Ultrasound Pulse Echo Research Articles

Analysis of the attenuative behaviour of accelerated cement based materials through a series of ultrasound Pulse Echo measurements

Analysis of the attenuative behaviour of accelerated cement based materials through a series of ultrasound Pulse Echo measurements

Bubble Size Measurement by the Ultrasonic Pulse Echo with Tracking Technique

Bubbly flows appear in many different industrial fields and the measurement of bubble sizes is crucial for understanding phase interactions. The ultrasound pulse echo can be used for a non-intrusive measurement of the bubble surface position in one dimension even when there is no optical access to the bubble. A simultaneous measurement from two opposing directions gives the bubble size but has been performed only on single bubbles. This work applies the tracking technique, which allows a simultaneous measurement of multiple bubbles. The performance of the bubble size measurement was tested experimentally by comparing ultrasonic results with the sizes measured by a high-speed camera and also with metal cylinders. Possible sources of measurement uncertainty were analysed and discussed. The tested range of bubble sizes was up to 10 mm and the void fraction was lower than 1.25%.

Sensitization in Aluminum Alloys: Effect on Acoustic Parameters

Velocity and attenuation of shear and longitudinal sound waves were measured as a function of sensitization level in AA5083-H116 and AA5456-H116 aluminum alloys using two different techniques: resonant ultrasound spectroscopy (RUS) and pulse echo (PE). The frequency range for RUS was 0.3 MHz to 1 MHz. For PE, longitudinal 3.5 MHz and shear 1 MHz transducers were used. Sensitization was artificially induced in the laboratory by isothermally heating specimens at temperatures of 120°C, 175°C, 185°C, and 240°C for fixed periods of time (12 h to 96 h, the longer times for the lower temperatures). Measurements were repeated after each heating sequence. The overall changes are reported as percent difference between the as received and the fully sensitized states. The quantity that was found to be most sensitive to the degree of sensitization in this study is the attenuation coefficient of longitudinal waves, αL. The measured change in αL exceeds 20%, with error bars within 1% to 4%. Despite the magnitude of the error bars, the αL vs. degree-of-sensitization curve is clear and smooth. The shear wave velocity changed by 1.2% to 1.5%, with error bars within 0.01% to 0.1%. The larger change was observed for the AA5456 alloy, which contains more Mg. The longitudinal wave velocity was found to change by 0.5% for the 5456 alloy, with error bars within 0.004% to 0.02%. The attenuation coefficient for shear waves was not measured. This study identifies multiple ultrasonic parameters that can be combined into a new, on-site, nondestructive tool for quantitatively monitoring the sensitization level in Mg-rich aluminum alloys, with possible extensions to other materials.

Acoustic and mechanical characterization of 3D-printed scaffolds for tissue engineering applications

The acoustic and mechanical properties of 3D-printed porous poly-(ethylene glycol)-diacrylate (PEGDA) hydrogel scaffolds were investigated using an ultrasound pulse echo technique on different scaffold microstructures (solid, hexagonal and square pores). Acoustic parameters such as speed of sound, acoustic impedance and attenuation coefficient as well as physical parameters such as the pore structure, effective density and elastic moduli were determined. The results show that microstructure (porosity and pore geometry) plays a crucial role in defining properties of 3D-printed scaffolds, achieving the highest attenuation for the scaffold with hexagonal pores and showing a decrease in sound speed and elastic moduli with increasing porosity. The properties were also found to be similar to those of soft tissues, making PEGDA scaffolds a suitable candidate for tissue engineering applications. To evaluate their cellular performance, adhesion and proliferation of human mesenchymal stem cells (hMSCs) in these scaffolds were investigated. The porous scaffolds performed better than the solid one, recording the highest cell attachment and growth for the scaffold with the square pores.

Ultrasound Pulse-Echo Coupled with a Tracking Technique for Simultaneous Measurement of Multiple Bubbles.

