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In ultrasonic tomography that employs the technique of digital focusing with an antenna (DFA), the problem of increasing the inspection performance is inextricably linked with the problem of increasing the speed of producing synthesized images. This problem can be effectively solved by concurrently using several approaches aimed at increasing the image production speed. In the framework of this paper, we consider the algorithm of nonuniform fast Fourier transform (NUFFT). The NUFFT can be used in the existing computationally efficient spatiotemporal processing algorithms with calculations in the frequency domain and is capable of correctly reconstructing synthesized images with sparse and non-uniform antenna arrays (AAs). The experimental data obtained indicate the ability of the NUFFT-based algorithm to restore synthesized images with high resolution.

Two-phase flow widely exists in the process industry, where ultrasonic tomography provides reliable visualization with benefits of noninvasion, nonradiation, and low-cost. To provide real-time reconstruction of low acoustic impedance contrast medium distribution existed in two-phase flow, a novel approach using continuous-wave excitation is proposed. With the basic measurement model introduced, a subspace filtered reconstruction algorithm is introduced with improvements on both accuracy and speed. Through nonuniform shape constrained range filter, the relative image error (RE) is reduced by 32.94% and 33.03% compared to simultaneous algebraic reconstruction technique (SART) and filter back projection (FBP) methods. Through derivation of offline iteration/online reconstruction (OIOR) method and truncated singular value decomposition (TSVD), the computing speed increases to 122 frame/s, which fits the requirement of online monitoring. A prototype of the measurement system is introduced with improved design of bipolar high-voltage excitation module and fan-beam angle piezoelectric transducers. Qualitative and quantitative results show that the proposed method has better image accuracy compared to conventional methods.

A non-destructive testing system requires multiple system configuration parameters during the operation process. For a given transducer, scanning frequency and number of measurements for averaging are just among those parameters. This work tests the central limit theorem to optimally set these parameters. The authors have designed a compact ultrasound computer tomography scanner from scratch just to test this criterion. It is shown that optimal frequency value changes with respect to the scanning angle for an object with a heterogeneous inner profile. The proposed criterion helps to estimate the multi-spectral combination before the recovery stage minimum error. Possible industrial applications of such a system are 2D/3D multiphase flow profile recovery or crack detection in the composite matter, non-invasively.

Ultrasound computer tomography (USCT) is a promising modality for breast cancer diagnosis which images the reflectivity, sound speed and attenuation of tissue. Elastic properties of breast tissue, however, cannot directly be imaged although they have shown to be applicable as a discriminator between different tissue types. In this work we propose a novel approach combining USCT with the principles of strain elastography. Socalled USCT-SE makes use of imaging the breast in two deformation states, estimating the deformation field based on reconstructed images and thereby allows localizing and distinguishing soft and hard masses. We use a biomechanical model of the breast to realistically simulate both deformation states of the breast. The analysis of the strain is performed by estimating the deformation field from the deformed to the undeformed image by a non-rigid registration. In two experiments the non-rigid registration is applied to ground truth sound speed images and simulated SAFT images. Results of the strain analysis show that for both cases soft and hard lesions can be distinguished visually in the elastograms. This paper provides a first approach to obtain mechanical information based on external mechanical excitation of breast tissue in a USCT system.

The current quality detection methods for building materials concrete are inaccurate in the processing results of sound waves and amplitude signals, resulting in low accuracy of the propagation velocity and wave velocity dispersion in the detected concrete, and inaccurate quality strength detection results, so based on ultrasonic tomography technology The characteristics of the design of construction materials concrete quality inspection methods. Collect ultrasonic velocity and amplitude signals, and eliminate the abnormal signals in the collected sound velocity and amplitude; make full use of the ultrasonic tomography technology in the internal propagation of the medium, and the characteristics of digital imaging, complete the image transformation, establish the concrete mathematical model, output the internal image of concrete, and complete the concrete quality detection. Experimental results: The proposed construction material concrete quality inspection method, when inspecting the construction material concrete, the dispersion of the propagation velocity and the wave velocity in the detected concrete, compared with other inspection methods, the construction material concrete quality inspection method The result is more accurate.

As an important part of Process Tomography (PT), Ultrasound Tomography (UT) has the advantages of no invasion, no radiation, and low cost. However, UT systems are usually physically limited by the transmitter's emission angle of the transducer, and only three to five receiving transducers which are opposite the excitation transducer can receive the signal. This limitation will lead to insufficient prior information, insufficient data utilization, and severe reconstructed image artifacts, which will affect its practical application. In order to improve the accuracy of reconstruction, a multi-channel Convolutional Neural Network (CNN) method is proposed. The main structure of the U-net network, input of the network has two channels: channel one is the image reconstructed by traditional algorithm, and channel two is the measured voltage value. The training database contains 23,355 samples. After 235 epochs of training, the correlation coefficient of verification set is 0.85 and compared with LBP and SART, the proposed model has better reconstruction results.

The paper presents the results of research on the hybrid industrial tomograph electrical impedance tomography (EIT) and ultrasonic tomography (UST) (EIT-UST), operating on the basis of electrical and ultrasonic data. The emphasis of the research was placed on the algorithmic domain. However, it should be emphasized that all hardware components of the hybrid tomograph, including electronics, sensors and transducers, have been designed and mostly made in the Netrix S.A. laboratory. The test object was a tank filled with water with several dozen percent concentration. As part of the study, the original multiple neural networks system was trained, the characteristic feature of which is the generation of each of the individual pixels of the tomographic image, using an independent artificial neural network (ANN), with the input vector for all ANNs being the same. Despite the same measurement vector, each of the ANNs generates its own independent output value for a given tomogram pixel, because, during training, the networks get their respective weights and biases. During the tests, the results of three tomographic methods were compared: EIT, UST and EIT-UST hybrid. The results confirm that the use of heterogeneous tomographic systems (hybrids) increases the reliability of reconstruction in various measuring cases, which is used to solve quality problems in managing production processes.

