Ultrasonic Echo Data Research Articles

Application of iterative elastic reverse time migration to shear horizontal ultrasonic echo data obtained at a concrete step specimen

AbstractThe ultrasonic echo technique is broadly applied in non‐destructive testing (NDT) of concrete structures involving tasks such as measuring thickness, determining geometry and locating built‐in elements. To address the challenge of enhancing ultrasonic imaging for complex concrete constructions, we adapted a seismic imaging algorithm – reverse time migration (RTM) – for NDT in civil engineering. Unlike the traditionally applied synthetic aperture focusing technique (SAFT), RTM takes into account the full wavefield including primary and reflected arrivals as well as multiples. This capability enables RTM to effectively handle all wave phenomena, unlimited by changes in velocity and reflector inclinations. This paper concentrates on applying and evaluating a two‐dimensional elastic RTM algorithm that specifically addresses horizontally polarized shear (SH) waves only, as these are predominantly used in ultrasonic NDT of concrete structures. The elastic SH RTM algorithm was deployed for imaging real ultrasonic echo SH‐wave data obtained at a concrete specimen exhibiting a complex back wall geometry and containing four tendon ducts. As these features are frequently encountered in practical NDT scenarios, their precise imaging holds significant importance. By applying the elastic SH RTM algorithm, we successfully reproduced nearly all reflectors within the concrete specimen. In particular, we were capable of accurately reconstructing all vertically oriented reflectors as well as the circular cross sections of three tendon ducts, which was not achievable with traditional SAFT imaging. These findings demonstrate that elastic SH RTM holds the ability to considerably improve the imaging of complex concrete geometries, marking a crucial advancement for accurate, high‐quality ultrasonic NDT in civil engineering.

Concrete Defect Localization Based on Multilevel Convolutional Neural Networks.

Concrete structures frequently manifest diverse defects throughout their manufacturing and usage processes due to factors such as design, construction, environmental conditions and distress mechanisms. In this paper, a multilevel convolutional neural network (CNN) combined with array ultrasonic testing (AUT) is proposed for identifying the locations of hole defects in concrete structures. By refining the detection area layer by layer, AUT is used to collect ultrasonic signals containing hole defect information, and the original echo signal is input to CNN for the classification of hole locations. The advantage of the proposed method is that the corresponding defect location information can be obtained directly from the input ultrasonic signal without manual discrimination. It effectively addresses the issue of traditional methods being insufficiently accurate when dealing with complex structures or hidden defects. The analysis process is as follows. First, COMSOL-Multiphysics finite element software is utilized to simulate the AUT detection process and generate a large amount of ultrasonic echo data. Next, the extracted signal data are trained and learned using the proposed multilevel CNN approach to achieve progressive localization of internal structural defects. Afterwards, a comparative analysis is conducted between the proposed multilevel CNN method and traditional CNN approaches. The results show that the defect localization accuracy of the proposed multilevel CNN approach improved from 85.38% to 95.27% compared to traditional CNN methods. Furthermore, the computation time required for this process is reduced, indicating that the method not only achieves higher recognition precision but also operates with greater efficiency. Finally, a simple experimental verification is conducted; the results show that this method has strong robustness in recognizing noisy ultrasonic signals, provides effective solutions, and can be used as a reference for future defect detection.

Application of Iterative Elastic SH Reverse Time Migration to Synthetic Ultrasonic Echo Data

