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BRL Abstracts Database |
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Your search for ultrasound produced 3296 results. Page 182 out of 330
| Title |
Myocardial ultrasonic backscatter for characterization of ischemia and reperfusion: Relationship to wall motion. |
| Author |
Barzilai B, Vered Z, Mohr GA, Wear KA, Courtois M, Sobel BE, Miller JG, Perez JE. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1990 |
| Abstract |
We have previously shown that cardiac cycle-dependent variation of integrated backscatter occurs in normal myocardium. To determine whether myocardial ischemia and reperfusion can be distinguished by real-time integrated backscatter imaging we performed 10 min balloon occlusion of the Left Anterior Descending (LAD) coronary artery followed by reperfusion in 10 closed-chest anesthetized dogs. Images were obtained at baseline, during occlusion, and up to 120 min after reperfusion. We measured the magnitude and delay of cyclic variation of integrated backscatter in segments with and without asynergy. Radiolabeled microspheres were used to verify both ischemia and reperfusion. Ischemic segments exhibited decreased magnitude and increased normalized delay of cyclic variation of integrated backscatter (from 3.3 +/- 0.3 dB to 1.4 +/- 0.2 dB, mean +/- SE; and from 0.95 +/- 0.03 to 1.67 +/- 0.15, respectively, all p less than or equal to 0.001). Reperfusion promptly restored the magnitude of cyclic variation toward normal. However, the delay of the cyclic variation was restored only partially. Wall motion analysis of the ischemic sites revealed persistent abnormalities throughout the reperfusion interval despite return to normal of the magnitude and delay of cyclic variation. Thus, real-time integrated backscatter imaging permits detection and differentiation of changes in myocardial acoustic properties indicative of ischemia and of subsequent reperfusion. |
| Title |
Myocardium-targeted delivery of endothelial progenitor cells by ultrasound-mediated microbubble destruction improves cardiac function via an angiogenic response. |
| Author |
Zen K, Okigaki M, Hosokawa, Y, Adachi Y, Nozawa Y, Takamiya M, Tatsumi T, Urao N, Tateishi K, Takahashi T, Matsubara H. |
| Journal |
J Mol Cell Cardiol |
| Volume |
|
| Year |
2006 |
| Abstract |
Application of ultrasound-mediated destruction of microbubbles (US + Bubble) to skeletal muscle creates capillary ruptures leading to leakage of the cell components. We studied whether US + Bubble combined with bone-marrow-derived mononuclear cells (BM-MNCs) infusion enables the targeted delivery of endothelial-lineage cells into the myocardium and improves cardiac function of the cardiomyopathy model due to the paucity of neocapillary formation. Pulsed US was applied to the anterior chest of BIOTO2 cardiomyopathy hamsters for 90 s after the intravenous injection of microbubble (OptisonR) followed by infusion of BM-MNCs. Cardiac samples from US + microbubble + BM-MNCs (US + Bubble + BM), US + Bubble, US + BM without Bubble, and saline infusion control groups were analyzed 12 weeks after treatment. Labeled BM-MNCs transplanted by US + Bubble were found to be mainly localized in the microvessels, but not by US stimulation without microbubble (121.2 ± 24.5 vs. 2.80 ± 1.30 cells/mm2, P < 0.001). Capillary densities in US + Bubble + BM group were increased 1.7-fold (P < 0.05) over the control, and neither US + Bubble nor US + BM enhanced neocapillary formation. 99mTc-Tetrofosmin scintigraphy revealed that blood perfusion area in the US + Bubble + BM group was 48% greater than the control (P < 0.01). US + Bubble stimulation induces the expression of adhesion molecules (VCAM-1 and ICAM-1) in capillaries, and the US + Bubble-mediated supply of BM-MNCs increased the myocardial content of VEGF and bFGF. The left ventricular wt/body wt, area of cardiac fibrosis, and apoptotic cell numbers in the US + Bubble + BM group significantly (P < 0.05) decreased by 82%, 73%, and 64% relative to the control, respectively. The cardiac function in myopathic hamsters (assessed by fractional shortening) was markedly improved 36% (P < 0.05) by US + Bubble + BM treatment. Targeted delivery of BM-MNCs by US + Bubble to the myocardium of the cardiomyopathic hamster increased the capillary densities and regional blood flow and inhibited cardiac remodeling, resulting in the prevention of heart failure. This non-invasive cell delivery system may be useful as a novel efficient approach for angiogenic cell therapy to the myocardium. |
| Title |
Nanointerrogation of ultrasonic contrast agent microbubbles using atomic force microscopy. |
| Author |
Sboros V, Glynos E, Pye SD, Moran CM, Butler M, Ross J, Short R, McDicken WN, Koutsos V. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
2006 |
| Abstract |
Predicting the acoustic response of an encapsulated previous termmicrobubblenext term to ultrasound requires an accurate assessment of the mechanical properties of the previous termmicrobubblenext term shell. previous termAtomic force microscopynext term (AFM) provides an unprecedented spatial and previous termforcenext term resolution of the order of Angstroms and subnanonewtons, respectively. It is introduced here as a means to interrogate previous termmicrobubblesnext term manufactured for previous termultrasonicnext term imaging. The advantage of AFM over scanning electron previous termmicroscopynext term (SEM) is that the previous termmicrobubblesnext term need not be subjected to a low temperature or low-pressure environment. The previous termmicrobubblesnext term were interrogated in a liquid environment, which could potentially be a simulated physiological environment. AFM was used in tapping mode imaging to reveal topographical detail of biSphere® previous termmicrobubbles. Because microbubblesnext term are large objects compared with the overall size of usual AFM tips, a convolution between the AFM tip and the previous termmicrobubblenext term was typical of the acquired topographies. However, a part of the top half of the bubble was imaged with nanometer resolution, and roughness measurements are reported. previous termForcenext term-distance curves were captured previous termusingnext term contact mode AFM. The range of stiffness or effective spring constant of biSphere® was found to be between 1 and 6 N m–1. In conclusion, the AFM is proposed here for the first time as a tool to image the surface of bubbles at the nanometer range in liquid and to perform reproducible measurements on the mechanical properties of individual previous termmicrobubbles.next term |