Non-destructive testing of concrete for defects detection, using acoustic techniques, is currently performed mainly by human inspection of recorded images. The images consist of the inside of the examined elements obtained from testing devices such as the ultrasonic tomograph. However, such an automatic inspection is time-consuming, expensive, and prone to errors. To address some of these problems, this paper aims to evaluate a convolutional neural network (CNN) toward an automated detection of flaws in concrete elements using ultrasonic tomography. There are two main stages in the proposed methodology. In the first stage, an image of the inside of the examined structure is obtained and recorded by performing ultrasonic tomography-based testing. In the second stage, a convolutional neural network model is used for automatic detection of defects and flaws in the recorded image. In this work, a large and pre-trained CNN is used. It was fine-tuned on a small set of images collected during laboratory tests. Lastly, the prepared model was applied for detecting flaws. The obtained model has proven to be able to accurately detect defects in examined concrete elements. The presented approach for automatic detection of flaws is being developed with the potential to not only detect defects of one type but also to classify various types of defects in concrete elements.

Assessing internal decay in tree trunks can be of crucial importance for industrial, environmental and public safety reasons [1]. To this effect, non-destructive testing (NDT) methods can provide information on the structural condition of trees with minimum intrusion. In this work, authors have analysed the capabilities of ultrasonic tomography in evaluating the internal structure of living trees, with a special focus on the identification of internal decay areas and tree bark inclusions.The presented ultrasonic tomography provides an image of the distribution of the ultrasonic velocity of propagation within the investigated section of a mature horse chestnut (Aesculus hippocastanum). This technique has proven its viability to detect fungal decomposition [2]. However, there exist some open issues with regard to: a) the coupling of the transducers to the tree, b) the anisotropy of the wood, c) the signal attenuation and the resolution of the tomographic inversion. To overcome these challenges, research is underway to explore the integration and new data-fusion strategies with other NDT methods, such as ground penetrating radar (GPR), which have proven their effectiveness within this area of endeavour [3].Within this context, data have been obtained from a “diseased” horse chestnut tree located at the Kensington Gardens – The Royal Parks – in London, UK, using two different ultrasonic equipment, i.e., the PICUS Sonic Tomograph and the Arbotom Sonic Tomograph. After compilation of data, the tree was felled and cut at the two sections where ultrasonic tomography tests were performed. In more detail, 12 sensors were arranged around the perimeter of the tree in compliance with the manufacturer’s recommendations concerning the inspection methodology (sensors installed within the bark of the tree without any intrusion to the core of the tree). The adopted methodology takes to account the shape and size of the trunk [1]. The processed data were mapped against the cut sections of the tree for validity purposes. Results presented in this abstract are part of a major ongoing research project that the authors have undertaken for the last three years. AcknowledgementsThe authors would like to express their sincere thanks and gratitude to the following trusts, charities, organisations and individuals for their generosity in supporting this project: Lord Faringdon Charitable Trust,The Schroder Foundation,Cazenove Charitable Trust,Ernest Cook Trust,Sir Henry Keswick,Ian Bond, P.F. Charitable Trust,Prospect Investment Management Limited,The Adrian Swire Charitable Trust,The John Swire 1989 Charitable Trust,The Sackler Trust,The Tanlaw Foundation, and The Wyfold Charitable Trust. We would like to thank also Ian Rodger – Royal Parks Arboricultural Manager– for providing us with the tested tree. This paper is dedicated to the memory of our colleague and friend Jonathan West, one of the original supporters of this research project. References[1] Gilbert, G.S. et al. (2016). Use of sonic tomography to detect and quantify wood decay in living trees, Applications in Plant Sciences 4(12): 1600060.[2] Bucur, V. Acoustics of Wood. CRC Press Inc., Boca Raton,Argentina (1995).[3] Alani, A.M. et al. (2019). The Use of Ground Penetrating Radar and Microwave Tomography for the Detection of Decay and Cavities in Tree Trunks. Remote Sensing 11: 2073.

Post-tensioning systems provide safe and efficient construction solutions for long span bridges. Despite the improved grouting practices over the past decade, existing post-tensioning systems may have significant amount of grout defects, which could lead to corrosion of the strands. Condition assessment of post-tensioning systems is necessary to allow bridge owners to take timely, proactive actions to mitigate or prevent further deterioration and unanticipated tendon failures. A detailed experimental study conducted to assess the performance of nondestructive evaluation techniques in detecting grout defects within internal tendons is presented herein. Nondestructive evaluation techniques that include Ground Penetrating Radar, Impact Echo, Ultrasonic Tomography, and Ultrasonic Echo are evaluated in terms of detecting the location and severity of fabricated grout defects in a full-scale post-tensioned U-girder mock-up specimen. While Ground Penetrating Radar can identify the location and profile of the internal tendons, particularly metal ducts due to strong reflections, this method did not provide any information about the defect conditions within the tendon. Both Impact Echo and Ultrasonic Echo techniques are effective in identifying the location of grout defects, but could not differentiate between water, void, or compromised grout conditions. The study clearly demonstrates the need for NDE techniques that are applicable to anchorage regions, and that are capable of estimating the severity and nature of grout defects in internal tendons.

Applying ultrasonic-tomography systems makes it possible to precisely determine the shape and dimensions of flaws with the aim of establishing the degree to which the flaws influence safe operation of tested objects. This problem is solved by using special algorithms that make use of echo-signals recorded by an ultrasonic transducer to generate synthesized images of flaws in the sample. The use of phased arrays in ultrasonic tomography is explained by their ability to provide exhaustive data about the internal structure of a test object, thus allowing formation of the high-quality synthesized images of flaws in the object. Increasing the speed of ultrasonic tomography by using phased arrays necessitates the development and implementation of fast data-processing algorithms. In this connection, of interest are calculation algorithms in the frequency domain, which ensure the high speed of producing synthesized images. An ultrasonic-tomography algorithm is proposed that is based on calculations in the frequency domain. The algorithm takes the complex nature of the propagation of ultrasonic waves into account and is connected with the presence of media with different acoustic properties (e.g., in the case of immersion tests). Possibilities offered by the algorithm are investigated by computer simulations using the licensed CIVA 2016 software package and experimentally.

