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BRL Abstracts Database |
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Your search for ultrasound produced 3296 results. Page 305 out of 330
| Title |
Ultrasound characterization of acute myocardial ischemia by quantitative texture analysis. |
| Author |
McPherson DD, Aylward PE, Knosp BM, Bean JA, Kerber RE, Collins SM, Skorton DJ. |
| Journal |
Ultrason Imaging |
| Volume |
|
| Year |
1986 |
| Abstract |
In this study we tested the efficacy of quantitative texture analysis in the identification of acute myocardial ischemia using an ultrasound data acquisition system that digitizes and stores echocardiographic data in polar format. In nine closed-chest dogs, data were acquired before and after coronary occlusion using a 2.4 MHz echocardiographic system. Regions of interest were analyzed at end-diastole and end-systole from the ischemic area and normal area at the same depth of field. Ultrasound data were evaluated using previously reported quantitative gray level texture measures. After occlusion, texture changes indicative of ischemia were found in systolic images. The directional component of the data analysis was important; analysis in the azimuthal direction was more accurate than in the axial direction. Six texture measures exhibited significant changes in the ischemic region from control to occlusion when analyzing data in the azimuthal direction. One false positive result occurred (significant texture change in the normal region from control to occlusion) in the azimuthal direction. Several false positive alterations in the normal regions from control to occlusion were found when the texture was evaluated in the axial direction. For accurate assessment of ischemic changes, preocclusion image data were required. We conclude that quantitative echocardiographic texture analysis using polar format data can identify subtle changes in myocardial texture such as that due to acute ischemia, using data acquired through the chest wall. |
| Title |
Ultrasound characterization of ocular tissue in the frequency range from 50 MHz to 100 MHz. |
| Author |
Ye S,. Harasiewicz KA, Pavlin CJ, Foster FS . |
| Journal |
Proc Ultrason Symp IEEE |
| Volume |
|
| Year |
1992 |
| Abstract |
The ultrasonic properties of ocular tissues including sclera, cornea, ciliary body and iris are studied over the frequency range from 50 to 100 MHz using the ultrasound backscatter microscopic technique. The scleral tissue shows the highest speed, the highest attenuation coefficient, and the highest backscatter coefficient. The speed of sound for the four eye tissues ranges from 1622 m/s for sclera to 1542 m/s for iris. At 50 MHz, attenuation coefficients range from 1.3 dB/mm to 4.3 dB/mm with frequency dependency ranging from 1.4 to 1.56. The first measurements of backscatter coefficients are reported. It is shown that the ultrasound backscatter microscopic technique is a useful device for tissue characterization in the high frequency range. |
| Title |
Ultrasound characterization of three animal mammary tumors from three-dimensional acoustic tissue models. |
| Author |
Mamou J, Oelze ML, O'Brien WD Jr., Zachary JF. |
| Journal |
Proc Ultrason Symp IEEE |
| Volume |
|
| Year |
2005 |
| Abstract |
With very few exceptions, the tissue microstructures responsible for ultrasonic scattering remain unidentified. Identification of these structures would leas to potentially improved methodologies for characterizing tissue and diagnosing disease from ultrasonic backscatter measurements. Three-dimensional (3D) acoustic models of tissue microstructure termed 3D impedance maps (3DZMs) were obtained for three tumors (a rat fibroadenoma, a mouse carcinoma, and a mouse sarcoma). 3DZMs were inferred from a 3D histological data set of tissue, and are independent of ultrasonically acquired data. The Fourier transform of the 3D spatial autocorrelation of the 3DZM was used to estimate the backscattered power spectrum. Spectral estimates (scatterer size and acoustic concentration) were then obtained by fitting an assumed scattering model (form factor, FF) to the power spectrum. At first, a Gaussian FF was used to allow comparison with the independent in vivo measurements from the same three tumor tissues. Then, a tissue-specific FF was deduced from each 3DZM. The 3DZM estimates using the Gaussian FF led to scatterer estimates very similar (within 10%) to those obtained with the independent ultrasonic backscatter measurements. However, a clear distinction could not be made between the sarcoma and carcinoma using the estimates obtained with the Gaussian FF. Statistical distinction was finally obtained when the 3DZM-deduced FF was used to obtain estimates. Thus, 3DZMs are unique computational phantoms that can to help identify ultrasonic scattering sites, and to develop advanced models and sensitive ultrasonic techniques to diagnose disease. |
| Title |
Ultrasound chemical effects on pure organic liquids. |
| Author |
Weissler A, Pecht I, Anbar M. |
| Journal |
Science |
| Volume |
|
| Year |
1965 |
| Abstract |
