猪的软组织超声背向散射的初步研究

本文探讨了超声背向散射系数的测量原理,在远场测量的情况下推导出了由平均背向散射传递函数求平均背向散射系数的一般公式,报道了我们已建立的背向散射测量系统及利用此系统对一些动物软组织样品所作的测量结果。     

超声背向散射积分与心肌组织定征

背向散射积分是超声组织特性的一种参数，研究表明，它与心肌生理、病理特性变化有较好的一致性，且能定量描述这些特征，因此，用背向散射积分参数作为心肌组织定征，是一种简便、无创且优于超声二维显像的方法。本文对国外近期这方面的研究作一综述。     

超声背向散射积分在判断脂肪肝程度中的初步研究

目的测量单纯肥胖青少年合并脂肪肝减肥前后肝脏、脾脏、肾脏超声背向散射积分的变化,探讨超声背向散射积分在判断脂肪肝程度中的应用价值。方法 60例单纯肥胖青少年,其中男性30例,女性30例;年龄9～24岁,平均年龄14岁;身高(1.61±0.11)m,体质量(76.68±18.36)kg,体质量指数(BMI)29.39±4.73。参加减肥训练营1个月,使用HP-SONOS5500型超声诊断仪,配置AD装置及声学定量分析系统,测量减肥前后肝脏、脾脏、肾脏超声背向散射积分值,同时监测血脂、血糖的变化。结果单纯肥胖青少年减肥前后肝脏和肾脏超声背向散射积分值变化有统计学意义(P<0.05),脾脏背向散射积分值变化无明显统计学意义。结论超声背向散射积分可以用于定量判断脂肪肝的程度,监测脂肪肝的变化,观察治疗效果,其他临床应用有待进一步研究。     

心肌背向散射积分检测的方法研究

心肌超声背向散射积分（ＩＢ）中心动周期中起伏的幅度的大小直接反映心肌缺血的程度，有着重要的临床意义。本文利用本实验室建立的一套ＩＢ检测的实验系统，以６名成年男性（针心脏病史）为受试者，对于检测中系统及算法的参数设置对正常心肌ＩＢ曲线的影响进行考察，发现回波段的选取及带宽的设定都对ＩＢ的检测结果产生显著的影响，而不同的计算方法也对ＩＢ的数值及计算时间有影响，该地其推向临床具有指导意义。     

超声骨密度仪高精度测量技术的研究

目的对市售的韩国超声骨密度仪（型号为OsteoProUBD2002A）进行改进,设计以现场可编程门阵列（fieldprogrammablegatearray,FPGA）作为控制芯片的高精度超声骨密度仪,克服其准确度不高及检测速率低等问题。方法该系统以FPGA芯片XC3S250E-4为核心,采用MAX1449芯片进行模数转换,使用K6T4016V3C—TF70进行数据存储,通过USB芯片FT232H进行数据传输。最后对系统的传输速度和整体性能进行了测试。结果实验结果证实该系统采样率高,数据传输速度快。结论该高精度测量系统是超声骨密度仪性能提升的核心。     

超声背向散射积分与心肌组织定征

背向散射积分是超声组织特性的一种参数，研究表明，它与心肌生理、病理特性变化有较好的一致性，且能定量描述这些特征，因此，用背向散射积分参数作为心肌组织定律，是一种简便、无创且优于超声二维显像的方法。本文对国外近期这方面的研究和一综述。     

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.     

高频超声中血流散射信号的实验研究

目的分析高频条件下红细胞对超声的背向散射情况,探索高频血流成像的条件。方法在现有理论的基础上,利用瑞利散射公式推导红细胞背向散射回声强度与超声频率的关系,并采用10、20、50 MHz超声进行成像,观察血流散射情况。结果实验对同一人体样本的手臂不同深度浅表静脉成像,实验结果在一定程度上验证了理论推导的结论,表明在1~4 mm的深度范围内高频超声成像可获得较强的血流散射回声。结论在高频超声条件下探测浅表血管,即使采用单脉冲探测,依然可获得较丰富的血流回声信号,采用20 MHz的超声频率,可获得较理想的血流散射信息,为高频血流成像提供了条件。     

基于临界角侧波原理的一种轴向传输超声骨密度仪

目的为实现高便携性、高精度、高检测效率的骨密度测量,介绍了基于临界角侧波原理的轴向透射技术的原理和应用,并基于该原理设计了一种以FPGA为核心的前端超声采集单元和PC机端信号处理的检测系统。方法系统使用现场可编程门阵列(Field Programmable Gate Array,FPGA)Spartan-6(XC6SLX9)为核心,控制14 bit的AD6645以100 MHz进行高速采样,并通过USB2.0高速转换芯片FT232H进行数据传输。供电部分采用USB 5V供电并控制开关电源芯片LM3674和低压差线性电源芯片(LDO)WDY05D0505分别对数字和模拟电路供电。结果在Windows7系统下利用C#测试软件测得USB传输速率可达到40 Mb/s,每次采集数据的传输时间仅为12.5 ms。结论基于临界角侧波原理的轴向传输超声骨密度仪的高采样率和高USB传输速率可提升骨密度测量重复性与速度。     