Bubbly flows are commonly used in various applications and their measurement is an important research topic. The ultrasound pulse-echo technique allows for the detection of each bubble and the measurement of the position of its surface. However, so far it has been used only to measure single bubbles. This paper investigates whether the pulse-echo technique can be applied for measuring multiple bubbles concurrently. The ultrasonic transducer wavelength and diameter were selected based on expected bubble diameters so that each bubble produced a strong reflection. The pulse-echo was implemented to obtain good accuracy without sacrificing the signal processing speed. A tracking technique was developed for the purpose of connecting detected reflections to trajectories. The technique was tested experimentally by measuring the horizontal position of rising air bubbles in a water tank. The results show that the pulse-echo technique can detect multiple bubbles concurrently. The pulse-echo technique detected almost the same number of bubbles as a high-speed video. For average void fractions up to around (and instantaneous void fraction reaching ), the rate of bubbles missed by the pulse-echo and the rate of noise trajectories both stayed less than 5%. The error rate increased with the void fraction, limiting the technique’s application range.

Combining Ultrasound Pulse-Echo and Transmission Computed Tomography for Quantitative Imaging the Cortical Shell of Long-Bone Replicas

We demonstrate a simple technique for quantitative ultrasound imaging of the cortical shell of long bone replicas. Traditional ultrasound computed tomography instruments use the transmitted or reflected waves for separate reconstructions but suffer from strong refraction artefacts in highly heterogenous samples such as bones in soft tissue. The technique described here simplifies the long bone to a two-component composite and uses both the transmitted and reflected waves for reconstructions, allowing the speed of sound and thickness of the cortical shell to be calculated accurately. The technique is simple to implement, computationally inexpensive and sample positioning errors are minimal.

Acoustic monitoring of aluminum-alloy sensitization

Segregation of atomic species in metastable solid-solution alloys results in a gradual change of the alloy’s properties, sometimes rendering the materials ineffective for the particular task they were designed for. An example of such a case is the sensitization of strong and lightweight Mg-rich aluminum alloys used in marine applications. The ASTM standard is an acid-corrosion test (G67), a destructive and lengthy procedure that requires large specimens analyzed off-site. Ultrasound is a well-known tool for nondestructive material characterization and it can offer a solution for on-site testing. To this end, the sensitivity of ultrasonic parameters to the degree of material degradation through sensitization has been identified. Velocity and attenuation for shear and longitudinal waves were measured as a function of sensitization for 5083 and 5456 aluminum alloys with two different methods: Resonant Ultrasound Spectroscopy (RUS) and Pulse Echo (PE). The longitudinal and shear velocities change by 0.5% and 1.5%, respectively, while the attenuation coefficient of longitudinal waves changes by of 20% (all represent saturation values). The JMAK equation for phase kinetics is used to understand the observed evolution of the acoustic parameters vs. sensitization.

Improving high-intensity focused ultrasound beam imaging via a backscattering suppression algorithm

In an ultrasound-guided high-intensity focused ultrasound (HIFU) device, a HIFU focal error may be observed in an ultrasound pulse–echo image due to the difference between the HIFU and imaging beam aberrations occurring in the heterogeneous propagative medium, which was verified by simulating the ultrasound beams passing through an abdominal wall. The HIFU focal error could reduce the accuracy of targeting the HIFU focal spot at a tumor. To measure the focal error, HIFU beam imaging based on backscattered wave reconstruction can be used; however, its image qualities deteriorate due to inhomogeneous backscattering. Hence, we proposed a novel backscattering suppression algorithm based on an inverse problem approach to retrieve HIFU beam components. The proposed algorithm was validated in ex vivo experiments in conjunction with focal spot shifts and beam width variations, demonstrating the clear improvement of HIFU beam imaging quality.

Adaptive Light Modulation for Improved Resolution and Efficiency in All-Optical Pulse-Echo Ultrasound.

