Artigos de revistas: "2D array transducer"

1

Roh, Yongrae. "Design and Fabrication of a 2D Array Ultrasonic Transducer". JOURNAL OF THE ACOUSTICAL SOCIETY OF KOREA 32, n.º 5 (2013): 393. http://dx.doi.org/10.7776/ask.2013.32.5.393.

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Lu, Jian-Yu, e Jiqi Cheng. "Field Computation for Two-Dimensional Array Transducers with Limited Diffraction Array Beams". Ultrasonic Imaging 27, n.º 4 (outubro de 2005): 237–55. http://dx.doi.org/10.1177/016173460502700403.

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A method is developed for calculating fields produced with a two-dimensional (2D) array transducer. This method decomposes an arbitrary 2D aperture weighting function into a set of limited diffraction array beams. Using the analytical expressions of limited diffraction beams, arbitrary continuous wave (cw) or pulse wave (pw) fields of 2D arrays can be obtained with a simple superposition of these beams. In addition, this method can be simplified and applied to a 1D array transducer of a finite or infinite elevation height. For beams produced with axially symmetric aperture weighting functions, this method can be reduced to the Fourier-Bessel method studied previously where an annular array transducer can be used. The advantage of the method is that it is accurate and computationally efficient, especially in regions that are not far from the surface of the transducer (near field), where it is important for medical imaging. Both computer simulations and a synthetic array experiment are carried out to verify the method. Results (Bessel beam, focused Gaussian beam, X wave and asymmetric array beams) show that the method is accurate as compared to that using the Rayleigh-Sommerfeld diffraction formula and agrees well with the experiment.

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3

Dong, Zhijie, Shuangliang Li, Chengwu Huang, Matthew R. Lowerison, Dongliang Yan, Yike Wang, Shigao Chen, Jun Zou e Pengfei Song. "Real-time 3D ultrasound imaging with a clip-on device attached to common 1D array transducers". Journal of the Acoustical Society of America 155, n.º 3_Supplement (1 de março de 2024): A102. http://dx.doi.org/10.1121/10.0026955.

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Performing 3D ultrasound imaging at a real-time volume rate (e.g., >20 Hz) is a challenging task. While 2D array transducers remain the most practical approach for real-time 3D imaging, the large number of transducer elements (e.g., several thousand) that are necessary to cover an effective 3D field-of-view impose a fundamental constraint on imaging speed. Although solutions such as multiplexing and specialized transducers, including sparse arrays and row-column-addressing arrays, have been developed to address this limitation, they inevitably compromise imaging quality (e.g., SNR, resolution) in favor of speed. Coupled with the high equipment cost of 2D arrays, these compromises hinder the widespread adoption of 3D ultrasound imaging technologies in clinical settings. In this presentation, we introduce an innovative transducer clip-on device comprising a water-immersible, fast-tilting electromechanical acoustic reflector and a redirecting reflector to enable real-time 3D ultrasound imaging using common 1D array transducers. We will first introduce the principles underlying our novel technique, followed by validation studies incorporating simulation and experimental data. We will also demonstrate the feasibility of using the clip-on device to achieve a high 3D imaging volume rate that is suitable for advanced imaging modes such as shear wave elastography, blood flow imaging, and super-resolution ultrasound localization microscopy.

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4

Li, Xiaotong, Anthony Gachagan e Paul Murray. "Design of 2D Sparse Array Transducers for Anomaly Detection in Medical Phantoms". Sensors 20, n.º 18 (19 de setembro de 2020): 5370. http://dx.doi.org/10.3390/s20185370.

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Aperiodic sparse 2D ultrasonic array configurations, including random array, log spiral array, and sunflower array, have been considered for their potential as conformable transducers able to image within a focal range of 30–80 mm, at an operating frequency of 2 MHz. Optimisation of the imaging performance of potential array patterns has been undertaken based on their simulated far field directivity functions. Two evaluation criteria, peak sidelobe level (PSL) and integrated sidelobe ratio (ISLR), are used to access the performance of each array configuration. Subsequently, a log spiral array pattern with −19.33 dB PSL and 2.71 dB ISLR has been selected as the overall optimal design. Two prototype transducers with the selected log spiral array pattern have been fabricated and characterised, one using a fibre composite element composite array transducer (CECAT) structure, the other using a conventional 1–3 composite (C1–3) structure. The CECAT device demonstrates improved coupling coefficient (0.64 to 0.59), reduced mechanical cross-talk between neighbouring array elements (by 10 dB) and improved operational bandwidth (by 16.5%), while the C1–3 device performs better in terms of sensitivity (~50%). Image processing algorithms, such as Hough transform and morphological opening, have been implemented to automatically detect and dimension particles located within a fluid-filled tube structure, in a variety of experimental scenarios, including bespoke phantoms using tissue mimicking material. Experiments using the fabricated CECAT log spiral 2D array transducer demonstrated that this algorithmic approach was able to detect the walls of the tube structure and stationary anomalies within the tube with a precision of ~0.1 mm.

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Light, Edward D., Salim F. Idriss, Kathryn F. Sullivan, Patrick D. Wolf e Stephen W. Smith. "Real-Time 3D Laparoscopic Ultrasonography". Ultrasonic Imaging 27, n.º 3 (julho de 2005): 129–44. http://dx.doi.org/10.1177/016173460502700301.

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We have previously described 2D array ultrasound transducers operating up to 10 MHz for applications including real time 3D transthoracic imaging, real time volumetric intracardiac echocardiography (ICE), real time 3D intravascular ultrasound (IVUS) imaging, and real time 3D transesophageal echocardiography (TEE). We have recently built a pair of 2D array transducers for real time 3D laparoscopic ultrasonography (3D LUS). These transducers are intended to be placed down a trocar during minimally invasive surgery. The first is a forward viewing 5 MHz, 11 times 19 array with 198 operating elements. It was built on an 8 layer multilayer flex circuit. The interelement spacing is 0.20 mm yielding an aperture that is 2.2 mm × 3.8 mm. The O.D. of the completed transducer is 10.2 mm and includes a 2 mm tool port. The average measured center frequency is 4.5 MHz, and the −6 dB bandwidth ranges from 15% to 30%. The 50 Ω insertion loss, including Gore MicroFlat cabling, is −81.2 dB. The second transducer is a 7 MHz, 36 times 36 array with 504 operating elements. It was built upon a 10 layer multilayer flex circuit. This transducer is in the forward viewing configuration and the interelement spacing is 0.18 mm. The total aperture size is 6.48 mm x 6.48 mm. The O.D. of the completed transducer is 11.4 mm. The average measured center frequency is 7.2 MHz, and the −6 dB bandwidth ranges from 18% to 33%. The 50 Ω insertion loss is −79.5 dB, including Gore MicroFlat cable. Real-time in vivo 3D images of canine hearts have been made including an apical 4-chamber view from a substernal access with the first transducer to monitor cardiac function. In addition, we produced real time 3D rendered images of the right pulmonary veins from a right parasternal access with the second transducer, which would be valuable in the guidance of cardiac ablation catheters for treatment of atrial fibrillation.

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6

Wang, Xu-Bo, Le-Ming He, You-Cao Ma, Wen-Juan Liu, Wei-Jiang Xu, Jun-Yan Ren, Antoine Riaud e Jia Zhou. "Development of Broadband High-Frequency Piezoelectric Micromachined Ultrasonic Transducer Array". Sensors 21, n.º 5 (5 de março de 2021): 1823. http://dx.doi.org/10.3390/s21051823.

