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BRL Abstracts Database |
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Your search for ultrasound produced 3296 results. Page 327 out of 330
| Title |
Variation of transducer frequency output and receiver band-pass characteristics for improved detection and image characterization of solid breast masses. |
| Author |
Kelly-Fry E, Morris ST, Jackson VP, Holden RW, Sanghvi NT. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1988 |
| Abstract |
A new approach has been used for ultrasound detection of small benign and malignant breast masses, namely, control of scattering in such a manner that a small mass can be easily recognized because of the effect of the scattering on the contrast between the mass and the surrounding normal tissue. Maintenance of good resolution as scattering is varied is an essential aspect of this approach. Image contrast is dependent on a number of instrumentation parameters but, in a fundamental sense, it is related to differences in the amount of scattering between a solid breast mass and the surrounding normal tissue. In the subject studies, modification of image contrast is accomplished by varying either the center frequency output of the transducer or the band-pass of the receiver. These approaches take advantage of differences in the frequency dependence of scattering coefficients of solid breast masses and normal tissue. A unique technique for varying center frequency without switching transducers was developed, namely, use of a wide bandwidth, co-polymer PVDF transducer, in combination with certain instrumentation conditions which allow the center frequency output of a single ultrasound transducer to vary over a relatively wide frequency range. Using this technique, an automatic B-mode ultrasound imaging breast instrument which allows emission of 3.5, 4.5, 6.5 and 11 MHz ultrasound frequencies from the same co-polymer transducer was used to examine patients with solid breast masses. Both a wide band-pass receiver, similar to that commonly used in clinical ultrasound systems and a tunable receiver (which allows variation of the band-pass from wide to narrow) was used with this automated system. Using the standard receiver system, it was found that there are advantages to having a range of transducer frequencies immediately available for breast examination. These include: (1) improved detection of masses located in highly attenuating regions of breast (by decreasing frequency); (2) availability of diagnostically relevant information at some one frequency which may not be apparent at other frequencies. Using the multiple frequency system and the standard receiver, it was found that the most appropriate examination frequencies for detection and diagnosis of fibroadenomas are higher frequencies (8 to 11 MHz). This is particularly true in the case of fibroadenomas in fatty breasts. |
| Title |
Variations in acoustic velocity in skeletal muscle determined by acoustic microscopy. |
| Author |
Vinson FS, Eggleton RC, Meiss RA. |
| Journal |
Ultrasound Med |
| Volume |
|
| Year |
1978 |
| Abstract |
No abstract available. |
| Title |
Vascular effects induced by combined 1-MHz ultrasound and microbubble contrast agent treatments in vivo. |
| Author |
Hwang JH, Brayman AA, Reidy MA, Matula TJ, Kimmey MB, Crum LA. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
2005 |
| Abstract |
Previous in vivo studies have demonstrated that microvessel hemorrhages and alterations of endothelial permeability can be produced in tissues containing microbubble-based ultrasound contrast agents when those tissues are exposed to MHz-frequency pulsed ultrasound of sufficient pressure amplitudes. The general hypothesis guiding this research was that acoustic (viz., inertial) cavitation, rather than thermal insult, is the dominant mechanism by which such effects arise. We report the results of testing five specific hypotheses in an in vivo rabbit auricular blood vessel model: (1) acoustic cavitation nucleated by microbubble contrast agent can damage the endothelia of veins at relatively low spatial-peak temporal-average intensities, (2) such damage will be proportional to the peak negative pressure amplitude of the insonifying pulses, (3) damage will be confined largely to the intimal surface, with sparing of perivascular tissues, (4) greater damage will occur to the endothelial cells on the side of the vessel distal to the source transducer than on the proximal side and (5) ultrasound/contrast agent-induced endothelial damage can be inherently thrombogenic, or can aid sclerotherapeutic thrombogenesis through the application of otherwise subtherapeutic doses of thrombogenic drugs. Auricular vessels were exposed to 1-MHz focused ultrasound of variable peak pressure amplitude using low duty factor, fixed pulse parameters, with or without infusion of a shelled microbubble contrast agent. Extravasation of Evans blue dye and erythrocytes was assessed at the macroscopic level. Endothelial damage was assessed via scanning electron microscopy (SEM) image analysis. The hypotheses were supported by the data. We discuss potential therapeutic applications of vessel occlusion, e.g., occlusion of at-risk gastric varices. |
| Title |
Vascular lesions and s-thrombomodulin concentrations from auricular arteries of rabbits infused with microbubble contrast agent and exposed to pulsed ultrasound. |
| Author |