| Title |
Nearfield analysis for ultrasound transducers. |
| Author |
Engelbrecht J, Chivers RC, Feldmann M. |
| Journal |
Acoust Lett |
| Volume |
|
| Year |
1986 |
| Abstract |
No abstract available. |
| Title |
Nearfield of a piston source of ultrasound in an absorbing medium. |
| Author |
Nyborg WL, Steele RB. |
| Journal |
J Acoust Soc Am |
| Volume |
|
| Year |
1985 |
| Abstract |
Approximate expressions are discussed which are applicable for acoustic quantities in the vicinity of a plane piston source of ultrasound which radiates into an absorbing medium. A particularly useful approach for nearfield calculations combines an expression valid near the axis with another, given by Pierce [Acoustics, An Introduction to Its Physical Principles and Applications (McGraw-Hill, New York, 1981), Chap. 5], which is valid elsewhere. This approach gives reasonable accuracy at relatively low computational cost. Computed plots are presented, showing spatial distributions of the square of the pressure amplitude. Most of the plots are for a source diameter of 1.2 cm, a frequency of 3 MHz, and an absorption coefficient of 0.15 Np/cm; these are representative of conditions for medical applications of ultrasound. |
| Title |
Nearfield of a piston source of ultrasound in an absorbing medium. |
| Author |
Nyborg WL, Steele RB. |
| Journal |
J Acoust Soc Am |
| Volume |
|
| Year |
1985 |
| Abstract |
Approximate expressions are discussed which are applicable for acoustic quantities in the vicinity of a plane piston source of ultrasound which radiates into an absorbing medium. A particularly useful approach for nearfield calculations combines an expression valid near the axis with another, given by Pierce [Acoustics, An Introduction to Its Physical Principles and Applications (McGraw-Hill, New York, 1981), Chap. 5], which is valid elsewhere. This approach gives reasonable accuracy at relatively low computational cost. Computed plots are presented, showing spatial distributions of the square of the pressure amplitude. Most of the plots are for a source diameter of 1.2 cm, a frequency of 3 MHz, and an absorption coefficient of 0.15 Np/cm; these are representative of conditions for medical applications of ultrasound. |
| Title |
Negative effect of long duration pulsed ultrasonic irradiation on the mitotic activity in regenerating rat liver. |
| Author |
Barnett SB, Kossoff G. |
| Journal |
Proc Twenty-first Annu Meet AIUM |
| Volume |
|
| Year |
1976 |
| Abstract |
The cells in the adult mammalian liver can be stimulated into regenerative mitotic cell division in response to an urgent demand for cells as occurs after partial liver removal. Irradiating the liver tissue of the right lobe prior to removal of the other lobes will affect these cells in the interphase stage in the mitotic cycle and any effect of ultrasound will be reflected directly on the subsequent regeneration activity of the cellular components within this lobe. |
| Title |
Neglected techs seek footing in ultrasound. |
| Author |
Eckley AK. |
| Journal |
Diagn Imaging |
| Volume |
|
| Year |
1983 |
| Abstract |
No Abstract Available. |
| Title |
Neurosonicsurgery. |
| Author |
Fry WJ, Fry FJ. |
| Journal |
Ultrasound Biol Med |
| Volume |
|
| Year |
1957 |
| Abstract |
Dr. W. J. Fry presented a 16 mm. sound, color motion picture entitled "Neurosonicsurgery." The article is an abstract of the film. |
| Title |
New acoustic beams designed for rapid lesion formation: limitations near the skin during multiple lesion treatments. |
| Author |
Hunt JW, Xuan AY, Seto E, Worthington AE, Chen L, Kolios MC, Sherar MD. |
| Journal |
Proc IEEE Ultrason Symp |
| Volume |
|
| Year |
1997 |
| Abstract |
Minimally invasive surgery by intense focused ultrasound beams producing defined lesions is being studied extensively by different groups. Lesion formation from a single pulse, depending on treatment time, tissue temperature, and pulse repetition of about 1 minute, should produce little damage near the skin. However, this scheme results in unacceptably long treatment times when used on larger tumors. A possible solution is to generate more rapid treatment times, or larger lesion volumes per pulse. However, hyperthermic temperatures in the overlying normal tissues including the skin may limit these treatments. In a previous presentation, simulations using an “ideal” transducer, pulses as short as 4 s and rapid stirring of the coupling bolus would reduce the temperature rise near the skin. Thus pulse repetitions as short of 10 s would be acceptable. However, real transducer beams show large aberrations which can greatly increase the near-field intensities, and make them unacceptable for hyperthermia therapy. Some artifacts are be caused by clamping of the transducer, others are related to thickness variations of the transducers which generate heterogenous phase shifts from different parts of the transducer which produce unwanted spreads at beam's focus. The authors present detailed amplitude and phase scans near different transducers demonstrating the artifacts, and confirm them using novel ultrasound/magnetic-resonance phantoms showing the measured temperatures at the focus, and at 1 cm depth from the “skin” where the heating is considerably larger than that predicted by theory. Finally, we will discuss solutions for problems in the near field by improving the transducer mounting and reducing the unwanted phase shifts. |
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