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Piezoelectric micromachined ultrasonic transducers (PMUT) are promising elements to fabricate a two-dimensional (2D) array with a pitch small enough (approximately half wavelength) to form and receive arbitrary acoustic beams for medical imaging. However, PMUT arrays have so far failed to combine the wide, high-frequency bandwidth needed to achieve a high axial resolution. In this paper, a polydimethylsiloxane (PDMS) backing structure is introduced into the PMUTs to improve the device bandwidth while keeping a sub-wavelength (λ) pitch. We implement this backing on a 16 × 8 array with 75 µm pitch (3λ/4) with a 15 MHz working frequency. Adding the backing nearly doubles the bandwidth to 92% (−6 dB) and has little influence on the impulse response sensitivity. By widening the transducer bandwidth, this backing may enable using PMUT ultrasonic arrays for high-resolution 3D imaging.

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7

Choi, Jae Hoon, e Kwan Kyu Park. "2D Sparse Array Transducer Optimization for 3D Ultrasound Imaging". Journal of the Korean Society for Nondestructive Testing 34, n.º 6 (30 de dezembro de 2014): 441–46. http://dx.doi.org/10.7779/jksnt.2014.34.6.441.

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8

Bybi, Abdelmajid, Driss Khouili, Christian Granger, Mohammed Garoum, Ahmed Mzerd e Anne-Christine Hladky-Hennion. "Experimental Characterization of A Piezoelectric Transducer Array Taking into Account Crosstalk Phenomenon". International Journal of Engineering and Technology Innovation 10, n.º 1 (1 de janeiro de 2020): 01–14. http://dx.doi.org/10.46604/ijeti.2020.4348.

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Ultrasonic transducer arrays are generally composed of several piezoelectric elements arranged in 1D or 2D ways. Crosstalk is an undesirable phenomenon decreasing the performance of these devices. It generates parasitic displacements at the elements' radiating surfaces, which changes the directivity of the array. Furthermore, the transducer's displacement plays a critical role in terms of the focal area and transferred intensities. The objective of this paper is to characterize a piezoelectric array composed of seven-elements made of PZ 27 ceramic experimentally. It investigates the effects of the crosstalk phenomenon on the array's performance in particular. The results have shown that the array's elements vibrate mainly in thickness mode, but the displacement is not uniform along their length due to the contribution of a parasitic length mode. Moreover, the major parasitic displacements are obtained on the neighboring passive elements: about -7.3 dB, -11 dB, and -12 dB, on the first, the second, and the third elements, respectively.

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9

Hua, Shao Yan, Yu Chi Ming e Ming Yue Ding. "Computer Simulation for Medical Ultrasound C-Mode Imaging Based on 2d Array". Advanced Materials Research 532-533 (junho de 2012): 719–23. http://dx.doi.org/10.4028/www.scientific.net/amr.532-533.719.

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C-mode imaging is one of the ultrasound imaging modalities. Compared with other modalities, e.g. A-mode, B-mode, M-mode, and Doppler, C-mode is mainly developed and used in industry testing. The potential of C-mode imaging for medical application has not been fully explored. In this paper, we design one 2-d plane array transducer through using the point spread function (PSF), and apply the 2d array transducer for C-mode imaging. The simulation results show that the generated C-mode images can display the anatomic structure and the pathological changes on the biological tissue.

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10

Joshi, Sanjog Vilas, Sina Sadeghpour e Michael Kraft. "Polyimide-On-Silicon 2D Piezoelectric Micromachined Ultrasound Transducer (PMUT) Array". Sensors 23, n.º 10 (17 de maio de 2023): 4826. http://dx.doi.org/10.3390/s23104826.

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This paper presents a fully addressable 8 × 8 two-dimensional (2D) rigid piezoelectric micromachined ultrasonic transducer (PMUT) array. The PMUTs were fabricated on a standard silicon wafer, resulting in a low-cost solution for ultrasound imaging. A polyimide layer is used as the passive layer in the PMUT membranes on top of the active piezoelectric layer. The PMUT membranes are realized by backside deep reactive ion etching (DRIE) with an oxide etch stop. The polyimide passive layer enables high resonance frequencies that can be easily tuned by controlling the thickness of the polyimide. The fabricated PMUT with 6 µm polyimide thickness showed a 3.2 MHz in-air frequency with a 3 nm/V sensitivity. The PMUT has shown an effective coupling coefficient of 14% as calculated from the impedance analysis. An approximately 1% interelement crosstalk between the PMUT elements in one array is observed, which is at least a five-fold reduction compared to the state of the art. A pressure response of 40 Pa/V at 5 mm was measured underwater using a hydrophone while exciting a single PMUT element. A single-pulse response captured using the hydrophone suggested a 70% −6 dB fractional bandwidth for the 1.7 MHz center frequency. The demonstrated results have the potential to enable imaging and sensing applications in shallow-depth regions, subject to some optimization.

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11

Light, Edward D., Victor Lieu e Stephen W. Smith. "New Fabrication Techniques for Ring-Array Transducers for Real-Time 3D Intravascular Ultrasound". Ultrasonic Imaging 31, n.º 4 (outubro de 2009): 247–56. http://dx.doi.org/10.1177/016173460903100403.

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We have previously described miniature 2D array transducers integrated into a Cook Medical, Inc. vena cava filter deployment device. While functional, the fabrication technique was very labor intensive and did not lend itself well to efficient fabrication of large numbers of devices. We developed two new fabrication methods that we believe can be used to efficiently manufacture these types of devices in greater than prototype numbers. One transducer consisted of 55 elements operating near 5 MHz. The interelement spacing is 0.20 mm. It was constructed on a flat piece of copper-clad polyimide and then wrapped around an 11 French catheter of a Cook Medical, Inc. inferior vena cava (IVC) filter deployment device. We used a braided wiring technology from Tyco Electronics Corp. to connect the elements to our real-time 3D ultrasound scanner. Typical measured transducer element bandwidth was 20% centered at 4.7 MHz and the 50 Ω round trip insertion loss was −82 dB. The mean of the nearest neighbor cross talk was −37.0 dB. The second method consisted of a 46-cm long single layer flex circuit from MicroConnex that terminates in an interconnect that plugs directly into our system cable. This transducer had 70 elements at 0.157 mm interelement spacing operating at 4.8 MHz. Typical measured transducer element bandwidth was 29% and the 50 Ω round trip insertion loss was −83 dB. The mean of the nearest neighbor cross talk was −33.0 dB.

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12

Wei, Bo, Chuanlin He, Siyu Xing e Yi Zheng. "Accelerated Deconvolved Imaging Algorithm for 2D Multibeam Synthetic Aperture Sonar". Sensors 22, n.º 16 (12 de agosto de 2022): 6016. http://dx.doi.org/10.3390/s22166016.