The ultrasonic echo technique is widely used in non-destructive testing (NDT) of concrete objects for thickness measurements, geometry determinations and localization of built-in components. To improve ultrasonic imaging of complex concrete structures, we transferred a seismic imaging technique, the Reverse Time Migration (RTM), to NDT in civil engineering. RTM, in contrast to the conventionally used synthetic aperture focusing technique (SAFT) algorithms, considers all wavefield types and thus, can handle complex wave propagations in any direction with no limit on velocity variations and reflector dip. In this paper, we focused on the development, application and evaluation of a two-dimensional elastic RTM algorithm considering horizontally polarized shear (SH) waves only. We applied the elastic SH RTM routine to synthetic ultrasonic echo SH-wave data generated with a concrete model incorporating several steps and circular cavities. As these features can often be found in real-world NDT use cases, their imaging is extremely important. By using elastic SH RTM, we were able to clearly reproduce almost all reflectors inside the concrete model including the vertical step edges and the cross sections of the cavities. We were also capable to show that more features could be mapped compared to SAFT, and that imaging of complex reflectors could be sharpened compared to elastic P-SV (compressional-vertically polarized shear) RTM. Our promising results illustrate that elastic SH RTM has the potential to significantly enhance the reconstruction of challenging concrete structures, representing an important step forward for precise, high-quality ultrasonic NDT in civil engineering.

Application of Elastic Reverse Time Migration to Ultrasonic Echo Data in Civil Engineering

The ultrasonic echo technique is widely used in non-destructive testing for investigation and damage analysis of concrete constructions. To improve the ultrasonic imaging of complicated structures in concrete, we transferred a seismic migration technique, the Reverse Time Migration (RTM), to non-destructive testing. In a preliminary study, we tested a 2D acoustic RTM algorithm on measured ultrasonic echo data acquired at a concrete foundation slab. Compared to the conventional used synthetic aperture focusing technique (SAFT) algorithms for ultrasonic data reconstruction, our acoustic RTM results showed a significant improvement in imaging the interior structure of the concrete slab. In contrast to SAFT, RTM is a wavefield-continuation method in time and uses the full wave equation. RTM is, thus, able to include multiple reflections and to handle multi-pathing as well as many other complex situations. As a drawback RTM requires extensive computing power and memory capacity. An RTM algorithm that uses the full elastic wave equation instead of the full acoustic one (as applied in our preliminary work) has the potential to optimize the imaging results even further. This is due to the fact, that our ultrasonic data are generated by exciting elastic waves. In a first step, we tested two 2D elastic RTM algorithms on synthetic ultrasonic echo data generated with a concrete model. Our synthetic elastic RTM results showed an enhancement in imaging the features inside the test model compared to acoustic RTM and SAFT. In a second step, we acquired ultrasonic measurement data at a concrete specimen consisting of three steps and four air-filled tendon ducts. Processing the real ultrasonic data with our elastic RTM codes was successful and improved the reconstruction of the geometries of the steps and tendon ducts. With our study we have shown that elastic RTM is a step forward for ultrasonic testing in civil engineering.

Ultrasonic Echo Localization Using Seismic Migration Techniques in Engineered Barriers for Nuclear Waste Storage

In the framework of non-destructive-testing advanced seismic imaging techniques have been applied to ultrasonic echo data in order to examine the integrity of an engineered test-barrier designed to be used for sealing an underground nuclear waste disposal site. Synthetic data as well as real multi-receiver ultrasonic data acquired at the test site were processed and imaged using Kirchhoff prestack depth migration reverse time migration (RTM). In general, both methods provide a good image quality as demonstrated by various case studies, however deeper parts within the test barrier containing inclined reflectors were reconstructed more accurately by RTM. In particular, the image quality of a specific target reflector at a depth of 8 m in the test-barrier has been significantly improved compared to previous investigations using synthetic aperture focusing technique, which justifies the considerable computing time of this method.

An Ultrasonic Signal Denoising Method for EMU Wheel Trackside Fault Diagnosis System Based on Improved Threshold Function

