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BRL Abstracts Database |
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Your search for ultrasound produced 3296 results. Page 139 out of 330
| Title |
High-Intensity Focused Ultrasound (HIFU) Phased Arrays: Recent Developments in Transrectal Transducers and Driving Electronics Design |
| Author |
R. Seip, W. Chen, J. Tavakkoli, L.A. Frizzell, N.T. Sanghvi |
| Journal |
ISTU3 |
| Volume |
|
| Year |
2003 |
| Abstract |
This work presents the design and characterization of 4 specific transrectal HIFU phased array transducers (9 to 826 elements, 2.0 to 4.0 MHz) for the non-invasive treatment of prostate diseases, and a general-purpose HIFU phased array driving electronics design capable of controlling up to 1024 channels. Four different HIFU phased arrays have been simulated during the last 3 years while investigating optimum array geometries, high-power transducer materials (piezoelectric and/or
piezocomposite), interconnect structures, and excitation methods.The developed electronics were used to test three of the 4 arrays that have actually been fabricated, and were used to steer the HIFU beam in real time from 25 mm from the face of the array to 45 mm deep. The characteristics of these arrays and the results of these investigations are presented. The implementation details of the electronic driving system, consisting of a small footprint (25 cm x 25 cm) scalable architecture able to individually control the phase and amplitude of each channel (2 ns phase resolution, 7-bit amplitude resolution,1024 maximum channel count), operate over a frequency range of 1 to 5 MHz, deliver up to 15 W of
power to each channel, and drive elements with electrical impedances up to 2 kW are also presented. This flexible electronic driving system can be used to control a variety of HIFU phased arrays. |
| Title |
High-intensity focused ultrasound in the treatment of experimental liver cancer. |
| Author |
Yang R, REilly CR, Rescorla FJ, Faught PR, Sangvhi NT, Fry FJ, Franklin TD, Lumeng L, Grossfield JL. |
| Journal |
Arch Surg |
| Volume |
|
| Year |
1991 |
| Abstract |
High-intensity focused ultrasound (HIFU) was used to treat Morris rat hepatoma 3924A implanted in the liver. Treatment was administered with a lens-focused 4-MHz transducer that created a focused beam of 550 W/cm2 at peak intensity. One hundred twelve rats with liver tumors were divided into two groups of 56 each. Group 1 received HIFU therapy while group 2 (the control group) did not. All rats were killed immediately or 1, 3, 7, 14, 21, or 28 days after treatment. Eight rats in each group were killed at each interval for pathologic and biochemical studies. Significant inhibition of the tumor growth was seen in the HIFU-treated group, with tumor growth inhibition rates of 65.4% to 93.1% from the third to the 28th day after treatment. Ultrasound-treated tumors showed direct thermal cytotoxic necrosis and fibrosis. An additional 56 ACl rats with liver tumors were divided into four groups of 14 each. Group 1 received doxorubicin hydrochloride intraperitoneally and HIFU therapy; group 2, HIFU therapy; group 3, doxorubicin hydrochloride; and group 4 (the control group), neither HIFU nor doxorubicin hydrochloride. Significantly improved survival rates were noted in HIFU-treated animals (groups 1 and 2) compared with those of groups 3 and 4. These data suggest that HIFU may be a useful method for local treatment of hepatic tumors. |
| Title |
High-intensity focused ultrasound in the treatment of prostatic tissue. |
| Author |
Bihrle R, Foster RS, Sanghvi NT, Fry FJ, Donohue JP. |
| Journal |
Urology |
| Volume |
|
| Year |
1994 |
| Abstract |
Objective. Beginning in 1987, high-intensity focused ultrasound was investigated in the canine model to determine the feasibility of destroying prostate tissue. After demonstrating the ability to ablate prostate tissue reliably in a canine model, a 15-patient pilot clinical study was undertaken at Indiana University in the fall of 1992. This pilot study was undertaken to assess the safety in the human clinical situation, as well as to give some early efficacy results.
Methods. The early canine feasibility studies were conducted via a suprapubic extracorporeal approach using two separate transducers, one for imaging and the other for therapy. Subsequent to this, a transrectal probe, which had the dual capability of both imaging and therapy, was developed and used to treat canine prostates in a formal, “good laboratory practice” study to determine the safety of this technology prior to beginning treatment of human benign prostatic hypertrophy.
