Molecular structure dependence of acoustic nonlinearity parameter B/A for silicone oils

Exploring new acoustic parameters is essential to develop a noninvasive imaging technique for the surgery of silicone oil tamponades. In this study, the acoustic nonlinearity parameters B/A of varied silicone oil samples （e.g., linear or hyper-branched） are experimentally measured by using a modified thermodynamic method. The results show that： （i） when the concentration of the silicone oil with a molecular weight of 5 × 10^4 increases from 0.5 g/100 ml to 8 g/100 ml, the corresponding B/A value increases by about 18%, but the acoustic velocity only increases by about 0.1%; （ii） when the molecular weight of the hyper-branched silicone oil is enhanced from 2 × 10^5 to 1 × 10^6, the B/A value increases by about 22%, while the acoustic velocity is only raised by about 0.2%. This study suggests that the B/A parameter of the silicone oil is more sensitive to the change in its molecular structure than that of the acoustic velocity. Thus, the B/A parameter might be utilized as an effective index for the development and optimization of the noninvasive imaging of the surgery of silicone oil tamponades.

Study on Noninvasive Temperature Measurement in Biological Media Using Ultrasonic Nonlinear Parameter B/A

Application of the temperature dependence of ultrasound nonlinear parameter B/A can realize noninvasive temperature measurement in biological media. The principle of temperature measurement is described and an experiment system is set up. The experiments for measuring the nonlinear parameter B/A and estimating their temperature dependences in tested media are described. Preliminary experiment results are presented.

A semi-analytical method to compute acoustic nonlinearity parameter of Cu,Ag and Au

In this paper,a semi-analytical method was proposed to evaluate the acoustic nonlinearity parameter for single crystals of Cu,Ag and Au.The acoustic nonlinearity parameter can be derived analytically by general expressions in terms of the interatomic potentials with the distances between each pair of atoms in these transition metals.To evaluate the acoustic nonlinearity parameter,one needs to conduct one step molecular static simulation and obtain the equilibrium positions of all the atoms.Further,based on this method,numerical experiments with molecular dynamic code LAMMPS were given to compute the acoustic nonlinearity parameter of Cu,Ag and Au.To illustrate the validity of these expressions,comparison was made between calculation results and data in the literature.Reasonable agreement is observed.Because of the analytical nature of this method,it provides a fundamental understanding of the nonlinear elastic behavior of these transition metals.

Computation of the acoustic nonlinearity parameter in organic liquid binary mixtures

Based on Jacobson’s molecular free length theory in liquids and the relationship between the ultrasonic velocity and the molecular free length in organic liquids, the equation of the acoustic nonlinearity parameter in organic liquid binary mixtures is derived. The calculated values from the equation are in good agreement both with those from Apfel’s and from Sehgal’s mixture laws.

Relationship between the temperature and the acoustic nonlinearity parameter in biological tissues

Recently with the rapid development of the high-intensity focused ultrasound (HIFU) in biomedical ul- trasound, much attention has been paid to the noninvasive temperature estimation in biological tissue in order to de- termine the region and degree of the ultrasound-induced lesions. In ultrasound hyperthermal therapy it is highly de- sirable to study the real-time noninvasive monitoring of temperature distribution in biological tissue. In this paper, the relationship between the nonlinearity parameter B/A and the temperature in biological tissue is studied and compared with the theoretical model as well as the experimental results from the thermocouple. Results indicated that B/A could be used as an effective tool to monitor the temperature distribu- tion in biological media.

Nonlinearity acoustic parameter B/A in organic liquids

Based on Jacobson's free length theory and the dependence of ultrasonic velocity on the free length in organic liquids, the equation of nonlinearity acoustic parameter B/A was given, and the calculated nonlinearity acoustic parameter B/A in some organic liquids are in good agreement with the measured results.

Computed tomography of the acoustic nonlinearity parameter B/A for biological tissues via difference frequency wave from a parametric array in reflection mode

Based on the finite amplitude insert-substitu- tion method, a novel technique to reconstruct the acoustic nonlinear parameter B/A tomography for biological tissues in reflection mode via the difference frequency wave generated by a parametric array is developed in this paper. An experimental system is established, and the beam pattern of the difference frequency wave is measured and compared with that excited directly from a transmitter at the same frequency. B/A tomography for several biological tissues including normal and pathological tissues, is experimentally obtained with satisfying quality. Results indicate that B/A imaging using this mode may become a novel modality in ultrasonic diagnosis.