In recent years, due to the destructive and unproductive character of pavement specimen extraction, pavement maintenance technology intensified the use of non-destructive techniques for pavement evaluation which resulted in the development of several devices and evaluation methods. This paper describes the use of technology based on low frequency ultrasonic tomography for evaluation of concrete pavement parameters. The equipment was applied in three experimental sections with different concrete pavements built at the University of Sao Paulo campus. The ultrasonic signal processing is given. The results analysis enables the efficient and reliable identification of thickness and reinforcement position within the concrete slab. Construction problems were evidenced in one of experimental sections with thickness deficiencies and reinforcement in a position below projected. Furthermore, the use of a novel concrete quality indicator was correlated with the presence of transverse cracks and alkali-silica reaction within the sections.

The accuracy of transmission ultrasonic tomography for the detection of brittle damage in concrete beams can be effectively supported by the graph theory and, in particular, by Dijkstra’s algorithm. It allows determining real paths of the fastest ultrasonic wave propagation in concrete containing localized elastically degraded zones at any stage of their evolution. This work confronts this type of approach with results that can be obtained from non-local isotropic damage mechanics. On this basis, the authors developed a method of reducing errors in tomographic reconstruction of longitudinal wave velocity maps which are caused by using the simplifying assumptions of straightness of the fastest wave propagation paths. The method is based on the appropriate elongation of measured propagation times of the wave transmitted between opposite sending-receiving transducers if the actual propagation paths deviate from straight lines. Thanks to this, the mathematical apparatus used typically in the tomography, in which the straightness of the fastest paths is assumed, can be still used. The work considers also the aspect of using fictitious wave sending-receiving points in ultrasonic tomography for which wave propagation times are calculated by interpolation of measured ones. The considerations are supported by experimental research conducted on laboratory reinforced concrete (RC) beams in the test of three-point bending and a prefabricated damaged RC beam.

Робота присвячена дослідженню та аналізу методів визначення санітарного стану деревних насаджень. Визначено основні вимоги до методів та засобів визначення санітарного стану деревних насаджень. Встановлено, що серед методів з найвищим рівнем інформативності є метод ультразвукової томографії. Проте такі недоліки цього методу, як висока вартість, складність в експлуатації та необхідність обслуговування оператором високої кваліфікації, а також велика вага технічного оснащення не дають змоги використовувати цей метод на практиці проведення мобільного моніторингу санітарного стану дерев у польових умовах. У роботі запропоновано якісно новий підхід до вирішення проблемного питання проведення високоефективного та оперативного визначення санітарного стану деревних насаджень шляхом розроблення нового комплексного методу, що базується на методичноматематичному й технічному забезпеченні іонометричного методу і враховує такі негативні фактори навколишнього середовища, як солоність та рН ґрунту, температура повітря, а також встановлення закономірностей між цими факторами та якісними показниками деревного соку (рН, сахаристість та в’язкість). Складено алгоритм проведення високоефективного та оперативного дослідження, а також описано й проаналізовано методики визначення зовнішніх та внутрішніх показників, від яких залежить якість деревного соку та, відповідно, санітарний стан деревних насаджень. The work is devoted to the research and analysis of methods for determining the sanitary condition of wood plantations. Among these methods the most methods, used in practice, such as: visual, resistographic, boroscopic, ultrasonic tomography, thermometric and ionometric ones are selected. The advantages and disadvantages of these methods are identified and compared. The basic requirements to the methods and means for determining the sanitary condition of wood plantations are determined. It is established that among the methods with the highest level of information content, the method of ultrasound tomography is promising. However, such disadvantages of this method as the high cost, the complexity of operation and the need for service by high qualified operator, as well as the heavy weight of technical equipment do not allow to use this method in practice of conducting the mobile monitoring of the sanitary condition of wood plantations in the field conditions. The work proposes a qualitatively new approach to solving the problem of conducting a highly effective and efficient determination of the sanitary condition of wood plantations by developing a new integrated method based on methodological, mathematical and technical support of the ionometric method and taking into account such negative environmental factors as salinity and soil pH, air temperature, as well as the establishment of patterns between these factors and quality indicators of wood sap (pH, sugar content and viscosity). An algorithm for conducting a highly effective and operational research is compiled, and methods for determining external and internal indicators that determine the quality of wood sap and, accordingly, the sanitary condition of tree plantations are described and analyzed

Due to the nature of their use, concrete structures are typically subjected to various aggressive actions derived from the loads and the environmental agents, which make the concrete condition change over time. Constant monitoring of structures is a necessary procedure since the preventive detection of problems allows the use of more straightforward and cost-effective methods for evaluation and repair. In order to carry out continuous monitoring of the state condition of concrete elements, there are many tools available. Nondestructive Testing (NDT) applications are a new strategy to monitor the state of concrete structures continually. Recent advancements in NDT technologies are increasingly turning them into attractive and viable strategies to support this type of monitoring and visual inspection. In particular, besides been viable and attractive, ultrasonic tests are a relatively cheap alternative and represent a range of different methods, each one with its benefits, to analyze concrete structures. The Research Group of LEME-UFRGS has developed research and application of NDT methods in general, and ultrasonic based methods in particular, for the last 15 years. The research done by the group demonstrates that these methods can contribute to monitoring deterioration and the quality of concrete structures. The present study demonstrates particular cases involving ultrasonic pulse testing and ultrasonic tomography. The aim was to check for these technique improvements for the analysis of concrete elements. The results highlight the potentialities and shortcomings of each technique.

In the process of creating digital images of concrete, wave propagation can be used to generate a suitable inner representation of this element, producing an ultrasonic tomography. Although tomography devices are efficient in generating images, they are high-cost and not very accessible. On the other hand, images obtained through ultrasound tests allow identifying the presence of flaws in different types of materials at lower costs. In ultrasonic tests, ultrasonic wave velocity paths are generated from different measurement points. Thus, in order to improve the data range, interpolation techniques can be used to estimate the acoustic velocity at the unmeasured test points, completing the image creation process. This work aims to evaluate the influence on the quality of the generated image of (1) the spatial resolution and (2) the number of measurement points in the ultrasonic test. Experiments were carried out using Inverse Distance Weighting interpolation technique and ultrasonic tomography on concrete beams with and without flaws. The resulting images indicated the importance of the appropriate choice of number and arrangement of measuring points in the ultrasonic test to properly detect internal flaws. In addition, we verify that a higher spatial resolution may also interfere in the identification of internal flaws in the image.