In the safety protection system of the railway electric multiple unit (EMU), the safety of the running part is extremely important. The daily detection of the internal hazard defects of the wheels in the running parts relies on a professional trackside fault online diagnosis system based on the ultrasonic sensor probe array data. However, the on-line ultrasonic diagnosis of EMU wheels is usually accompanied by various interference noises. The defect echo signals collected by the sensor probe array are weak and are easily submerged by noise, which makes it impossible to perform effective defect identification. This paper proposes an improved threshold function to overcome the discontinuous shortcomings of the classical wavelet soft threshold function and hard threshold function in view of the non-stationary characteristics of the ultrasonic detection signal of the EMU wheels. This paper proposes a sine-type threshold processing function. It is characterized by adopting gradual compression processing to denoise the echo signal of the ultrasonic sensor probe array. In order to verify the validity, the continuity at the threshold is observed through the linear space vector signal, and the algorithm is simulated and tested through the three-dimensional Gaussian echo mathematical model of the ultrasonic signal and the measured ultrasonic envelope signal. Experimental results show that the improved threshold function can suppress the noise in the ultrasonic echo data, improve the signal-to-noise ratio, and retain the waveform characteristics of the defect signal, which is conducive to defect recognition.

Current status of artificial intelligence applications in urology and their potential to influence clinical practice.

To investigate the applications of artificial intelligence (AI) in diagnosis, treatment and outcome predictionin urologic diseases and evaluate its advantages over traditional models and methods. A literature search was performed after PROSPERO registration (CRD42018103701) and in compliance with Preferred Reported Items for Systematic Reviews and Meta-Analyses (PRISMA) methods. Articles between 1994 and 2018 using the search terms "urology", "artificial intelligence", "machine learning" were included and categorized by the application of AI in urology. Review articles, editorial comments, articles with no full-text access, and nonurologic studies were excluded. Initial search yielded 231 articles, but after excluding duplicates and following full-text review and examination of article references, only 111 articles were included in the final analysis. AI applications in urology include: utilizing radiomic imaging or ultrasonic echo data to improve or automate cancer detection or outcome prediction, utilizing digitized tissue specimen images to automate detection of cancer on pathology slides, and combining patient clinical data, biomarkers, or gene expression to assist disease diagnosis or outcome prediction. Some studies employed AI to plan brachytherapy and radiation treatments while others used video based or robotic automated performance metrics to objectively evaluate surgical skill. Compared to conventional statistical analysis, 71.8% of studies concluded that AI is superior in diagnosis and outcome prediction. AI has been widely adopted in urology. Compared to conventional statistics AI approaches are more accurate in prediction and more explorative for analyzing large data cohorts. With an increasing library of patient data accessible to clinicians, AI may help facilitate evidence-based and individualized patient care.

Laser ultrasonic quantitative recognition based on wavelet packet fusion algorithm and SVM

With the development of industrialization and modern technology, laser ultrasonic technique is more and more used in aerospace, machinery and electronics, measurements, metallurgy chemical engineering, materials science, railway transportation, bridge engineering, etc. In order to maintain the excellent characteristics of new materials (such as thermal properties, mechanical properties, chemical properties and optical properties, material structure must be early diagnosed and monitored before properties change. Nondestructive Testing technology plays a great role in monitoring reliability of industry products. This paper proposes a new feature selection method based on wavelet packet algorithm, and applies SVM (support vector machine) for quantitative classification on the ultrasonic echo data generated by cracks in Laser ultrasonic experiment. By combining the nondestructive device and dimension reduction method in machine learning, this paper analyses the scatter plot of two cracks in 2d and the fitting surface in 3d and give the quantitative index for determining the performance of used methods.

Overview of Ultrasound Imaging Algorithms Based on Synthetic Aperture Focusing Technique

Synthetic aperture focusing ultrasound imaging technique used signal processing method to analysis ultrasonic echo data. It let the performance of transducer with small apertures be as well as the transducer with large aperture. It can still obtain high azimuth resolution image and form three-dimensional image, when it was operated at lower operating frequency. This paper describes the history and the theory of synthetic aperture focusing ultrasound imaging technology. It also contains the development of the synthetic aperture focusing ultrasound imaging technology in China and at abroad. And lots of excellent synthetic aperture focusing ultrasound imaging algorithms were listed in this paper. We analyzed the deficiencies and problems of the existing ultrasound focusing algorithms. And we made forecast about the development of synthetic aperture technology in nondestructive testing.

