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IEEE Ultrasonics Symposium

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

ISBN: (纸本)9781424413836

The difficulty in fabricating and connecting large numbers of 2-d array elements has limited the development of 2-d transducer array with more than 5000 elements. In this paper, we propose a dual-layer transducer array design which uses perpendicular 1-d arrays for 3-d imaging. This transducer design reduces the complexity of fabrication and the number of channels while maintaining adequate performance compared to a fully sampled 2-d transducer array. To demonstrate feasibility, we constructed a 4cm x 4cm prototype dual-layer transducer array which consists of 256 elements for each layer operating at 4MHz. Both layers used P[VdF-TrFE] material. The -6dB fractional bandwidth was 130% without matching layer. The measured crosstalk of P[VdF-TrFE] layer was -24dB in the frequency range of 3MHz-10MHz. We also verified the performance of this transducer using a wire target phantom. The theoretical beamwidth was 0.62mm compared to the measured beamwidth of 0.53mm using coherence factor when f-number is 1.6.

关键词： P[VdF-TrFE] dual-layer 2-d array 3-d imaging

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Small-pitch flip-chip-bonded VCSEL arrays enabling transmitter redundancy and monitoring in, 2-d 10-Gbit/s space-parallel fiber transmission

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IEEE JOURNAL OF SELECTEd TOPICS IN QUANTUM ELECTRONICS 2007年第5期13卷 1279-1289页

作者： Roscher, Hendrik Rinaldi, Fernando Michalzik, Rainer Univ Ulm Inst Optoelect D-89069 Ulm Germany

We demonstrate novel pixel architectures in 2-d vertical-cavity surface-emitting laser (VCSEL) arrays offering additional functionality without sacrificing efficient fabrication, compactness, and low module cost. Very high flip chip VCSEL packing densities enable both a built-in 3-per-channel VCSEL redundancy as well as simple intracell VCSEL monitoring. Each pixel has three individually addressable oxide-confined and substrate-removed 850-nm-wavelength VCSELs directly flip bonded to the mesas that are extremely close-spaced to permit equal butt coupling to 50-mu m-core-diameter multimode fibers (MMFs) without the need for external coupling optics. Built-in radial VCSEL-to-fiber launch offsets as small as 7.8 mu m were reached, leading to offset coupling penalties of only 0.4 dB. Quasi-error-free transmission of 10 Gbit/s signals is achieved over 500-m-long MMFs even under offset launch conditions. New opportunities for a range of further applications offered by high-density VCSEL arrays are discussed.

关键词： 2-d array data transmission flip chip bonding optical interconnect redundancy space-division multiplexing vertical-cavity surface-emitting laser (VCSEL)

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Improved spatial resolution in a three-dimensional acoustic medical imaging system based on a hybrid method using a synthetic aperture technique

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JAPANESE JOURNAL OF APPLIEd PHYSICS PART 1-REGULAR PAPERS BRIEF COMMUNICATIONS & REVIEW PAPERS 2007年第7B期46卷 4827-4833页

作者： Taki, Hirofumi Sato, Toru Kyoto Univ Grad Sch Informat Kyoto 6068501 Japan

For an acoustic real-time three-dimensional (3-d) imaging system with high spatial resolution, we propose a system based on a hybrid method using a synthetic aperture technique. We can change the transmit point in this system;thus, the coherent integration of multiple receive signals from different transmit points improves spatial resolution using a synthetic aperture technique. In the case of a time resolution of 300 3-d images/s, the -3 dB lateral resolution of the proposed system is 1.30 lambda in the x-z section and 1.17 lambda in the y-z section for a 0.07 m depth, where the lateral resolution is improved from 16 transmit and receive events. The number of elements can be reduced to about 1/7.5 of a dense two-dimensional (2-d) array of a digital beamforming imager having the same time and spatial resolution.

关键词： ultrasound hybrid method real-time 3-d imaging reflector 2-d array synthetic aperture digital beamforming phased array

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Real-time transrectal 3-d ultrasound using synthetic aperture

Real-time transrectal 3-D ultrasound using synthetic apertur...

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Medical Imaging 2006 Conference

