Ultrasonic Imaging System Research Articles

Dual-energy wave subtraction imaging for evaluation of barely visible impact damage with an ultrasonic propagation imaging system

Barely visible impact damage from low-velocity impacts have been studied as critical design factors of composite structures. In this article, a dual-energy wave subtraction algorithm using an ultrasonic propagation imaging system is proposed to evaluate barely visible impact damage as a strategy of fast in situ nondestructive evaluation or structural health monitoring (SHM). The ultrasonic propagation imaging system is a type of nondestructive evaluation or SHM system and is based on scanning laser-induced guided ultrasound and fixed sensors. The amplitude of ultrasonic signals generated by the ultrasonic propagation imaging system increases with the increasing energy of the laser beam. Two ultrasonic signals generated by different excitation energies of the laser beam can be equalized by multiplying a constant factor to one of them. Therefore, the residuals after subtraction of two signals may be close to zero. However, the two different energy induced signals in the damaged area will be nonzero due to the change in material conditions regarding the laser ultrasonic generation mechanism. The dual-energy wave subtraction algorithm eliminates most of the incident ultrasonic waves and amplifies anomalous waves. A composite wing skin including two barely visible impact damages as well as a composite sandwich panel, including a single barely visible impact damage, were inspected to validate the proposed algorithm.

Toroidal sensor arrays for real-time photoacoustic imaging.

This article addresses theoretical and numerical investigation of image formation in photoacoustic (PA) imaging with complex-shaped concave sensor arrays. The spatial resolution and the size of sensitivity region of PA and laser ultrasonic (LU) imaging systems are assessed using sensitivity maps and spatial resolution maps in the image plane. This paper also discusses the relationship between the size of high-sensitivity regions and the spatial resolution of real-time imaging systems utilizing toroidal arrays. It is shown that the use of arrays with toroidal geometry significantly improves the diagnostic capabilities of PA and LU imaging to investigate biological objects, rocks, and composite materials.

The research of compression and generation of high-precision dynamic focusing delay data for ultrasound beamformer

In an ultrasound imaging system, dynamic focusing is crucial in improving the spatial resolution and signal-to-noise ratio. However, the generation of focusing delay data (FDD) requires complex calculations and a large amount of memory. The dynamic focusing system may become extremely complex as the number of focusing channels and the focal depth increase. This paper presents a simplified scheme of a high-precision generator for the FDD in Field-programmable Gate Array (FPGA). First, the original FDD are pre-calculated, quantized, decomposed, and compressed by exploiting the recursive characteristics between focusing channels. Then, the initial value and changing locations of each channel are stored as a reference data set. Finally, the FDD are generated in real time by decompressing the preloaded reference data set during the focusing process. The results indicate that the proposed approach consumes less than l% of the memory space of the original method, which may provide significant resource savings and low hardware power consumption. The proposed method can also be applied to convex or flat transducers array in compact beamformers. Moreover, the focusing accuracy and compression ratio can be flexibly adjusted, and the compression ratio can be further improved when the proposed approach is combined with the dynamic aperture. The proposed approach is contribute to the solution of the problem of the complex and large amount of data in ultrasonic imaging system. It is suitable for designing a specific compact focusing beamformer, particularly for a portable ultrasound imaging system.

FPGA-based ultrasonic energy mapping with source removal method for damage visualization in composite structures

This paper presents the implementation of an ultrasonic energy mapping (UEM) method in a field programmable gate array (FPGA)-based processing board. This method is integrated into an ultrasonic propagation imaging (UPI) system for real-field application. UEM method involves two-dimensional Fourier transform and wavenumber filtering to capture the energy scattering waves. Performing multi-dimensional Fourier transform in FPGA is a challenging task because it cannot fit into a single FPGA chip, and therefore, external memory is required to handle a large amount of data. The row–column decomposition method is used to perform 2D Fourier transform using two DDR3 SDRAM memories. Additionally, a source removal function is added into the system to highlight the damage when high energy at the source location occurs. The UPI system was applied for inspection of a composite wing box with impact damages. The UEM results showed that a damage of 20 × 20 mm2 was detected successfully in the presence of the source inside the scan area. Moreover, the UEM result is produced in less than 5 s for 57,600 points, which is practical for a real-world, non-destructive testing application.