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High-accuracy level underwater acoustical surveying plays an important role in ocean engineering applications, such as subaqueous tunnel construction, oil and gas exploration, and resources prospecting. This novel imaging method is eager to break through the existing theory to achieve a higher accuracy level of surveying. Multibeam Synthetic Aperture Sonar (MBSAS) is a kind of underwater acoustical imaging theory that can achieve 3D high-resolution detecting and overcome the disadvantages of traditional imaging methods, such as Multibeam Echo Sounder (MBES) and Synthetic Aperture Sonar (SAS). However, the resolution in the across-track direction inevitably decreases with increasing range, limited by the beamwidth of the transducer array of MBES. Furthermore, the sidelobe problem is also a significant interference of imaging sonar that introduces image noise and false peaks, which reduces the accuracy of the underwater images. Therefore, we proposed an accelerated deconvolved MBSAS beamforming method that introduces exponential acceleration and vector extrapolation to improve the convergence velocity of the classical Richardson-Lucy (R-L) iteration. The method proposed achieves a narrow beamwidth with a high sidelobe ratio in a few iterations. It can be applied to actual engineering applications, which breaks through the limitation of the actual transducer array scale. Simulations, tank, and field experiments also demonstrate the feasibility and advantages of the method proposed. 3D high-accuracy level underwater acoustical surveying can be achieved through this 2D MBES transducer array system, which can be widely promoted in the field of underwater acoustical remote sensing.

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13

Ahn, Bong Young, Ki Bok Kim, Hae Won Park, Young Joo Kim e Yong Seok Kwak. "Design and Characterization of Capacitive Micromachined Ultrasonic Transducer". Key Engineering Materials 321-323 (outubro de 2006): 132–35. http://dx.doi.org/10.4028/www.scientific.net/kem.321-323.132.

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As cMUTs (capacitive Micromachined Ultrasonic Transducer) offer numerous advantages over traditional transducers in terms of efficiency, bandwidth, and cost, they are expected to replace piezoelectric transducers in many applications. In particular, 2D-array cMUTs have aroused great interest in the medical engineering society because of their ability to materialize a true volumetric ultrasonic image. In this study, single element cMUTs with 32 x 32 and 64 x 64 cells were successfully fabricated. The diameter and thickness of the membrane are 35 and 1000 nm, respectively, with a sacrificial layer thickness of 600 nm. The electric characteristics of the fabricated cMUT were measured. Tests on the efficiencies of the cMUT in terms of wave generation and in terms of detection according to the bias and pulse voltage were performed in an air atmosphere.

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Zehnter, Sebastian, Marco A. B. Andrade e Christoph Ament. "Acoustic levitation of a Mie sphere using a 2D transducer array". Journal of Applied Physics 129, n.º 13 (7 de abril de 2021): 134901. http://dx.doi.org/10.1063/5.0037344.

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Robinson, Andrew L. "2D ultrasonic transducer array for two dimensional and three dimensional imaging". Journal of the Acoustical Society of America 113, n.º 2 (2003): 696. http://dx.doi.org/10.1121/1.1560305.

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Carrion, Alexis, Ibrahima Touré, Tamara Krpic, Maxime Bilodeau, Patrice Masson e Nicolas Quaegebeur. "Separate emission/reception transducers for 3D ultrafast ultrasound imaging". Journal of the Acoustical Society of America 155, n.º 3_Supplement (1 de março de 2024): A139. http://dx.doi.org/10.1121/10.0027084.

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Recent advancements in ultrafast 3D ultrasound imaging have revolutionized the field of echography, enabling its extension to novel applications such as cerebral dynamics, cardiac electrophysiology and the quantitative imaging of intrinsic mechanical properties of tumors. To facilitate these advancements, two primary transducer strategies are employed in 3D imaging. The first involves dense 2D probes equipped with a large number of elements, typically exceeding 1024. The second strategy uses row-column addressing, which simplifies the electronic control of the probe elements. Despite their effectiveness, these methods entail complexities in design and fabrication. Addressing these challenges, our study introduces an innovative transducer configuration that distinctly separates emission and reception functionalities. This separation not only simplifies the overall transducer design but also significantly reduces the system's complexity. A sparse array of PVDF transducers, which have been laser micro-machined to ensure acoustic transparency, is used at the reception. For the emission aspect, we employ a specialized acoustic concentrator to emulate point-like emission. The paper presents the detailed design requirements, assembly process, and the operational principles of this novel transducer. Furthermore, an experimental validation is conducted using a CIRS 040GSE phantom model. This validation is crucial to demonstrate the practical applicability and reliability of our transducer in real-world medical imaging scenarios.

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Mihalache, Ovidiu, e Toshihiko Yamaguchi. "Fast reconstruction of the magnetization of a Halbach magnet in EMAT using experimental measurements". International Journal of Applied Electromagnetics and Mechanics 64, n.º 1-4 (10 de dezembro de 2020): 905–12. http://dx.doi.org/10.3233/jae-209404.

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The paper presents a fast and accurate algorithm to reconstruct the magnetization model of parallelepiped magnet (parts of a Halbach magnet array) or the Halbach magnet array used in an electromagnetic acoustic (EMAT) transducer. The model accuracy is validated against measurements of the magnetic flux distributions above surface of block magnets or Halbach magnet array using 2D/3D theoretical formula to compute magnetic flux distribution, validated by 2D/3D FEM simulations, and based on a non-uniform distribution of reconstructed magnetization model (using only main magnetization component). The illness of inverse reconstruction model is controlled through very small enough increments steps in an adaptive iterative algorithm but large enough increments to assure faster reconstruction, and converging to the same magnetization model of magnet blocks or Halbach array magnet, independent of the initial magnetization values.

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Lee, Chang Hoon, Beom Hoon Park, Young Hun Kim, Hyeong Geun Jo e Kwan Kyu Park. "Particle Manipulation in 2D Space Using a Capacitive Micromachined Ultrasonic Transducer". Micromachines 13, n.º 4 (29 de março de 2022): 534. http://dx.doi.org/10.3390/mi13040534.

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Ultrasonic particle manipulation is a noncontact method for controlling microscale objects, such as cells or microparticles, using an acoustic field. In this study, a 2D array of capacitive micromachined ultrasonic transducers (CMUTs), placed horizontally in immersion, generated ultrasonic waves in the vertical direction, and the oil’s surface increased due to the radiation force of the ultrasonic waves. In addition, the radiation force directly exerted a force on a floating particle. By measuring the movement of the reflected laser light by the moving oil surface, the height of the oil’s surface deformed by the acoustic radiation force (ARF) was measured. The ARF made a floating particle, as well as the oil’s surface, move. The particle moved radially away from the surface position above the transducer, and its velocity was determined by its position on the fluid’s surface. When a single channel was operated, it moved 0.4 mm at an average speed of 90 μm/s, and when two adjacent channels were operated, it moved 1.2 mm at a speed of 272 μm/s. The particles moved in any direction on the surface of the oil by controlling the actuation channel using an electrical switch.

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Wang, Hongliang, Xiangjun Wang, Changde He e Chenyang Xue. "Directivity Theory and Analysis of 2D Capacitive Micro-Machined Ultrasonic Transducer Array". Journal of Nanoelectronics and Optoelectronics 12, n.º 8 (1 de agosto de 2017): 786–94. http://dx.doi.org/10.1166/jno.2017.2141.

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Han, Jun Sae, Chang Woo Gal, Jae Man Park, Jong Hyun Kim, Seung Hee Lee, Bong Whan Yeo, Baik Woo Lee, Sung Sik Park e Seong Jin Park. "Powder injection molding process for fabrication of piezoelectric 2D array ultrasound transducer". Smart Materials and Structures 27, n.º 7 (22 de junho de 2018): 075058. http://dx.doi.org/10.1088/1361-665x/aab27c.