Design and Development of Ultrasonic Testing Virtual Instrument

The optimization problem of ultrasonic testing instrument is studied in this paper. Using ultrasonic nondestructive testing technology to detect quality of products or parts, because the function of conventional ultrasonic testing instruments is custom-built and defined by manufacturers, it is very difficult to meet ever-changing testing requirements such as testing accuracy, testing efficiency and testing automation. In order to meet different testing needs in practical ultrasonic testing, an ultrasonic testing virtual instrument system is designed and developed by combining ultrasonic testing technology with virtual instrument technology, the system hardware is designed by combining FPGA with ARM, data is transmitted via Ethernet, echo signal noise is processed by using wavelet analysis, the system software is mainly developed by LabVIEW. The experimental results show that ultrasonic echo data can be collected, processed, analyzed and displayed by this system and be transmitted via Ethernet, this system is characterized by simple operation, flexible expansion, versatility and high performance.

ULTRASONIC IMAGE GENERATING METHOD

An ultrasonic image generating method for generating an ultrasonic image based on ultrasonic echo data obtained by transmitting/receiving ultrasonic waves to/from an inspection object, according to the present invention, includes reference position setting steps for determining the reference position on each image with respect to a plurality of consecutive two-dimensional tomograms; correction steps for obtaining regular and consecutive two-dimensional tomograms-by-correcting irregularity of the reference position of each of the two-dimensional tomograms determined by the reference position setting steps; and an ultrasonic image generating step for generating the ultrasonic images based on the regular and consecutive two-dimensional tomograms corrected by the correction steps.

Damage Condition of GFRP Large Scrubber Used in Acid-Gas Environment for Long Term

This study investigated damage condition of the large GFRP scrubber which was used to cleanse acid-gas for 35 years without large maintenance. Samples were obtained from four typical parts of the scrubber and optically observed on the inside surfaces and the cross-sections in detail. Ultrasonic-echo inspection and bending tests were further carried out for the obtained samples. The results showed that fishnet-like cracks were formed on the inside surface of the scrubber. Since acid-gas or clearing fluid invaded the inside of GFRP through the fishnet-like cracks, the damage such as delamination was induced in the chopped strand mats existing under the surfacing mats. However, the bending strength of each part was suitably maintained because the damage was generated in limited area. Furthermore, a relatively clear relationship was found between the ultrasonic-echo data and the residual bending strength. This result suggested the possibility of practical application of the ultrasonic-echo inspection for GFRP products.

Quantitative Ultrasonic Elastography for Gel Dosimetry

Advanced radiation techniques such as intensity-modulated radiotherapy (IMRT) for complex geometries in which targets are close to organs at risk have been introduced in radiation therapy, creating a need for procedures that allow easy three-dimensional (3-D) measurement of dose for verification purposes. Polymer gels that change their material properties when irradiated have been suggested for such use. For example, the change in their magnetic properties has been thoroughly investigated with magnetic resonance imaging (MRI). Also, we have previously shown that the mechanical stiffness, i.e., Young's modulus, of these gels changes with dose. This finding prompted us to assess whether we can image a radiation-induced stiffness distribution with quantitative ultrasound elastography and whether the stiffness distribution is correlated with the dose distribution. A methacrylic-acid-based gel was loaded with scatterers to create an ultrasound echoic signal. It was irradiated to create a rod-like region of increased stiffness with a 10 × 10 mm 2 cross-section. The gel block was compressed in a frame that restricted the movement of the gel to planes orthogonal to the long axis of the irradiated region and ultrasonic echo data were acquired in the central plane during compression. This simplified irradiation pattern and experimental set-up were designed to approximate plane-strain conditions and was chosen for proof of concept. The movement of the gel was tracked from ultrasound images of a different compressional state using cross-correlation, enabling a displacement map to be created. The shear modulus was reconstructed using an inverse algorithm. The role of the magnitude of the regularization parameter in the inverse problem and the boundary conditions in influencing the spatial distribution of stiffness and, thus, final dose contrast was investigated through parametric studies. These parameters were adjusted using prior knowledge about the stiffness in parts of the material, e.g., the background was not irradiated and therefore its stiffness was homogeneous. It was observed that a suitable choice for these reconstruction parameters was essential for a quantitative application of stiffness measurement such as dosimetry. The dose contrast and distribution found with the optimal parameters were close to those obtained with MRI. Initial results reported in this article are encouraging and indicate that with ongoing refinement of ultrasound elastography techniques and accompanying inverse algorithms, this approach could play an important role in gel dosimetry. ( jeff.bamber@icr.ac.uk).