Multi-functional Ultrasonic Micro-elastography Imaging System

In clinical decision making, in addition to anatomical information, biomechanical properties of soft tissues may provide additional clues for disease diagnosis. Given the fact that most of diseases are originated from micron sized structures, an elastography imaging system of fine resolution (~100 µm) and deep penetration depth capable of providing both qualitative and quantitative measurements of biomechanical properties is desired. Here, we report a newly developed multi-functional ultrasonic micro-elastography imaging system in which acoustic radiation force impulse imaging (ARFI) and shear wave elasticity imaging (SWEI) are implemented. To accomplish this, the 4.5 MHz/40 MHz transducer were used as the excitation/detection source, respectively. The imaging system was tested with tissue-mimicking phantoms and an ex vivo chicken liver through 2D/3D imaging. The measured lateral/axial elastography resolution and field of view are 223.7 ± 20.1/109.8 ± 6.9 µm and 1.5 mm for ARFI, 543.6 ± 39.3/117.6 ± 8.7 µm and 2 mm for SWEI, respectively. These results demonstrate that the promising capability of this high resolution elastography imaging system for characterizing tissue biomechanical properties at microscale level and its translational potential into clinical practice.

Ultrasonic signal classification and imaging system for composite materials via deep convolutional neural networks

Automated ultrasonic signal classification systems are finding increasing use in many applications for the recognition of large volumes of inspection signals. Wavelet transform is a well-known signal processing technique in fault signal diagnosis system. Most of the proposed approaches have mainly used low-level handcraft features based on wavelet transform to encode the information for different defect classes. In this paper, we proposed a deep learning based framework to classify ultrasonic signals from carbon fiber reinforced polymer (CFRP) specimens with void and delamination. In our proposed algorithm, deep Convolutional Neural Networks (CNNs) are used to learn a compact and effective representation for each signal from wavelet coefficients. To yield superior results, we proposed to use a linear SVM top layer in the training process of signal classification task. The experimental results demonstrated the excellent performance of our proposed algorithm against the classical classifier with manually generated attributes. In addition, a post processing scheme is developed to interpret the classifier outputs with a C-scan imaging process and visualize the locations of defects using a 3D model representation.

On the use of an optoacoustic and laser ultrasonic imaging system for assessing peripheral intravenous access

We describe a universal system for research in combined real-time optoacoustic (OA) and laser-ultrasonic (LU) imaging. The results of its testing on the task of needle insertion into the blood vessel model diagnostics are presented. In OA mode, where laser light is absorbed directly in the sample, the contents of blood vessel model is clearly visible. In LU mode, where the short ultrasonic probe pulse scattered on the sample is detected, the needle is clearly visible. The developed solution combining OA and LU imaging modalities due to the common detection system allowed real-time diagnostics of the position of medical needles (0.63mm and 0.7mm in diameter) inside blood vessel models (1.6mm and 2.4mm in diameter). Frame rate was 10Hz. High longitudinal spatial resolution of the system − 0.1mm − allows distinguishing the two walls of the vessel model and the position of the needle inside.

Simulation and experimental study of the sensor emitting frequency for ultrasonic tomography system in a conducting pipe

Ultrasonic tomography techniques provide flow visualization capability, non-invasively and non-intrusively, to enhance the understanding of complex flow processes. There is limited ultrasonic research in tomography imaging systems in the tomogram analysis of fluid flow in a conducting pipe because of a high acoustic impedance mismatch, which means that very little ultrasonic energy can be transmitted through the interface. The majority of industrial pipelines are constructed from metallic composites. Therefore, the development and improvement of ultrasonic measurement methods to accommodate a stainless steel pipe are proposed in this paper. Experimental and simulation distribution studies of the ultrasonic emitting frequency in acrylic versus stainless steel pipes were studied, measured and analyzed. During the simulation, ultrasonic transducers were placed on the surface of the investigated pipe to inspect the ultrasonic sensing field. The distribution of the sound wave acoustic pressure was simulated based on the physical dimensions and parameters of the actual experimental hardware set-up. We developed ultrasonic acoustic models using the finite element method with COMSOL software, and experiments were carried out to validate the simulation results. Finally, by performing the static phantoms tests, a feasibility study of ultrasonic tomography system was presented to investigate the void fraction of liquid column inside a stainless steel pipe.