Ultrasonic testing of concrete by modern equipment has grown in importance in recent years in non-destructive testing. Measuring concrete cover thickness and estimating steel rebar position and diameter is main focus for assessment of existing reinforcement concrete facilities. Voids, entrained air and potential delamination are important to detect in order to evaluate the quality of the executed concrete members. This paper presents the latest two modern non-destructive techniques – ultrasonic tomography and electromagnetic pulse induction – suitable for testing reinforcement concrete members. The capabilities of these techniques for locating defects, reinforcement bars and determining their size in unilaterally accessible concrete members are described.

Industrial Process Tomography possesses unique advantages in biphasic medium measurement and has received broad attention in the past decades. Aiming at the widely existed low contrast biphasic medium, this paper proposed a nonlinear Ultrasonic Transmission Tomography (UTT). Approach using continuous wave excitation. Considering the refraction effect at the biphasic interface, the reconstruction method with nonlinear forward problem and the improved Simultaneous Algebraic Reconstruction Technique (SART) is proposed with high reconstruction accuracy and reconstruction speed. The performance of the reconstruction is quantitatively compared with the state-of-art reconstruction algorithms, where the proposed method can reconstruct inclusions with their number, size and position clearly identified. Quantitatively, the average Relative Error (RE) is 0.4835 using the proposed method, which is reduced by 49.34% and 40.57% compared with FBP and SART separately. Under parallel computation, the computing time of the proposed method reduced 16.56 times compared with the existing bent-ray tracing method. The proposed image reconstruction algorithm is proved to be an effective and improved approach to the liquid-liquid two-phase flow ultrasonic tomography.

This paper presents the development of an ultrasonic tomography system for multiphase flow imaging. Ultrasonic tomography (UT) modality has a hard-field sensing principle which makes feasible to measure liquid-gas, liquid-liquid and liquid-solid flow composition within a pipe vessel. The sensor configuration for the UT system is discussed along with its signal conditioning circuitry and image reconstruction technique. The feasibility of the system is experimentally carried out on a 100 mm acrylic pipe for a stratified multiphase flow measurement to reconstruct tomographic images.

The problem of image reconstruction in ultrasonic tomography (UST) consists in both performing measurements using a set of sensors and creating of reconstruction based on these measurements. The image reconstruction requires accurate modeling of area, which presents field of view. To determine the inclusion in analyzed area the logistic regression has been applied. Additionally to select the predictors in logistic regression the elasticnet method has been used.

Computerized ultrasonic tomography is an important radiological technique because of its non-ionizing properties. However, it has been the subject of several studies due to the complexity of its visualization. In this work, a Ram-Lak filter is implemented in the Radon domain to reduce the noise levels in the images and facilitate their observation. Results obtained were superior to those reported in the state of the art with an average improvement of 8.1512 dB.

X-ray tomography and magnetic resonance imaging (MRI) are excellent techniques for non-destructive or non-invasive inspections, however, they have shotcomings including the expensive cost in both the devices themselves and their protection facilities, the harmful side effects of the X-rays to human bodies and to the environment. In view of this argument, it is necessary to develop new, inexpensive, safe and reliable tomographic techniques, especially in medical imaging and non-destructive inspections. There are new tomographic techniques under development such as optical tomography, photo-acoustic tomography, ultrasonic tomography and so on, from which we take ultrasonic tomography as the topic in this paper. We introduce a review of the known ultrasonic tomographic techniques and discuss their future development.

Oil-water biphasic medium widely existed in mining and transportation process of petroleum industry, where visualized measurement processes vital importance in production increase, state monitoring and fault prognosis. Ultrasonic Tomography (UT) is a non-invasive and non-radioactive sensing modality in industrial Process Tomography, which is demonstrated as a competitive monitoring technique with great potential. However, facing the refraction effect of Ultrasound wave at oil-water interfaces, the accuracy of reconstruction algorithm is with large error and serious artifacts. To address the issue, a modified ray-tracing image reconstruction algorithm is proposed. The amplitude attenuation during ultrasound propagation in nonhomogeneous medium is quantitatively modeled to form absolute UT model. With ray tracing strategy applied and improved, the nonlinear refraction effect is characterized in the form of iterative update of sensitivity matrix, followed by which the sound speed mapping transfers reconstructed attenuation images to sound speed distribution for ray tracing computation. Numerical tests indicate that the proposed method significantly improves reconstruction accuracy through projection-based, regularization-based and algebraic-based inverse algorithms, which demonstrate its benefits in conducting oil-water biphasic medium imaging.

Non-destructive tests play a crucial role for rehabilitation, restoration and strengthening of historical masonry constructions: this justifies increasing research interests on this issue. In particular, sonic and ultrasonic tomography are among the most used NDT techniques for applications to historical constructions since they are relatively fast, reliable and inexpensive. Anyway, the resolution and the capability of those techniques in assessing hidden defects, voids, damage, the masonry layout and the mechanical properties of masonry can be further substantially improved. To this aim, several issues about the experimental setup, the modeling of propagation phenomena of acoustic waves, and the inversion algorithms should be addressed. In this paper some improvements of the ultrasonic tomography for masonry constructions are proposed, based on the implementation of advanced inversion algorithms, on the use of the information about wave attenuation (attenuation tomography) in addition to those related to the time of flight of acoustic waves, and on the enhancement of the experimental setup, in particular for what concerns the coupling between probes and masonry. With reference to tuff samples having known internal defects like holes, cuts and inclusions, the capability of the proposed approach is compared with the standard ultrasonic tomography. The experimental results show the effectiveness of the proposed approach, and suggest some directions for further improvements.