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

ISBN: (纸本)0819461903

In previous work, we investigated 3-d synthetic aperture imaging with 2-d array designs for real-time rectilinear volumetric imaging of targets near the transducer such as the breast and carotid artery. Here we present results for cylindrical 3-d imaging for 3-d transrectal ultrasound (TRUS). The major benefit of this design is the interconnect where an expensive multilayer flex circuit is no longer required. The interconnect uses a row-column addressing scheme to enable different groups of elements. Over 256 transmissions, this design is capable of synthesizing a 256 x 256 = 65,536 element fully sampled 2-d cylindrical array if desired. In receive, the echoes from individual elements along a row are recorded by the system receive channels. For faster volume acquisition time, we present a design where all elements of the 2-d array transmit simultaneously, and signals are recorded one row at a time. For a depth of 6 cm, a volume rate of 50 volumes/s can be achieved. We have performed computer simulations of a 10 MHz 256 x 256 synthetic cylindrical 2-d array with a radius of curvature of 10 min to determine the radiation pattern. For an 128 x 128 subaperture, the on-axis case (x,y,z) = (0,0,20) mm showed a narrow beam down to -40 dB. In the transversal direction, on-axis lateral beamwidths at -6, -20, and -40 dB were 0.47 mm, 0.81 mm, and 2.54 mm, respectively. As for the longitudinal direction, the beamwidths are slightly narrower than in transversal direction, giving 0.39 mm, 0.72 mm, and 1.51 min for the same corresponding dB levels.

关键词： 3-d ultrasound prostate 2-d array real-time synthetic aperture

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Real-time 3d transesophageal echocardiography

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ULTRASONIC IMAGING 2004年第4期26卷 217-232页

作者： Pua, EC Idriss, SF Wolf, Pd Smith, SW Duke Univ Dept Biomed Engn Durham NC 27708 USA Duke Univ Med Ctr Dept Pediat Durham NC 27708 USA

Transesophageal echocardiography (TEE) is an essential diagnostic tool in patients with poor transthoracic echocardiographic windows or when detailed imaging of structures distant from the chest wall is necessary. A real-time 3 d TEE probe has been fabricated in our laboratory in order to increase the amount of information available during a transesophageal procedure. The I cm diameter esophageal probe utilizes a 2-dimensional, 5 MHz array at its tip with a 6.3 mm diameter aperture, including 50 Omega active channels. The array has a periodic vernier geometry with an element pitch of 0.18 mm, built onto a multi layer flexible (MLF) interconnect circuit. In order to accommodate 504 channels within the device, a 1 to long Gore MicroFlat (TM) cable was utilized for wiring the MLF to the corresponding system connectors. Pulse-echo tests in a water tank have yielded a -6 dB bandwidth of 25.3%. Fully connected to the system through 3 m of cable, the probe shows an average 50 Omega insertion loss of -85 dB with a standard deviation of 4 dB, as determined through pitch-catch measurements for a sampling of 10 elements. Using the completed 3 d TEE probe with the Volumetrics Medical Imaging 3d scanner, real-time volumetric images of in vivo canine cardiac anatomy have been acquired, displaying atrial views, mitral valve function and interventional catheter guidance.

关键词： 2-d array real-time transesophageal echocardiography volumetric

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dual lumen transducer probes for real-time 3-d interventional cardiac ultrasound

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ULTRASOUNd IN MEdICINE ANd BIOLOGY 2003年第9期29卷 1297-1304页

作者： Lee, W Idriss, SF Wolf, Pd Smith, SW Duke Univ Dept Biomed Engn Durham NC 27708 USA Duke Univ Med Ctr Dept Pediat Durham NC 27710 USA

We have developed dual lumen probes incorporating a forward-viewing matrix array transducer with an integrated working lumen for delivery of tools in real-time 3-d (RT3-d) interventional echocardiography. The probes are of 14 Fr and 22 Fr sizes, with 112 channel 2-d arrays operating at 5 MHz. We obtained images of cardiac anatomy and simultaneous interventional device delivery with an in vivo sheep model, including: manipulation of a 0.36-mm diameter guidewire into the coronary sinus, guidance of a transseptal puncture using a 1.2-mm diameter Brockenbrough needle, and guidance of a right ventricular biopsy using 3 Fr biopsy forceps. We have also incorporated the 22 Fr probe within a 6-mm surgical trocar to obtain apical four-chamber ultrasound (US) scans from a subcostal position. Combining the imaging catheter with a working lumen in a single device may simplify cardiac interventional procedures by allowing clinicians to easily visualize cardiac structures and simultaneously direct interventional tools in a RT3-d image. (C) 2003 World Federation for Ultrasound in Medicine Biology.

关键词： 2-d array volumetric ultrasound imaging intracardiac echocardiography forward-viewing catheter

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Real-time cylindrical curvilinear 3-d ultrasound imaging

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ULTRASONIC IMAGING 2003年第3期25卷 137-150页

作者： Pua, EC Yen, JT Smith, SW Duke Univ Dept Biomed Engn Durham NC 27705 USA

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 120degrees in the curved, azimuth direction and 65degrees 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 180degrees by *** 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

关键词： 2-d array curvilinear cylindrical endoscopic real-time transesophageal volumetric

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Real-time rectilinear volumetric imaging using a periodic array

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ULTRASOUNd IN MEdICINE ANd BIOLOGY 2002年第7期28卷 923-931页