Isolated left ventricular diastolic dysfunction in diabetes mellitus: opinions change

Aim — to compare the features of diastolic dysfunction (DD) with preserved left ventricular (LV) ejection fraction (EF) in patients with diabetes mellitus type 2 (DM2) with arterial hypertension (AH) and in patients with essential hypertension (EH) without diabetes.Material and methods. The study involved 87 patients with DD with preserved LV EF: 53 patients with DM2 with AH and 34 patients EH without diabetes. Transthoracic echocardiography was performed by ultrasonic imaging system iE33 xMATRIX («Philips», USA). DD was determined in a complex: type on the basis of the ratio parameters of pulsed-wave (E/A) and tissue (e/a) Doppler; and severity on the Е/e values and pulmonary capillary wedge pressure (PCWP). Myocardial contractile function was assessed by traditional LVEF by Simpson and more exactly, in details on the basis of the longitudinal, radial and circular deformation of the LV myocardium by speckle-tracking echocardiography (using the program Q-lab 3.0 Advanced Ultrasound Quantification software).Results. The groups were comparable in clinical characteristics. The average level of HbA1c in patients with DM2 was 8.2±1.7%. The average LV EF by Simpson in the EH group was 59.9±8.1, in DM2 — 58.3±6.7 (p=0.228). There were more severe disorders of LV Diastolic function in DM2 patients: the values of E/e (p=0.000) and PCWP (p=0.001) were significantly higher in diabetic patients (14,1±5,5 and 15,3±4,7 mm Hg) than in EH (9.7±2.3 and 11.9±1.3 mm Hg). Although that the LV EF (by traditional echocardiographic method of Simpson) was preserved in both groups , the LV global longitudinal strain (12.4±3.0) was significantly lower in DM2 (p=0.005), than patients with EH (16.6±2.0) by speckle-tracking echocardiography.Conclusion. Severity of LV DD are harder in Patients with diabetes and hypertension, than in patients with EH with the similarity of clinical manifestations and data of traditional echocardiographic methods. There were found initial disorders of LV longitudinal myocardial fibers contraction by speckle-tracking echocardiography in patients with DM and preserved LV EF. The combination of impairment of systolic and diastolic function in diabetes is inseparable. Early development of combined systolic and diastolic dysfunction in DM2 is associated with a poor prognosis: a higher risk of early development of atrial fibrillation, ventricular arrhythmias and progressive heart failure.

FPGA-based design and implementation of data acquisition and real-time processing for laser ultrasound propagation

Ultrasonic propagation imaging (UPI) has shown great potential for detection of impairments in complex structures and can be used in wide range of non-destructive evaluation and structural health monitoring applications. The software implementation of such algorithms showed a tendency in time-consumption with increment in scan area because the processor shares its resources with a number of programs running at the same time. This issue was addressed by using field programmable gate arrays (FPGA) that is a dedicated processing solution and used for high speed signal processing algorithms. For this purpose, we need an independent and flexible block of logic which can be used with continuously evolvable hardware based on FPGA. In this paper, we developed an FPGA-based ultrasonic propagation imaging system, where FPGA functions for both data acquisition system and real-time ultrasonic signal processing. The developed UPI system using FPGA board provides better cost-effectiveness and resolution than digitizers, and much faster signal processing time than CPU which was tested using basic ultrasonic propagation algorithms such as ultrasonic wave propagation imaging and multi-directional adjacent wave subtraction. Finally, a comparison of results for processing time between a CPU-based UPI system and the novel FPGA-based system were presented to justify the objective of this research.

Multi-directional adjacent wave subtraction and shifted time point mapping algorithms and their application to defect visualization in a space tank liner

We propose the multi-directional adjacent wave subtraction (MAWS), shifted time point (STP) mapping and variable time window amplitude (VTWA) mapping algorithms for crack visualization based on our finding that the processing direction of the adjacent wave subtraction with respect to crack orientation can dramatically affect crack visibility. The proposed MAWS, STP and VTWA mapping algorithms were implemented in a laser ultrasonic propagation imaging system and were applied in a nondestructive evaluation of an Al-alloy tank liner for space applications. A crack and void on the fusion zone of a weld were more effectively visualized using the proposed algorithms, and the crack could be visualized regardless of its orientation. The multi-directional processing results of the anomalous wave propagation imaging were visualized as video clips. The STP mapping algorithm, which maps the number of shifted time points to minimize the difference between adjacent waves, was developed to enhance the crack visualization capability of the system. Additionally, the multi-directional VTWA mapping algorithm performed data projection using the residuals of MAWS processing and provided stationary mapping results of crack-induced anomalous waves. The presented results demonstrate that the proposed visualization algorithms are promising techniques that do not overlook unknown crack orientations.