Nonlinear tomographic ultrasound reconstructions can provide quantitative data about material parameters like the speed of sound also in reflection-mode imaging. However, these methods suffer from the cycle skipping issue which is caused by the high center frequencies usual in medical ultrasound hardware. As these algorithms are based on minimization of a misfit function where the high frequency signals lead to local minima, false reconstruction are the result. Previous approaches try to circumvent this problem by low pass filtering the measured signals. This method is limited by the bandwidth and SNR of the measurement system. In this contribution, we applied the optimal transport distance known from seismic reconstructions. This approach uses all frequency components while enhancing the included traveltime information. We compare the misfit functions and show reconstructions using the standard and the optimal transport method. The results demonstrate an at least 1.6 times higher convergence limit.

The need for flow measurements throughout the production cycle has led to the development of a variety of multiphase flow meters. An ultrasonic tomographic multiphase flow meter is being developed in which it can potentially replace radioactive and invasive types of multiphase flow meters. The meter is configured to generate cross-sectional images of the flow inside the pipe in a non-invasive manner yet with direct contact to the fluid. Image reconstruction is generally carried out via inversion which requires a high level of computation complexity and processing time. It can be further challenged by the limited amount of data available. Compressed Sensing (CS) optimizes the conventional structure for data acquisition and compression. CS is based upon recovering certain data from very few measurements. Loosely speaking, most CS algorithms fall into either two categories; convex optimization recovery and greedy pursuits. In this paper, CS greedy pursuit algorithms are used to reconstruct sound speed images to find the most suitable algorithm in terms of image quality. Specifically, we made a comparative analysis of three greedy CS algorithms; Orthogonal Matching Pursuit (OMP), Compressive Sampling Matching Pursuit (CoSaMP), and Fast Bayesian Matching Pursuit (FBMP). We further compare the CS greedy reconstruction results to a conventional approach for image recovery based on the least-squares problem. Simulation results show that CS algorithms highly outperform the conventional approach for image recovery. Results demonstrate that high quality image recovery can be achieved using these simple greedy pursuit algorithms, sometimes even at increased system efficiency. Out of the three greedy algorithms, CoSaMP shows the highest quality for image recovery. Results also suggest that careful selection of the number of measurements used for recovery is necessary to obtain an accurate image reconstruction. As presented in this paper, our purpose is to adapt a CS approach, specifically greedy pursuit algorithms, for an efficient and an improved reconstruction of images generated by the ultrasonic tomographic multiphase flow meter to accurately quantify phase fractions in producing oil wells.

The authors are trying to develop an ultrasonic CT technique for concrete structures. As the first step of its development, we study how the ultrasonic waves propagate in concrete structures and pose a problem to develop ultrasonic CT, applying which we give a non-destructive inspection technique for concrete cover by application of the idea of the ultrasonic CT. The authors claim that this study gives the foundation of the theory of ultrasonic CT for concrete structures.

Ultrasound Tomography (UT) is a non-invasive, safe, dynamic and relatively inexpensive imaging technique for abdominal diagnosing and monitoring. With the mature of pulse-echo technique, the Ultrasound Reflection Tomography (URT) is widely used in a variety of applications. However, such methods have the disadvantages of low resolution with limited information contained in received signal when operated in human abdomen. Here, to deal with this issue, a continuous wave UT method is presented to image the lesion in upper human abdomen. A series of numerical simulation are conducted to analyze the human abdominal ultrasound field under continuous wave excitation while the incident frequency is optimized according to the resolution and signal intensity synthetically as indicators. The reconstruction result shows that the proposed method has a preferable accuracy locating primary tumors in the major organs, which proves the feasibility of using continuous wave ultrasonic tomography in the examination of human abdominal cancer.

Ultrasonic tomography (UT) is a non-invasive multiphase flow detection technique. In ultrasonic transmission tomography, reconstruction images are derived from a direct wave signal transmitted through the materials in the sensing area. The maximum values of the received direct wave from the reference pattern and the measured pattern are normally used to reconstruct the images. The speed of sound in the pipe wall and the materials in the sensing area affect the received signal. This in turn affects image quality—especially when the arrival time of the direct wave propagated through the sensing area is close to the arrival time of the direct wave propagated through the pipe wall. Here, we describe a novel shielding structure for ultrasonic transmission tomography. The relative variation ratio (RVR) is defined and used to evaluate the validity of the shielding structure. Larger RVR values imply better signal resolution and better signal suppression. A simplified mode is discussed including the influence of the shielding structure’s design parameters on the received direct wave. The optimized shielding structure size was determined. A comparison of the results between the normal pipe and the shielding pipe indicated that the RVR increased from 57.25 to 91.27%. This proves that the shielding structure can suppress the effect of the signal from the pipe wall on received direct wave signals.

Spent nuclear fuel (SNF) is one of the most hazardous types of nuclear power plant waste. This fact emphasizes the importance of careful handling and storage of SNF. There are two current state-of-the art technologies of SNF storage facility: wet and dry. It is important to mention that IAEA does not determine which kind of handling strategy should be chosen, however it is noted that dry storage of SNF could be used for one hundred years. Mining and Chemical Enterprise (MCE) is one of the leading Russian companies that deals exclusively with the dry storage of SNF. This company has implemented a long-term storage scheme. At the same time MCE faced the challenge of nondestructive monitoring of the degradation process of structural material of cask and its sealing with weld seam. Currently, X-ray testing is used for this purpose but in order to provide an effective nonradioactive method of monitoring MCE has initiated a collaborative R&D project with TPU supported by the Russian Government. Ultrasonic industrial tomography technique was proposed as the solution. The method is based on application of phased and sparse arrays transducer with real-time visualization algorithm. Received acoustic data is processed and realized by means of Sampling Phased Array technology which is a collaborative development of TPU and I-Deal Technology, GmbH. The multichannel ultrasonic set-up of immersion control was assembled for performing testing of seven experimental specimens with representative defects (side drill-holes, notches, natural welding flaws). X-ray tomography of high-resolution was chosen as the reference method. All indications were successfully reconstructed in B and C-scans and 3D image. The next step is to automate the monitoring procedure completely and to introduce an evaluation tool for current flaw state and prediction of its further behavior.

