Ultrasonic Reflection Research Articles

Ultrasonic reflection imaging with a heterogeneous background for breast cancer detection and diagnosis

Sound speeds and densities of breast tissue vary in space, and those of tumors are different from the surrounding tissues. These differences in mechanical properties cause scattering of ultrasonic waves, particularly in dense breasts. An ultrasonic reflection imaging method using a heterogeneous background is presented to properly account for scattering off heterogeneities within the breast. The method is based on downward continuation of ultrasonic wave fields in the frequency‐space and frequency‐wave‐number domains. Synthetic ultrasonic data for scatterers within a heterogeneous breast model were used to investigate the imaging resolution of the method. Imaging examples using ultrasonic data acquired using a clinical prototype, consisting of an ultrasound scanner with a ring transducer array, are presented. The heterogeneous background sound‐speed models were obtained using transmission tomography. The imaging results are compared with those obtained using a homogeneous background. The study demonstrate...

Nondestructive Determination of Ply-Layup Error in Cured/Uncured CF/Epoxy Composites

A nondestructive technique would be very beneficial, which could be used to test the part before (uncured) and after curing CF/Epoxy. A new method for nondestructively determining the ply layup in a composite laminate is presented. The method employs a normal-incidence longitudinal ultrasound to perform C-scan of ply interfaces of the laminate, and extracts fiber orientation information from the ultrasonic reflection in the laminate. Using two-dimensional spatial Fourier transform, interface C-scan images were transformed into quantitatively angular distribution plots to show the fiber orientation information therein and to determine the orientation of the ply. In order to develop these methods into practical inspection tools, an automated system using a motor has been developed for different measurement modalities for acquiring ultrasonic effects of ply-layup error. Therefore, it is found that the efficiency of developed system shows between the practical testing and model in characterizing cured/uncured ply-layup error of the laminates. A C-scan image of a ply interface seem to have the ply-layup error information of the two neighboring plies of CF/Epoxy composite laminates.

In situ monitoring of the growth of ice films by laser picosecond acoustics

Ultrashort optical pulses are used to excite and probe picosecond acoustic pulses in a sample consisting of an opaque material upon which ice is continuously deposited from the vapor phase at ∼110K. By analysis of the ultrasonic propagation and reflection inside the submicron ice film and taking into account the scattering of the probe light by the acoustic waves, the thickness, sound velocity, refractive index, ultrasonic attenuation, and photoelastic constant of the ice film are derived. This method should find applications for the in situ monitoring of thin transparent films during growth.

Wavelet-based deconvolution of ultrasonic signals in nondestructive evaluation

In this paper, the inverse problem of reconstructing reflectivity function of a medium is examined within a blind deconvolution framework. The ultrasound pulse is estimated using higher-order statistics, and Wiener filter is used to obtain the ultrasonic reflectivity function through wavelet-based models. A new approach to the parameter estimation of the inverse filtering step is proposed in the nondestructive evaluation field, which is based on the theory of Fourier-Wavelet regularized deconvolution (ForWaRD). This new approach can be viewed as a solution to the open problem of adaptation of the ForWaRD framework to perform the convolution kernel estimation and deconvolution interdependently. The results indicate stable solutions of the estimated pulse and an improvement in the radio-frequency (RF) signal taking into account its signal-to-noise ratio (SNR) and axial resolution. Simulations and experiments showed that the proposed approach can provide robust and optimal estimates of the reflectivity function.

The interaction of oblique incidence ultrasound with rough, partially contacting interfaces

The ultrasonic reflection coefficients of solid–solid interfaces, such as those found in fatigue cracks, are known to be a function of the compressive load. In this paper, the combined effects of crack face roughness and closure on ultrasonic detectability at oblique incidence are considered. Experimental results are described in which the pitch–catch reflection coefficients of compressively loaded steel–steel interfaces were measured over a range of frequencies (2–24 MHz) at both 45 and 60° incident angles. The results obtained are compared with quasi-static spring model predictions and the limitations of this model discussed. For the surfaces considered (R a ≈ 4 μm), the spring model was shown to be in agreement only at the lower end of the considered frequency range (i.e. 2–3 MHz).