温水中に長期間浸漬されたGFRPの損傷状態と超音波エコーの関係

This study was conducted to investigate damage condition of glass-fiber reinforced plastic (GFRP) which was immersed in hot water for a long time. Furthermore, we aimed to establish a non-destructive method based on ultra-sonic echo data for estimating the damage condition and strength of GFRP. For those purposes, we made three kind of GFRPs in which base resins (isophthalic-type UP, bisphenol-type VE and novolak-type VE) possessed different corrosion resistance, and then immersed them in hot water maintained at 368K for 2.6-31.1Ms (1-12 months). The GFRP, whose base resin was isophthalic-type UP possessing relatively low corrosion resistance, suffered to remarkable damage such as interfacial debonding between glass-fibers and the base resin, delamination of glass-fiber cloths and cracking of glass-fibers, so that the bending strength was rapidly reduced. On the other hand, the damage condition in the other GFRPs was not striking because of the base resins having higher corrosion resistance, and their bending strengths were maintained at relatively high levels. Moreover, since the damage condition of the GFRPs was reflected to the ultra-sonic echo data, the bending strengths could be roughly estimated by such data.

Sonohistology – Ultrasonic tissue characterization for prostate cancer diagnostics

A computer-aided diagnostic system for imaging prostate cancer has been developed in order to supplement today's conventional methods for the early detection of prostate carcinoma. The system is based on analysis of the spectral content of radiofrequency ultrasonic echo data in combination with evaluations of textural, contextual, morphological and clinical features in a multiparameter approach. A state-of-the-art, non-linear classifier, the so-called adaptive network-based fuzzy inference system, is used for higher-order classification of the underlying tissue-describing parameters. The system has been evaluated on radio-frequency ultrasound data originating from 100 patients using histological specimens obtained after prostatectomy as the gold standard. Leave-one-out cross-validation over patient data sets results in areas under the ROC curve of 0.86 +/- 0.01 for hypoechoic and hyperechoic tumors and of 0.84 +/- 0.02 for isoechoic tumors, respectively.

Evaluation of Radar and Complementary Echo Methods for NDT of Concrete Elements

Non-destructive testing (NDT) of concrete structures plays an increasing role in civil engineering. This paper presents the results of systematic measurements carried out in the laboratory at BAM and on-site at several bridges using reconstructed and fused radar and ultrasonic echo data sets. For investigating the influence of concrete mixture, radar and ultrasonic measurements were performed at test specimens consisting of concrete mixtures with different pore content and distribution as well as with steel fibres. Further, it is demonstrated how the fusion of data sets recorded with different methods at the same structure (here: concrete bridges) enhances the information content in the fused data set. Different approaches for data fusion algorithms are discussed. The results of these investigations show the high potential of reconstruction and data fusion for the improvement and simplification of the interpretability of large data sets measured with impulse-echo methods. The presented results are based on the research project FOR384 funded by the DFG (Deutsche Forschungsgemeinschaft).

Damage Condition of GFRP Tank Used for Long Term in Acid Environment and Damage Inspection Based on Ultrasonic Echo Measurement

This study was conducted to investigate damage conditions of a large GFRP tank which was employed in the chemical industry to store mixture of nitric acid and phosphoric acid during 19 years. Further, an attempt was made to establish a damage inspection method based on ultrasonic echo measurement for GFRP products. Detailed optical observations were carried out on the inside surface and cross-section of four typical positions of the tank. The results showed that the acid environment invaded the inside of GFRP through cracks and pin holes made on the inside surface of the tank, and then the environment gave remarkable damage to chopped strand mats existing under a surfacing mat. Degree of the damage was adequately predicted, using ultrasonic echo data. Although the above inspection method could predict decrease in the strength of the roof part which suffered severe damage, further investigation was needed to predict remaining strengths of parts where damage was relatively mild.