In biomedical all-optical pulse-echo ultrasound systems, ultrasound is generated with the photoacoustic effect by illuminating an optically absorbing structure with a temporally modulated light source. Nanosecond range laser pulses are typically used, which can yield bandwidths exceeding 100 MHz. However, acoustical attenuation within tissue or nonuniformities in the detector or source power spectra result in energy loss at the affected frequencies and in a reduced overall system efficiency. In this work, a laser diode is used to generate linear and nonlinear chirp optical modulations that are extended to microsecond time scales, with bandwidths constrained to the system sensitivity. Compared to those obtained using a 2-ns pulsed laser, pulse-echo images of a phantom obtained using linear chirp excitation exhibit similar axial resolution (99 versus 92 μm, respectively) and signal-to-noise ratios (SNRs) (10.3 versus 9.6 dB). In addition, the axial point spread function (PSF) exhibits lower sidelobe levels in the case of chirp modulation. Using nonlinear (time-stretched) chirp excitations, where the nonlinearity is computed from measurements of the spectral sensitivity of the system, the power spectrum of the imaging system was flattened and its bandwidth broadened. Consequently, the PSF has a narrower axial extent and still lower sidelobe levels. Pulse-echo images acquired with time-stretched chirps as optical modulation have higher axial resolution (64 μm) than those obtained with linear chirps, at the expense of a lower SNR (6.8 dB). Using a linear or time-stretched chirp, the conversion efficiency from optical power to acoustical pressure improved by a factor of 70 or 61, respectively, compared to that obtained with pulsed excitation.

Whole-body live mouse imaging by hybrid reflection-mode ultrasound and optoacoustic tomography.

We present a hybrid preclinical imaging scanner that optimally supports image acquisition in both reflection-mode ultrasonography and optoacoustic (OA) tomography modes. The system comprises a quasi-full-ring tomographic geometry capable of the simultaneous dual-mode imaging through entire cross sections of mice with in-plane spatial resolution in the range of 150 and 350 μm in the respective OA and ultrasound (US) imaging modes with an imaging speed of up to 10 two-dimensional frames per second. Three-dimensional whole-body data is subsequently rendered by rapid scanning of the imaged plane. The system further incorporates rapid laser wavelength tuning for real-time acquisition of multispectral OA data, which enables studies of longitudinal dynamics as well as fast kinetics and biodistribution of contrast agents. In vivo imaging performance is demonstrated by label-free hybrid anatomical scans through living mice, as well as real-time visualization of optical contrast agent perfusion. By setting new standards for whole-body tomographic imaging performance in both the OA and pulse-echo US modes, the developed hybrid imaging approach is expected to benefit numerous applications where the availability of high-quality structural information provided by the tomographic reflection-mode US can ease interpretation of the functional and molecular imaging results attained by the OA modality.

Analysis of cooling effect by blood vessel on temperature rise due to ultrasound radiation in tissue phantom

Ultrasound diagnostic equipment using ultrasound pulse–echo techniques is considered minimally invasive and highly versatile. However, one of the causes of damage due to ultrasound radiation is temperature rise caused by the absorption of sound energy. Therefore, it is very important to estimate the temperature rise caused by the radiation of ultrasound. Sound intensity in a medium is analyzed by the finite-difference time-domain (FDTD) method, and the temperature distribution caused by sound is estimated by the heat conduction equation (HCE) method in this study. Because blood vessels keep the temperature constant in tissues, the cooling effect of blood flow has to be taken into account for the precise estimation of temperature rise in human tissues. In general, it is well known that capillary vessels are mainly responsible for the cooling effect in tissues and their effect can be estimated as a function of bloodstream ratio. In this paper, a preliminary study on the cooling effect by a large vessel is described for the precise estimation of temperature rise. Blood flow in blood vessels is analyzed using the Navier–Stokes equation. To confirm the precision of the numerical analysis, the results of the numerical analysis are compared with the experimental results using a soft tissue phantom.

Monitoring Local Solids Fraction Variations in Multiphase Flow using Pulse-echo Ultrasound

This paper presents an ultrasonic pulse-echo technique for on-line monitoring of variations in solids concentrations in particle suspensions. The method is based on time-frequency analysis of the backscatter signals, exploring variations in spectral content of the backscatter as function of depth in the suspension. Experiments on a settling of magnetite particles in water, at varying solids concentrations, show that the settling process can be followed by studying the energy of backscattered ultrasound.

