Pulse-echo Method Research Articles

Finite Element Modeling of Quantitative Ultrasound Analysis of the Surgical Margin of Breast Tumor.

Ultrasound is commonly used as an imaging tool in the medical sector. Compared to standard ultrasound imaging, quantitative ultrasound analysis can provide more details about a material microstructure. In this study, quantitative ultrasound analysis was conducted through computational modeling to detect various breast duct pathologies in the surgical margin tissue. Both pulse-echo and pitch-catch methods were evaluated for a high-frequency (22–41 MHz) ultrasound analysis. The computational surgical margin modeling was based on various conditions of breast ducts, such as normal duct, ductal hyperplasia, DCIS, and calcification. In each model, ultrasound pressure magnitude variation in the frequency spectrum was analyzed through peak density and mean-peak-to-valley distance (MPVD) values. Furthermore, the spectral patterns of all the margin models were compared to extract more pathology-based information. For the pitch-catch mode, only peak density provided a trend in relation to different duct pathologies. For the pulse-echo mode, only the MPVD was able to do that. From the spectral comparison, it was found that overall pressure magnitude, spectral variation, peak pressure magnitude, and corresponding frequency level provided helpful information to differentiate various pathologies in the surgical margin.

Structural health monitoring of fastener hole using ring-design direct-write piezoelectric ultrasonic transducer

Fatigue cracks initiated from fastener holes are common in aircraft structures. Implementation of effective structural health monitoring (SHM) system to detect or monitor fatigue cracks near fastener holes is desired for realizing condition-based maintenance with improved aircraft safety at reduced cost. In this work, direct-write piezoelectric ultrasonic transducers were used for monitoring crack near fastener hole. Made of poly (vinylidenefluoride-co-trifluoroethylene) [P(VDF-TrFE)] film and annular array electrodes, the direct-write piezoelectric ultrasonic transducers were both directly coated and patterned around the fastener holes. A novel ring-design using annular array electrodes with small footprint was proposed to detect fatigue crack initiated in the vicinity of a fastener hole using pulse-echo and pitch-catch methods. The ring-design direct-write piezoelectric ultrasonic transducers were designed to operate with Lamb wave modes at 1.5 MHz. A numerical simulation study was conducted to investigate the interaction of Lamb wave modes with the fatigue crack. Experimental ultrasonic testing was performed with signal gates determined using wavelet analysis. Fatigue crack detection was demonstrated using an energy ratio method by comparing energy parameter of gated ultrasonic signal with baseline signal. Using the pulse-echo method, the direction of the fatigue crack was able to be determined. The pitch-catch method was found to have higher sensitivity in fatigue crack detection but could not determine the direction of the fatigue crack. These transducers made of thin films promise high conformability even on curved surface and around irregular objects with limited space, compared to conventional discrete ultrasonic transducers. The analysis and results showed that the ring-design direct-write piezoelectric ultrasonic transducers have great potential for fastener hole SHM.

Hybrid Coded Excitation of the Torsional Guided Wave Mode T(0,1) for Oil and Gas Pipeline Inspection

Ultrasonic guided wave testing is an essential technique in non-destructive testing for structural integrity of oil and gas pipelines. This technique, based on the pulse-echo method, is often used for the long-range detection of pipelines at any location. However, guided waves suffer from high attenuation when they propagate in attenuative material structures and multiple wave modes due to the excitation, which reduces the power of echo signals and induces corruption caused by coherent noise. In this paper, a developed hybrid coded excitation method that uses the convolution of a Barker code and Golay code pair is proposed and applied for an ultrasonic guided wave testing system to excite the torsional guided wave mode T(0,1) in a steel pipe. The proposed method combines the advantages of these two coding methods and increases the flexibility of code lengths. The performance is evaluated by signal to noise ratio and peak sidelobe level of the processed signal. Both theoretical simulations and experiments have investigated using the proposed codes composed of Barker codes and Golay code pairs of different lengths and combinations. The experimental results show the significant improvement of the signal to noise ratio and the peak sidelobe level due to the proposed hybrid code usage for the excitation of guided waves. The values are further improved to around 32 dB and around −24 dB, respectively. Overall, the proposed hybrid coded method for improving the echo SNR can benefit from guided wave testing to reduce coherent and random noise levels and many other potential applications.