Validating and expanding the theoretical frameworks that relate ultrasonic backscatter to scatterer properties

Backscattered echo signals are related to scatterer properties in theoretical frameworks published independently by Lizzi and Insana. These frameworks are based on assumptions that may not consistently apply to tissue scatterers. Our study aims to confirm and expand the theory to include scattering under a variety of scatterer conditions. A 35‐MHz transducer was used to scan suspended 12‐μm‐diam uveal melanoma cells. Using Fourier methods, spectral parameters were computed from ultrasonic echo data acquired from the suspension. Normalization was implemented in two ways. First, a glass‐plate calibration spectrum was subtracted from the experimental data. Second, the spectrum acquired from suspended 20‐μm beads was compared to the spectrum predicted by Faran’s theory. The difference between expected and experimental spectra was attributed to system effects. Cell acoustic impedance was estimated from cell‐pellet density and propagation velocity. Theoretical spectral values were computed from cell size, concentration, and acoustic impedance using the Lizzi framework. The cell pellet propagation velocity was 1550 m/s, and the acoustic impedance was 3587 kg/m‐s. The normalized, experimental spectral parameters agreed closely with the theoretical predictions. Future work will include different scatterer sizes and geometries and a comparison of results obtained using the Lizzi and Insana frameworks.

Viscoelasticity imaging using ultrasound: parameters and error analysis

Techniques are being developed to image viscoelastic features of soft tissues from time-varying strain. A compress-hold-release stress stimulus commonly used in creep-recovery measurements is applied to samples to form images of elastic strain and strain retardance times. While the intended application is diagnostic breast imaging, results in gelatin hydrogels are presented to demonstrate the techniques. The spatiotemporal behaviour of gelatin is described by linear viscoelastic theory formulated for polymeric solids. Measured creep responses of polymers are frequently modelled as sums of exponentials whose time constants describe the delay or retardation of the full strain response. We found the spectrum of retardation times τ to be continuous and bimodal, where the amplitude at each τ represents the relative number of molecular bonds with a given strength and conformation. Such spectra indicate that the molecular weight of the polymer fibres between bonding points is large. Imaging parameters are found by summarizing these complex spectral distributions at each location in the medium with a second-order Voigt rheological model. This simplification reduces the dimensionality of the data for selecting imaging parameters while preserving essential information on how the creeping deformation describes fluid flow and collagen matrix restructuring in the medium. The focus of this paper is on imaging parameter estimation from ultrasonic echo data, and how jitter from hand-held force applicators used for clinical applications propagate through the imaging chain to generate image noise.

Development of New Ultrasonic Inspection Technique for Spot Welds with Matrix Arrayed Probe and SAFT

A portable type of 3D ultrasonic inspection system, named “Matrixeye”, was applied to the spot welds, in which a matrix-arrayed probe was used as a sensing unit, and the welding zone in the spot welds was visualised 3-dimensionally. The matrix-arrayed probe, in which 64 piezoelectric elements are embedded as 8 × 8 matrix arrangement, can acquire more than 4 000 ultrasonic echo data points due to their transmission and reception in 0.2 seconds. This system can synthesise 3-dimensional ultrasonic images by SAFT (Synthetic Aperture Focusing Technique) installed in the parallel signal processing board. This system can also inspect the weld quality of spot welds with additional data; e.g., an averaged diameter, area, major axis, minor axis, thickness, and indentation depth of the welded region. In addition, this system has an automatic measurement function, in which the measurement automatically starts by sensing the probe contact with the welding surface, and automatically stops by sensing the position and tilt of the probe within a setting level. The results measured by this system have good correlation with the weld size on the fracture faces and the tensile-shear strength in the destructive tests. It was shown from the evaluated performance of the system that the developed system is applicable to the inspection of spot welds.