Results. The formal canine studies demonstrated that prostatic tissue could be reliably ablated in the therapy zone. The dosimetry and duty cycle required to ablate canine prostatic tissue effectively was also determined in this study. The study also demonstrated that the prostatic tissue could be ablated without injury to the intervening rectal tissue or periprostatic tissue. The human pilot study has also demonstrated safety of high-intensity focused ultrasound, as well as early efficacy.
conclusions. These early clinical results are encouraging, but assessment of efficacy will require a randomized study comparing high-intensity focused ultrasound to sham and to transurethral prostatectomy. This multicenter trial is currently planned. |
| Title |
High-reolution real-time ultrasonic scanner. |
| Author |
Berson M, Vaillant L, Patat F, Pourcelot L. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1992 |
| Abstract |
High spatial resolution is required for echographic exploration of the skin, microvessels or small laboratory animals. With the scanner described here, high resolution is obtained by means of a strongly focused, wide-band 17 MHz center frequency transducer (−6 dB bandwidth: 22 MHz). The movement of this transducer above the skin provides a 6 mm wide and 5 mm deep echographic cross-section with an image rate of 15 images/s. The resolution is about 0.08 mm in axial and 0.2 to 0.3 mm in lateral directions. The device was tested on phantoms in water and in vivo on normal and pathological skin in the Department of Dermatology. With the easy-to-handle probe, explorations were made on psoriasis, basocellular carcinoma, malignant melanoma and sarcoidosis. |
| Title |
High-resolution and fast 3D ultrasonic imaging technique. |
| Author |
Benenson ZM, Elizarov AB, Yakovleva TV, O'Brien WD Jr. |
| Journal |
Proc Ultrason Symp IEEE |
| Volume |
|
| Year |
2003 |
| Abstract |
The paper considers a 3D ultrasound imaging technique based upon usage of a probe that consists of 2 one-dimensional transmitting phased arrays and 3 receiving phased arrays. By controlling the transmit process on the elements of the transmitting array and simultaneous receiving the signals by all the elements of the receiving arrays, this method yields algorithmically synthesized signals of a 2D phased array, the so called virtual 2D phased array. This allows for achieving short volume scan time and high lateral and axial resolution. Lateral resolution is 2 times better than the Rayleigh limit of the original ID phased arrays. The paper contains a mathematical simulation and experiment results. |
| Title |
High-resolution sonographic assessment of the fetal extremities. |
| Author |
Mahony BS, Filly RA. |
| Journal |
J Ultrasound Med |
| Volume |
|
| Year |
1984 |
| Abstract |
Recent advances in ultrasound technology, especially phased-array sonography, now permit striking visualization of fetal morphology. Although several reports document the sonographic appearance of the fetal appendicular skeleton, no reports describe the nonosseous structures of the fetal limbs. 1-3 Prior to the middle of the second trimester of pregnancy, adequate size and intrinsic subject contrast enable distinction among numerous liimb structures. The sonographic features of the fetal limbs are described, with emphasis upon the visible nonosseous structures. All images were obtained between August 1983 and January 1984 using a 128-channel phased-array real-time scanner (Acuson) with a 3.5-MHz transducer. |
| Title |
High-resolution, reflection mode tomographic imaging. Part I: Principles and methods. |
| Author |
Herment A, Guglielmi JP, Péronneau P, Dumée P. |
| Journal |
Acoust Imaging |
| Volume |
|
| Year |
1989 |
| Abstract |
A general method for improving image resolution is derived and applied to ultrasound signals; it combines the principles of both reflection mode tomography and deconvolution. The different possibilities of applying these principles allow two types of approaches to be defined, depending upon whether image reconstruction is achieved on radiofrequency or detected signals. A thorough description of three methods that are of particular interest due to their lower computation costs is presented, and their results quantified. They permit a gain in resolution of the order of ten with respect to two-dimensional deconvolution of images, as well as an improvement of the S/N ratio, which is related to the square root of the number of projections used in the reconstruction process, and a decrease of about four in computation time. |
| Title |
High-speed data acquisition in a diffraction tomography system employing large-scale toroidal arrays. |
| Author |
Andre MP, Janee HS, martin PJ, Otto GP, Spivey BA. Palmer DA. |
| Journal |
Ultrason Imaging |
| Volume |
|
| Year |
1997 |
| Abstract |