Ultrasound diagnostics of the patient's surperficial tissues

A new method of ultrasonic examination of the superficial tissues of a patient in vivo has been proposed. The design of ultrasonic measuring module for complex non-invasive diagnostics of the physiological conditions and processes in the superficial tissues of a patient has been developed. Precise measurements of the speed and attenuation of ultrasonic waves were made using the echo-pulse and transmission methods. An experimental verification of the developed ultrasonic method was carried out on reference solutions and superficial tissues of the patient. Keywords: ultrasound diagnostics, echo-pulse method, superficial tissues, ultrasonic diagnostic module, sound speed, attenuation coefficient.

Preparation and characterization of physico-mechanical and structural properties of phthalimide derivative polymeric nanocomposites

In this study, phthalimide derived polymer-TiO2 nanocomposites were prepared by direct mixing method and their mechanical properties were compared. The high content filler polymer nanocomposites with sufficient interface bonding with the polymer matrix have been prepared to maximize the properties of the filler. In the direct mixing method, the polymer obtained by free radical polymerization of the monomer was mixed with TiO2 in high weight percentages. The pulse-echo method was used to characterize the elastic constants of the polymer and polymer-TiO2 nanocomposites through detection of the ultrasonic waves. Transverse and longitudinal ultrasonic velocities have been used to calculate Young?s modulus of these samples. The ultrasonic velocity and Young?s modulus values of polymer-TiO2 nanocomposites showed a linear relationship with the weight percentage of the polymer, which is due to the strong and effective interaction between the particles resulting from by reinforcing TiO2 to the polymer structure. The clustering that emerged with the increase in the amount of reinforcement in the SEM images became more pronounced and it was observed that pure polymer and TiO2 were homogeneously distributed. The porosity and hardness measurements of the polymer and polymer-TiO2 nanocomposites were examined. The hardness and porosity of the polymer structure approximately increased as the percentage values of TiO2 increased. Moreover, TGA results of polymer nanocomposites obtained by direct mixing showed that the thermal stability increased linearly as the weight ratio increase of TiO2 in comparison with the pure polymer.

Passive Ultrasound Localization Microscopy of Nanodroplet Vaporizations During Proton Irradiation

Superheated nanodroplets (NDs) were recently proposed for <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in vivo</i> proton range verification, owing to their ability to vaporize into echogenic microbubbles (MBs) upon exposure to ionizing radiation. In a previous publication, vaporization events were detected with 2D Ultrasound Localization Microscopy (ULM) based on a pulse-echo method. Here, we introduce P-ULM, a passive version of ULM, based on the detection of acoustic signatures emitted by vaporizing NDs, without actively transmitting ultrasound. Due to the lack of a time reference for the trigger of the ND vaporization, the time differences of arrival to each transducer element are used to retrieve the position of vaporizing NDs. P-ULM, compared to ULM, can continuously detect and super-localize sparse radiation-induced vaporization events with inherent specificity against already existing microbubbles, which otherwise would hinder range verification in the presence of vascular flow. We evaluated the localization performances of both methods theoretically and experimentally, by interleaving active and passive acquisitions on ND-phantoms irradiated with protons. P-ULM offered a higher sensitivity to vaporizations, as it detected twice as many events as ULM. Both methods retrieved, in the acoustic lateral direction, the proton range and range dispersion with sub-millimeter accuracy. In the acoustic axial direction, despite a degraded theoretical resolution limit, P-ULM retrieved the proton spot size with an accuracy similar to ULM. Importantly, P-ULM detected vaporization events with high specificity in the presence of flowing MBs, which makes the technique a candidate for in vivo proton range verification in the presence of flow.