Molecular fragmentation of organic liquids was produced by cavitation due to ultrasound waves, even in the absence of water. The sonolysis of acetonitrile under argon yielded N(2), CH(4), and H(2); but under oxygen the products were N(2), CO, CO(2), and H(2)O. Pure nonaqueous carbon tetrachloride also underwent sonolytic decomposition under wither argon or oxygen, with the production of elemental chlorine. |
| Title |
Ultrasound chemical relaxation spectroscopy. |
| Author |
Slutsky LJ. |
| Journal |
Methods Exp Phys |
| Volume |
|
| Year |
1981 |
| Abstract |
No abstract available. |
| Title |
Ultrasound computed tomography: from the past to the future. |
| Author |
Schmitt RM. |
| Journal |
Acoust Imaging |
| Volume |
|
| Year |
2002 |
| Abstract |
No Abstract Available. |
| Title |
Ultrasound computerized tomography using transmission and reflection mode: application to medical diagnosis. |
| Author |
Hiller D. Ermert H. |
| Journal |
Acoust Imaging |
| Volume |
|
| Year |
1982 |
| Abstract |
No Abstract Available. |
| Title |
Ultrasound contrast agent behavior near the fragmetation threshold. |
| Author |
Chen W,Matula TJ,Crum LA. |
| Journal |
Proc IEEE Ultrasonic Symposium |
| Volume |
|
| Year |
2000 |
| Abstract |
Understanding the fragmentation process of ultrasound contrast agents is important in therapeutic ultrasound applications (such as ultrasound-enhanced drug delivery), as well as in certain imaging applications (such as “flash echo”
imaging[ I]). In the fragmentation of OptisonTM microbubbles, our observations suggest that there are two pressure thresholds, a threshold which leads to shell rupture and the production of smaller daughter bubbles, and another one leading to the onset of sustained inertial cavitation (IC) activity. Between the shell-disruption threshold and sustained IC threshold is a region where intermittent inertial cavitation activity was detected. The acoustic
signature of the intermittent region, the pressure level for the various thresholds, and the strength of the subsequent cavitation activity are all highly
dependent on the acoustic pulse parameters. |
| Title |
Ultrasound contrast agents affect the angiogenic response. |
| Author |
Johnson CA, Miller RJ, O'Brien WD Jr. |
| Journal |
J Ultrasound Med |
| Volume |
|
| Year |
2011 |
| Abstract |
Objectives- The interaction of ultrasound contrast agents (UCAs) and ultrasound (US) provides a way to spatially and temporally target tissues. Recently, UCAs have been used therapeutically to induce localized angiogenesis. Ultrasound contrast agents, however, have been documented to induce negative bioeffects. To further understand the balance of risks and benefits of UCAs and to examine the mechanism of US-UCA-induced angiogenesis, this study explored the role of UCAs, in particular Definity (Lantheus Medical Imaging, Inc, North Billerica, MA), in producing an angiogenic response.
Methods- The gracilis muscles of Sprague Dawley rats were exposed to 1-MHz US. The rats were euthanized the same day or allowed to recover for 3 or 6 days post exposure (DPE). Ultrasound peak rarefactional pressures (P(r)s) of 0.25, 0.83, 1.4, and 2.0 MPa were used while rats were infused with either saline or Definity. Assessments for angiogenesis included capillary density, inflammation, and vascular endothelial growth factor (VEGF), both acutely (0 DPE) and at 3 and 6 DPE.
Results- The results of this study suggest that the angiogenic response is dependent on infusion media, P(r), and DPE. While capillary density did not reach significance, VEGF expression was significant for infusion media, P(r), and DPE with inflammation co-occurrence (P < .05). Conclusions- These results suggest that the angiogenic response is elicited by a mechanical effect of US-UCA stimulation of VEGF that is potentially optimized when collapse occurs. |
| Title |
Ultrasound contrast agents nucleate inertial cavitation in vitro. |
| Author |
Miller DL, Thomas RM. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1995 |
| Abstract |
Some ultrasound contrast agents contain stable bodies of gas, and this study was undertaken to determine if these agents could provide nuclei for inertial cavitation. Inertial cavitation was detected and assessed by the measurement of the sonochemical hydrogen peroxide after exposure to 2.17-, 2.95- or 3.8-MHz ultrasound. A noncavitating system was obtained by removing cavitation nuclei from the rotating tube exposure chambers by vacuum degassing, and from the phosphate-buffered saline medium by filtering. Albunex added at 10-2, 10-3 or 10-4 dilutions, or Levovist added at 2 mg mL-1, 0.2 mg mL-1 or 0.02 mg mL-1 all initiated significant H2O2 production for 2.17-MHz ultrasound at 0.41 MPa or higher spatial peak pressure amplitude for 5 min exposure gated at 0.25 s on and off with 60-rpm rotation. Not rotating the tube virtually eliminated H2O2 production. For 2.5-min continuous exposure, both agents initiated significant H2O2 production for 2.95-MHz exposure at 0.58 MPa or higher, but not for 3.8-MHz exposure up to 1.16 MPa. Bubble-based ultrasound contrast agents therefore appear to be able to provide nuclei for inertial cavitation in the rotating tube exposure system. |
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