in vivo, using broadband pulsed ultrasound at 25 MHz. Images were formed by processing digitized A-mode waveforms and displaying the resulting two-dimensional cross sections using a digital imaging system. Images obtained by rectifying the A-modes are compared to those derived using a software-based cross-correlation technique. Scans of test targets demonstrate that an axial resolution of 100 m can be achieved at 25 MHz when the digital correlation method is employed. Lateral resolution is limited by the 0.25 mm half-power focal beamwidth of the transducer. Seventeen in vitro ultrasonic scans of human skin were compared to frozen section histology. Average skin depth was well correlated between the two techniques ( = 0.99, p less than 0.001). Application of cross-correlated processing to 25 MHz in vivo images produced good delineation of epidermis, papillary, and reticular dermis. Conversion to a 50 MHz transducer did not delineate skin layers as well as the 25 MHz transducer due to inherent difficulties with transducer reverberations.     

Development of an ultra-broadband ultrasonic imaging system: prototype mechanical sector device

Purpose We constructed an ultra-broadband ultrasonic transducer in a mechanical sector device, and prototyped a system to generate real-time images with higher harmonics. The potential of the system to reduce speckle was also studied. Methods To efficiently detect the higher harmonic components in echo signals, in addition to the transmitting transducer, another transducer only for broadband reception is necessary. We constructed a receiving transducer by bonding a polyvinylidene fluoride (PVDF) high-polymer piezofilm to the radiation surface of the transmitting lead zirconate titanate (PZT) transducer. By building this PZT-PVDF bi-layered ultrasonic probe into a mechanical sector scanner of an ultrasonic diagnosis system, an ultra-broadband ultrasonic imaging system capable of real-time imaging was prototyped. Results Using images of phantoms in water acquired using the prototype system, the acquisition of higher harmonic images with less noise up to the fourth order was demonstrated. In addition, we confirmed that the logarithmic summation of harmonic components from the fundamental to the fourth harmonic effectively reduces speckle noise in the images. Conclusions By obtaining an echo signal from phantoms using a PZT-PVDF bi-layered ultrasonic mechanical sector probe, real-time imaging was carried out, and the effectiveness of its higher harmonic components from the fundamental to the fourth harmonic was confirmed with respect to speckle reduction.     

海绵肾的超声表现及特点

目的分析海绵肾的声像图表现特点,提高对该病的认识。方法收集经静脉肾盂造影或CT证实的海绵肾12例,对其进行回顾性分析。所有病例均行双肾的超声检查。结果11例表现为双侧肾脏髓质的病变,1例表现为单侧肾脏髓质的病变,病变的髓质均显示其回声有明显的增强。有10例肾髓质表现为边缘较毛糙的强回声团。有2例在增强的部分髓质中可见到细小的筛状结构。结论海绵肾声像图具有其表现特征,超声是诊断海绵肾的一种有价值的检查方法。     

A combined ultrasonic linear array scanner and pulsed Doppler velocimeter for the estimation of blood flow in the foetus and adult abdomen--I: Technical aspects

A method is proposed for estimating the volume blood flow of deep lying vessels in the foetus and in adult portal vein and renal vessels. The equipment combines a 3.5 MHz linear array scanner with a 2 or 4 MHz pulsed Doppler. The pulsed Doppler tranducer is connected to the linear array by two movable arms. A real time spectrum analyser is used to process the Doppler signals. A water bath was used to perform an in vitro calibration of the complete system and to adjust the registration of the Doppler sample volume with the echo picture. Several possible inaccuracies in vessel diameter measurement are discussed and the mean of several caliper measurements described by Eik-Ness (1982) is used. Time Motion is thought to be the better method but is more complicated in practice.     

The practical significance of two-dimensional deconvolution in echography

This paper evaluates deconvolution (inverse filtering) as applied to ultrasonic imaging systems, and discusses the obstacles which are encountered employing the technique in practice. A minicomputer is used to generate artificial echo signals, simulating rf signals resulting from a set of point reflectors in a homogeneous medium, as recorded by an electronically focused group-steered linear array scanner. Two-dimensional deconvolution in combination with a Wiener noise reduction filter (i.e., a Wiener-Inverse filter) is applied to these simulated rf signals, which were contaminated with white noise. The efficacy of the Wiener-Inverse filter is defined in terms of its ability to resolve two point reflectors with a lateral spacing equal to the local -6 dB width of the ultrasonic beam. In favorable circumstances, the targets are resolved at signal-to-noise ratios (SNR) better than 20 dB, where SNR is defined as the maximum signal power divided by the average noise power level. Nonlinear effects due to quantization or signal clipping are investigated. In order to improve the resolution of an rf signal with a dynamic range of 40 dB, the input signal should be digitized at a minimum of 12 bits. The problem of signal clipping can be circumvented by oversampling. The two-dimensional Wiener-Inverse filter is defined in terms of both temporal and spatial properties of the insonification. Effects of wave diffraction give rise to a depth-dependent ultrasonic beam. As a result of a misfit of the Wiener-Inverse filter and the local properties of the ultrasonic beam, erroneous noisy texture arises in the image. Adaptation of the Wiener-Inverse filter with respect to the beam properties gives acceptable results, at the expense of a rather large computational effort.     

