Wigner-Ville分布法估计生物组织散射元平均间距

生物组织散射元平均间距是描述生物组织微观结构和超声散射特性的重要参数。文中构造了生物组织散射元一维超声散射模型,提出用Ｗｉｇｎｅｒ－Ｖｉｌｅ分布函数方法估计生物组织散射元平均间距,仿真结果表明这一方法具有良好的空间分辨率,能检测出生物组织散射元平均间距细微的非均匀性变化,且有良好的抗噪声性等一系列优良特性     

不同资料处理方法对猪顿抑心肌背向散射积分和室壁增厚周期性变异测定的影响

本研究在顿抑心肌探讨背向散射积分和心肌壁增厚运动的关系。对不同定义的周期性变异进行评价并相互比较。超声资料由10只开胸的Yorkshire猪获得。在局部缺血期间和30分钟顿抑期间,将宽频(3-7MHz)超声探头直接缝在左室的心肌壁上。背向散射积分的周期性变异由文献中的三种不同定义的方法计算获得。无论其定义方法如何,在急性缺血期间,室壁增厚的周期性变异和背向散射积分的周期性变异均被顿抑。再灌注的第一分钟恢复或高于基线水平,随后,在顿抑期间渐渐降到基线以下。无论使用什么资料处理方法,在实验猪中,未观察到背向散射积分周期性变异的早期恢复现象。背向散射积分和室壁增厚的关系一直保持着。     

超声组织定征估测心肌梗塞范围

背景:超声组织定征(UTC)能够区分正常与梗塞心肌。梗塞心肌的背向散射积分增加和心动图期依赖的背向散射变异消失。背向散射的周期性变异与局部心肌的收缩功能密切相关,而后者是心肌缺血的一个标志。本研究拟对一个假设进行检测:描记心室壁的超声周期性散射,并以此估计心肌梗塞区的范围。方法与结果:对12只麻醉的狗,开胸,完全阻塞冠状动脉前降支4小时,使之产生透壁性心肌梗塞。图形显示背向散射积分Rayleigh5心动周期依赖的散射变异、散射的周期性变异类型、用作描记风险区的大小。采用2、3、4triphenyltrazolium chloride(TTC)和专利蓝染料染色,以估测梗塞区的大小和梗塞风险区域。梗塞大小与可能梗塞区域的比率,由UTC和TTC确定,其相关良好(r=0.862,y=23.7±0.792x)。梗塞大小和风险区域的相关系数也较好(梗塞区r=0.736,y=12.3±0.737x,风险区r=0.714,y=5.80±1.012x)。然而,UTC低估了梗塞区和风险区的大小。结论:超声组织定征可以提供一个可行的、无创伤性的估测心肌梗塞大小的方法。     

等容收缩期心肌背向散射积分与灌注压和室壁厚度的关系

为研究心肌的室壁厚度与心肌灌注压分别对背向散射积分的影响,实验设计:在正常灌注的心肌组织,当室壁厚度的周期性变化降到最小时,测量心肌的背向散射。对9只分离的猪的心脏以血液灌注。灌注压不是由左室的压力产生,其等客收缩和舒张期,由左室内插入一只不可压缩的水囊来实现。第一个实验,灌注压恒定(85mmHg),背向散射积分(3～7MHz)、心肌壁厚度和左心室压同时由水囊的容积来决定(5～25ml)。水囊容量半静止地增加50％,室壁厚度平均增加6.5％(P<0.01),背向散射积分平均增加1.1dB(p<0.01)。室壁厚度每降低百分之一,背向散射显著增加0.14±0.014dB。于收缩末期心室壁厚度范围从-10％到+10％进行测量,平均0.15±4.5％(NS);心动周期背向散射积分的变异范围从-3.9到+3.9dB,平均0.19±1.5dB(NS)。第二个实验,于恒定的中等范围的水囊容量,用不同的灌注压(20～120mmHg)进行同样参数的测量,灌注压增加50％,引致的心肌壁增厚虽然小,但是有统计学意义的增加(1.5％)。此现象可用血管内容量增加来解释。但是,背向散射积分水平却无具有统计学意义的变化。收缩末期心肌壁增厚由-8.9到+7.8％,平均0.13±4.0％,而背向散射积分的周期性变化范围为-1.8至+4.2dB,平均0.37±1.3dB(NS)。当心肌的增厚被阻碍时,心肌组织心动周期     

超声组织定征的最近经验

最近,斯坦福大学医学中心研究室,试图用超声背向散射积分的周期性变异(CVIBS)参数,进行组织定征。主要是观察超声背向散射积分的周期性变化,而不是测定其绝对水平参数。观察者之间的重复性很好。一般而言,心室后壁的CVIBS的幅度较心室间隔的大。CVIBS的幅度与年龄有一定的关系。无并发症的压力负荷性心肌肥厚与肥厚型心肌病,其左心室后壁所测得的CVIBS都是相似的,然而,在室间隔肥厚组与正常比较,室间隔测值降低。对于人类的心肌排异反应,也用CVIBS进行了观察研究。于排异期间,CVIBS参数的幅度降低,与正常比较,其特征性显而易见。目前的各种超声组织定征的研究中,CVIBS在特定的研究中是成功的。     