전영역 펄스-에코 초음파전파영상화 시스템의 CN-235의 도색된 샌드위치 조종면 In-situ 비파괴평가 기술

전영역 펄스-에코 초음파전파영상화 시스템의 CN-235의 도색된 샌드위치 조종면 In-situ 비파괴평가 기술

Analysis of fluctuation for pixel-pair distance in co-occurrence matrix applied to ultrasonic images for diagnosis of liver fibrosis.

Chronic liver disease requires careful follow-up during long-term treatment, and development of a quantitative diagnosis method for liver fibrosis based on an ultrasonic imaging system is highly desired. Texture analysis using a co-occurrence matrix was applied to both clinical and simulated ultrasonic images of fibrotic livers. A sequence of matrices was generated for pixel-pair distance, r, and texture feature contrast was chosen to examine the response to r in combination with statistical analysis of echo amplitude distribution using a multi-Rayleigh model. The contrast converged with a larger value and fluctuated more significantly in response to r as fibrosis progressed in both the clinical and simulated ultrasonic images. The convergent value rapidly increased at the early stage of fibrosis, and the fluctuation became larger at the advanced stage of fibrosis. Analysis using simulated ultrasonic images with a known fibrous tissue structure theoretically clarified the relationship between contrast behavior and fibrosis progression. It was revealed that contrast convergent value and contrast fluctuation provided information on the fibrous tissue structure, and they are expected to be used for quantitative diagnosis of the degree of liver fibrosis.

In situ non-destructive evaluation of an aircraft UHF antenna radome based on pulse-echo ultrasonic propagation imaging

Most aircraft antennas are protected by radomes made of composite materials. However, antenna radome structures are easily damaged by external forces and internal manufacturing defects. To detect damage in the composite antenna radomes while in service, a full-field pulse-echo ultrasonic propagation imaging (PE UPI) system is proposed as an in situ non-destructive inspection technique, which is mobile inside a hangar. The radome is generally a double-curvature structure, and thus, a curvature compensation algorithm is also developed to increase damage visibility. The proposed hardware and software have been tested by detecting a resin rich region formed between the E-glass/epoxy plies. To visualize the damage, PE ultrasonic wave propagation imaging has been performed, and ultrasonic energy mapping has also been applied. A curvature compensating algorithm has been newly developed and compared for its performance in damage visibility improvement. To verify the size of the real defects of a UHF antenna radome, destructive testing has been performed by cutting the defect area, polishing the cross section and investigating the section using a 50× microscope. The results have shown the feasibility of the proposed PE UPI system and the inspection strategy as an in situ non-destructive evaluation technique for radome structures.

Defect visualization of aircraft UHF antenna radome using full-field pulse-echo ultrasonic propagation imaging system

Most of aircraft antennas usually have various types of radome made of composite materials for protecting antenna structures. However, these antenna radome structures, which are installed on the outside of airplane, are easy to be damaged by external forces such as drag, foreign object, bird strike and others. In this study, full-field pulse-echo ultrasonic propagation imaging (PE UPI) system is proposed as the non-destructive inspection technique to visualize manufacturing defects in composite antenna radome. Based on the results of the sample case study, it is shown that the ultrasonic wave propagation imaging (UWPI) that is generated by the proposed full-field PE UPI system is able to highlight the intact internal condition of antenna structure and its defect area. Additional damage visualization techniques like ultrasonic energy mapping (UEM), variable time window amplitude map (VTWAM) and also ultrasonic spectral imaging (USI) algorithms are applied to improve the reliability of the damage visualization. It can be concluded that the proposed PE UPI system is an effective non-destructive inspection technique for the composite radome structures.

Ultrasonic imaging of sum frequency components by crossed beam contrast echo method

In a breast cancer diagnosis, the clinical usefulness of the contrast echo harmonic imaging has been reported. The authors proposed a contrast echo method by crossing the two ultrasonic beams to improve the accuracy. The microbubbles in the crossed region re-emit the secondary wave including the sum frequency components. It is capable of discriminating between the echo from microbubbles and the echo from tissue without microbubbles, since the sum frequency are not generated during the nonlinear propagation of primary wave outside the crossed region. Thus the contrast of the resultant image is improved. This study measured the sum frequency components in the echoes from the microbubbles of Sonazoid® in degassed water by using the ultrasonic imaging system with 64 channels. The ultrasonic wave of 5 MHz was transmitted from the array probe of central frequency of 6 MHz equipped with the imaging system. Since the beam formed by the array probe crossed the other beam of 2 MHz at the position 8 cm apart from th...