Ultrasound Computer Tomography (USCT) is used to map local wave propagation parameters, such as speed-of-sound (SoS), as potential imaging biomarkers. Reflector-based USCT is a technique for the implementation of USCT using commercial transducer arrays, in contrast to complex USCT hardware setups requiring suspension in a water bath. In this work, we model a prototype 2D-matrix transducer and study reflector-based 3D-USCT reconstruction feasibility and resolution via numerical simulations. Modeling the ultrasound wavefronts using rays, we employ 3D-ray tracing methods to compute acoustic travel paths on a reconstruction voxel grid, and subsequently utilize optimization techniques to solve the inverse problem of SoS reconstruction. We show the feasibility of generating 3D USCT images and study the resolution for varying tissue SoS contrast.

Ultrasonic tomography is a practical method to detect cracks or voids in nonmetallic materials. The typical inversion results were presented by grids based velocity map, and it can not characterized the rapid changes or discontinuities in defects area. When the grid is dense, the solution is non-unique, and the regularization and stochastic method were induced to solve it. However, the regularization constraint will induce subjective judgment thus distort the results, and the using of stochastic method is highly computational cost. Both of them will inhibit the in-situ application. Here we present a new algorithm to depict the defects boundary. The process base on the rough tomography results, which enhance the solution's uniqueness. The model after interpolation will be refined to expected resolution, and we further perform morphological operation to complete defects identification. Fast marching method is induced to calculate the refine model travel time. The output of the proposed algorithm will directly give the optimal solution of defects, and eliminate the human judgment. Two filed data examples will be shown where the tomography results were compared with the algorithm result. The result shows that the proposed algorithm can recur the defects contour properly, without extra measurements and excessively computational cost.

In this paper we present a structural health monitoring (SHM) paradigm based on the simultaneous use of ultrasounds and electromechanical impedance (EMI) to monitor waveguides. The paradigm uses guided ultrasonic waves (GUWs) in pitch-catch mode and EMI simultaneously. The two methodologies are driven by the same sensing/hardware/software unit. To assess the feasibility of this unified system an aluminum plate was monitored for varying damage location. Damage was simulated by adding small masses to the plate. The results associated with pitch-catch GUW testing mode were used in ultrasonic tomography, and statistical analysis was used to detect the damages using the EMI measurements. The results of GUW and EMI monitoring show that the proposed system is robust and can be developed further to address the challenges associated with the SHM of complex structures.

Synthetic Aperture Focusing Technique (SAFT) allows fast data acquisition and optimally focused images. The computational burden for 3D imaging is large as for each voxel the delay for each acquired A-scan has to be calculated, e.g. O(N5) for N3 voxels and N2 A-scans. For 3D reconstruction of objects which are large in terms of the wavelength, e.g. ≥ (100 λ)3, the computation of one volume takes several days on a current multicore PC. If the 3D distribution of the speed of sound is applied to correct the delays, the computation time increases further. In this work a time of flight interpolation based GPU implementation (TOFI-SAFT) is presented which accelerates our previous GPU implementation of speed of sound corrected SAFT by a factor of 7 to 16 min. with only minor reduction of image quality.

As today's standard screening methods frequently fail to detect breast cancer before metastases have developed, early diagnosis is still a major challenge. With the promise of high-quality volume images, three-dimensional ultrasound computer tomography is likely to improve this situation, but has high computational needs. In this work, we investigate the acceleration of the ray-based transmission reconstruction by a GPU-based implementation of the iterative numerical optimization algorithm TVAL3. We identified the regular and transposed sparse-matrix-vector multiply as the performance limiting operations. For accelerated reconstruction we propose two different concepts and devise a hybrid scheme as optimal configuration. In addition we investigate multi-GPU scalability and derive the optimal number of devices for our two primary use-cases: a fast preview mode and a high-resolution mode. In order to achieve a fair estimation of the speedup, we compare our implementation to an optimized CPU version of the algorithm. Using our accelerated implementation we reconstructed a preview 3D volume with 24,576 unknowns, a voxel size of (8?mm)3 and approximately 200,000 equations in 0.5?s. A high-resolution volume with 1,572,864 unknowns, a voxel size of (2mm)3 and approximately 1.6 million equations was reconstructed in 23?s. This constitutes an acceleration of over one order of magnitude in comparison to the optimized CPU version. We accelerate a ray-based 3D ultrasound CT reconstruction by GPU processing.By use-case optimized SpMV variants a speedup of one order of magnitude is obtained.We derive the optimal number of GPUs for reconstructions that do not fit on one GPU.A 3D-preview is reconstructed in 0.5 s, a high-resolution volume in 23 s.

Ultrasound computer tomography (USCT) is a promising candidate for early breast cancer detection. This paper presents a prototype system for ultrasound computer tomography. It consists of four parts: a 2.5-MHz ring array with 1024 elements, front-end circuits, a 128-channel data acquisition system and a computer workstation. The effectiveness of the captured raw data was analyzed. The system was tested with one nylon thread phantom and one breast phantom. The former had 6 nylon threads with a diameter of 0.6mm each and spacing of 3.2 mm for spatial resolution evaluation. Each nylon thread could be clearly distinguished in the reconstructed image. The latter was used for contrast resolution evaluation. The cyst tissue in the phantom could be shown in the scanned image.