Measurement of the acoustic nonlinearity parameter BIA of lossy medium in a focused field

An analytical description for the linear and nonlinear acoustic fields in lossy medium of a focusing source is derived. The relationship of pressure amplitudes at focus for fundamental and the second harmonic waves is discussed. At high linear focusing gain G, a new method using the insert substitution method for measuring the acoustic nonlinear parameter BIA of biological tissues is presented. Results for some biological tissues are experimentally obtained.

INVESTIGATION OF ACOUSTIC NONLINEARITY PARAMETER B/A IN BIOLOGICAL MEDIA USING PHASE SHIFT METHOD

I. INTRODUCTION It has become a very important subject to investigate the acoustic nonlinearity parameter B/A in biological media since 1980. Experimental evidence indicates that there are nonlinear phenomena under biological frequencies and intensities. B/A is one of the ba-

STUDY OF THE ACOUSTIC NONLINEARITY PARAMETER B/A IN BINARY BIOLOGICAL MIXTURE

I. INSTRUCTIONThe study of the acoustic nonlinearity parameter B/A in the biological medium has been of the basic importance and has been treated as the frontier in the field of biomedical acoustics since 1980 when the nonlinear acoustic effects were found in that area. In those years, the measurement of B/A shows that B/A value varies with the physical,

The influence of molecular structure of protein on the acoustic nonlinearity parameter B/A

In this paper, the influence of molecular structure of proteins on the acoustic non-linearity parameter B/A has been studied. By using biochemical technique, three proteins such as bovine serum albumin, bovine hemoglobin and pepsin were employed and their quarternary,tertiary and secondary protein structures were perturbed by the denaturing agent sodium do-decyl sulfate (SDS) solution, while their primary structures of protein were not changed. This means that only the structural features were altered and the chemical composition maintained unchanged. B/A has been measured by using improved thermodynamic method. The experi-mental results show that when the concentration of SDS solution increases, the alterations of the protein structure increase, and the contribution of protein to the B/A value decreases. Re-sults indicate that the B/A values can display the destruction of molecular structure of protein.Some explanation of these phenomena has also been made in this paper.

Acoustic Nonlinearity Parameters Due to Microstructural Defects

This study presents a general approach to derive the acoustic nonlinearity parameters induced by various types of dislocation configurations including dislocation strings （monopoles）, dislocation dipoles, dislocation pileups and extended dislocations. It is found that expressions of the acoustic nonlinearity parameter induced by such a variety of dislocation con- figurations share a common mathematical form. They are all scaled with （Lch/b）n, where Lch is a characteristic length of the dislocation configuration, b is the magnitude of the Burgers vector, and n is either 3 or 4. Semiquantitative analysis is presented to compare the magnitudes of the acoustic nonlinearity parameters among different types of dislocation configurations.

用双超声脉冲法测量生物介质的非线性参数B/A

利用生物介质的超声非线性参数B A与温度的相关性可实现超声无创测温 ,本文介绍了一种用双超声脉冲法测量介质非线性参数B A的方法。这种方法是把探测波叠加在泵波之上 ,利用这两个波的非线性作用来测出参数B A。实验结果表明该方法切实可行 ,能准确地测得参数B A ,为实现高质量的超声无损伤测温提供了可能。

高频聚焦超声声场和温度场的仿真研究

为探究临床常用的7 MHz高频聚焦超声在多层生物组织中的声传播以及毫秒级时间内的生物传热规律问题,基于Westervelt方程和Pennes传热方程,使用有限元方法建立高频聚焦超声辐照多层组织的非线性热黏性声传播及传热模型。首先分析了线性模型和非线性模型之间的差异,然后在非线性模型下探究换能器的参数对声场和温度场的影响。仿真结果显示:在7 MHz频率下,当换能器输出声功率超过5 W时,声波传播的非线性效应不可忽视(p<0.05);当声功率从5 W增大到15 W时,非线性模型与线性模型预测的温度偏差从20%增加到34.703%;高频聚焦超声波的非线性行为比低频更加显著,基频能量向高次谐波转移的程度增大,声功率为10 W和15 W时4次谐波与基波之比分别达到7.33%和12.12%;高频换能器参数的改变对组织中声场和温度场分布的影响较大,换能器焦距从12 mm减小到11.2 mm,焦点处最高温度增加了77%。结果表明,7 MHz聚焦超声的非线性声传播需要考虑到4次谐波的影响。该文提出的多层组织非线性仿真模型可为高频聚焦超声换能器参数优化及制定安全、有效的术前治疗方案提供理论参考。