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21

Yin, Jiawei, Zhixin Zhou e Liang Lou. "A Novel Nondestructive Testing Probe Using AlN-Based Piezoelectric Micromachined Ultrasonic Transducers (PMUTs)". Micromachines 15, n.º 3 (23 de fevereiro de 2024): 306. http://dx.doi.org/10.3390/mi15030306.

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Ultrasonic nondestructive testing (NDT) usually utilizes conventional bulk piezoelectric transducers as transceivers. However, the complicated preparation and assembly process of bulk piezoelectric ceramics limits the development of NDT probes toward miniaturization and high frequency. In this paper, a 4.4 mm × 4.4 mm aluminum nitride (AlN) piezoelectric micromachined ultrasonic transducer (PMUT) array is designed, fabricated, characterized, and packaged for ultrasonic pulse–echo NDT of solids for the first time. The PMUT array is prepared based on the cavity silicon-on-insulator (CSOI) process and packaged using polyurethane (PU) material with acoustic properties similar to water. The fabricated PMUT array resonates at 2.183 MHz in air and at around 1.25 MHz after PU encapsulation. The bandwidth of the packaged PMUT receiver (244 kHz) is wider than that of a bulk piezoelectric transducer (179 kHz), which is good for axis resolution improvement. In this work, a hybrid ultrasonic NDT probe is designed using two packaged PMUT receivers and one 1.25 MHz bulk transmitter. The bulk transmitter radiates an ultrasonic wave into the sample, and the defect echo is received by two PMUT receivers. The 2D position of the defect could be figured out by time-of-flight (TOF) difference, and a 30 mm × 65 mm detection area is acquired. This work demonstrates the feasibility of applying AlN PMUTs to ultrasonic NDT of solids and paves the way toward a miniaturized NDT probe using AlN PMUT technology.

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Trots, Ihor. "Mutually Orthogonal Golay Complementary Sequences in Synthetic Aperture Imaging Systems". Archives of Acoustics 40, n.º 2 (1 de junho de 2015): 283–89. http://dx.doi.org/10.1515/aoa-2015-0031.

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Abstract The main objective of this study is to improve the ultrasound image by employing a new algorithm based on transducer array element beam pattern correction implemented in the synthetic transmit aperture (STA) method combined with emission of mutually orthogonal complementary Golay sequences. Orthogonal Golay sequences can be transmitted and received by different transducer elements simultaneously, thereby decreasing the time of image reconstruction, which plays an important role in medical diagnostic imaging. The paper presents the preliminary results of computer simulation of the synthetic aperture method combined with the orthogonal Golay sequences in a linear transducer array. The transmission of long waveforms characterized by a particular autocorrelation function allows to increase the total energy of the transmitted signal without increasing the peak pressure. It can also improve the signal-to-noise ratio and increase the visualization depth maintaining the ultrasound image resolution. In the work, the 128-element linear transducer array with a 0.3 mm pitch excited by 8-bits Golay coded sequences as well as one cycle at nominal frequencies of 4 MHz were used. The comparison of 2D ultrasound images of the phantoms is presented to demonstrate the benefits of a coded transmission. The image reconstruction was performed using the synthetic STA algorithm with transmit and receive signals correction based on a single element directivity function.

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Pua, E. C., J. T. Yen e S. W. Smith. "Real-Time Cylindrical Curvilinear 3-D Ultrasound Imaging". Ultrasonic Imaging 25, n.º 3 (julho de 2003): 137–50. http://dx.doi.org/10.1177/016173460302500302.

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In patients who are obese or exhibit signs of pulmonary disease, standard transthoracic scanning may yield poor quality cardiac images. For these conditions, two-dimensional transesophageal echocardiography (TEE) is established as an essential diagnostic tool. Current techniques in transesophageal scanning, though, are limited by incomplete visualization of cardiac structures in close proximity to the transducer. Thus, we propose a 2D curvilinear array for 3D transesophageal echocardiography in order to widen the field of view and increase visualization close to the transducer face. In this project, a 440 channel 5 MHz two-dimensional array with a 12.6 mm aperture diameter on a flexible interconnect circuit has been molded to a 4 mm radius of curvature. A 75% element yield was achieved during fabrication and an average −6dB bandwidth of 30% was observed in pulse-echo tests. Using this transducer in conjunction with modifications to the beam former delay software and scan converter display software of the our 3D scanner, we obtained cylindrical real-time curvilinear volumetric scans of tissue phantoms, including a field of view of greater than 120° in the curved, azimuth direction and 65° phased array sector scans in the elevation direction. These images were achieved using a stepped subaperture across the cylindrical curvilinear direction of the transducer face and phased array sector scanning in the noncurved plane. In addition, real-time volume rendered images of a tissue mimicking phantom with holes ranging from 1 cm to less than 4 mm have been obtained. 3D color flow Doppler results have also been acquired. This configuration can theoretically achieve volumes displaying 180° by 120.° The transducer is also capable of obtaining images through a curvilinear stepped subaperture in azimuth in conjunction with a rectilinear stepped subaperture in elevation, further increasing the field of view close to the transducer face. Future work includes development of an array for adapting these modifications to a 6 mm diameter en do scope probe.

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Præsius, Sebastian K., Lasse T. Jørgensen e Jørgen A. Jensen. "Volumetric beamforming in real-time using commodity hardware". Journal of the Acoustical Society of America 155, n.º 3_Supplement (1 de março de 2024): A138. http://dx.doi.org/10.1121/10.0027081.

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Ultrasound imaging is widely used in medicine for its safety and affordability. However, it demands large transducer arrays because the image resolution is proportional to the number of elements, N, typically around 128 for 2D imaging. Three-dimensional imaging requires N2 audio channels (≈350 GB/s of data) if the equivalent 2D matrix array is used, which is practically impossible to process. To solve this issue, row-column arrays (RCAs) aggregate rows and columns of elements, reducing data rate and processing demands by a factor of N. A novel dual-stage beamforming algorithm further lowers the beamforming operations by N/2, with negligible impact on the image quality. For N = 128, the processing is 8192 times faster than with a matrix array, and it is hypothesized the 3D RCA beamforming can be done in real-time using a commodity graphics card. The beamforming rate of an NVIDIA RTX 4090 GPU was measured for in-vivo data from a rat kidney, achieving 1394 full volumes per second, which is over 150 times faster than previous implementations. Combining RCAs with the new beamforming algorithm and GPU processing thus enables volumetric beamforming to be done affordably at the bedside in real-time using a standard scanner and PC.

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Mozaffarzadeh, Moein, Mehdi Soozande, Fabian Fool, Michiel A. P. Pertijs, Hendrik J. Vos, Martin D. Verweij, Johan G. Bosch e Nico de Jong. "Receive/Transmit Aperture Selection for 3D Ultrasound Imaging with a 2D Matrix Transducer". Applied Sciences 10, n.º 15 (31 de julho de 2020): 5300. http://dx.doi.org/10.3390/app10155300.