Anisotropy of the Electromechanical Characteristics of SH-Waves and Lamb Waves in Yttrium Aluminum Borate Single Crystals

The anisotropy of the electromechanical properties of SH-waves and Lamb waves in yttrium aluminum borates, which are nonmagnetic representatives of the RMe3(BO3)4 single crystals family (where R=Y, La-Lu; M=Fe, Al, Cr, Ga, Sc) with unique properties of magnetoelectrics and multiferroics, has been studied. In the process of the numerical simulation of the acoustic waves characteristics, the values of linear electromechanical constants of YAl3(BO3)4 single crystals, previously measured by ultrasonic pulse echo and quasi-static methods, have been used

Metallographic and ultrasonic studies of fatigue failure of ASTM 1020 steel in the base metal and heat affected zone

This paper deals with optical and ultrasonic investigations in the base metal and heat affected zone of welded specimens of ASTM 1020 steel under low-cycle fatigue. Development of persistent slip bands on the surface was observed using optical microscope. Differences in development of slip bands in the base metal and heat affected zone were analyzed. Acoustic birefringence of shear waves was measured by the ultrasonic pulse echo method. For the base metal, acoustic birefringence was found to decrease monotonously. For heat affected zone, acoustic birefringence was found to change non-monotonously up to cycle ratio of 0.3 and decrease monotonously after cycle ratio of 0.3. Based on the linear dependence of acoustic birefringence on the relative number of loading cycles, an ultrasonic technique is proposed for assessing fatigue damage.

The eddy-current and ultrasonic investigations of the nickel-base superalloy the gas turbine engine blades after exploitation

The work carried out microstructural, eddy-current and ultrasonic studies of the material of spent blades of gas turbine engines made of nickel-base superalloy. To determine the degree of damage to the material of the spent blades, studies of the microstructure were carried out on a scanning electron microscope. It was found that γ' coagulation occurred in some specimens, which corresponds to overheated material. Acoustic studies of the material were carried out using the ultrasonic pulse echo method. Comparative analysis showed that in such specimens there is a significant decrease in the velocity of propagation and attenuation of longitudinal ultrasonic waves. It is found that the readings of the eddy-current flaw detector in overheated specimens differ more than twice in comparison with non-overheated specimens. This fact can be used for operational non-destructive testing of the actual state of the metal structure by the eddy current method with the aim of further safe operation of gas turbine engines.

Milk fraud by the addition of water using an ultrasonic echo-pulse technique

Milk is one of the essential food commodities and plays a crucial role in the diet of human nutrition. The quality of milk has been challenge in industry due to the threat of adulteration. Adulteration in food products has many aspects such as the addition of prohibited substance either partly or wholly for the state of financial gain, the lack of hygienic conditions of processing and storing, the decreasing of the amounts of original ingredients, or the changing of their chemistry itself which leads to the consumer being cheated. Ignorance of this fact is not fair since this may endanger consumer health. With the aim of monitoring milk quality at distribution points, a non-destructive pulse-echo method was proposed to evaluate the water content in powdered milk. The results indicate the ability to measure the adulterant level based on the value of the peak to peak amplitude at room temperature. In addition, the technique that is developed in the present work involves only one transducer which is non-invasive and considered as a very important in the food industry for hygiene reasons.

Study of the dependence of the strength characteristics of metals on variations in the modes of manufacturing process using microstructure-sensitive acoustic parameters

