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IEEE International Ultrasonics Symposium

作者： Alexander Sampaleanu Roger Zemp Department of Electrical and Computer Engineering University of Alberta

ISBN: (纸本)9781467356855

Crossed electrode arrays, wherein electrodes are connected in individually addressable rows and columns, have been previously investigated as a means to reduce the number of channels in two-dimensional ultrasound arrays for three-dimensional imaging. Previously envisioned imaging schemes have been limited in their resolution and focusing ability due to their inability to perform active focusing in both the lateral and elevational direction for both transmit and receive. As well, signal-to-noise ratio (SNR) can be compromised when transmitting or receiving on only one row or column at a time. A new imaging method is proposed for this array architecture using capacitive micromachined ultrasound transducers (CMUTs) which can provide two-way focusing in both lateral and elevational directions while providing optimal SNR. This method is a variation of synthetic aperture imaging wherein the columns active upon transmit and receive events are determined by applying a bias to specific columns upon transmission and reception in an S-sequence encoded pattern. Mathematical derivations of this method are presented and simulations are done to compare this imaging method to previously published crossed-electrode array imaging schemes, as well as to fully-populated 2-d phased array imaging.

关键词： 3-d imaging 2-d array CMUTs Crossed-Electrode array Three dimensional imaging TRANSMITTING signal to noise ratios array structure Synthetic aperture Imaging Lateral Ultrasonography electrode configuration FOCUSING arrays

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High-power vertical-cavity surface-emitting lasers for diode pumped solid-state lasers

High-power vertical-cavity surface-emitting lasers for diode...

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Conference on Laser Technology for defense and Security VIII

作者： Van Leeuwen, Robert Xiong, Yihan Seurin, Jean-Francois Xu, Guoyang Miglo, Alexander Wang, Qing Xu, Bing Zou, Wei-Xiong Li, daizong Wynn, James d. Khalfin, Viktor Ghosh, Chuni L. Princeton Optron Inc Princeton NJ 08619 USA

ISBN: (纸本)9780819490599

Vertical-cavity surface-emitting lasers can be processed in large two-dimensional arrays of single devices to scale up the power for solid-state laser pumping. These arrays emit in a circular, uniform beam, with a narrow and stable emission spectrum that is well suited to the absorption spectra of solid-state gain media. kW-class 808 nm QCW VCSEL pump modules were developed to pump compact Nd:YAG lasers. An end-pumped Nd: YAG laser was constructed that produced 7.1 W average IR power, as well as a dual side-pumped passively Q-switched frequency-quadrupled Nd: YAG laser that generated 0.8 mJ UV pulses at a 240 Hz repetition rate.

关键词： Semiconductor laser diode-pumped solid-state laser vertical-cavity surface-emitting laser high power laser 2-d array 808 nm UV laser

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Recent results using a 256 x 256 2-d array transducer for 3-d Rectilinear Imaging

Recent results using a 256 x 256 2-D array transducer for 3-...

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IEEE Ultrasonics Symposium

作者： Seo, Chi Hyung Yen, Jesse T. Univ So Calif Dept Biomed Engn Los Angeles CA 90089 USA

ISBN: (纸本)9781424424283

In previous work, we presented initial experimental results using a 256 x 256 2-d array with row-column methods. The main benefits of this design are a reduced number of interconnects, a T/R switching scheme with a simple diode circuit, and an ability to perform transmit beamforming in azimuth and receive beamforming in elevation for volumetric imaging of targets near the transducer. In this paper, we present 3-d images of axial wires embedded in a clear gelatin phantom, of an 8 mm diameter cylindrical anechoic cyst phantom and of a 10 min diameter spherical anechoic cyst phantom acquired from a new 256 x 256 2-d array transducer. dAX processing was used to reduce clutter due to 1-way beamforming.