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Recently, we realized a prototype matrix transducer consisting of 48 rows of 80 elements on top of a tiled set of Application Specific Integrated Circuits (ASICs) implementing a row-level control connecting one transmit/receive channel to an arbitrary subset of elements per row. A fully sampled array data acquisition is implemented by a column-by-column (CBC) imaging scheme (80 transmit-receive shots) which achieves 250 volumes/second (V/s) at a pulse repetition frequency of 20 kHz. However, for several clinical applications such as carotid pulse wave imaging (CPWI), a volume rate of 1000 per second is needed. This allows only 20 transmit-receive shots per 3D image. In this study, we propose a shifting aperture scheme and investigate the effects of receive/transmit aperture size and aperture shifting step in the elevation direction. The row-level circuit is used to interconnect elements of a receive aperture in the elevation (row) direction. An angular weighting method is used to suppress the grating lobes caused by the enlargement of the effective elevation pitch of the array, as a result of element interconnection in the elevation direction. The effective aperture size, level of grating lobes, and resolution/sidelobes are used to select suitable reception/transmission parameters. Based on our assessment, the proposed imaging sequence is a full transmission (all 80 elements excited at the same time), a receive aperture size of 5 and an aperture shifting step of 3. Numerical results obtained at depths of 10, 15, and 20 mm show that, compared to the fully sampled array, the 1000 V/s is achieved at the expense of, on average, about two times wider point spread function and 4 dB higher clutter level. The resulting grating lobes were at −27 dB. The proposed imaging sequence can be used for carotid pulse wave imaging to generate an informative 3D arterial stiffness map, for cardiovascular disease assessment.

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Wang, Zihao, Shangchun Fan, Chujian Ren, Xiaorui Wei, Dezhi Zheng, Shuai Wang, Weiwei Xing e Xiaolei Qu. "Enhancing Image Contrast in Breast USCT Reflection Imaging Using Coherence Factor Beamforming". Journal of Physics: Conference Series 2822, n.º 1 (1 de setembro de 2024): 012020. http://dx.doi.org/10.1088/1742-6596/2822/1/012020.

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Abstract Breast cancer is the most common cancer worldwide, and early screening is essential. Existing breast ultrasound is affordable and convenient, but its 2D image quality is poor, and it heavily relies on the doctor’s skills. The novel breast ultrasound computed tomography (USCT) can use a ring array probe to implement hundreds of single transducer emission for full-view focusing synthetic aperture reflection imaging, thereby obtaining high-resolution 3D images. However, single transducer emission results in low acoustic intensity, which further leads to low signal-to-noise ratio and low contrast of reflection images. To improve image contrast, this study incorporated beamforming with coherence factor (CF) into reflection imaging using ring transducers, promising to produce high-contrast USCT reflection images. For evaluation, we developed a USCT prototype with 2048 elements and conducted phantom experiments. We conducted phantom experiments. Results showed that the contrast achieved by the coherence factor method of the breast phantom image is improved from 24.54 dB to 63.18 dB, and the artifacts are significantly suppressed. It can be seen that the CF method could significantly improve the contrast of the breast USCT reflection image.

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Hoskins, P. R. "Ultrasound techniques for measurement of blood flow and tissue motion". Biorheology: The Official Journal of the International Society of Biorheology 39, n.º 3-4 (maio de 2002): 451–59. http://dx.doi.org/10.1177/0006355x2002039003004024.

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This article will review the ability of ultrasound techniques to provide 3D information on arterial geometry, blood flow and tissue motion. 3D systems. 3D datasets can be obtained by sequential acquisition of 2D slices. Ideally a transducer is required in which there is full control of beam steering within a 3D volume. This requires a 2D array consisting of several thousand elements. Prototype 2D arrays have been built which provide several 3D datasets per second. Blood velocity measurement. Current Doppler systems estimate only the component of velocity in the direction of the Doppler beam. Lack of knowledge of the direction of blood motion and also other effects associated with ‘spectral broadening’ limit the accuracy of velocity measurement. Improved accuracy can be obtained using vector Doppler systems using 2 or 3 beam directions; this approach is referred to as ‘vector Doppler’. Tissue motion. Doppler techniques can also be used to detect tissue motion (Tissue Doppler Imaging or TDI). Motion of the artery wall can be calculated from the TDI images. It is possible to estimate simultaneously motion for adjacent diameters within the longitudinal plane, and to visualise the relative motion at different parts of the wall.

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Nicolas, Barbara, François Varray, Jean-Christophe Bera, Audrey sivadon e Bruno Gilles. "Experimental demonstration of 3D passive cavitation imaging using adaptive beamforming". Journal of the Acoustical Society of America 153, n.º 3_supplement (1 de março de 2023): A269. http://dx.doi.org/10.1121/10.0018810.

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Interest in passive cavitation imaging has increased in recent years with the development of cavitation-based treatments. Using cross-spectral matrix formalism, adaptive beamformers, such as Capon beamforming, MUSIC, and p-DAS, have been adapted to 2D passive cavitation imaging (PAM) (Polichetti et al., 2020). More recently, we adapted this formalism in 3D to enhance the resolution of PAM using a commercial imaging array. Three beamformers have been extended in both 3D and the Frequency Domain: the DAS beamformer, the Robust Capon Beamformer (RCB) and the MidWay (MW) beamformer. A random sparse array configuration of a multiplexed commercial 2D array is used to reduce the number of channels used for the acquisition and to reconstruct 3D-PAM without degrading the quality of the reconstructed images. Such an approach allows for achieving a versatile well-resolved PAM using conventional research systems. In an experimental situation, the cavitation is initiated by a HIFU transducer at the tip of a needle and monitored with a high-speed camera confirming the presence of cavitation. This initial work allows us to envisage a possible future for 3D cavitation imaging using adaptive algorithms and sparse probes.

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Marhenke, Torben, Sergio Sanabria, Bhaskara Chintada, Roman Furrer, Jürg Neuenschwander e Orcun Goksel. "Acoustic Field Characterization of Medical Array Transducers Based on Unfocused Transmits and Single-Plane Hydrophone Measurements". Sensors 19, n.º 4 (19 de fevereiro de 2019): 863. http://dx.doi.org/10.3390/s19040863.

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Medical ultrasonic arrays are typically characterized in controlled water baths using measurements by a hydrophone, which can be translated with a positioning stage. Characterization of 3D acoustic fields conventionally requires measurements at each spatial location, which is tedious and time-consuming, and may be prohibitive given limitations of experimental setup (e.g., the bath and stage) and measurement equipment (i.e., the hydrophone). Moreover, with the development of new ultrasound sequences and modalities, multiple measurements are often required to characterize each imaging mode to ensure performance and clinical safety. Acoustic holography allows efficient characterization of source transducer fields based on single plane measurements. In this work, we explore the applicability of a re-radiation method based on the Rayleigh–Sommerfeld integral to medical imaging array characterization. We show that source fields can be reconstructed at single crystal level at wavelength resolution, based on far-field measurements. This is herein presented for three practical application scenarios: for identifying faulty transducer elements; for characterizing acoustic safety parameters in focused ultrasound sequences from 2D planar measurements; and for estimating arbitrary focused fields based on calibration from an unfocused sound field and software beamforming. The results experimentally show that the acquired pressure fields closely match those estimated using our technique.

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Wong, Voon-Kean, Yue Hu, Zi Wen Tham, Yi Fan Chen, Menglong Liu, Kai En Lim, Sung Joon Park, Fangsen Cui e Lei Zhang. "Measurement of Elastic Constant Matrix of Carbon Fiber Composites With an Ultrasonic 2D-Array Transducer". IEEE Sensors Journal 22, n.º 6 (15 de março de 2022): 5562–70. http://dx.doi.org/10.1109/jsen.2022.3149241.

