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BRL Abstracts Database |
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Your search for ultrasound produced 3296 results. Page 81 out of 330
| Title |
Design and evaluation of linear intracavitary ultrasound phased array for MRI-guided prostate ablative therapies. |
| Author |
Sokka SD. King RL, Mcdannold NJ, Hynynen KH. |
| Journal |
Proc IEEE Ultrasonic Symposium |
| Volume |
|
| Year |
1999 |
| Abstract |
In this study, a linear, transrectal, ultrasound phased array capable of ablating large tissue volumes was fabricated and evaluated in tissue. The device was designed to be MRI compatible for use with MRI thermometry and guidance. The intracavitary applicator increases the treatable tissue volume by utilizing an ultrasonic motor to provide up to a 100-degree mechanical rotation angle to a 62-element 1D aperiodic ultrasound array. MRI guided in vivo and ex vivo experiments were performed to verify the array's large volume ablative capabilities. The array generated 3 cm×2 cm×2 cm lesions with 8-12 half-minute sonications equally spaced in the volume. The results indicate that transrectal ultrasound coagulation of the whole prostate is feasible with the method developed. |
| Title |
Design and experimental evaluation of an intracavitary ultrasound phased array system for hyperthermia. |
| Author |
Buchanan MT, Hynynen K. |
| Journal |
IEEE Trans Biomed Eng |
| Volume |
|
| Year |
1994 |
| Abstract |
For evaluating the feasibility of treating prostate cancer, a 64-element linear ultrasound phased array applicator for intracavitary hyperthermia was designed and constructed. A 64-channel ultrasound driving system including amplifiers, phase shifters, and RF power meters was also developed to drive the array. The design of the array and driving equipment are presented, as are the results of acoustical field measurements and in vitro perfused phantom studies performed with the array. Several techniques for heating realistically sized tumor volumes were also investigated, including single focus scanning and two techniques for producing multiple stationary foci. The results show that the operation of the array correlated closely with the theoretical model. When producing a single stationary focus, the array was able to increase tissue temperature by 12 degrees C in vitro in perfused phantom. With some minor improvements in array design, intracavitary phased arrays could be evaluated in a clinical environment. |
| Title |
Design and first clinical implementation of the ultrasound CT tm system for breast imaging. |
| Author |
Johnson SA, Bell R, Bgerggren M, Borup D, Hanover B, Hanover R, Kammeyer M, Olsen S, Pattee J, Robinson D, Setinsek F, Stewart S, Wiskin J. |
| Journal |
TechniScan Med Sys |
| Volume |
|
| Year |
N/A |
| Abstract |
No Abstract Available. |
| Title |
Design and optimization of an aperiodic ultrasound phased array for intracavitary prostate thermal therapies. |
| Author |
Hutchinson EB, Buchanan MT, Hynynen K. |
| Journal |
Med Phys |
| Volume |
|
| Year |
1996 |
| Abstract |
A 57 element aperiodic linear phased array was designed and constructed to investigate the feasibility of using transrectal ultrasound for the thermal therapeutic treatment of prostate cancer and benign prostatic hyperplasia. A method of reducing grating lobe levels by using optimized random distributions of unequally sized elements is introduced. Using this technique, array periodicity is avoided, making it feasible to use larger elements and hence fewer elements and amplifier channels, while still achieving acceptable power field patterns. Acoustic power field simulations determined that the grating lobe levels associated with selected aperiodic element distributions were approximately 30%-45% less than those associated with periodic element spacing and the same average element width. Or by using aperiodic rather than periodic element distributions, the average element width could be increased by approximately 20%-35% (approximately lambda/4.4), while maintaining a constant grating lobe level. Prior to construction of the 57 element array, the power capabilities of this type of array were demonstrated with a 16 element aperiodic phased array, which delivered over 28 W of acoustical power per cm of array length while focused. The power field patterns produced by the 57 element array closely matched the field patterns predicted by the theoretical model used in the simulations. The array produced acceptable power field patterns for foci at depths up to 5 cm and up to 2 cm off the center axis, in addition to producing multiple foci simultaneously. Based on the power capabilities and field patterns, this aperiodic array design has the potential to be incorporated into a clinical heating device as a means of delivering thermal therapies to the prostate and other target volumes close to body cavities. |
| Title |
Design method for ultrasound transducers using experimental data and computers. |
| Author |
Sigelmann RA, Caprihan A. |
| Journal |
J Acoust Soc Am |
| Volume |
|
| Year |
1977 |
| Abstract |
An approach is described for designing thickness mode ultrasound transducers. A computer subroutine is used to simulate the frequency response of a transducer in the transmitting or receiving mode. The physical parameters of the piezoelectric ceramic required for the design are obtained with conventional instrumentation. Two of the parameters (e(33) and an equivalent resistance to represent losses) are calculated with the aid of a computer program which makes use of the measured impedance versus frequency. An example of design is presented. |
| Title |
Design of Albumin-Coated Microbubbles Loaded With Polylactide Nanoparticles |
| Author |
Gauthier M, Yin Q, Cheng J, O'Brien WD Jr. |
| Journal |
J Ultrasound Med |
| Volume |
|
| Year |
2015 |
| Abstract |
Objectives—A protocol was designed to produce albumin-coated microbubbles (MBs)
loaded with functionalized polylactide (PLA) nanoparticles (NPs) for future drug delivery studies.
