Sound speed uncertainty in Acousto-Electric Tomography

The goal in Acousto-Electric Tomography (AET) is to reconstruct an image of the unknown electric conductivity inside an object from boundary measurements of electrostatic currents and voltages collected while the object is penetrated by propagating ultrasound waves. This problem is a coupled-physics inverse problem. Accurate knowledge of the propagating ultrasound wave is usually assumed and required, but in practice tracking the propagating wave is hard due to inexact knowledge of the interior acoustic properties of the object. In this work, we model uncertainty in the sound speed of the acoustic wave, and formulate a suitable reconstruction method for the interior power density and conductivity. We also establish theoretical error bounds, and show that the suggested approach can be understood as a regularization strategy for the inverse problem. Finally, we numerically simulate the sound speed variations from a numerical breast tissue model, and computationally explore the effect of using an inaccurate sound speed on the error in reconstructions. Our results show that with reasonable uncertainty in the sound speed reliable reconstruction is still possible.

On the modeling of ultrasound wave propagation in the frame of inverse problem solution

In this paper we consider the inverse problem of detecting the inclusions inside the human tissue by using the acoustic sounding wave. The problem is considered in the form of coefficient inverse problem for first-order system of PDE and we use the gradient descent approach to recover the coefficients of that system. The important part of the sceme is the solution of the direct and adjoint problem on each iteration of the descent. We consider two finite-volume methods of solving the direct problem and study their Influence on the performance of recovering the coefficients.

On the question of finding a universal mechanism for the transmission of sound wave energy in iron during heating and deformation

The paper presents a theoretical analysis of the experimental data on the ultrasound speed change in iron during heating and elastic deformation. The mathematical models proposed for assessing the change in the ultrasound speed based on the “adiabatic approximation” method do not explain, using one model, the change in the ultrasound speed in iron during heating and elastic deformation. During theoretical analysis, a new model of ultrasound wave transmission has been proposed, in which the wave energy propagates in the volume of the interatomic bond, namely in the loop, which is formed by the “collectivization” of valence electrons located in the outer orbit of atoms. The new model explains why with an increase in the interatomic distance a, the crystal lattice parameter, and an increase in the natural vibration frequency of atoms Vat during heating and elastic deformation, in one case (heating), the speed of the sound wave decreases, but in the other case (elastic deformation), the speed of the wave increases with a general decrease in the temperature of the rod.

Physical Alteration and Color Change of Granite Subjected to High Temperature

Cylindrical specimens obtained from the monzogranite host rock of the National Radioactive Waste Repository of Hungary were tested at room temperature and 250 °C, 500 °C, and 750 °C of heat treatment. Reflectance spectra (color), bulk density, Duroskop surface hardness, and ultrasound-wave velocity values were measures before and after thermal stress. According to CIE L*a*b* colorimetric characteristics, the specimens’ color became brighter and yellower after the heat treatment. At 750 °C, a significant volume increase was recorded linked to the formation of macro-cracks, and it also led to the drop in bulk density. Smaller temperature treatment (250 °C) caused a minor decrease in density (−1.3%), which is higher than the reduction of density at 500 °C (−0.8%). Duroskop surface strength showed a slight decrease until 500 °C, and then a drastic decline at 750 °C. P- and S-wave velocity values tend to decrease uniformly and significantly from room temperature to 750 °C. P-wave velocity and Duroskop values have a high exponential correlation at elevated temperatures. Physical alterations originated from the differential thermal-induced expansion of minerals, the formation of micro-cracks. Mineralogical changes at higher temperatures also contribute to the volume change and the loss in strength.

Quantitative ultrasound imaging of soft biological tissues: a primer for radiologists and medical physicists

Quantitative ultrasound (QUS) aims at quantifying interactions between ultrasound and biological tissues. QUS techniques extract fundamental physical properties of tissues based on interactions between ultrasound waves and tissue microstructure. These techniques provide quantitative information on sub-resolution properties that are not visible on grayscale (B-mode) imaging. Quantitative data may be represented either as a global measurement or as parametric maps overlaid on B-mode images. Recently, major ultrasound manufacturers have released speed of sound, attenuation, and backscatter packages for tissue characterization and imaging. Established and emerging clinical applications are currently limited and include liver fibrosis staging, liver steatosis grading, and breast cancer characterization. On the other hand, most biological tissues have been studied using experimental QUS methods, and quantitative datasets are available in the literature. This educational review addresses the general topic of biological soft tissue characterization using QUS, with a focus on disseminating technical concepts for clinicians and specialized QUS materials for medical physicists. Advanced but simplified technical descriptions are also provided in separate subsections identified as such. To understand QUS methods, this article reviews types of ultrasound waves, basic concepts of ultrasound wave propagation, ultrasound image formation, point spread function, constructive and destructive wave interferences, radiofrequency data processing, and a summary of different imaging modes. For each major QUS technique, topics include: concept, illustrations, clinical examples, pitfalls, and future directions.

Sintering behavior and physical properties of Bi0.5(Na1–xKx)0.5SnO3 lead-free ceramics

In this study, Bi0.5(Na1–xKx)0.5SnO3 (BNKS) ceramics (x = 0, 0.1, 0.2, 0.3, and 0.4) were fabricated via ultrasound wave before milling. The time of ball milling decreased from 20 to 1 h. The X-ray diffraction patterns show that the BNKS has a single-phase structure. When the potassium content increases, the phase structure of the ceramics changes from rhombohedral to tetragonal. When sintered at 1100 °C and x = 0.2, the ceramics’ physical properties are the best with the mass density of 5.59 g/cm3, the electromechanical coupling constants kp of 0,31 and kt of 0.27, the remanent polarization of 11.9 µC/cm; the dielectric constant εr of 1131, and the highest dielectric constant emax of 4800.

Ultrasonic dyeing of wool fabric with aqueous extract of Ratanjot (Onosma echioides) natural dye

The purpose of this study is to compare the conventional and ultrasonic dyeing methods in terms of its colour strength and colour fastness properties of wool fabric dyed with Ratanjot root. The results suggested that dyeing of wool fabric with natural dye Ratanjot (Onosma echioides) using ultrasonic waves, significantly improved the dye uptake percentage to 12.31 per cent from conventional heating methods. The fastness grade were found to be higher with ultrasonic than conventional heating. Additionally, the fabric dyed using ultrasonic waves gave a deeper shade and good colour intensity even at lower dyeing time (75min) and temperature (60°C). Therefore, ultrasound wave represents a promising technique for increasing diffusion of dye by the effect of cavitation, as well as for improving the effectiveness of processes when compared to conventional heating