Статья посвящена разработке эффективных методов решения обратных задач волновой томографии. Предложена новая схема послойной томографии трехмерных объектов с экспериментальными данными, которые измеряются на цилиндрической поверхности. Такая схема обеспечивает измерение как отраженных, так и проходящих волн и легко реализуема на практике. Для решения обратной задачи используется математическая модель, которая хорошо описывает как дифракционные эффекты, так и эффект поглощения ультразвукового излучения. Предложены эффективные численные методы восстановления скоростного разреза по экспериментальным томографическим данным на цилиндрической поверхности. Разработанные методы ориентированы в первую очередь на диагностику рака молочной железы на ранних стадиях заболевания. Обратные задачи ультразвуковой томографии являются нелинейными и очень сложными с вычислительной точки зрения. Численные алгоритмы реализованы на графических процессорах. Эффективность разработанных алгоритмов иллюстрируется модельными расчетами., This paper is dedicated to developing efficient methods to solve inverse problems of wave tomography. The proposed new scheme of layer-by-layer tomography of 3D objects uses the experimental data measured on a cylindrical surface. This scheme provides the measurements of both the reflected and the transmitted waves and can easily be implemented in practice. The mathematical model used to solve the inverse problem takes into account the ultrasound diffraction and absorption effects. The authors developed efficient numerical methods to reconstruct the sound speed cross section using the tomographic data measured on the cylindrical surface. These methods are aimed primarily at early breast cancer diagnosis. The inverse problems of ultrasonic tomography are nonlinear and very computationally expensive. The efficiency of the developed methods is illustrated via numerical simulations. The numerical algorithm is implemented on GPU., ВЫЧИСЛИТЕЛЬНЫЕ МЕТОДЫ И ПРОГРАММИРОВАНИЕ: НОВЫЕ ВЫЧИСЛИТЕЛЬНЫЕ ТЕХНОЛОГИИ, Выпуск 3 2017

A promising candidate for breast cancer imaging is ultrasound computer tomography (USCT). At Karlsruhe Institute of Technology (KIT) a 3D USCT with a semiellipsoidal aperture consisting of several hundreds of US transducers was built. The utilized imaging methods require accurate and reliable temperature information over the measured space and acquisition time. Several methods were applied which improved the temperature accuracy and reliability beyond the hardware defaults by one order of magnitude from ±1°C to approx. 0.005°C beyond the requirement of 0.1°C.

In our first clinical study with a full 3D Ultrasound Computer Tomography (USCT) system patient data was acquired in eight minutes for one breast. In this paper the patient movement during the acquisition was analyzed quantitatively and as far as possible corrected in the resulting images. The movement was tracked in ten successive reflectivity reconstructions of full breast volumes acquired during 10 s intervals at different aperture positions, which were separated by 41 s intervals. The mean distance between initial and final position was 2.2 mm (standard deviation (STD) ± 0.9 mm, max. 4.1 mm, min. 0.8 mm) and the average sum of all moved distances was 4.9 mm (STD ± 1.9 mm, max. 8.8 mm, min. 2.7 mm). The tracked movement was corrected by summing successive images, which were transformed according to the detected movement. The contrast of these images increased and additional image content became visible.

Ultrasound Computer Tomography (USCT) is a promising new imaging method for breast cancer diagnosis. We developed a 3D USCT system and tested it in a pilot study with encouraging results: 3D USCT was able to depict two carcinomas, which were present in contrast enhanced MRI volumes serving as ground truth. To overcome severe differences in the breast shape, an image registration was applied. We analyzed the correlation between average sound speed in the breast and the breast density estimated from segmented MRIs and found a positive correlation with R=0.70. Based on the results of the pilot study we now carry out a successive clinical study with 200 patients. For this we integrated our reconstruction methods and image post-processing into a comprehensive workflow. It includes a dedicated DICOM viewer for interactive assessment of fused USCT images. A new preview mode now allows intuitive and faster patient positioning. We updated the USCT system to decrease the data acquisition time by approximately factor two and to increase the penetration depth of the breast into the USCT aperture by 1 cm . Furthermore the compute-intensive reflectivity reconstruction was considerably accelerated, now allowing a sub-millimeter volume reconstruction in approximately 16 minutes. The updates made it possible to successfully image first patients in our ongoing clinical study.

In the field of non-destructive evaluation of structures, 2D and 3D imaging of internal flaws is a critical task. Defect imaging allows making informed follow-up decisions based on the morphology of the flaw. This paper will present advances in ultrasonic tomography for the 2D and 3D visualization of internal flaws in solids. In particular, improvements to the conventional tomographic imaging algorithms have been made by utilizing a mode-selective image reconstruction scheme that exploits the specific displacement field, respectively, of the longitudinal wave modes and the shear wave modes, both propagating simultaneously in the test volume. The specific mode structure is exploited by an adaptive weight assignment to the ultrasonic tomographic array. Such adaptive weighting forces the imaging array to look at a specific scan direction and better focus the imaging onto the actual flaw (ultrasound reflector). Moreover, the introduction of a global matched coefficient, computed through the matching of measured and expected times of flight for each pixel, is illustrated. The benefits deriving from the application of this coefficient to conventional imaging frameworks are shown. This study shows that the adaptive weighing based on wave structure and the integration of the global matched coefficient improve image contrast and resolution compared to a conventional ultrasonic imaging technique based on a delay-and-sum or minimum variance distortionless method. Results will be shown from experimental tests of simulated flaws in solids.

Ultrasound Computer Tomography (USCT), developed at KIT, is a promising new imaging system for breast cancer diagnosis, and was successfully tested in a pilot study. The 3D USCT II prototype consists of several hundreds of ultrasound (US) transducers on a semi-ellipsoidal aperture. Spherical waves are sequentially emitted by individual transducers and received in parallel by many transducers. Reflectivity volumes are reconstructed by synthetic aperture focusing (SAFT). However, straight forward SAFT imaging leads to blurred images due to system imperfections. We present an extension of a previously proposed approach to enhance the images. This approach includes additional a priori information and system characteristics. Now spatial phase compensation was included. The approach was evaluated with a simulation and clinical data sets. An increase in the image quality was observed and quantitatively measured by SNR and other metrics.