Methods—Microbubbles resulted from the sonication of 5% bovine serum albumin
and 15% dextrose solution. Functionalized NPs were produced by mixing fluorescent PLA and PLA-polyethylene glycol-carboxylate conjugates. Nanoparticle-loaded MBs resulted from the covalent conjugation of functionalized NPs and MBs. Three NP/MB volume ratios (1/1, 1/10, and 1/100) and unloaded MBs were produced and compared. Statistical evaluations were based on quantitative analysis of 3 parameters at 4 time points (1, 4, 5, and 6 days post MB fabrication): MB diameter using a circle detection routine based on the Hough transform, MB number density using a hemocytometer, and NP-loading yield based on MB counts from fluorescence and light microscopic images. Loading capacity of the albumin-coated MBs was evaluated by fluorescence.
Results—Loaded MB sizes were stable over 6 days after production and were not significantly different from that of time-matched unloaded MBs. Number density evaluation showed that only 1/1 NP/MB volume ratio and unloaded MB number densities were stable over time, and that the 1/1 MB number density evaluated at each time point was not significantly different from that of unloaded MBs. The 1/10 and 1/100 NP/MB volume ratios had unstable number densities that were significantly different from that of unloaded MBs (P < .05). Fluorescence evaluation suggested that 1/1 MBs had a higher NP-loading yield than 1/10 and 1/100 MBs. Quantitative loading evaluation suggested that the 1/1 MBs had a loading capacity of 3700 NPs/MB.
Conclusions—A protocol was developed to load albumin MBs with functionalized PLA
NPs for further drug delivery studies. The 1/1 NP/MB volume ratio appeared to be
the most efficient to produce stable loaded MBs with a loading capacity of 3700
NPs/MB.
Key Words—fluorescence; functionalized nanoparticles; microbubbles; stability |
| Title |
Design of an analogy beamformer for very high frequency ultrasound transducer arrays. |
| Author |
Wu Q, Tutwiler RL, Shung KK. |
| Journal |
Proc SPIE |
| Volume |
|
| Year |
2000 |
| Abstract |
beamformer is described that is used to process the data from a high frequency linear array with frequencies up to 75MHz. This unit is one part of a test system, which has the capability to characterize ultrasound transducer arrays up to 128 elements. This beamformer consists of three stages: delay unit, delay switches and summing unit. They have the following characteristics: the delay and summing units are realized in the analog domain, utilizing 4-zone dynamic focusing, and dynamic aperture switching with very wide bandwidth. The delay unit consists of a set of fixed delays with 5 ns resolution, and a set of adjustable delay lines with a resolution of 1 ns. A set of 4:1 multiplexers is used to switch the different delays for different focusing zones. In our system, the focal range is divided into 4 zones consisting of a near, middle, far and fourth zone with a different set of delays for each zone. Dynamic aperture switching is accomplished by sequential selection of the multiplexer network. The aperture is set according to the focusing zone. For near zone, middle zone, far zone and fourth zone focusing, apertures are set to 8,12,16 and 16 elements respectively. In the last stage, very wide band summing amplifiers are used with surface mount resistor networks to decrease phase errors. Test signals have been generated. The multiplexing system and delay lines have been characterized. The beamformer lateral and axial resolution have been characterized by a simulated phantom utilizing the FIELD program. The future work is to interface the beamforming architecture with a high frequency array. |
| Title |
Design of focused ultrasound phased arrays for prostate treatment. |
| Author |
Tan JS, Frizzell LA, Sanghvi NT, Seip R, Wu JS, Kouzmanoff JT. |
| Journal |
Proc Ultrason Symp IEEE |
| Volume |
|
| Year |
2000 |
| Abstract |
The design of phased arrays for transrectal ultrasound therapy of the prostate presents significant challenges due to anatomical constraints on the size and shape of the probe. To maximize the array performance under these constraints, the effect of array geometry was examined theoretically. Studies were conducted on spherical segment, cylindrical, and curved cylindrical arrays. Fields were computed by dividing the array elements into many point sources. The effectiveness of various configurations was evaluated by defining a parameter, G, as the ratio of the intensity at the desired focus to the maximum intensity of any unwanted lobes. |
| Title |
Design of low-loss wide-band ultrasonic transducers for noninvasive medical application. |
| Author |
Souquet J, Defaranould P, Desbois J. |
| Journal |
IEEE Trans UFFC |
| Volume |
|
| Year |
1979 |
| Abstract |
In recent years ultrasound has become an effective and practical tool for obtaining information from within the bodoyr about different kinds of materials without exposing themto X-rays. Roper design of the ultrasonic transducer is the ketyo a successful equipmentpatient interface. The emphasis in this paper is put on tdhees ign of low-loss wide-band transducers. The approach we have used consists of impedance matching the fronfta ce of the transducer with the
propagating medium and totally unmatching the rearf ace. The front face matching is achieved using one or two quarter-wave layers, depending on the desired bandwidth. Several transducers have been built to illustrate this design, and gao od agreement between theory and experiment has been achieved. |
| Title |
Design of the C.A.L. ultrasonic generator for the treatment of meniere's disease. |
| Author |
Kossoff G. |
| Journal |
IEEE Trans Sonics Ultrason |
| Volume |
|
| Year |
1964 |
| Abstract |
When the balance mechanism of the human ear is disturbed the patient suffers from attacks of vertigo and, as in the case of an affliction called Meniere?s disease, from a progressive loss of hearing. Several years ago it was discovered that ultrasound could be used for the effective treatment of this disease. An improved ultrasound generator for this purpose has been developed at the Commonwealth Acoustic Laboratories in Australia. This paper gives design details for the applicator and the electronic circuitry. The equipment is completely transistorized and the applicator does not require a cooling system. |
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