The microstructure-sensitive acoustic parameters (MSA parameters) of metal of the object under control are determined using measurements of the propagation time of bulk elastic waves of the ultrasonic range by the echo-pulse method. The structural features of the metal are thus evaluated not only in the surface layer, but also throughout the entire volume. We present the results of practical application of the MSA-parameters to estimation of the deviation of the velocity ratios of longitudinal and shear waves relative to the «basic» state with known strength characteristics. A correlation of the MSA-parameters with variations in the elastic moduli of metals attributed to modification of their microstructure is discussed. The generalized values of the ratios of wave velocities for steels of the same group are used in calculations to characterize the «base» state. It is shown that when calculating the MSA-parameters for a certain kind of construction steel, it is possible to use the averaged ratios of the velocities measured for quasi-isotropic reference samples made of the same type of steel. The generalized baseline ratios of the longitudinal and shear wave velocities are determined for the samples made of carbon steel, low-alloy, and alloyed steels. We present experimental evidence of using MSA-parameters to detect microstructural changes in metal samples and accompanying changes in their strength characteristics that occur during changes in modes and conditions of welding and heat treatment. A comparative analysis of the MSA parameters with the values of the mechanical properties and parameters of the crack resistance of the metal is carried out. It was shown that the accuracy of measuring the MCA parameters provided by modern hardware significantly exceeds changes in them occurred under significant deviations of the strength characteristics. The experimental results obtained clearly indicate that the MSA-parameters can be successfully used to improve the methods of quantitative non-destructive assessment of the features of metal microstructures

THE STUDY OF THE INFLUENCE OF X-RAY IRRADIATION ON DISLOCATION CHARACTERISTICS IN LiF CRYSTALS

The dependences of the absorption α and the ultrasound velocity in LiF single crystals with residual deformation ε = 0.65% at 300 K in the range of radiation doses 0...1057 R were studied using the acoustic pulse echo method at a frequency of 7.5 MHz. Based on the results of measurements of the acoustic characteristics, the absolute values of the parameters of the dislocation structure – the average effective length of the dislocation loop L and the dislocation density Λ and their dependences on the irradiation time are determined. The calculated characteristics are compared with the previously obtained results for the high-frequency branch of the damped dislocation resonance and using the selective etching method. The revealed noticeable discrepancy in the values of these parameters is explained by the impossibility of describing a single attenuation mechanism for acoustic measurements carried out in a wide frequency range.

Ultrasonic Heating Detects Lipiodol Deposition within Liver Tumors after Transarterial Embolization: An In Vivo Approach.

Simple SummaryThe accumulation of Lipiodol (ethiodized oil) after transarterial embolization is known to reflect tumor necrosis. In general, the treatment effect is evaluated by computed tomography; there has been no development in imaging modalities for several decades. A new technique, ultrasonic heating, can differentiate biological tissues based on the fact that tissues’ characteristic sound velocity varies depending on the temperature. This technique could have the potential to evaluate treatment effect after transarterial embolization as an alternative to computed tomography.Computed tomography (CT) is the standard method to evaluate Lipiodol deposition after transarterial embolization (TAE) for a long period. However, iodine but not Lipiodol can be observed on CT. A minimally invasive other method to detect Lipiodol has been needed to evaluate accurate evaluation after procedure. The purpose of this study was to evaluate the efficacy of using the rate of change in sound velocity caused by ultrasonic heating to reflect Lipiodol accumulation after TAE in a rat liver tumor model. We analyzed the association of this developed technique with CT images and histological findings. Eight rats bearing N1S1 cells were prepared. After confirmation of tumor development in a rat liver, Lipiodol was injected via the hepatic artery. Seven days after TAE, CT scan and sound velocity changes caused by ultrasonic heating were measured, and then the rats were sacrificed. An ultrasonic pulse-echo method was used to measure the sound velocity. The temperature coefficient of the sound velocity in each treated tumor was evaluated and compared with the mean CT value and the histological Lipiodol accumulation ratio. Pearson’s correlation coefficients were calculated to assess the correlation between the measured values. The correlation coefficient (r) of the mean CT value and histological Lipiodol accumulation ratio was 0.835 (p = 0.010), which was considered statistically significant. Also, those of the temperature coefficient of the sound velocity and the histological Lipiodol accumulation ratio were statistically significant (r = 0.804; p = 0.016). To our knowledge, this is the first study that reported the efficacy of ultrasonic heating to detect Lipiodol accumulation in rat liver tumors after TAE. Our results suggest that the rate of change in sound velocity caused by ultrasonic heating can be used to evaluate Lipiodol accumulation in liver tumors after TAE, and thus could represent an alternative to CT in this application. This new innovative technique is easy to treat and less invasive in terms of avoiding radiation compared with CT.