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Wang, Ziping, Xingjia Li, Fuh-Gwo Yuan e Zhujie Bao. "Research on the Actuation Performance of 2D-Orthotropic Piezoelectric Composite Materials Linear Phased Array Transducer". Journal of Nanoscience and Nanotechnology 19, n.º 8 (1 de agosto de 2019): 5205–10. http://dx.doi.org/10.1166/jnn.2019.16814.

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Kim, Ji-Yun, e Je-Heon Han. "Optimal Transducer Placement for Deep Learning-Based Non-Destructive Evaluation". Sensors 23, n.º 3 (25 de janeiro de 2023): 1349. http://dx.doi.org/10.3390/s23031349.

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In this study, the Convolution Neural Network (CNN) algorithm is applied for non-destructive evaluation of aluminum panels. A method of classifying the locations of defects is proposed by exciting an aluminum panel to generate ultrasonic Lamb waves, measuring data with a sensor array, and then deep learning the characteristics of 2D imaged, reflected waves from defects. For the purpose of a better performance, the optimal excitation location and sensor locations are investigated. To ensure the robustness of the training model and extract the feature effectively, experimental data are collected by slightly changing the excitation frequency and shifting the location of the defect. The high classification accuracy for each defect location can be achieved. It is found that the proposed algorithm is also successfully applied even when a bar is attached to the panel.

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Talic, Almir, Samir Cerimovic, Roman Beigelbeck, Franz Kohl, Thilo Sauter e Franz Keplinger. "FEM-Analysis of 2D Micromachined Flow Transduers based on aGe-Thermistor Arrays and a Double Bridge Readout". Sensors 19, n.º 16 (15 de agosto de 2019): 3561. http://dx.doi.org/10.3390/s19163561.

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This paper reports on a design and simulation study aiming at high-accuracy 2D micromachined thermal flow transducers. The scope is restricted to micromachined devices featuring a square-shaped membrane incorporating central symmetric thin-film devices. A microthermistor array probed spatial excess temperature variations while the main heat supply was alternatively established by optional heating resistors or by pronounced self-heating of the thermistor devices. Proper device designs enable leading edge transducer performance without sophisticated signal conditioning schemes. We found that a high azimuthal uniformity of flow magnitude transduction is tantamount to a precise azimuthal accuracy. The most advanced result gave a maximum azimuthal aberration of 0.17 and 1.7 degrees for 1 m/s and 10 m/s, respectively, while the corresponding magnitude uniformity amounted to 0.07% and 0.5%. Such excellent specifications exceed the need of ordinary meteorological applications by far. However, they are essential for, e.g., precise non-contact measurements of 2D relative movements of two quasi-planar surfaces via the related Couette flow in intermediate air gaps. The simulations predicted significantly better device characteristics than achieved by us in first experiments. However, this gap could be attributed to imperfect control of the flow velocity field by the measurement setup.

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Danilov, V. N. "Operation of a model of a transducer with a 2D-phased array in the transmission mode". Russian Journal of Nondestructive Testing 47, n.º 7 (julho de 2011): 452–67. http://dx.doi.org/10.1134/s1061830911070047.

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Tutschek, Boris, Patricia Robertson, Solange Wyatt, Christine Sahn, Ling Hui e David Sahn. "Fetal cardiac ventricular volumes derived from real-time 3D ultrasound using a 2D matrix array transducer". American Journal of Obstetrics and Gynecology 195, n.º 6 (dezembro de 2006): S77. http://dx.doi.org/10.1016/j.ajog.2006.10.248.

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Li, Jian. "On Circumferential Disposition of Pipe Defects by Long-Range Ultrasonic Guided Waves". Journal of Pressure Vessel Technology 127, n.º 4 (4 de março de 2005): 530–37. http://dx.doi.org/10.1115/1.2083867.

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Ultrasonic guided waves have been used extensively for long-range pipe inspections. The technique is based on detecting the guided wave echoes reflected from pipe defects located at a remote distance. The axial location of the defect from the transducer can be determined by the arrival time of the echo. However, further information about the defect, such as the circumferential size or distribution of the defect, is hard to obtain with conventional guided waves. This problem will be a critical issue for applications, such as discriminating the pipe corrosion defects from pipe welds. In this paper, a circumferential guided wave array is built for sending and receiving guided waves along the pipe. All of the elements are connected to a single channel pulser/receiver through multiplexers. An algorithm based on two-dimensional (2D) blind deconvolution is developed to process the guided wave echoes acquired by the multiplexed circumferential transducer array. The output of the algorithm can be utilized for evaluating the circumferential distributions and geometry of the defects. The processing algorithm is verified via both numerical simulations and experiments in the paper. This circumferential sizing algorithm can serve as an effective postanalysis tool for most available guided wave pipe inspection systems.

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Mizota, Hirohisa, Yuui Amano e Kazuyuki Nakahata. "Application of the Reverse Time Migration Method to Ultrasonic Nondestructive Imaging for Anisotropic Materials". Materials Evaluation 80, n.º 8 (1 de agosto de 2022): 28–37. http://dx.doi.org/10.32548/2022.me-04244.

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In this study, we applied the reverse time migration (RTM) method to ultrasonic defect imaging in anisotropic materials. RTM offered that the defect shape could be uniquely determined by calculating a cross correlation of the incident and the reverse propagated waves from the array transducer. 2D simulations demonstrated that defect imaging by the RTM method requires an accurate numerical setup. We validated our technique using measured scattered waves from a slit in unidirectional solidified 316L stainless steel. By using the elastic constants determined from the ultrasonic wavefield data, the slit shape was correctly reconstructed. This provides a proof of principle that the RTM method is effective in nondestructive imaging of composite structures containing anisotropic materials.

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Wei, Bo, Haisen Li, Tian Zhou e Siyu Xing. "Obtaining 3D High-Resolution Underwater Acoustic Images by Synthesizing Virtual Aperture on the 2D Transducer Array of Multibeam Echo Sounder". Remote Sensing 11, n.º 22 (8 de novembro de 2019): 2615. http://dx.doi.org/10.3390/rs11222615.

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In recent decades, imaging sonar has been the most widely employed remote sensing instruments in the field of underwater detection. The multibeam echo sounder (MBES) plays an important role in obtaining high-accuracy seabed topography. However, the resolution of the MBES substantially decreases with the increasing distance. Synthetic aperture sonar (SAS) achieves constant resolution on the along-track, improving the fineness of the image. However, conventional side-scan SAS usually only achieves 2D images, and gaps always exist. In this modeling and experimental research paper, we propose a novel underwater acoustic imaging scheme to improve the imaging performance of MBES, based on the complementarity of MBES and SAS systems. We design a 2D transducer array to increase the detection efficiency and obtain spatial gain. Moreover, the processing scheme is analyzed to design the working parameters in actual engineering applications. We exploit a target echo simulation approach to establish the research basics of the imaging algorithms, which also reflects the shapes and shadows of targets to match actual situations as realistically as possible. The proposed imaging algorithm synthesizes a virtual aperture receiving array on the along-track and reserves the multi-element manifold on the across-track. This helps to improve the imaging quality of the MBES and achieves high-resolution 3D detection with no gaps. Simulation and tank experimental results demonstrate that the proposed scheme can significantly improve the detection ability of the MBES, especially for small 3D target detection, thus making it suitable for 3D high-resolution underwater detection applications.

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Lu, Jian-yu. "A phase-shifting method for computation reduction for high-frame-rate imaging". Journal of the Acoustical Society of America 152, n.º 4 (outubro de 2022): A245. http://dx.doi.org/10.1121/10.0016153.