基于交互式数字化自动乳腺容积超声教学资源平台软件设计与开发

摘要 目的 本研究旨在研发一种包含临床、影像、病理等全套资料的交互式数字化自动乳腺容积超声教学资源平台软件，以改进并完善超声医学教学体系，缩短专业化影像人才的培养周期，实现远程培训与考核的目标。方法 建立教学数据库管理软件，以包含完整病史、影像学资料及相关临床诊治信息的病例为主体，设计五组模块：基本信息及病史模块、三维容积超声成像模块、相关影像模块、病理及随访模块、相关临床诊治信息模块，实现差异登录、快捷搜索、生成习题和试题、远程教学四种功能。结果 交互式数字化自动乳腺容积超声教学资源平台软件提供完整的乳腺器官容积超声影像资料和相关临床信息，可模拟真实容积超声诊断场景，实现全新的超声影像教学、培训和考核模式。结论 交互式数字化自动乳腺容积超声教学资源平台软件提供了一种新的乳腺超声诊断教学方法，有助于缩短专业影像人才的培养周期，完善超声医学教学体系，提高教学质量。 关键字 交互式；数字化教学资源平台；自动乳腺全容积超声成像；教学软件     

Enhancement of stents using interference of low-frequency ultrasonic echo signals

Purpose We set out to enhance the imaging of stents used for coronary coarctation surgery without imaging the reticulation of the stent. Because the stent is a reticulated structure, there is a relation between ultrasound wavelength and the interstice reticulation that produces the echo.Methods First we performed computer simulation by ultrasound frequency of transmitted signals to analyze this relation. Then, instead of controlling the transmitted wave, we processed the returned signals through a band-pass filter because of the difficulty of controlling the transmitted waves of diagnostic ultrasound equipment. Following this, we conducted experiments on an agar gel phantom containing a stent to verify the effectiveness of this method.Results The simulation confirmed that the stent was apparent when the ultrasonic wavelength equaled the product of an integer and twice the interval of the reticulation of the stent. Application of a band-pass filter of 0.8 to 1.5MHz to the waveform returned from the agar gel phantom containing the stent.Conclusions The effectiveness of this method in depicting the stent was confirmed.     

The application of a new sampling theorem for non-bandlimited signals on the sphere: Improving the recovery of crossing fibers for low b-value acquisitions

Recent development in sampling theory now allows the sampling and reconstruction of certain non-bandlimited functions on the sphere, namely a sum of weighted Diracs. Because the signal acquired in diffusion Magnetic Resonance Imaging (dMRI) can be modeled as the convolution between a sampling kernel and two dimensional Diracs defined on the sphere, these advances have great potential in dMRI. In this work, we introduce a local reconstruction method for dMRI based on a new sampling theorem for non-bandlimited signals on the sphere. This new algorithm, named Spherical Finite Rate of Innovation (SFRI), is able to recover fibers crossing at very narrow angles with little dependence on the b-value. Because of its parametric formulation, SFRI can distinguish crossing fibers even when using a DTI-like acquisition (≈32 directions). This opens new perspective for low b-value and low number of gradient directions diffusion acquisitions and tractography studies. We evaluate the angular resolution of SFRI using state of the art synthetic data and compare its performance using in-vivo data. Our results show that, at low b-values, SFRI recovers crossing fibers not identified by constrained spherical deconvolution. We also show that low b-value results obtained using SFRI are similar to those obtained with constrained spherical deconvolution at a higher b-value.     

Evaluating tissue changes with ultrasound during radiofrequency ablation

The purpose of this study was to estimate tissue changes during radiofrequency (RF) ablation by correlating echo frequency shifts and temperature elevations. Experiments were performed on phantoms (tissue mimicking gel) and in-vitro turkey breast. Heating was performed with a modified RF-ablation system. Intermittent RF was applied and the temperature at the electrode tip was continually measured by an embedded thermocouple. Various voltages (10-30V) were applied to achieve a wide range of temperature elevations between 10 and 80 degrees C and ablation sizes between 5 and 27 mm in width. B-mode images and raw data were acquired every 5 s by a modified ultrasound imaging system. The raw data from each line and frame was processed using an algorithm to measure spectral shifts of the echo signals in the power spectrum. The phantom experiments showed positive frequency shifts as the temperature rose, with dependency on the heating rate. A linear relationship (R(2) > 0.96) was found between the RF-applied voltage and the width of the heated area, defined by frequency changes larger than 0.05 MHz. In-vitro experiments showed a correlation (R(2) = 0.84) between the width of the coagulated area and the maximal width of the region with more than 0.12 MHz frequency shifts, but a lower correlation (R(2) = 0.4) between the width of the coagulated area and the temperature elevation. In conclusion, correlation was found between echo frequency shifts and temperature elevations and between echo frequency shifts and the width of the ablated area during intermittent RF ablation. Our results suggest that, with further refinement and validation, ultrasound could be used to measure RF heating and its induced coagulation.     