Zachary JF, Blue JP, Miller RJ, O'Brien WD Jr. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
2006 |
| Abstract |
Arterial injury resulting from the interaction of contrast agent (CA) with ultrasound (US) was studied in rabbit auricular arteries and assessed by histopathologic evaluation and s-thrombomodulin concentrations. Three sites on each artery were exposed (2.8 MHz, 5-min exposure duration, 10-Hz pulse repetition frequency, 1.4-μs pulse duration) using one of three in situ peak rarefactional pressures (0.85, 3.9 or 9.5 MPa). Saline, saline/CA, and saline/US infusion groups (n = 28) did not have histopathologic damage. The saline/CA/US infusion group (n = 10) at exposure conditions below the FDA mechanical index limit of 1.9 did not have histopathologic damage, whereas the saline/CA/US infusion group (n = 9) at exposure conditions above the FDA limit did have damage (5 of 9 arteries). Lesions were characteristic of acute coagulative necrosis. Mean s-thrombomodulin concentrations, a marker for endothelial cell injury, were highest in rabbits exposed to US at 0.85 and 3.9 MPa, suggesting that vascular injury may be physiological and not accompanied by irreversible cellular injury. |
| Title |
Vast diagnostic potential seen for ultrasound. |
| Author |
Unknown. |
| Journal |
World Medical Report |
| Volume |
|
| Year |
1972 |
| Abstract |
No abstract available. |
| Title |
Velocity and absorption of ultrasound in some viscous liquids at pressures up to 1000 atm. |
| Author |
Mikhailov IG, Polunin VM. |
| Journal |
Soviet phy Acoustic |
| Volume |
|
| Year |
1971 |
| Abstract |
No abstract available. |
| Title |
Velocity of spread and absorption of ultrasound in cell suspensions of the alga Chlorella. [Rate of propagation and absorption of ultrasonic waves in cell suspensions of Chlorella algae.] |
| Author |
Kaufman AD, El'piner IE. |
| Journal |
Biofizika |
| Volume |
|
| Year |
1972 |
| Abstract |
Measurements have been made of the velocity of spread at a frequency of 10 Mc/s and the absorption of ultrasound over the frequency range 10-70 Mc/s in a suspension of chlorella cells. The dependence of the velocity and the absorption of ultrasound on the concentration of chlorella has been obtained . We noted that on death of the cells the velocity of ultrasound changes. It is shown that the absorption of ultrasound occurs practically completely on the cells and is of a relaxation character. |
| Title |
Velocity of ultrasound in binary solutions of pyridine with heavy water. |
| Author |
Stumpf FB, Gupta PK. |
| Journal |
J Acoust Soc Am |
| Volume |
|
| Year |
1975 |
| Abstract |
No abstract available. |
| Title |
Velocity of ultrasound in potassium-ammonia solutions: Concentrated solutions. |
| Author |
Bowen DE. |
| Journal |
J Chem Phys |
| Volume |
|
| Year |
1969 |
| Abstract |
The velocity of 10-MHz sound waves in potassium-ammonia solutions has been determined using a new apparatus for 35 different metal concentrations between 1.5 and 15.5 MPM (mole percent metal) over the temperature range 200? to 240?K. The adiabatic compressibility of these solutions has been determined by combining this data with the available density data. The concentration dependence of the sound velocity changed abruptly at a concentration of 3.2 MPM. This change is quite similar to the one previously observed in the lithium-ammonia solutions although it occurs at a lower concentration. Comparison of the sound velocities in Li-NH(3) solutions and K-NH(3) solutions shows that the sound velocity is solute independent for concentrations less than about 4 MPM and that the Mott transition is not solute independent but apparently depends on the radius of the solute ion. |
| Title |
Vibrating microbubbles poking individual cells: Drug transfer into cells via sonoporation. |
| Author |
Wamel AV, Kooiman K, Harteveld M, Emmer M, Cate FJ, Versluis M, Jong ND. |
| Journal |
J Cont Rel |
| Volume |
|
| Year |
2006 |
| Abstract |
Ultrasound contrast previous termmicrobubblesnext term have the ability to enhance endothelial previous termcellnext term permeability and thus may be used as a new way to deliver previous termdrugs.next term It facilitates the previous termtransfernext term of extracellular molecules into previous termcellsnext term activated through ultrasound driven previous termmicrobubbles.next term The present study is designed to correlate the relationship between previous termmicrobubblenext term induced previous termcellnext term deformation and enhanced previous termcellnext term membrane permeability. Propidium iodide (PI) was used as a membrane integrity probe. Using high-speed imaging of previous termvibrating microbubblesnext term against endothelial previous termcellsnext term and imaging transport of PI into these previous termcellsnext term showed a direct correlation between previous termcellnext term deformation and resulting previous termcellnext term membrane permeability. The membrane permeabilization lasted for a short period without affecting endothelial previous termcellsnext term viability. We identified that previous termmicrobubblesnext term are crucial to enhance transient previous termcellnext term membrane permeability. Thus, permeability of previous termindividual cellsnext term is increased. The roles of ultrasound contrast previous termmicrobubblesnext term as the trigger for improved previous termdrugnext term efficacy are discussed. |
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