This report describes the development of an experimental system for ultrasound computed tomography and its application to breast imaging. Details of the system design and methods of high-speed data acquisition are presented. The method uses low-power discrete frequency sound in the range of 0.3–1.2 MHz, two cylindrical arrays of 512 and 1024 PZT transducers, high spatial sampling of the wavefront, and unique diffraction tomographic reconstruction methods. One transducer at a time is activated and allowed to reach steady state at which point the remaining measure phase and amplitude of the ultrasound signal. A total of 64 MB of data are acquired in <1 s for the 512-element array and 128 MB in <3 s for the 1024 array. Several algorithms have been developed to produce the diffraction tomogram which is reconstructed as either a 512 × 512 or 1024 × 1024 matrix of the scattering potential of the object dependent on speed of sound and attenuation. The effects of aberration are greatly diminished by a hybrid iterative algorithm. To date, human images have been made of the female breast which show good depiction of glandular structures and differentiation of gland and fat, and the coronal format provides a novel of the entire breast in life-size display. The results demonstrate that the technique provides a unique quantitative ultrasound image with high resolution over a very large global field of view of the breast. The method shows promise for improved imaging of the breast. |
| Title |
High-speed imaging of an ultrasound-driven bubble in contact with a wall:"Narcissus" effect and resolved acoustic streaming. |
| Author |
Marmottant P,Versluis M,de Jong N,Hilgenfeldt S,Lohse D. |
| Journal |
Exp Fluid |
| Volume |
|
| Year |
2006 |
| Abstract |
We report microscopic observations of the primary flow oscillation of an acoustically driven bubble in contact with a wall, captured with the ultra high-speed camera Brandaris 128 (Chin et al. 2003). The driving frequency is up to 200 kHz, and the imaging frequency is up to 25 MHz. The details of the bubble motion during an ultrasound cycle are thus resolved, showing a combination of two modes of oscillations: a radius oscillation and a translation oscillation, perpendicular to the wall. This motion is interpreted using the theory of acoustic images to account for the presence of the wall. We conclude that the bubble is subjected to a periodic succession of attractive and repulsive forces, exerted by its own image. Fast-framing recordings of a tracer particle embedded in the liquid around the particle are performed. They fully resolve the acoustic streaming flow induced by the bubble oscillations. This non-linear secondary flow appears as a tiny drift of the particle position cycle after cycle, on top of the primary back and forth oscillation. The high oscillation frequency accounts for a fast average particle velocity, with characteristic timescales in the millisecond range at the lengthscale of the bubble. The features of the bubble motion being resolved, we can apply the acoustic streaming theory near a wall, which provides predictions in agreement with the observed streaming velocity. |
| Title |
High-speed imaging of an ultrasound-driven bubble in contact with a wall:"Narcissus" effect and resolved acoustic streaming. |
| Author |
Marmottant P,Versluis M,de Jong N,Hilgenfeldt S,Lohse D. |
| Journal |
Exp Fluid |
| Volume |
|
| Year |
2006 |
| Abstract |
We report microscopic observations of the primary flow oscillation of an acoustically driven bubble in contact with a wall, captured with the ultra high-speed camera Brandaris 128 (Chin et al. 2003). The driving frequency is up to 200 kHz, and the imaging frequency is up to 25 MHz. The details of the bubble motion during an ultrasound cycle are thus resolved, showing a combination of two modes of oscillations: a radius oscillation and a translation oscillation, perpendicular to the wall. This motion is interpreted using the theory of acoustic images to account for the presence of the wall. We conclude that the bubble is subjected to a periodic succession of attractive and repulsive forces, exerted by its own image. Fast-framing recordings of a tracer particle embedded in the liquid around the particle are performed. They fully resolve the acoustic streaming flow induced by the bubble oscillations. This non-linear secondary flow appears as a tiny drift of the particle position cycle after cycle, on top of the primary back and forth oscillation. The high oscillation frequency accounts for a fast average particle velocity, with characteristic timescales in the millisecond range at the lengthscale of the bubble. The features of the bubble motion being resolved, we can apply the acoustic streaming theory near a wall, which provides predictions in agreement with the observed streaming velocity. |
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