Speed-of-sound imaging using diverging waves

Purpose.Due to its safe, low-cost, portable, and real-time nature, ultrasound is a prominent imaging method in computer-assisted interventions. However, typical B-mode ultrasound images have limited contrast and tissue differentiation capability for several clinical applications.Methods.Recent introduction of imaging speed-of-sound (SoS) in soft tissues using conventional ultrasound systems and transducers has great potential in clinical translation providing additional imaging contrast, e.g., in intervention planning, navigation, and guidance applications. However, current pulse-echo SoS imaging methods relying on plane wave (PW) sequences are highly prone to aberration effects, therefore suboptimal in image quality. In this paper we propose using diverging waves (DW) for SoS imaging and study this comparatively to PW.Results.We demonstrate wavefront aberration and its effects on the key step of displacement tracking in the SoS reconstruction pipeline, comparatively between PW and DW on a synthetic example. We then present the parameterization sensitivity of both approaches on a set of simulated phantoms. Analyzing SoS imaging performance comparatively indicates that using DW instead of PW, the reconstruction accuracy improves by over 20% in root-mean-square-error (RMSE) and by 42% in contrast-to-noise ratio (CNR). We then demonstrate SoS reconstructions with actual US acquisitions of a breast phantom. With our proposed DW, CNR for a high contrast tumor-representative inclusion is improved by 42%, while for a low contrast cyst-representative inclusion a 2.8-fold improvement is achieved.Conclusion.SoS imaging, so far only studied using a plane wave transmission scheme, can be made more reliable and accurate using DW. The high imaging contrast of DW-based SoS imaging will thus facilitate the clinical translation of the method and utilization in computer-assisted interventions such as ultrasound-guided biopsies, where B-Mode contrast is often to low to detect potential lesions.

Transmission Phase Control of Annular Array Transducers for Efficient Second Harmonic Generation in the Presence of a Stress-Free Boundary

The through-transmission (TT) method is mainly used to measure the amplitude of the second harmonic from which the acoustic nonlinear parameter is determined for early damage detection of materials. The pulse echo (PE) method, however, has been excluded from nonlinear studies of solid materials because the stress-free boundary suppresses the generation of second harmonics. It is more demanding to develop the PE method for practical applications and this paper considers a novel phase shift technique of annular array transducers to improve second harmonic generation (SHG) at the stress-free boundary. The fundamental and second harmonic fields after phase-shifted radiation are calculated, and their received amplitudes are investigated. The phase difference between the two second harmonic components after reflection from the stress-free boundary is analyzed to explain the enhanced SHG. The PE method with optimal phase shift can generate an improved second harmonic amplitude as high as about 45% of the TT method. Four element array transducers are also found to be more efficient in improved SHG than two element transducers.

An ultrasound method for characterization of viscoelastic properties in frequency domain at small deformations

Background The ultrasound technique, usually based on the transmission mode, is capable of providing the viscoelastic properties of polymers. Further techniques involving pulse-echo methods were also described in literature, but they still exhibit inaccuracies in the evaluation of the acoustic properties. Objective The manuscript focuses on an innovative approach for the characterization of the viscoelastic behavior of polymers employing the ultrasound methodology. The proposed procedure is based on the pulse-echo method in order to overcome possible inaccuracies in acoustic properties evaluation and in issues related to transmitter mode applications. Methods Starting from the pulse-echo method adopted for the acquisition, a novel formulation for data processing has been developed and described, allowing to determine the wave attenuation coefficient, in comparison to the commonly employed procedures involving ultrasound in polymers characterization, based on transmitter mode inspections. To carry out the study, a specifically designed ultrasound bench has been set up and three different polymers have been tested in the temperature range of interest. Results According to the proposed methodology, the loss factor towards the temperature is determined starting from the data acquired considering the identified attenuation coefficient and the measured sound velocities. The trustworthiness of the novel procedure has been proved comparing the obtained viscoelastic loss factor quantities to the reference master curves obtained by the standard Dynamic Mechanical Analysis characterizations carried out on the same polymer specimens. Conclusions A novel methodology involving ultrasound technology aiming to evaluate the viscoelasticity of the polymers using non-destructive approach has been developed. The results obtained are agreement with the standard viscoelastic master curves determined through the DMA.