Inexpensive spatial position system for the automation of inspection with mobile robots

Purpose – The purpose of this paper is to develop a wireless positioning system. The automation of non-destructive testing (NDT) of large and complex geometry structures such as aircraft wings and fuselage is prohibitively expensive, though automation promises to improve on manual ultrasound testing. One inexpensive way to achieve automation is by using a small wall-climbing mobile robot to move a single ultrasound probe over the surface through a scanning trajectory defined by a qualified procedure. However, the problem is to guide the robot though the trajectory and know whether it has followed it accurately to confirm that the qualified procedure has been carried out. Design/methodology/approach – The approach is to use sophisticated bulk electronics developed for game playing in combination with MATLAB to develop a wireless positioning system. Findings – The paper describes the development of an inexpensive wireless system comprising an optical spatial positioning system and inertial measurement unit that relates the 3D location of an NDT probe carried by a mobile robot to a computer-aided drawing (CAD) representation of the test structure in a MATLAB environment. The probe is located to an accuracy of ± 2 mm at distances of 5 m. Research limitations/implications – Positioning range is limited to 5 m. Further development is required to increase this range. Practical implications – The wireless system is used to develop tools to guide the robot remotely to follow a desired scanning trajectory, obtain feedback about the actual trajectory executed by the robot, know exactly where an ultrasound pulse echo was captured, map identified defects on the CAD and relate them to the real test object. Originality/value – An inexpensive spatial positioning system with sufficient accuracy for automated NDT purposes.

Methodology for Measurement of Residual Stress in Welded Joints by the Technique of Pulse-Echo Ultrasound

ABSTRACTRecently they have discovered a large number of oil wells, however these are found in deeper waters. So it is necessary to develop a repair's methodology and inspection for this type of system to prove its operation. This research was focused to establish a methodology for evaluating residual stress generated from the application of solder in a subsea environment, in order to establish whether there is a relationship between residual stress and the depth of the sea. For this purpose was used underwater electrodes (UW -CS- 1) and an API 5L X65 steel to the development of underwater welds, which was welded at 10 and 15 meters depth by a diver welder on site. The measurement of residual stress is developed using non-destructive techniques, the first one was ultrasound technique (UT) which was the technique proposed by viability to being applied in site and as a second option, was applied X-ray diffraction (XRD), with the objective to validate the results obtained by ultrasound technician. The results showed a similar behavior between both non-destructive techniques. In this study was observed the tendency to increase the level of residual stress with increasing the work depth.

A Novel Mobility Aid for the Blind through Ultrasound Pulsed Echo Modulated Nerve Stimulation

There are no affordable and widely available technology based aid to give a blind person the power of free movement avoiding obstacles and dangers. Some ultrasound pulse echo based electronic aids deliver the information obtained through the echo through audio signals conveyed by means of ear phones, but these affect the capability of such an important sense organ which a blind person uses greatly to receive and discern information of the surroundings. In the present work this limitation is overcome by passing this information through nerve stimulations at a suitable point on the body, possible wrist. Here the delays of the received ultrasound echo-pulses are used to modulate the frequency of nerve stimulation, to give higher frequency for shorter distances. This was designed to match the common psychological response of attributing higher frequencies to danger, creating a natural reaction for moving away when an object is too close. The highest frequency a human nerve can be stimulated to is about 500Hz, and pulses with heights of 100V to 200V are required for stimulating nerves passing just under the skin using surface electrodes. Necessary electronic circuit design was developed and a prototype fabricated in the present work. The prototype was tested for short distances up to 20cm giving very good linear response between object distance and the stimulating frequency, with the inverse characteristics as mentioned above. Reduction of noise through proper housing and shielding will allow the device to be useful to a practical distance of about 10m using 40kHz ultrasound transducers. DOI: http://dx.doi.org/10.3329/bjmp.v4i1.14692 Bangladesh Journal of Medical Physics Vol.4 No.1 2011 87-94

Compressed Sensing for Fast Image Acquisition in Pulse-Echo Ultrasound

Compressed Sensing for Fast Image Acquisition in Pulse-Echo Ultrasound

Characterisation of polymer-shelled microbubbles in wall-less flow phantom using high-frequency ultrasound and video microscopy