关键词： component 2-d array 1-3 composite 3-d imaging row-column dAX

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Real-Time Volumetric Imaging System for CMUT arrays

Real-Time Volumetric Imaging System for CMUT Arrays

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IEEE International Ultrasonics Symposium (IUS)

作者： Choe, Jung Woo Oralkan, Oemer Nikoozadeh, Amin Bhuyan, Anshuman Lee, Byung Chul Gencel, Mustafa Khuri-Yakub, Butrus T. Stanford Univ Edward L Ginzton Lab Stanford CA 94305 USA

ISBN: (纸本)9781457712524

We designed and implemented a flexible real-time volumetric ultrasound imaging system for capacitive micromachined ultrasonic transducer (CMUT) arrays, consisting of an ultrasound data acquisition system, an FPGA board, and a host PC. The system works with arbitrary-shaped CMUT arrays and non-standard beamforming methods, as well as with regular-shaped CMUT arrays and conventional beamforming methods. In this paper, we present the system design and real-time imaging results obtained using this system with a ring array, a rectangular array, and a linear array. In synthetic phased array (SPA) imaging with a 64-element ring array, we could display 3 image planes with a total of about 70,000 pixels in real time, at a frame rate of 9 frames per second (fps) which was limited by the computational load on the CPU required for synthetic beamforming. On the other hand, the frame rate in classic phased array (CPA) imaging is limited by the data transfer time. In CPA imaging with a 16x16-element rectangular array, a frame rate of 5.4 fps was achieved for 1,250 acquisitions per frame and a 2.5-cm imaging depth. The frame rate can be increased by reducing the number of pixels processed in SPA, or by reducing the number of beams received in CPA, at the expense of degraded image quality or reduced field of view.

关键词： CMUT Real-time imaging Volumetric imaging Ring array 2-d array

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256x256 2-d array transducer with row-column addressing for 3-d imaging

256x256 2-D array transducer with row-column addressing for ...

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IEEE Ultrasonics Symposium

作者： Seo, Chi Hyang Yen, Jesse T. Univ So Calif Dept Biomed Engn Los Angeles CA 90089 USA

ISBN: (纸本)9781424413836

In previous work we presented experimental results using a prototype 64 x 64 2-d array with row-column methods. The main benefits of this row-column design are a reduced number of interconnects, a T/R switching scheme with a simple diode circuit, and an ability to perform transmit beamforming In azimuth direction and receive beamforming in elevational direction for a volumetric imaging of targets near the transducer. In this paper, we present experimental results acquired from a new 256 x 256 2-d array transducer. The center frequency was 6.4 MHz with a -6 dill bandwidth of 57%. The series resonant impedance was 120 Ohms near 5.8 MHz. The mean crosstalk of the adjacent element was -22 dB in the frequency range of interest. For a wire target, in azimuth direction with transmit beamforming, we measured the -6 dB beamwidth to be 0.75 rum at a depth of 25.5 mm compared to a theoretical beamwidth of 0.68 mm. We successfully acquired 3-d images of a wire target and a cylindrical anechoic cyst of 10 mm in diameter made of graphite scatterers in gelatin.

关键词： 2-d array 1-3 composite 3-d imaging row-column

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3d strain imaging using a rectilinear 2d array

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ULTRASONIC IMAGING 2007年第4期29卷 220-230页

作者： Awad, Samer I. Yen, Jesse T. Univ So Calif Viterbi Sch Engn Los Angeles CA 90089 USA

Under mechanical compression, tissue movements are inherently three-dimensional. 2-d, strain imaging can suffer from decorrelation noise caused by out-of-plane tissue movement in elevation. With 3-d strain imaging, all tissue movements can be estimated and compensated, hence minimizing out-of-plane decorrelation noise. Promising 3-d strain imaging results have been shown using 1-d arrays with mechanical translation in elevation. However, the relatively large slice thickness and mechanical translation can degrade image quality. Using 2-d arrays, an improved elevational resolution can be achieved with electronic focusing. Furthermore, scanning with 2-d arrays is also done electronically, which eliminates the need for mechanical translation. In this paper, we demonstrate the feasibility of 3-d strain imaging using a 4 cm x 4 cm ultrasonic sparse rectilinear 2-d array operating at 5MHz. The signal processing combinations of 2-d or 3-d beamforming followed by 2-d or 3-d strain imaging are studied and compared to each other to evaluate the performance of our 3-d strain imaging system. 3-d beamforming followed by 3-d strain imaging showed best performance in all experiments.