Characterisation of IC packaging interfaces and loading effects

In IC packaging, the quality of the interfaces such as that between mold compound and silicon is a critical issue in the reliability testing during the manufacturing process and in-service. Weak interfaces have often gone undetected and may become potentially defective at a later stage. Furthermore, the stress due to mechanical or thermal loading may further deteriorate the interface quality, making the interface unreliable. There is a desire to study the interface quality quantitatively, so potential defects can be evaluated and identified early. In this paper, finite element analysis using multilayer interface model is used to study the reflection coefficient from the interface of varying quality. Different conditioning techniques were used to degrade the interface quality. Characterisation of the interface quality of the MC/Si interface was conducted using longitudinal ultrasonic wave propagation with contact transducers. A combined test that measures the reflection coefficient of the interface under stress load was also conducted to quantify the effect of the load. A nondestructive evaluation methodology is proposed that measures the available strength of the interface by using ultrasonic reflection coefficients, and it shows the correlation between the reflection coefficient and available strength of the interface can be developed and used as a quantitative indicator.

A theoretical analysis in the time-domain of wave reflection on a bone plate

This paper presents an original method for simulating ultrasonic wave reflection on a fluid-loaded plate. Geometrical and material parameters used are relevant to the “axial transmission technique” (ATT) setup. Devices based on the ATT are used for the assessment of cortical bone strength (estimate of a fracture risk). In this work, the cortical bone layer is represented as a plate of infinite extent surrounded by fluid (soft tissues). A line source and a receiver are placed in the fluid. Transient waves generated upon reflection at the plate–fluid interfaces are addressed. Analytic Green's functions are derived with the generalized ray/Cagniard-de Hoop method. The acoustic response is obtained upon convolution of Green's functions with a given source pulse. The method associates each wave amplitude in the time-domain (lateral waves, reflected body waves, etc.) to a specific term of the final solution. The method is ideally suited to a detailed analysis of the ultrasonic signal for various geometrical and mechanical parameters. The results presented highlight the potential of the method for the understanding of wave phenomena involved in the ATT and similar setups. They also bring new elements that reinforce our theoretical knowledge of the ATT.

Early textural and functional alterations of left ventricular myocardium in mild hypothyroidism

The aim of the present study was to evaluate cardiac function and texture in patients with subclinical hypothyroidism (sHT) both by conventional and new ultrasonic intramyocardial tissue techniques. sHT was characterized by normal serum free tetraiodotironine and free triiodotironine levels and slightly increased serum TSH level. Twenty-four patients affected by sHT and 24 sex- and age-matched healthy volunteers were studied. All subjects were submitted to conventional two-dimensional (2D)-color Doppler echocardiography, pulsed wave tissue Doppler imaging (PWTDI) for the analysis of the diastolic function, color Doppler myocardial imaging (CDMI) for the analysis of regional strain and strain-rate and integrated backscatter (IBS) for the evaluation of intrinsic contractility and tissue characterization. The results of the present study were: (a) the detection in sHT subjects of a lower cyclic variation index (CVI) indicating an altered myocardial intrinsic contractility; (b) a higher ultrasonic myocardial reflectivity indicating an altered myocardial texture; (c) the detection of lower systolic strain and strain-rate indicating an alteration of myocardial regional deformability; (d) an initial impairment of left ventricular diastolic function indicated by a decrease of peak E mitral flow velocity and an increase of peak A mitral flow velocity. All parameters studied with conventional 2D-echo in sHT patients were comparable with controls, except for a mild alteration in diastolic function. A significant correlation among systo-diastolic modifications detected by CDMI and IBS and serum TSH levels were found. The CVI at septum, the PWDTI S-peak wave and the systolic strain at septum were inversely related to the serum TSH levels. In conclusion, the new intramyocardial ultrasonic techniques confirm and extend the previous knowledge on the effect of the sHT on the heart, allowing the detection of early ultrastructural and regional functional systolic and diastolic abnormalities.