Characterization of the full matrix constants of Bi4Ti3O12 ceramics

Fabricating high-quality, large-size Bi4Ti3O12 (BIT) ceramics is challenging; therefore, the full matrix constants of BIT ceramics have not been characterized, which notably hinders their applications. In this study, the elastic stiffness constants c11E and c33D of the BIT ceramics were determined using the ultrasonic pulse-echo method. In addition, the elastic stiffness constants c12E, c13E, c33E, and c44E were determined using resonant ultrasound spectroscopy. Furthermore, the piezoelectric stress constants e15, e31, and e33 of BIT ceramics were calculated using the formula for the relationship between different material constants.

Implementation of Ultrasonic Ranger Finder

In this paper, the operation style of “measuring distance” is taken as the research content of this implementation. The expected goal is to use the characteristics of the double reflection type used in the transceiver circuit to perform the function of measuring distance. Finally, the operating principle of the adopted electric circuits and the performance of the proposed device are validated by experimental results. It reveals that the operations of the proposed device coincide with the requirements. Keywords: Ultrasound, Pulse echo method, Single frequency ranging, Verification.

Simultaneous measurement of liquid film thickness and temperature on metal surface

The flow and evaporation of liquid films widely exist in various industrial fields. The investigation into liquid films is essential to design and optimize the relevant industrial processes. In this work, a simultaneous measurement method of liquid film thickness and temperature on metal surface based on diode laser absorption spectroscopy (DLAS) was proposed, and a corresponding measurement system was developed. First, static liquid films of 200–800 μm on the horizontal metal plate were studied, ultrasonic pulse-echo method (UPEM) and thermocouple were employed to compare with DLAS data. It revealed that the relative deviations of film thicknesses and temperatures measured by different methods were 3.3% and 2.0%, respectively. Furthermore, the evaporation processes of static liquid films were investigated. For the liquid films with different initial thicknesses (490.0/624.6/744.5 μm), the average relative deviations of the film thicknesses and temperatures measured by different methods were 0.1%/0.8%/4.1% and 0.1%/2.6%/3.0%, respectively. Finally, the flow processes of liquid films at different initial temperatures (40.0/60.0/80.0 °C) on the inclined metal plate were researched. It was found that the variation trends of the liquid film thicknesses and temperatures measured by different methods were in good agreement. In the stable stages of flow processes, the average relative deviations of liquid film thicknesses and temperatures measured by different methods were 9.0%/8.4%/5.1% and 3.6%/1.2%/2.5%, respectively. This work is helpful to understand the heat and mass transfer mechanisms in the evaporation and flow processes of liquid films.

Elastic properties of iron and tantalum at high pressure and temperature

Iron and tantalum have many important applications in tools, infrastructure, and electronics. In service, metallic parts can experience extreme stresses and temperatures (e.g., jet engine components, chemical processing equipment, supports for large structures), thus it is important to understand their elastic properties as a function of both pressure and temperature in order to allow engineers to appropriately design components using these materials. To determine these properties, we measured sound speeds and densities of Fe and Ta samples as a function of pressure and temperature. These measurements were performed in a large volume hydraulic pressure cell in situ at the Advanced Photon Source. Ultrasound time-of-flight was measured using the pulse-echo method and the sample dimensions were measured using x-ray radiography. x-ray diffraction was used to determine the sample densities. The longitudinal and shear sound speeds and the density measurements were combined to determine the bulk, Young’s, and shear moduli and Poisson’s ratio as pressure and temperature was changed. This talk will present these elastic properties as a function of pressure (up to 7 GPa) and temperature (up to 1000 °C). Finally, electron microscopy techniques will be discussed as a method of quantifying texture evolution during sample compression.