生物组织光散射等效颗粒模型及Mie相函数计算

为研究生物组织的散射特性,将其从散射效果上等效为离散的球形散射体的集合,结合经典的Mie散射理论对生物组织散射相函数进行数值计算。计算结果表明:Mie散射相函数能够描述生物组织后向(大角度)散射光强振荡特性与等效粒径的对应关系,可为基于后向散射光的无创伤或微创伤诊疗提供理论依据;Mie散射相函数能够解释生物组织散射光空间分布与波长的相关性,为医学诊疗上入射光波长选择提供参考;合理选择集群散射体粒度分布参数,可实现对复杂生物组织散射相函数的精确描述。     

光声成像及其在生物医学中的应用

光声成像是一种新近迅速发展起来、基于生物组织内部光学吸收差异、以超声作媒介的无损生物光子成像方法,它结合了纯光学成像的高对比度特性和纯超声成像的高穿透深度特性的优点,以超声探测器探测光声波代替光学成像中的光子检测,从原理上避开了光学散射的影响,可以提供高对比度和高分辨率的组织影像,为研究生物组织的结构形态、生理特征、代谢功能、病理特征等提供了重要手段,在生物医学临床诊断以及在体组织结构和功能成像领域具有广泛的应用前景.对光声成像技术的机理、光声成像技术和方法、光声图像重建算法以及光声成像在生物医学上的应用情况作一个简单介绍,希望有助于推动我国在该领域的科研和开发应用工作的迅速发展.     

Mueller矩阵在生物医学检测方面应用的实验研究

Mueller矩阵是公认的能很好地表述介质偏振特性的一种方法,由于散射光偏振在生物组织无创伤诊断技术等诸多领域中的重要应用价值,对组织散射特性的Mueller矩阵的研究成为国际上组织光学的热点之一。研究设计了一种新的测量Mueller矩阵的实验装置:斜入射正接收装置,并推导出一组后续数据处理的算法。由此所获得的Mueller矩阵空间分布图的清晰度不亚于其它所报道的,并且测量方法具有结构简单、方便、准确等优点。实验结果表明:入射角影响Mueller矩阵空间分布图;随着介质浓度的增大,随机介质后向散射Mueller矩阵各元素的空间分布图样减小;同时列举了真实生物组织样品(肌肉组织)的后向散射Mueller矩阵的实测结果,由此证明各向异性生物组织的后向散射Mueller矩阵各元素的空间分布图样与纤维的走向有关。     

实验探索非靶组织光学参数对超声调制光的影响

生物组织是一种复杂的多层高散射介质,探索光在超声作用下的生物组织中的传播规律是超声调制光学成像术必须解决的一个基本问题,关系到最终进行图像处理与重建。通过实验探索超声调制光信号在双层和三层组织中的传播规律。实验结果表明非靶组织的光学属性（吸收系数和散射系数）和组织结构（单层或多层）都不影响超声调制光信号的调制深度。调制深度只与超声焦区介质（即靶组织）的声光属性有关,具有较佳的抗干扰性,适合用于图像重构。     

利用基于光学暗场反射测量的光学遥感技术探测飞行的农业害虫（英文）

【目的】本研究的目的是开发一种光学遥感技术实现在农田昼夜连续自动地监测农业害虫。【方法】一个望远镜通过对准远处的暗箱,得到一个低亮度水平的基线。当昆虫在望远镜的视野中飞过时,它散射的太阳光的光学信息就被连接到望远镜的记录系统采集到。在夜晚我们使用很强的灯光替代太阳光来照亮昆虫。【结果】昆虫计数、昆虫的振翅频率分析及反射光谱记录都获得成功。这表明使用暗场背向散射探测系统监测昆虫是可行的。手动释放的已知昆虫种类都具有独特的光谱特性。几种害虫特别是桃蛀螟Conogethes punctiferalis(Guenée)和短角异斑腿蝗Xenocatantops brachycerus(Willemse)都用本文描述的方法进行了成功识别。【结论】用暗场背向散射探测系统昼夜连续监测田间农业害虫是可行的。跟预期的一样,散射的振翅频率和光谱信息可以用来识别害虫。     

生物组织超声散射系数与温度相关性的研究

在随机起伏介质超声散射理论基础上,根据生物非均匀介质中声波动方程,推导出散射系数与温度的关系,然后分别采用了回波直接截取、经验模态分层（EDM）两种方法进行实验验证分析.结果表明超声散射系数与温度有依次递增的对应关系,可以运用它从超声回波信号中有效地提取组织温度信息.经验模态分层法的数据处理结果一致性要好些,总体趋势更接近理论分析.     