Ultrasonic model and system for measurement of corneal biomechanical properties and validation on phantoms

Non-invasive measurement of biomechanical properties of corneas may provide important information for ocular disease management and therapeutic procedures. An ultrasonic non-destructive evaluation method with a wave propagation model was developed to determine corneal biomechanical properties in vivo. In this study, we tested the feasibility of the approach in differentiating the mechanical properties of soft contact lenses as corneal phantoms. Three material types of soft contact lenses (six samples in each group) were measured using a broadband ultrasound transducer. The ultrasonic reflections from the contact lenses were recorded by a 500 MHz/8-bit digitizer, and displayed and processed by a PC. A reference signal was recorded to compute the normalized power spectra using Fast Fourier Transformation. An inverse algorithm based on least-squares minimization was used to reconstruct three parameters of the contact lenses: density, thickness, and elastic constants λ+2 μ. The thickness of each sample was verified using an electronic thickness gauge, and the averaged density for each type of lenses was verified using Archimedes’ principle and manufacturer's report. Our results demonstrated that the ultrasonic system was able to differentiate the elastic properties of the three types of the soft contact lenses with statistical significance ( P-value<0.001). The reconstructed thicknesses and densities agreed well with the independent measurements. Our studies on corneal phantoms indicated that the ultrasonic system was sensitive and accurate in measuring the material properties of cornea-like structures. It is important to optimize the system for in vivo measurements.

Evaluation of contact conditions in hot forging of pure aluminum using ultrasonic examination

In isothermal upset forging of pure aluminum, the change in the contact condition and the lubricant behavior were evaluated by continuously measuring the ultrasonic reflection intensity from the contact interface between the tool (die) and workpiece. The relationships between ultrasonic reflection intensity, forging temperature, lubrication, forging pressure and workpiece surface during forging were examined. Depending on forging temperature, the conditions of the lubricant entrapment on the surface of the workpiece exhibited significant changes. The condition of lubricant pools and lubricant film was evaluated during warm and hot forging using the ultrasonic reflection intensity. The change in the contact condition and the lubricant behavior during warm and hot forging were measured with high sensitivity by the proposed ultrasonic measurement. The lubrication conditions can be optimized based on the in situ evaluation of the contact conditions.

Nanoparticles as image enhancing agents for ultrasonography

Nanoparticles have drawn great attention as targeted imaging and/or therapeutic agents. The small size of the nanoparticles allows them to target cells that are beyond capillary vasculature, such as cancer cells. We investigated the effect of solid nanoparticles for enhancing ultrasonic grey scale images in tissue phantoms and mouse livers in vivo. Silica nanospheres (100 nm) were dispersed in agarose at 1–2.5% mass concentration and imaged by a high-resolution ultrasound imaging system (transducer centre frequency: 30 MHz). Polystyrene particles of different sizes (500–3000 nm) and concentrations (0.13–0.75% mass) were similarly dispersed in agarose and imaged. Mice were injected intravenously with nanoparticle suspensions in saline. B-mode images of the livers were acquired at different time points after particle injection. An automated computer program was used to quantify the grey scale changes. Ultrasonic reflections were observed from nanoparticle suspensions in agarose gels. The image brightness, i.e., mean grey scale level, increased with particle size and concentration. The mean grey scale of mouse livers also increased following particle administration. These results indicated that it is feasible to use solid nanoparticles as contrast enhancing agents for ultrasonic imaging.

Comparison of ultrasonic wave reflection method and maturity method in evaluating early-age compressive strength of mortar

Abstract This paper focuses on the comparison between the ultrasonic wave reflection method and the widely known maturity method in their ability to evaluate compressive strength development of portland cement mortars. The experiments were conducted under laboratory conditions on cement mortars with different water–cement ratios (0.35, 0.5, 0.6) cured under different isothermal and non-isothermal conditions (15 °C, 25 °C, 35 °C, 15–35 °C). The results show that the application of the maturity method for accurate strength estimation requires the knowledge of the limiting strength of the mixture for the specific curing condition that is considered. It is not sufficient to base this estimation on the values of the limiting strength obtained from the calibration tests. The relationship between reflection loss and compressive strength was found to be independent of curing temperature. This finding is an important step towards establishing the wave reflection method as a non-destructive method for estimating early-age strength in cement-based materials.