关键词： 2-d array 3-d imaging strain imaging ultrasound

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3-d Spatial Compounding Using a Row-Column array

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ULTRASONIC IMAGING 2009年第2期31卷 120-130页

作者： Awad, Samer I. Yen, Jesse T. Univ So Calif Viterbi Sch Engn Los Angeles CA 90089 USA

2-d spatial compounding has long been investigated to reduce speckle in ultrasound images. To further reduce speckle, several 3-d spatial compounding studies using 1-d and 1.5 d arrays with mechanical translation and position tracking have been reported. However, the fixed elevational focus and mechanical translation can degrade image quality in elevation. Using 2-d arrays, a better elevational resolution can be achieved with electronic focusing. Furthermore, 2-d arrays can generate greater number of independent images than 1-d arrays and the need for mechanical scanning is eliminated. In this paper, we present our 3-d spatial compounding images of two gel-based contrast phantoms and one resolution phantom. These images were acquired using a prototype 4 cm x 4 cm ultrasonic row-column prototype 2-d array operating at 5 MHz. Compounding nine decorrelated volumes showed a speckle signal-to-noise ratio (SNR) improvement of 2.68. The average improvement of the lesion contrast-to-noise ratio (CNR) was 2.45. However, using a smaller aperture to generate these volumes worsened the lateral resolution as predicted by theory.

关键词： 2-d array 3-d imaging spatial compounding ultrasound

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64 X 64 2-d array transducer with row-column addressing

64 X 64 2-D array transducer with row-column addressing

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IEEE Ultrasonics Symposium

作者： Seo, Chi Hyting Yen, Jesse T. Univ So Calif Dept Biomed Engn Los Angeles CA 90089 USA

ISBN: (纸本)9781424402014

We present experimental results from a prototype 5 MHz, 64 x 64 (4096 elements, 16 mm x 16 mm) 2-d array transducer with row-column addressing. The main benefits of our design are a reduced number of interconnects, a T/R switching scheme with a simple diode circuit, and an ability to perform transmit and receive beamforming. With transmit beamforming in elevational direction and receive beamforming in azimuth direction, it is possible to perform 3-d imaging of targets near the transducer. The series resonant impedance was measured at 120 Ohms near 5.5 MHz. The spectrum of the pulse has a center frequency of 5.6 MHz and a -6 dB fractional bandwidth of 43%. In azimuth direction with receive beamforming, we measured the -6 dB width to be 1.22 mm at a depth of 55 mm compared to a theoretical beamwidth of 0.91 mm. In elevational direction with transmit beamforming, -6 dB width was 0.92 mm at a depth of 27 mm compared to a theoretical beamwidth of 0.45 mm. Finally, we introduce results from 266 x 266 2-d array transducer. to 64

关键词： 2-d array 1-3 composite 3-d imaging Mills Cross

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Two-dimensional Planar array for digital Beamforming and direction-of-Arrival Estimations

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IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY 2009年第7期58卷 3137-3144页

作者： Kim, Shinho Wang, Yuanxun Ethan Univ Calif Los Angeles Dept Elect Engn Los Angeles CA 90034 USA

A compact uniplanar design of 2-d antenna arrays is presented for digital beamforming (dBF) and direction-of-arrival (dOA) estimations. The array is based on switchable microstrip slot antennas that are series fed in one dimension and parallel fed in the other dimension. In conjunction with spatial multiplexing of local elements (SMILE) techniques, the array is able to use both the series- and parallel-fed antennas for 2-d beamforming and dOA estimations. The combination of series and parallel feeding provides a simple way of constructing 2-d dBF arrays with a simple and uniplanar feed network. Other advantages are its low cost and compatibility with a microwave integrated circuit process for the receiver system. A 4 x 4 receiving array test bed at a 5.5-GHz operating frequency is fabricated, and dBF and dOA tests on this test bed are successfully demonstrated.

关键词： digital beamforming (dBF) direction-of-arrival (dOA) estimations planar array slot antennas spatial multiplexing of local elements (SMILE) 2-d array

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design method for large 2-d ultrasonic arrays with controlled grating lobes levels

Design method for large 2-D ultrasonic arrays with controlle...

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IEEE Ultrasonics Symposium

作者： Villazon, J. Ibanez, A. Parrilla, M. Nevado, P. CSIC IAI Arganda Del Rey Spain

ISBN: (纸本)9781424424283

A major problem in developing 2-d arrays is the large number of elements required for big apertures in order to produce high quality ultrasonic images. Recent advances in transducer technology have made possible to design arrays with fewer restrictions in the shape and layout or elements. In this paper we propose to use Evolutionary Algorithms to optimize these parameters to obtain large 2-d ultrasonic arrays with a low number of elements but maintaining a narrow mainlobe and low grating lobes level.

关键词： component: Optimization 2-d array Evolutionary algorithms

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