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High-frame rate (HFR) imaging using steered plane wave (SPW) or limited-diffraction beam has a high-temporal resolution and thus has found many applications. To further study the HFR imaging methods, computer simulations were performed. However, the simulations require a large number of computations, especially for 3D imaging with 2D array transducers for a large imaging volume. In this paper, a phase-shifting method was developed to reduce the number of computations. In the method, the grid points of the transmit and receive beams were calculated at 1-mm interval in the depth direction that is perpendicular to the transducer surface. The interval is much larger than the 1/4 of the 0.58-mm wavelength required for an accurate interpolation for millions of random scatterers in pulse-echo response without aliasing. Since the HFR imaging uses either SPW or LDB, the wave vectors of these beams are fixed at each frequency. Due to the fact that the amplitude of ultrasound beams changes very little over a couple of wavelengths, the interpolation in the depth direction was replaced with a phase shift. Results show that images reconstructed with the phase-shifting method removed the artifacts caused by aliasing when conventional tri-linear interpolations were used for 3D imaging.

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Bureau, Flavien, Louise Denis, Antoine Coudert, Justine Robin, Mathias Fink, Olivier Couture e Alexandre Aubry. "Three-dimensional ultrasound matrix imaging". Journal of the Acoustical Society of America 156, n.º 4_Supplement (1 de outubro de 2024): A71. https://doi.org/10.1121/10.0035153.

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Matrix imaging paves the way towards a next revolution in wave physics. Based on the response matrix recorded between a set of sensors, it enables an optimized compensation of aberration phenomena and multiple scattering events that usually drastically hinder the focusing process in heterogeneous media. Although it gave rise to spectacular results in optical microscopy or seismic imaging, the success of matrix imaging has been so far relatively limited with ultrasonic waves because wave control is generally only performed with a linear array of transducers [1]. In this talk, we will extend ultrasound matrix imaging to a 3D geometry [2]. Switching from a 1D to a 2D probe enables a sharper estimation of the transmission matrix that links each transducer and each medium voxel. Here, we first present an experimental proof of concept on a tissue-mimicking phantom through ex vivo tissues and then show the potential of our reflection matrix approach for transcranial imaging, with applications to ultrasound localization microscopy of a sheep brain [3]. [1] W. Lambert et al., Proc. Natl. Ac. Sci. U. S. A. 117, 14645–14656 (2020) [2] F. Bureau et al., Nat. Commun. 14, 6793 (2023) [3] F. Bureau, L. Denis et al., (to be submitted).

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Um, Ji-Yong. "Ultrasound Transceiver Beamformer and Delay-control Scheme for a Finger Vein-pattern Sensor based on a 2D Transducer Array". IEIE Transactions on Smart Processing & Computing 7, n.º 6 (31 de dezembro de 2018): 448–56. http://dx.doi.org/10.5573/ieiespc.2018.7.6.448.

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Wang, X., Z. Xie, F. Padilla, G. LeCarpentier e P. Carson. "TU-C-220-06: Photoacoustic Imaging of Deep Targets in the Breast Using a Multi-Channel 2D Array Transducer". Medical Physics 38, n.º 6Part29 (junho de 2011): 3764. http://dx.doi.org/10.1118/1.3613166.

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Kim, Hyun Cheol, Sang Won Kim e Dal Mo Yang. "2083788 What Are The Benefits of The Matrix Array Transducer in 2D And 3D Ultrasonographic Imaging of The Abdomen?" Ultrasound in Medicine & Biology 41, n.º 4 (abril de 2015): S131. http://dx.doi.org/10.1016/j.ultrasmedbio.2014.12.515.

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HOSAKA, Naoto, Shinya MIYAZAWA, Ren KODA, Takashi MOCHIZUKI, Shinya ONOGI e Kohji MASUDA. "2B23 Design and production of 3D acoustic field with time variation for active control of microbubbles using 2D array transducer". Proceedings of the Bioengineering Conference Annual Meeting of BED/JSME 2014.26 (2014): 305–6. http://dx.doi.org/10.1299/jsmebio.2014.26.305.

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Badalov, V. I., M. I. Spitsyn, K. E. Korostelev, R. V. Yarmoshuk e A. A. Rodionova. "Neuronavigation Assistance. Decreased radiation exposure during spinal surgery in patients with severe combined trauma". Bulletin of the Russian Military Medical Academy 22, n.º 2 (15 de junho de 2020): 59–65. http://dx.doi.org/10.17816/brmma50047.

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Absnract. The results of the study of intraoperative x-ray irradiation of the affected two arrays are presented: the main array using neuronavigation and the control group, where standard 2D fluoroscopy was used. The radiation load on the operating surgeon and auxiliary operating personnel was also evaluated. Intraoperative visualization was carried out using the second-generation iNtellect ENT Navigation rack of the Stryker company (United States of America) for the victims of the main array and the Ziehm Vision RFD optical-optical converter (Germany) of the company for the victims of the control group. The imaging option using an electron-optical transducer is especially important for minimally invasive procedures, where instrumentation is performed percutaneously without direct anatomical control, as opposed to open procedures or working with distorted anatomical structures during injuries. Biplanar fluoroscopy was one of the first intraoperative methods of imaging in real time, and remains one of the leading technologies in orthopedic and spinal surgery. However, radiation exposure from intraoperative fluoroscopy remains a serious problem for patients, surgeons, and operating support staff. The negative effect of ionizing radiation leads to cell damage through the induction of deoxyribonucleic acid and the release of reactive oxygen species. In this regard, cell death or genome instability occurs, which leads to various radiation-related pathologies. It was found that the use of neuronavigation reduces the number of errors, reduces intraoperative trauma, and significantly reduces intraoperative radiation exposure to the injured, operating surgeon and auxiliary operating personnel. The large-scale introduction of navigation technologies will reduce or completely eliminate the harmful effects of ionizing radiation on the injured and medical personnel.

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Xavierselvan, Marvin, Mithun Kuniyil Ajith Singh e Srivalleesha Mallidi. "In Vivo Tumor Vascular Imaging with Light Emitting Diode-Based Photoacoustic Imaging System". Sensors 20, n.º 16 (12 de agosto de 2020): 4503. http://dx.doi.org/10.3390/s20164503.

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Photoacoustic (PA) imaging has shown tremendous promise for imaging tumor vasculature and its function at deeper penetration depths without the use of exogenous contrast agents. Traditional PA imaging systems employ expensive and bulky class IV lasers with low pulse repetition rate, due to which its availability for preclinical cancer research is hampered. In this study, we evaluated the capability of a Light-Emitting Diode (LED)-based PA and ultrasound (US) imaging system for monitoring heterogeneous microvasculature in tumors (up to 10 mm in depth) and quantitatively compared the PA images with gold standard histology images. We used a combination of a 7 MHz linear array US transducer and 850 nm excitation wavelength LED arrays to image blood vessels in a subcutaneous tumor model. After imaging, the tumors were sectioned and stained for endothelial cells to correlate with PA images across similar cross-sections. Analysis of 30 regions of interest in tumors from different mice showed a statistically significant R-value of 0.84 where the areas with high blood vessel density had high PA response while low blood vessel density regions had low PA response. Our results confirm that LED-based PA and US imaging can provide 2D and 3D images of tumor vasculature and the potential it has as a valuable tool for preclinical cancer research.