医用超声系统增益补偿电路的设计

背景:为使深度不同但性质相同的界面反射的回波信号能显示出相同的幅值,必须根据深度(即时间)逐步增大放大器的增益,而使超声波在传播衰减过程中所引起远距离反射波弱的情况得到相应补偿.目的:为了补偿医学超声系统中回波信号的传输衰减问题,提出了一种时间增益补偿电路设计方案,阐述电路设计依据和原理.方法:针对医用超声系统的特点选择高信噪比、高带宽的可变增益放大器件VCA610,实现超声的增益补偿电路.结果与结论:该设计方案有效地解决了医用超声软组织测量过程中由声程导致的回波信号的非线性补偿问题.与传统的分立元件电路相比,该方案具有电路简单,TGC控制信号稳定可靠以及调节灵活等优点,能准确地补偿超声波在人体内的衰减,从而为医学测量系统的设计提供了一个新的可靠方法.     

A 20-MHz ultrasound system for imaging the intestinal wall

An ultrasound system has been developed which uses high-frequency (20 MHz) ultrasound to provide high-resolution images of tissue. The system provides 0.21-mm range and 0.65-mm lateral resolution. The transducer aperture size is 1.8 mm maximum. Miniature probes have been developed which can image via the biopsy channels of standard fiberoptic endoscopes as well as probes for imaging in vitro. A commercially available video "frame grabber" is used in conjunction with a standard microcomputer for image acquisition. This allows images to be displayed and recorded on standard television equipment and be stored and manipulated digitally. The features of the system allow in vivo imaging, in vitro imaging after resection, and histological images of the same tissue region to be acquired and compared. This method is particularly useful in learning how to correctly interpret ultrasonic images of the intestinal wall. The use of 20 MHz is advantageous in achieving excellent resolution and small size probes. The system provides a unique approach to imaging the intestinal wall.     

声学组织定量技术定量诊断脂肪肝价值

目的探讨声学组织定量技术在脂肪肝定量诊断中价值。方法对120例体检健康者（对照组）,150例脂肪肝患者（依据病情分为轻、中、重度脂肪肝组）,运用声学组织定量技术对肝脏进行检查,分析其肝实质超声原始回波信号,记录并比较分析其X2值直方图和参数：Mode（众数）、Average（均数）、SD（标准差）、B／R（蓝色曲线下面积与红色曲线下面积之比）。结果脂肪肝组的Mode和Average均高于正常对照组（P〈0．05）,而脂肪肝组的SD及B／R比值低于对照组（P〈0．05）;中、重度脂肪肝组与对照组间的声学组织定量技术参数比较差异有统计学意义（P〈0．05）。结论声学组织定量技术具有无创、准确、客观等优点,在不同程度脂肪肝病变定量诊断中有重要价值。     

Stimulated acoustic emission: pseudo-Doppler shifts seen during the destruction of nonmoving microbubbles

The purpose of this study was to evaluate the appearance and the characteristics of stimulated acoustic emission (SAE) as an echo contrast-specific color Doppler phenomenon with impact on myocardial contrast echocardiography (MCE). Stationary microbubbles of the new contrast agent SH-U 563A (Schering AG) were embedded within a tissue-mimicking gel material. Harmonic power Doppler imaging (H-PDI), color Doppler and pulse-wave Doppler data were acquired using an HDI-5000 equipped with a phased-array transducer (1.67/3.3 MHz). In color Doppler mode, bubble destruction resulted in random noise like Doppler signals. PW-Doppler revealed short "pseudo-Doppler" shifts with a broadband frequency spectrum. Quantification of SAE events by H-PDI demonstrated an exponential decay of signal intensities over successive frames. A strong linear relationship was found between bubble concentration and the square root of the linearized H-PDI signal for a range of concentrations of more than two orders of magnitude (R = 0.993, p < 0.0001). Intensity of the H-PDI signals correlated well with emission power (R = 0.96, p = 0.0014). SAE results from disintegration of microbubbles and can be demonstrated by all Doppler imaging modalities, including H-PDI. Intensity of SAE signals is influenced by the applied acoustic power and correlates highly with the concentration of microbubbles. Because intensity of SAE signals correlates highly with echo contrast concentrations, analysis of SAE signals might be used for quantitative MCE.     

How accurate is visual assessment of synchronicity in myocardial motion? An In vitro study with computer-simulated regional delay in myocardial motion: clinical implications for rest and stress echocardiography studies.

Asynchronicity in echocardiographic images is normally assessed visually. No prior quantitative studies have determined the limitations of this approach. To quantify visual recognition of myocardial asynchronicity in echocardiographic images, computer-simulated delay phantom loops were generated from a 3.3 MHz digital image data from a normal left ventricular short-axis heart cycle acquired at 55 frames per second. Six expert observers visually assessed 30 abnormal and 3 normal loops with differing computer-induced delay patterns on 3 occasions and in this optimally simulated environment could recognize only single delays of 89 ms or more. This was improved to 71 ms or more by use of side-by-side (normal versus abnormal) comparative review. Thus visual assessment of clinically important regional delay in rest or stress echo images is limited.