作者： Yen, JT Smith, SW Duke Univ Dept Biomed Engn Durham NC 27708 USA

Current real-time phased array volumetric scanners use a 2-d array to scan a pyramidal volume comprised of many sector scans stacked in the elevation direction. This scan format is primarily useful for cardiac imaging to avoid interference from the ribs. However, a real-time rectilinear volumetric scan with a wider field-of-view (FOV) close to the transducer could prove more useful for abdominal, breast or vascular imaging. In our previous work, a 94 X 94 Mills cross array operating at 5 MHz was fabricated, and the first real-time rectilinear volumetric images were made using a 2-d array and the duke real-time 3-d scanner. The FOV for the Mills cross was 30 X 8 X 60 mm. despite reasonable success with the Mills cross array, the array had limitations of poor off-axis sensitivity and a smaller FOV in one direction. To overcome these limitations, a new rectilinear array containing over 65,500 elements was developed with a periodic geometry to increase the FOV to 30 turn X 30 nun X 60 mm and improve the off-axis sensitivity. Images of tissue-mimicking phantoms and the carotid artery in vivo were obtained. In addition, spectral and color flow doppler results from a pulsatile flow phantom were obtained. (E-mail: ***@***) (C) 2002 World Federation for Ultrasound in Medicine Biology.

关键词： 2-d array real-time volumetric rectilinear

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Improved signal-to-noise ratio in hybrid 2-d arrays: Experimental confirmation

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ULTRASONIC IMAGING 1997年第2期19卷 93-111页

作者： Emery, Cd Smith, SW DUKE UNIV DEPT RADIOLDURHAMNC 27708

2-d array transducers have shown significant promise for medical ultrasound over conventional linear arrays, at the cost of increasing the number of channels, difficulty of fabrication and array element impedance. The increase in element impedance reduces the power coupled to a 2-d array element from a conventional 50 Ohm source in transmit mode. If the array is sparse, which is typical of 2-d arrays, then the net power coupled into the front acoustic load is reduced when compared to a fully sampled aperture. Furthermore, the received signal-to-noise ratio (SNR), when measured through a nonideal amplifier, is degraded because the high impedance 2-d array transducer element cannot efficiently drive the coaxial cable. The reduction in transmit sensitivity and received SNR can be circumvented with the application of multilayer piezoelectric elements. The improvement in transmit occurs because the transducer impedance is better matched to the impedance of the source. In receive, multilayer elements allow more of the open circuit received voltage to fall across the input of the high impedance preamplifier. In this case, the same number of layers are used in transmit and receive. Recently, it has been suggested that separate optimization of the transmit channel and receive channel (a hybrid array) would further improve the pulse-echo SNR. In this paper, we fabricated and tested a hybrid array operating at 1 MHz using a multilayer transmit element and single layer receive element. A 7 Ohm transmitter and high impedance preamplifier were placed adjacent to the transmit and receive elements within the transducer assembly. The hybrid pulse-echo SNR improved by 26.4 dB over the conventional array. The experimental result showed good agreement with the KLM model. Furthermore, KLM simulations showed that as the operating frequency of the array increases, the overall improvement over the conventional array increases. For example, a 1.5-d array operating at 2 MHz had an improvemen

关键词： 2-d array multilayer ceramic hybrid array transmit sensitivity received SNR noise spectrum

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Calculation of ultrasonic transducer signal-to-noise ratios using the KLM model

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IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS ANd FREQUENCY CONTROL 1997年第5期44卷 1018-1026页

作者： Oakley, CG Tetrad Corporation Englewood CO USA

This paper describes a method for adding thermal and amplifier noise to a KLM model for a transducer element. The model is used to compare the magnitudes of various noise sources in a 5 MHz array element typical of those used for linear array imaging with and without an amplifier. Fundamental signal-to-noise ratio (SNR) issues of importance to array and amplifier designers are explored, including the effect on SNR of effective dielectric constant of the piezoelectric material, individual element size, changing the number of elements, and adding an amplifier to an element before and after a cable. SNR is considered both for the case in which the acoustic output is limited by the maximum rarefactive pressure which is considered safe for a particular application (Mechanical Index limitation) and the case in which acoustic output is limited by the maximum transmit voltage than can be delivered by the imaging system or tolerated by the transducer, It is shown that the SNR performance depends on many controllable parameters and that significant improvements in SNR can be achieved through proper design, The implications for 1.5-d and 2-d array elements are discussed.

关键词： piezoelectric transducers random noise ultrasonic transducer arrays 1.5-d array 2-d array 5 MHz KLM model amplifier noise dielectric constant linear array imaging mechanical index piezoelectric material rarefactive pressure signal-to-noise ratio thermal signal to noise ratios Thermal dielectric properties Noise sources amplifier noise Piezoelectric materials Piezoelectric transducers Elements random noise ultrasonic transducer arrays Supernova remnants mechanical index dielectric constant

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