CMOS Ultrasonic Receiver With On-Chip Analog-to-Digital Front End for High-Resolution Ultrasound Imaging Systems

CMOS capacitive micromachined ultrasonic transducer (CMUT) with integrated front-end circuits for portable high resolution ultrasonic imaging systems is presented. The CMUT array operates with 30 V power supply. In addition, the interlayer metal CMUTs with non-uniform membrane are proposed to improve the sensitivity in this paper. A prototype chip containing 48 elements as 12 channels is implemented. The conversion efficiency of the proposed CMUTs is 5.84 times higher than that in the published literatures. The maximum ultrasonic signal bandwidth is 4.5 MHz. CMUT array and the transimpedance amplifiers are integrated on the same chip. In addition, a multibit continuous-time $\Delta \Sigma $ modulator was designed and fabricated in another chip using 0.18- $\mu \text{m}$ standard CMOS process. The chips size are 1.84 and 0.177 mm2, and the total power consumption in the receiving mode is approximately 3.01 mW with 1.8 V power supply.

Análisis de la implementación software de un conformador de señales ultrasónicas para tiempo real

This paper studies the software implementation in an ultrasonic imaging system of Total Focusing Method. In order to accomplish real-time requirements parallel programming techniques have been used. Then, using GPGPU techniques, two different implementation alternatives are analysed, showing how proper planning of access to data improves the performance of the algorithm.

Development of a long-range multi-area scanning ultrasonic propagation imaging system built into a hangar and its application on an actual aircraft

Materials such as aluminum alloys and carbon composites are widely used in aircraft structures. In the case of the use of Al-alloys in aircraft structures, fatigue cracks occur because of excessive and repeated loading and vibrations experienced during frequent flights. Meanwhile, composite materials are also damaged—for example, impact damage and debonding—and have defects, including voids, prepreg gaps, and overlaps created during the manufacturing process. Ultrasonic propagation imaging is a damage visualization technique that is used in structural inspections employing a laser scanning system and ultrasonic sensors. However, conventional ultrasonic propagation imaging or other scanning systems, such as a scanning laser Doppler vibrometer, only permit a single area to be inspected at one time. It is also difficult to inspect inaccessible areas, such as the upper skins of the aircraft wings. In this work, we describe a multi-area scanning ultrasonic propagation imaging system built in a hangar that is able to rapidly scan at a pulse repetition rate of 20 kHz. After acquiring the generated ultrasonic wave signal induced by laser excitation, ultrasonic propagation imaging videos for the in-plate guided wave are displayed. Finally, internal damage can be identified in a damage visualization platform. The developed multi-area scanning ultrasonic propagation imaging system is demonstrated by performing simultaneous inspections on two areas containing manufacturing defects in a large carbon/epoxy laminate. We also performed a demonstration of the hangar-based multi-area scanning ultrasonic propagation imaging system on an actual aircraft containing back surface cracks. The multi-area scanning ultrasonic propagation imaging system with tilting mirror systems installed in the hangar ceiling permitted a clear visualization of the damage. The damage visualization results confirm that the proposed multi-area scanning ultrasonic propagation imaging system and approach have excellent applicability as a built-in ultrasonic propagation imaging system for a Smart Hangar, which is a future structural health monitoring solution that will be used to realize a full-scale structural inspection of an actual aircraft.

Development of single channeled serial-connected piezoelectric sensor array and damage visualization based on multi-source wave propagation imaging

Piezoelectric sensors have been widely used for structural health monitoring. However, a single piezoelectric sensor has limited coverage, and multi-channel piezoelectric sensors require massive cabling and channeling devices. This article presents a serial-connected piezoelectric sensor array equipped with conductive fabric tape for damage diagnosis on a wide area, structure using an ultrasonic propagation imaging system. The sensor array was developed as a single channel sensing technique with multiple sensors. Using conductive fabric tape for installation provided convenient and compact installation, light weight, and comparatively low attenuation, compared with the lead wire for the easy smartilization of structures. An aluminum plate with various artificial damages was tested with the proposed sensor array combined with the ultrasonic propagation imaging system. The ultrasonic propagation imaging system stimulated the sensitive areas of the serially connected piezoelectrics and generated multi-wave sources covering a wide area. The multi-source wave propagation video visualized the damages in the form of anomalous waves. Consequently, multi-cabling and multi-channeling are not required because multiple piezoelectrics can be deployed by serial connections using conductive fabric tapes because of the multi-source wavefield generating capability of the ultrasonic propagation imaging system. Therefore, light-weight, compact, and easy installation of the sensor network and inspection for full-scale structures become possible.