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Lee, Seung-Eun, Jinhyun Park, Yun-Taek Yeom, Hak-Joon Kim e Sung-Jin Song. "Sizing-Based Flaw Acceptability in Weldments Using Phased Array Ultrasonic Testing and Neural Networks". Applied Sciences 13, n.º 5 (2 de março de 2023): 3204. http://dx.doi.org/10.3390/app13053204.

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Liquefied Natural Gas (LNG) is one of the major renewable energy sources and is stored and carried in a storage tank that is designed following international standards. Since LNG becomes highly unstable when it encounters oxygen in the air, a leakage from an LNG storage tank can cause a catastrophic industrial accident. Thus, the inspection of LNG storage tanks is one of the priorities to be completed before LNG is stored in a storage tank. Recently, the usage of Phased Array Ultrasonic Testing (PAUT) has been gradually increasing as the risks of RT emerge. PAUT has some obstacles to overcome in order to substitute RT, such as efficiency and accuracy. Specifically, the cost issue must be addressed. Therefore, many attempts to combine PAUT with Artificial Neural Networks (ANN) have been made. PAUT provides many types of 2D images of the inspected weldment. The S-scan is one of the 2D images provided by PAUT, and it displays the cross-sectional view of the specimen with a single transducer. The inspectors examine the S-scan image and other provided images of PAUT to detect, classify and size the flaw that exists in the weldment so that the decision of whether the inspected weldment with the flaw is acceptable can be made. Nowadays, most of the previous research on PAUT and ANN focuses on detecting and classifying the flaws in B-scan or S-scan images. However, the last step to determine the flaws’ acceptability is not yet covered. In this study, the flaw acceptance criteria of PAUT in various international standards are listed. EXTENDE CIVA is used to create the PAUT S-scan images. The S-scan images are labeled with the listed acceptance criteria. Then, they are used in Mask R-CNN training. After the training, some new S-scan images with flaws are used to test the performance, and this showed 96% precision and 87% recall. With the algorithm, the acceptability of a flaw in a weldment can be determined efficiently and it will reduce the burden of PAUT usage and reduce the time required for a full-length inspection.

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Daschner, Rosa, Holger Hewener, Wolfgang Bost, Steffen Weber, Steffen Tretbar e Marc Fournelle. "Ultrasound Thermometry for HIFU-Therapy". Current Directions in Biomedical Engineering 7, n.º 2 (1 de outubro de 2021): 554–57. http://dx.doi.org/10.1515/cdbme-2021-2141.

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Abstract High-Intensity Focused Ultrasound (HIFU) is an alternative tumour therapy with the ability for non-invasive thermal ablation of tissue. For a safe application, the heat deposition needs to be monitored over time, which is currently done with Magnetic Resonance Imaging. Ultrasound (US) based monitoring is a promising alternative, as it is less expensive and allows the use of a single device for both therapy and monitoring. In this work, a method for spatial and temporal US thermometry has been investigated based on simulation studies and in-vitro measurements. The chosen approach is based on the approximately linear dependence between temperature and speed of sound (SoS) in tissue for a given temperature range. By tracking the speckles of successive B-images, the possibility of detecting local changes in SoS and therefore in temperature is given. A speckle tracking algorithm was implemented for 2D and 3D US thermometry using a spatial compounding method to reduce artifacts. The algorithm was experimentally validated in an agar-based phantom and in porcine tissue for temperature rises up to △ 8°C. We used a focusing single element US transducer as therapeutic probe, a linear (/matrix array) transducer with 128 (/32∙32) elements for imaging and thermocouples for validation and calibration. In all experiments, both computational and in-vitro, we succeeded in monitoring the thermal induced SoS changes over time. The in-vitro measurements were in good agreement with the simulation results and the thermocouple measurements (rms temperature difference = 0.53 °C, rms correlation coefficient = 0. 96).

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Chen, Xin, Houjin Chen, Yahui Peng e Dan Tao. "Probe Sector Matching for Freehand 3D Ultrasound Reconstruction". Sensors 20, n.º 11 (2 de junho de 2020): 3146. http://dx.doi.org/10.3390/s20113146.

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A 3D ultrasound image reconstruction technique, named probe sector matching (PSM), is proposed in this paper for a freehand linear array ultrasound probe equipped with multiple sensors, providing the position and attitude of the transducer and the pressure between the transducer and the target surface. The proposed PSM method includes three main steps. First, the imaging target and the working range of the probe are set to be the center and the radius of the imaging field of view, respectively. To reconstruct a 3D volume, the positions of all necessary probe sectors are pre-calculated inversely to form a sector database. Second, 2D cross-section probe sectors with the corresponding optical positioning, attitude and pressure information are collected when the ultrasound probe is moving around the imaging target. Last, an improved 3D Hough transform is used to match the plane of the current probe sector to the existing sector images in the sector database. After all pre-calculated probe sectors are acquired and matched into the 3D space defined by the sector database, a 3D ultrasound reconstruction is completed. The PSM is validated through two experiments: a virtual simulation using a numerical model and a lab experiment using a real physical model. The experimental results show that the PSM effectively reduces the errors caused by changes in the target position due to the uneven surface pressure or the inhomogeneity of the transmission media. We conclude that the PSM proposed in this study may help to design a lightweight, inexpensive and flexible ultrasound device with accurate 3D imaging capacity.

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Szegedi, István, Dániel András Szabó, Miklós Emri, Mónika Béresova, Mariann Nagy, Sarolta Molnár, Attila Nagy, Ervin Berényi, László Oláh e László Csiba. "Comparison of pre-mortem 2D-3D ultrasound examination to post-mortem micro-CT of carotid arteries – first experiences". Ideggyógyászati szemle 77, n.º 1-2 (2024): 13–20. http://dx.doi.org/10.18071/isz.77.0013.

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Background and purpose – A prerequisite for the treatment of carotid atherosclerosis is the accurate measurement of the stenosis, that is most commonly evaluated by duplex ultrasonography. In this study, we aimed to verify the reliability of 2D and 3D ultrasonography, comparing the data to results of postmortem micro-CT examination. Methods – Neurological patients with any life-threatening, presumably fatal neurological disease were enrolled. Ultrasound examinations were performed with a Philips Epiq 5G machine, using a VL13-5 broadband linear volume array transducer. Plaque length, diameter and vessel area reduction (stenosis) were calculated using the 2D images. Finally, the stenosis was reassessed using automatized, 3D application as well. After the death of the patient, autopsy was performed, during which the previously examined carotid artery was removed. The samples were examined with micro-CT. Similar to the ultrasound examination, plaque length, diameter and vessel area reduction (stenosis) were determined. Results – Ten vessels of seven patients were eligible for complex comparison. Plaque diameter and length measured by CT did not correlate with the ultrasound data. CT-measured axial plaque and vessel areas showed no correlation with ultrasound results either. While determining the strength of correlation between stenoses measured by the different modalities, significant correlation was found between the results measured by ultrasound (2D) and CT (Pearson r: 0.902, P<0.001). Conclusion – Three-dimensional ultrasound analysis is a spectacular method for examining carotid plaques, as it can assist in a more detailed evaluation of the plaque morphology and composition, thereby identifying plaques with a particularly high risk of stroke. Micro-CT is an excellent tool for the exact determination of calcified plaque areas, but ultrasound images are not suitable yet for such a precise examination due to acoustic shadowing and artifacts.

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