Currently, breast cancer is one of the most common cancers in women all over the world. A novel 3D breast ultrasound imaging ring system using the linear array transducer is proposed to decrease costs, reduce processing difficulties, and improve patient comfort as compared to modern day breast screening systems. The 1 × 128 Piezoelectric Micromachined Ultrasonic Transducer (PMUT) linear array is placed 90 degrees cross-vertically. The transducer surrounds the mammary gland, which allows for non-contact detection. Once the experimental platform is built, the breast model is placed through the electric rotary table opening and into a water tank that is at a constant temperature of 32 °C. The electric rotary table performs a 360° scan either automatically or mechanically. Pulse echo signals are captured through a circular scanning method at discrete angles. Subsequently, an ultrasonic tomography algorithm is designed, and a horizontal slice imaging is realized. The experimental results indicate that the preliminary detection of mass is realized by using this ring system. Circular scanning imaging is obtained by using a rotatable linear array instead of a cylindrical array, which allows the size and location of the mass to be recognized. The resolution of breast imaging is improved through the adjustment of the angle interval (>0.05°) and multiple slices are gained through different transducer array elements (1 × 128). These results validate the feasibility of the system design as well as the algorithm, and encourage us to implement our concept with a clinical study in the future.

3D Ultrasound Computer Tomography (USCT) is a new imaging method for breast cancer diagnosis. In the current state of development it is essential to correlate USCT with a known imaging modality like MRI to evaluate how different tissue types are depicted. Due to different imaging conditions, e.g. with the breast subject to buoyancy in USCT, a direct correlation is demanding. We present a 3D image registration method to reduce positioning differences and allow direct side-by-side comparison of USCT and MRI volumes. It is based on a two-step approach including a buoyancy simulation with a biomechanical model and free form deformations using cubic B-Splines for a surface refinement. Simulation parameters are optimized patient-specifically in a simulated annealing scheme. The method was evaluated with in-vivo datasets resulting in an average registration error below 5mm. Correlating tissue structures can thereby be located in the same or nearby slices in both modalities and three-dimensional non-linear deformations due to the buoyancy are reduced. Image fusion of MRI volumes and USCT sound speed volumes was performed for intuitive display. By applying the registration to data of our first in-vivo study with the KIT 3D USCT, we could correlate several tissue structures in MRI and USCT images and learn how connective tissue, carcinomas and breast implants observed in the MRI are depicted in the USCT imaging modes.

Key message High-resolution imaging is possible if high-frequency sensors are used together with a signalprocessing and inversion algorithm that is well suited to a low signal-to-noise ratio and the effect of wood anisotropy. Wood is a biological growth medium, and given that standing trees adapt themselves in their growth to environmental conditions, their material properties vary with age. These changes result in variations that are far more complex than anisotropy. Wood quality and intraspecific variability can thus be studied to gain an understanding of the development mechanisms of trees, and this can be useful for clonal selection and the management of tree communities. A number of techniques are available to determine wood properties in standing trees, but the signal-processing approaches currently used are not always robust and do not always provide the image resolution needed in the particular cases of acoustic or ultrasonic tomography. This review paper thus aims to present important aspects that should be taken into account when using tomography techniques and addresses a number of open problems. A brief review of current non-destructive wood imaging techniques is initially presented followed by a comparison of the protocols, methods and models used in acoustic and ultrasonic tomography. The devices cited were studied in terms of measurement systems and signal processing. The analysis aimed to highlight and analyze the advantages and disadvantages of each device and describe challenges and trends. The effect of various parameters is discussed: frequency, signal-to-noise ratio, number of sensors and inversion algorithm. General conclusions are then drawn in relation to future signal-processing work in the acoustic and ultrasonic tomography of standing trees.

A promising candidate for improved imaging of breast cancer is ultrasound computer tomography (USCT). The aim of this work was to design a new aperture for our full 3D USCT which extends the properties of the current aperture to a larger ROI fitting the buoyant breast in water and decreasing artifacts in transmission tomography. The optimization resulted in a larger opening angle of the transducers, a larger diameter of the aperture and an approximately homogeneous distribution of the transducers, with locally random distances. The developed optimization methods allow us to automatically generate an optimized aperture for given diameters of apertures and transducer arrays, as well as quantitative comparison to other arbitrary apertures. Thus, during the design phase of the next generation KIT 3D USCT, the image quality can be balanced against the specification parameters and given hardware and cost limitations. The methods can be applied for general aperture optimization, only limited by the assumptions of a hemispherical aperture and circular transducer arrays.

Ultrasound tomography is an emerging modality for breast imaging. However, most current ultrasonic tomography imaging algorithms, historically hindered by the limited memory and processor speed of computers, are based on ray theory and assume a homogeneous background which is inaccurate for complex heterogeneous regions. Therefore, wave theory, which accounts for diffraction effects, must be used in ultrasonic imaging algorithms to properly handle the heterogeneous nature of breast tissue in order to accurately image small lesions. However, application of waveform tomography to medical imaging has been limited by extreme computational cost and convergence. By taking advantage of the computational architecture of Graphic Processing Units (GPUs), the intensive processing burden of waveform tomography can be greatly alleviated. In this study, using breast imaging methods, we implement a frequency domain waveform tomography algorithm on GPUs with the goal of producing high-accuracy and high-resolution breast images on clinically relevant time scales. We present some simulation results and assess the resolution and accuracy of our waveform tomography algorithms based on the simulation data.

A new technique using ultrasound computed tomography is explained. Reconstruction of pictures follows basically the algorithm of radiology CT in one plane. The computed data of several scan planes with different angles of the same subject are used for image reconstruction. In this manner, poor lateral resolution of reflections is eliminated. The improved quality of the CT ultrasound images is shown.

側音化構音を有する4症例の構音動態について, 超音波断層法により側音化構音時の舌の後方の動きを前額面にて観察した.その結果, 舌の後方の動きは音産生に先立ちまず舌全体が挙上する.そして, 破裂音や破擦音の産生時には呼気の流出する側の舌縁が急速に下がること, 摩擦音の時にはやや下がることが観察された.この舌縁の動きは, 正常な破裂音や摩擦音をつくる時の構音点における舌の動きと同様であった.また, ダイナミックパラトグラフにて舌の前方と硬口蓋の接触状況を観察したが, 接触パタンには差があるものの, 音産生時には舌は硬口蓋に接したままであることが観察された.以上の結果から, 側音化構音の構音点は, 呼気が流出する側の舌の後方の舌縁にあり, そこでつくられた音声および呼気は頬部と歯列の間を通って出るものと考えられた.