Experimental Characterization of Wheel-Rail Contact Patch Evolution

The contact area and pressure distribution in a wheel/rail contact is essential information required in any fatigue or wear calculations to determine design life, re-grinding, and maintenance schedules. As wheel or rail wear or surface damage takes place the contact patch size and shape will change. This leads to a redistribution of the contact stresses. The aim of this work was to use ultrasound to nondestructively quantify the stress distribution in new, worn, and damaged wheel-rail contacts. The response of a wheel/rail interface to an ultrasonic wave can be modeled as a spring. If the contact pressure is high the interface is very stiff, with few air gaps, and allows the transmission of an ultrasonic sound wave. If the pressure is low, interfacial stiffness is lower and almost all the ultrasound is reflected. A quasistatic spring model was used to determine maps of contact stiffness from wheel/rail ultrasonic reflection data. Pressure was then determined using a parallel calibration experiment. Three different contacts were investigated; those resulting from unused, worn, and sand damaged wheel and rail specimens. Measured contact pressure distributions are compared to those determined using elastic analytical and numerical elastic-plastic solutions. Unused as-machined contact surfaces had similar contact areas to predicted elastic Hertzian solutions. However, within the contact patch, the numerical models better reproduced the stress distribution, as they incorporated real surface roughness effects. The worn surfaces were smoother and more conformal, resulting in a larger contact patch and lower contact stress. Sand damaged surfaces were extremely rough and resulted in highly fragmented contact regions and high local contact stress.

Monitoring of Lubricant Film Failure in a Ball Bearing Using Ultrasound

A lubricant-film monitoring system for a conventional deep groove ball bearing (type 6016, shaft diameter 80 mm, ball diameter 12.7 mm) is described. A high-frequency (50 MHz) ultrasonic transducer is mounted on the static outer raceway of the bearing. The transducer is focused on the ball-raceway interface and used to measure the reflection coefficient of the lubricant in the “contact” ellipse between bearing components. The reflection coefficient characterizes the lubricant film and can be used to calculate its thickness. An accurate triggering system enables multiple reflection measurements to be made as each lubricated contact moves past the measurement location. Experiments are described in which bearings were deliberately caused to fail by the addition of acetone, water, and sand to the lubricant. The ultrasonic reflection coefficient was monitored as a function of time as the failure occurred. Also monitored were the more standard parameters, temperature and vibration. The results indicate that the ultrasonic measurements are able to detect the failures before seizure. It is also observed that, when used in parallel, these monitoring techniques offer the potential to diagnose the failure mechanism and hence improve predictions of remaining life.

Impact of Environmental Temperature on Skin Thickness and Microvascular Blood Flow in Subjects With and Without Diabetes

Glucose measurement from different skin areas might be influenced by changes in skin texture due to several environmental confounders. Our study was performed to investigate the effect of changes in ambient temperature on skin thickness and microvascular skin blood flow in subjects with and without diabetes at the lower forearm. Thirteen subjects with diabetes and seven without diabetes participated in the study. The investigations were performed in a temperature- and humidity-controlled climatic chamber (EMPA, St. Gallen, Switzerland). Starting at 25 degrees C, the environmental temperature was changed in 4 degrees C steps every 40 min. Skin thickness was measured by an ultrasonic reflection technique, and microcirculation was measured by laser Doppler fluxmetry at the lower forearm. Study participants underwent the entire procedure on up to four separate study trials. Our study revealed a significantly reduced skin thickness (P<0.05) and microvascular blood flow (P<0.05) in patients with diabetes mellitus compared with controls without diabetes during the entire investigation. During declining ambient temperature a significant reduction in skin thickness (with diabetes, -0.09+/-0.13 mm; without diabetes, -0.06+/-0.11 mm; P<0.05) and microvascular blood flow (with diabetes, -41+/-49 arbitrary units; without diabetes, -46+/-51 arbitrary units; P<0.05) could be observed in both groups without significant differences between the two. Although skin thickness and microvascular skin blood flow at the lower forearm were found to be reduced in patients with diabetes compared with controls without diabetes, both groups revealed comparable dynamics in skin thickness and microvascular blood flow during changes in environmental temperature.