A high frequency ultrasound pulse echo system and a video microscope were combined to investigate the relationship between backscatter from polymer shelled ultrasound contrast agents (UCAs) and their diameter. Individual UCAs (manufactured by Point Biomedical or Philips Research) were imaged while being sonicated with 40 MHz tone bursts. The backscatter magnitude produced by the Philips UCAs was proportional to UCA size, which is consistent with theoretically predicted behaviour of encapsulated microbubbles driven at frequencies above resonance. Despite being smaller, the Point UCAs produced a backscatter magnitude twice that of Philips UCAs, indicating that Point UCAs might behave quasi-resonantly when excited at 40 MHz.

Thermophysical Properties of a Fe-Cr-Mo Alloy in the Solid and Liquid Phase

Results of a thermophysical characterization of a Fe-Cr-Mo alloy in the solid and liquid phases are reported. Methods applied include calorimetry, dilatometry; the laser flash technique for thermal diffusivity measurement and ultrasound pulse echo for the measurement of the room temperature sound velocities and elastic constants. Density in the liquid phase and surface tension were measured by optical dilatometry and by the oscillating drop method on electromagnetic levitated specimen. In addition, surface tension and viscosity were measured by the oscillating drop method on board parabolic flights under reduced gravity conditions. The methods applied and results obtained are presented. This work represents a collaborative effort, including round robin measurements in different laboratories for a characterization of the basic thermophysical properties needed for process simulation.

Volumetric Flow Measurement Using an Implantable CMUT Array

This paper describes volumetric-flow velocity measurement using an implantable capacitive micromachined ultrasonic transducer (CMUT) array. The array is comprised of multiple-concentric CMUT rings for ultrasound transmission and an outmost annular CMUT array for ultrasound reception. Microelectromechanical-system (MEMS) fabrication technology allows reception CMUT on this flowmeter to be implemented with a different membrane thickness and gap height than that of transmission CMUTs, optimizing the performance of these two different kinds of devices. The silicon substrate of this 2-mm-diameter CMUT ring array was bulk micromachined to approximately 80 to 100 μm thick, minimizing tissue disruption. The blood-flow velocity was detected using pulse ultrasound Doppler by comparing the demodulated echo ultrasound with the incident ultrasound. The demodulated ultrasound signal was sampled by a pulse delayed in time domain from the transmitted burst, which corresponds to detecting the signal at a specific distance. The flow tube/vessel diameter was detected through the time-flight delay difference from near and far wall reflections, which was measured from the ultrasound pulse echo. The angle between the ultrasound beam and the flow was found by using the cross-correlation from consecutive ultrasound echoes. Artificial blood flowing through three different polymer tubes was experimented with, while keeping the same volumetric flow rate. The discrepancy in flow measurement results between this CMUT meter and a calibrated laser Doppler flowmeter is less than 5%.

Study of the Effect of Natural Rubber-graft-maleic Anhydride (NR-g-MA) on the Compatibility of NR-NBR Blends Using the Ultrasonic Technique

The grafted copolymer of natural rubber (NR) and maleic anhydride (MA) was synthesized in a solution state by using ultraviolet radiation. The NR-g-MA was characterized using infrared (IR) technique. The prepared NR-g-MA was added to a 50/50 blend of NR and acrylonitrile-butadiene copolymer (NBR) as a compatibilizer. The effect of compatibilizer (NR-g-MA) concentrations in the range of 2, 4, 5, 6, 8, and 10 wt.% on the ultrasonic velocity, attenuation coefficient, and ultrasonic viscosity was studied in order to study the compatibility of the 50NR-50NBR blend. Ultrasound pulse echo method was used to measure both the ultrasound velocities and attenuation coefficient at a frequency of 2 MHz. Testing for elastic constant, Poisson's ratio, cross-link density, and microhardness was carried out in different percentages of the blend components to study the degree of the compatibility of the blend. The structure of the blend system was established by differential scanning calorimetry. The addition of NR-g-MA to the blend showed improvement of compatibility in certain concentration ranges and deterioration of compatibility in other ranges.