不同背向散射条件对晨检仪QABC+测量结果的影响

目的:研究不同背向散射条件对晨检仪QABC+测量结果的影响。方法:将QABC+和参考电离室模块（由指型电离室和固体水构成）分别放在加速器治疗床的两个固定位置（头部A和网部B）,源到上表面距离100 cm。以QABC+和参考电离室模块下方铺垫的固体水厚度作为变量（0~8 cm、10 cm、15 cm）,测量对应背向散射因子[Bs]值。结果:固体水厚度超过5 cm之后,参考电离室测的[Bs]值趋于稳定,变化在1%内。QABC+测的[Bs]值偏大且在5~15 cm固体水之间仍有3.1%的增长;治疗床A位置等效为5 cm固体水。结论:QABC+测量结果受到背向散射的影响较常规电离室要大,且测得[Bs]值被放大,背向散射条件的轻微变化可能导致晨检仪误报。建议在晨检仪使用前应通过实验测量确定背向散射条件对其读数的影响,或者固定摆位条件以保证散射条件的稳定,使晨检设备高效、稳定、可靠地工作。 【关键词】晨检仪;背向散射;直线加速器;治疗床;质量控制     

一种便携式多部位超声骨密度测量仪的研究

目的设计了一款可测量桡骨、胫骨两部位超声骨密度测量仪以实现人体骨密度的精确测量,并通过分析其与双能X-ray吸收法(dual-energy X-ray absorptiometry,DEXA)测量结果的相关性,验证其有效性。方法超声探头的设计基于超声轴向传播技术,采用双发双收测量原理。探头前端内嵌体表温度传感器用于测量被测部位的温度,通过体表温度值修正超声测量结果。实验招募了25名志愿者(35.5岁±11.7岁),均通过本设备测量桡骨远端1/3处、胫骨1/2处超声特征参量(SOS_(FAS-radius)、SOS_(FAS-tibia))值,同时,通过DEXA测量腰椎L2-L4段骨密度(bone mineral density,BMD)。皮尔森相关性系数用于评估SOS_(FAS-radius),SOS_(FAS-tibia)和BMD之间的相关性。结果 SOS_(FAS-radius)、SOS_(FAS-tibia)与BMD相关性分别为r=0.68(P0.001),r=0.77(P0.001)。结论该设备的测量结果与DXEA的测量结果显著相关,同时,低成本、便携性使得该设备易于普及推广,为骨质疏松的大样本人群筛查提供了一种有效的手段。     

基于Android平台的超声骨密度仪的软件设计

目的目前常见的超声骨密度仪软件处理部分大多在PC端,不能满足使用者对便携性的要求,而已有的嵌入式架构多基于Linux+QT等。本文设计一款嵌入式基于Android平台的超声骨密度仪,解决了用户对便携性的需求。方法软件在eclipse环境中开发,配合测量模块对人跟骨进行测量,通过USB接收回波数据,应用程序对回波数据进行显示,并计算出回波参数声速(speed of sound,SOS)和超声宽带衰减(broadband ultrasound attenuation,BUA),并选取型号为OsteoPro的超声骨密度仪进行比较。结果该仪器实现了骨密度仪的功能,包括数据的高速采集、参数的计算等。此外,作为一个嵌入式应用设备,应用软件还支持对患者的信息和测量的结果进行存储,打印出测量报告。结论 Android平台和USB的使用,使仪器在便携性和可移植性都得到极大的提升。     

Ultrasonic characterization of cancellous bone using apparent integrated backscatter

Apparent integrated backscatter (AIB) is a measure of the frequency-averaged (integrated) backscattered power contained in some portion of a backscattered ultrasonic signal. AIB has been used extensively to study soft tissues, but its usefulness as a tissue characterization technique for cancellous bone has not been demonstrated. To address this, we performed measurements on 17 specimens of cancellous bone over two different frequency ranges using a 1 MHz and 5 MHz broadband ultrasonic transducer. Specimens were obtained from bovine tibiae and prepared in the shape of cubes (15 mm side length) with faces oriented along transverse (anterior, posterior, medial and lateral) and longitudinal (superior and inferior) principal anatomic directions. A mechanical scanning system was used to acquire multiple backscatter signals from each direction for each cube. AIB demonstrated highly significant linear correlations with bone mineral density (BMD) for both the transverse (R2 = 0.817) and longitudinal (R2 = 0.488) directions using the 5 MHz transducer. In contrast, the correlations with density were much weaker for the 1 MHz transducer (R2 = 0.007 transverse, R2 = 0.228 longitudinal). In all cases where a significant correlation was observed, AIB was found to decrease with increasing BMD.     