Ultrasound-biophysics mechanisms

Ultrasonic biophysics is the study of mechanisms responsible for how ultrasound and biological materials interact. Ultrasound-induced bioeffect or risk studies focus on issues related to the effects of ultrasound on biological materials. On the other hand, when biological materials affect the ultrasonic wave, this can be viewed as the basis for diagnostic ultrasound. Thus, an understanding of the interaction of ultrasound with tissue provides the scientific basis for image production and risk assessment. Relative to the bioeffect or risk studies, that is, the biophysical mechanisms by which ultrasound affects biological materials, ultrasound-induced bioeffects are generally separated into thermal and non-thermal mechanisms. Ultrasonic dosimetry is concerned with the quantitative determination of ultrasonic energy interaction with biological materials.

Whenever ultrasonic energy is propagated into an attenuating material such as tissue, the amplitude of the wave decreases with distance. This attenuation is due to either absorption or scattering. Absorption is a mechanism that represents that portion of ultrasonic wave that is converted into heat, and scattering can be thought of as that portion of the wave, which changes direction. Because the medium can absorb energy to produce heat, a temperature rise may occur as long as the rate of heat production is greater than the rate of heat removal. Current interest with thermally mediated ultrasound-induced bioeffects has focused on the thermal isoeffect concept. The non-thermal mechanism that has received the most attention is acoustically generated cavitation wherein ultrasonic energy by cavitation bubbles is concentrated. Acoustic cavitation, in a broad sense, refers to ultrasonically induced bubble activity occurring in a biological material that contains pre-existing gaseous inclusions. Cavitation-related mechanisms include radiation force, microstreaming, shock waves, free radicals, microjets and strain. It is more challenging to deduce the causes of mechanical effects in tissues that do not contain gas bodies. These ultrasonic biophysics mechanisms will be discussed in the context of diagnostic ultrasound exposure risk concerns.     

Ultrasound scatter-spacing based diagnosis of focal diseases of the liver

Ultrasound returns from liver shows periodicity arising from periodic scattering centers within tissue. Focal diseases such as tumors interrupt this structure. In this paper, we propose the use of a wavelet transform based technique to estimate the inter-scatterer-distribution (ISS) in diagnosing focal diaseases of the liver. The efficacy of the method is illustrated with simulated and clinical ultrasound images. The mean value (MSS) of the ISS has been proposed as a signature for focal diseases, but its effectiveness has not been established yet. We show that the ISS distribution may function as a feature to characterize focal diseases even when its mean value MSS fails. The method proposed in this paper works even when data is non-stationary.     

Kinetics of protein agglomeration. A nephelometric method for the determination of total protein in biological samples

The kinetics of agglomeration of proteins precipitating in a viscous solution was measured by light scattering. The resulting transitory maximum was linearly proportional to the mass of protein over three orders of magnitude. The change in scattering intensity is described as a change in scattering symmetry due to a continuous in particle size.This method is both fast (minutes) and sensitive (30 ng protein) and is independent of the chemical composition of the different protein species and is barely influenced by size and shape of the proteins.By solubilising the protein in an alkaline dedecyl sulfate solution this method can be applied to all types of biological samples (e.g. tissue homogenates proteins) and also to all types of biological preparations containing detergents as well as urea, sucrose, salts and lipids.     

肝脏超声图象局部分形指数研究

为了研究人体组织超声图象的局部特征,并为进行人体组织定征研究提供新的参数,提出了一个分析超声图象局部分形指数的新方法－局部分形指数小波分析法ＬＦＷＡＭ（ＬｏｃａｌＦｒａｃｔａｌＳｃａｌｅＷａｖｅｌｅｔＡｎａｌｙｓｉｓＭｅｔｈｏｄ）。应用此法研究了人体肝脏组织超声图象分形体的构造规则;进行了局部分形指数的分析。验证了ＬＦＷＡＭ法分析肝脏超声图象局部特性的有效性,得出了局部分形指数更能全面、细致地刻画肝脏组织超声图象分形特征的结论,为进而研究局部病变的识别与图象的分割提供了基础。     

Functional near infrared spectroscopy using spatially resolved data to account for tissue scattering: A numerical study and arm‐cuff experiment

Functional Near‐Infrared Spectroscopy (fNIRS) aims to recover changes in tissue optical parameters relating to tissue hemodynamics, to infer functional information in biological tissue. A widely‐used application of fNIRS relies on continuous wave (CW) methodology that utilizes multiple distance measurements on human head for study of brain health. The typical method used is spatially resolved spectroscopy (SRS), which is shown to recover tissue oxygenation index (TOI) based on gradient of light intensity measured between two detectors. However, this methodology does not account for tissue scattering which is often assumed. A new parameter recovery algorithm is developed, which directly recovers both the scattering parameter and scaled chromophore concentrations and hence TOI from the measured gradient of light‐attenuation at multiple wavelengths. It is shown through simulations that in comparison to conventional SRS which estimates cerebral TOI values with an error of ±12.3%, the proposed method provides more accurate estimate of TOI exhibiting an error of ±5.7% without any prior assumptions of tissue scatter, and can be easily implemented within CW fNIRS systems. Using an arm‐cuff experiment, the obtained TOI using the proposed method is shown to provide a higher and more realistic value as compared to utilizing any prior assumptions of tissue scatter.