Evaluation of Low Cycle Fatigue Damage Evolution in Stainless Steel Using Scanning Acoustic Microscope

The objective of present study is to develop a prediction method of residual fatigue crack initiation life of cyclically loaded metallic materials in early stage of its life. Measurements were conducted on a change of intensity of ultrasonic back reflection wave from the material surface under cyclic loading. The microscopic surface observations using optical microscope and atomic-force microscope were also conducted to examine the relation of the change to a fatigue damage of the material. An decrease of the ultrasonic back reflection intensity occurred due to the evolution of fatigue damage at the slip bands. This technique enables one to evaluate the remaining life to the initiation period of fatigue crack at a number of cycles.

Ultrasound attenuation behind coronary atheroma without calcification: Mechanism revealed by autopsy

When performing intravascular ultrasound studies, the backward echo image can show marked attenuation, although there are no calcified deposits and it may be impossible to detect the intraplaque architecture. The pathology underlying this phenomenon was investigated in autopsy specimens. We hypothesize that the mechanism responsible for the attenuation involves micro-calcification and lipid in unstable plaques causing ultrasonic wave reflection and dispersion.

超音波反射エコーを用いた地下水3次元流向・流速測定のための安定浮遊固体トレーサの開発

超音波反射エコーを用いた地下水3次元流向・流速測定のための安定浮遊固体トレーサの開発

An improved acoustic microimaging technique with learning overcomplete representation

Advancements in integrated circuit (IC) package technology are increasingly leading to size shrinkage of modern microelectronic packages. This size reduction presents a challenge for the detection and location of the internal features/defects in the packages, which have approached the resolution limit of conventional acoustic microimaging, an important nondestructive inspection technique in the semiconductor industry. In this paper, to meet the challenge the learning overcomplete representation technique is pursued to decompose an ultrasonic A-scan signal into overcomplete representations over a learned overcomplete dictionary. Ultrasonic echo separation and reflectivity function estimation are then performed by exploiting the sparse representability of ultrasonic pulses. An improved acoustic microimaging technique is proposed by integrating these operations into the conventional acoustic microimaging technique. Its performance is quantitatively evaluated by elaborated experiments on ultrasonic A-scan signals using acoustic microimaging (AMI) error criteria. Results obtained both from simulated and measured A-scans are presented to demonstrate the superior axial resolution and robustness of the proposed technique.

Interpretation of calcium sulfate deposition on reverse osmosis membranes using ultrasonic measurements and a simplified model

Many models of foulant deposition on a membrane surface during reverse osmosis (RO) are based on flux-decline data and scanning electron microscopy (SEM) to predict the mechanism of fouling. The actual mechanism of calcium sulfate deposition remains incompletely understood due to the lack of additional techniques to detect the calcium sulfate deposition during RO. An in situ ultrasonic testing technique has been employed extensively to detect calcium sulfate deposition and growth on a RO membrane surface. Crossflow and dead-end operations were conducted with 2 g/l calcium sulfate solution. The experimental results show good correspondence between the ultrasonic response signal and the development of a calcium sulfate foulant layer on a membrane surface. In particular, a fouling echo obtained in the time domain indicates the actual state of a fouling layer on a membrane surface. An increase in the relative amplitude of the fouling echo results from the build-up of the fouling layer. In addition, the movement of the fouling echo in the time-domain occurred due to an increase in the thickness of the fouling layer. The flux decline is relative to the increases in both the density and thickness of the deposit. The changes in the density of a fouling layer as well as the thickness can be substantiated by a predictive modeling program — ultrasonic reflection modeling. The predicted results were in good agreement with the actual observations obtained during ultrasonic testing of membranes.