Nondestructive evaluation of tissue engineered articular cartilage using time-resolved fluorescence spectroscopy and ultrasound backscatter microscopy

The goal of this study is to evaluate the ability of a bimodal technique integrating time-resolved fluorescence spectroscopy (TRFS) and ultrasound backscatter microscopy (UBM) for nondestructive detection of changes in the biochemical, structural, and mechanical properties of self-assembled engineered articular cartilage constructs. The cartilage constructs were treated with three chemical agents (collagenase, chondroitinase-ABC, and ribose) to induce changes in biochemical content (collagen and glycosaminoglycan [GAG]) of matured constructs (4 weeks); and to subsequently alter the mechanical properties of the construct. The biochemical changes were evaluated using TRFS. The microstructure and the thickness of the engineered cartilage samples were characterized by UBM. The optical and ultrasound results were validated against those acquired via conventional techniques including collagen and GAG quantification and measurement of construct stiffness. Current results demonstrated that a set of optical parameters (e.g., average fluorescence lifetime and decay constants) showed significant correlation (p<0.05) with biochemical and mechanical data. The high-resolution ultrasound images provided complementary cross-section information of the cartilage samples morphology. Therefore, the technique was capable of nondestructively evaluating the composition of extracellular matrix and the microstructure of engineered tissue, demonstrating great potential as an alternative to traditional destructive assays.     

An information-theoretic approach to estimating ultrasound backscatter characteristics

Analysis of backscatter in the ultrasound echo envelope, in conjunction with ultrasound B-scans, can provide important information for tissue characterization and pathology diagnosis. Statistical models have often proven useful in modeling backscatter. In this paper, an innovative approach to backscatter analysis based on generalized entropies and neural function approximation is presented. Entropy measures are shown to provide accurate estimates of scatterer density, regularity, and SNR of the amplitude distribution. Specific scattering distributions need not be assumed. Experimental results on ground truth envelopes show that generalized entropies can be used to accurately estimate backscatter properties.     

Design and test of a PC-based portable three-dimensional ultrasound software system Ultra3D

Currently, portable ultrasound units lack three-dimensional (3D) image display, limiting their potential usefulness especially under remote and hostile operating environments where information must be intuitive and objective. A freehand 3D image processing and visualization software package, Ultra3D, has been developed and tested, especially to work with a miniaturized linear-array transducer probe that is connected to a laptop PC. This paper presents the software design and method to integrate Ultra3D into Terason's miniaturized SmartProbe for freehand 3D ultrasound imaging. Since images generated by Ultra3D are in a digital imaging and communications in medicine (DICOM) format, data sharing with others is easy.     

Anatomy teaching with portable ultrasound to medical students

Background

The management of medical conditions is influenced by whether clinicians regard them as "disease" or "not a disease". The aim of the survey was to determine how medical students classify a range of conditions they might encounter in their professional lives and whether a different name for a condition would influence their decision in the categorisation of the condition as a 'disease' or 'not a disease'.

Methods

We surveyed 3 concurrent years of medical students to classify 36 candidate conditions into "disease" and "non-disease". The conditions were given a 'medical' label and a (lay) label and positioned where possible in alternate columns of the survey.

Results

The response rate was 96% (183 of 190 students attending a lecture): 80% of students concurred on 16 conditions as "disease" (eg diabetes, tuberculosis), and 4 as "non-disease" (eg baldness, menopause, fractured skull and heat stroke). The remaining 16 conditions (with 21-79% agreement) were more contentious (especially obesity, infertility, hay fever, alcoholism, and restless leg syndrome). Three pairs of conditions had both a more, and a less, medical label: the more medical labels (myalgic encephalomyelitis, hypertension, and erectile dysfunction) were more frequently classified as 'disease' than the less medical (chronic fatigue syndrome, high blood pressure, and impotence), respectively, significantly different for the first two pairs.

Conclusions

Some conditions excluded from the classification of "disease" were unexpected (eg fractured skull and heat stroke). Students were mostly concordant on what conditions should be classified as "disease". They were more likely to classify synonyms as 'disease' if the label was medical. The findings indicate there is still a problem 30 years on in the concept of 'what is a disease'. Our findings suggest that we should be addressing such concepts to medical students.     

A study on a non-contacting respiration signal monitoring system using Doppler ultrasound

We proposed non-contacting respiration signal monitoring system for sleep apnea syndrome. Experiments were conducted by emitting 40 kHz ultrasound beam, which is set tone burst mode by 1 ms period to a subject chest. Normal respiration condition and a simulated sleep apnea syndrome condition were measured while subjects were holding breath. To obtain the actual respiration signal from the raw signal, ultrasound attenuation characteristics were considered. The Doppler ultrasound signal was detectable once the received signal obtained by demodulation circuits passed through a low pass filter (LPF). The signal’s ripples were eliminated by moving average method and the signal’s peaks were detected by phase portrait reconstruction method to measure the respiration rate. This paper is the WC2006 special issue paper.