多元有机混合液声速特性与非线性声参量B/A的数值计算

根据Jacobson的液体分子自由程理论和液体声速与分子自由程的关系 ,推导出多元有机混合液声速的温度系数、压力系数和非线性声参量B/A的计算公式 ,并根据组成多元有机混合液各组分特性参量 (密度、自由程、非线性声参量B/A、等压膨胀系数、等温压缩系数等 ) ,利用给出的公式对声速的温度系数、压力系数、非线性声参量B/A进行了数值计算 ,并将计算结果与实验结果进行了比较 .

猪软组织的非线性声参量B／A和声速C研究

本文研究报道了五种猪软组织中非线性声参量Ｂ／Ａ和声速Ｃ与组织成份间的依赖关系。结果表明：该组织中上述参量与组织所含水份、脂肪、蛋白质的多少有密切关系，它们随组份含量变化的趋势基本上与Ｓｅｈｇａｌ、Ａｐｆｅｌ的声参量混合定则相一致。但Ｓｅｈｇａｌ、Ａｐｆｅｌ定则理论值与实测结果还有一定距离。

利用非线性参量B／A研究SDS水溶液液——固相变

报导了利用非线性参量Ｂ／Ａ研究ＳＤＳ水溶液随温度变化时发生液—固相变的情况，首次发现ＳＤＳ水溶液在发生液——固相变时Ｂ／Ａ随温度变化规律反常，这说明Ｂ／Ａ不仅能反映物质结构的变化。

非线性参量B/A超声成像的仿真与仿体实验研究

非线性参量 B/A是描述生物组织非线性效应的重要参量，其对组织特性的敏感度较线性参量高出1～2个数量级。将非线性参量 B/A用于生物组织成像，更有利于组织定征与医学超声诊断。目前已有的 B/A成像效果大多依赖于 B/A测量技术的准确性。为了获取较好的 B/A成像，通过仿真与仿体实验比较了有限振幅声波法测量非线性参量B/A 的几种经典方法，仿真和仿体实验结果均表明：扩展比较法（Extended Comparative Method, ECM）测量准确性高，其测量误差低于3%。运用该方法结合滤波反投影仿真实现 B/A 参量层析成像，成像结果能较好描述简单组织中的B/A参量分布。

Ultrasonic study on organic liquid and binary organic liquid mixtures by using Schaaffs＇ collision factor theory

Based on Schaaff＇s collision factor theory （CFT） in liquids, the equations for nonlinear ultrasonic parameters in both organic liquid and binary organic liquid mixtures are deduced. The nonlinear ultrasonic parameters, including pressure coefficient, temperature coefficients of ultrasonic velocity, and nonlinear acoustic parameter B/A in both organic liquid and binary organic liquid mixtures, are evaluated for comparison with the measured results and data from other sources. The equations show that the coefficient of ultrasonic velocity and nonlinear acoustic parameter B/A are closely related to molecular interactions. These nonlinear ultrasonic parameters reflect some information of internal structure and outside status of the medium or mixtures. From the exponent of repulsive forces of the molecules, several thermodynamic parameters, pressure and temperature of the medium, the nonlinear ultrasonic parameters and ultrasonic nature of the medium can be evaluated. When evaluating and studying nonlinear acoustic parameter B/A of binary organic liquid mixtures, there is no need to know the nonlinear acoustic parameter B/A of the components. Obviously, the equation reveals the connection between the nonlinear ultrasonic nature and internal structure and outside status of the mixtures more directly and distinctly than traditional mixture law for B/A, e.g. Apfel＇s and Sehgal＇s laws for liquid binary mixtures.

基于自适应增益补偿的B/A成像方法

非线性参量B/A是超声波在介质传播过程中非线性效应大小的度量,利用B/A实现超声新参量成像具有良好的应用前景。目前的超声医学诊断大多是依赖于RF回波信号,因此RF回波信号下的扩展比较法(ECM)为B/A成像的临床应用提供了可能。本文研究RF回波信号下的B/A成像,利用自适应时间增益补偿技术补偿声波在组织中的衰减,简化拓展比较法(ECM),仿真与仿体实验表明该方法成像结果较好且操作简单。