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BRL Abstracts Database |
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Your search for ultrasound produced 3296 results. Page 291 out of 330
| Title |
Ultrasonic grey scale visualization of the thyroid gland. |
| Author |
Jellins J, Kossoff G, Wiseman J, Reeve T, Hales I. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1975 |
| Abstract |
Ultrasonic examination of the thyroid provides an accurate method of differentiating between solid and cystic lesions. With grey scale echography contents of many solid lesions give rise to a characteristic echo pattern which may eventually allow the ultrasonic classification of these lesions. This preliminary study of 40 patients presents the echograms associated with some of the more common pathological conditions of the thyroid gland. |
| Title |
Ultrasonic heart investigation. |
| Author |
Hertz CH. |
| Journal |
Med Electron Biol Eng |
| Volume |
|
| Year |
1964 |
| Abstract |
For several years the ultrasound reflectoscope has been used for the diagnosis of certain heart diseases, especially disease of the heart valves. The technical and physical properties of the tranducers used for these investigations are discussed. By different methods of registration the movement of the heart structures to be investigated can be recorded as curves, together with other heart parameters, e.g. ECG, phonocardiogram etc. These curves, which are called ultrasonic cariograms (UCG), show typical alterations of form in the case of a pathological change in the heart structure in question and thus can be used for diagnostic purposes. The fields of application of the method will be discussed. |
| Title |
Ultrasonic heating of the skull. |
| Author |
Carstensen EL, Child SZ, Norton S, Nyborg W. |
| Journal |
J Acoust Soc Am |
| Volume |
|
| Year |
1990 |
| Abstract |
Comparatively simple analysis shows that diagnostic ultrasound devices, in some.cases, may approach output levels that can produce significant heating of tissues,.particularly if the propagation path includes bone. Experimental tests of these.predictions using rodents show that temperature increments of the order of 3 degrees.C/W/cm2 are produced in skull bone with sharply focused fields at medically relevant.frequencies. |
| Title |
Ultrasonic heating of tissues. |
| Author |
Frizzell LA. |
| Journal |
Thesis(PhD): Univ of Rochester |
| Volume |
|
| Year |
1975 |
| Abstract |
Ultrasonic heating of tissues was investigated with two purposes in mind. Firstly, to determine if a thermal mechanism would explain the destruction of tissues other than brain at intensities below 200 W/cm*cm. Secondly, to examine localized heating observed at impedance discontinuities is tissue...To determine the mode of action of the ultrasound for intensities in the range of interest further data on the absorption coefficient of ultrasound in liver tissue were obtained. The intensity-time thresholds for lesion production in rabbit liver, kidney and testicle were then measured at 2 and 6 MHz and single pulse exposures of 5, 15 and 60 seconds duration. These data were compared to similar data on brain tissue that had been reported by other investigators. It was found that the differences between tissues could be explained on the basis of a thermal model for the action of ultrasound on tissue...It was hypothesized that mode conversion to shear waves at impedance discontinuities and subsequent absorption of these waves in a very small distance was the explanation for localized heating at these interfaces. To test this hypothesis rough measurements of the acoustic properties of soft tissues at low megahertz frequencies were made. At these frequencies soft tissues are viscosity dominated, but the viscosities are orders of magnitude below those reported at lower frequencies. The low viscosities result in low velocities and extremely high absorption coefficients for shear waves in tissue. A mathematical model for mode conversion at a plane interface between two viscoelastic media was developed. Longitudinal and shear properties of tissue were then used to calculate the amount of mode conversion at muscle ? air, muscle - water, muscle ? cholesteryl linoleate and muscle ? bone interfaces. Although, on the basis of this study, it was agreed that shear waves in bone are important, shear waves in muscle and second media other than bone gave negligible contribution to heating at the interfaces examined...Ultrasonic heating at tissue ? air and tissue ? water interfaces was investigated further including analysis of possible contributions from surface waves, non-linear effects and superposition of the incident and reflected beams. It was found that consideration of changing beam profile, absorption and superposition of incident and reflected beams could explain the heating pattern observed at these interfaces. |
| Title |
Ultrasonic heating of tissues. |
| Author |
Frizzell LA, Carstensen EL. |
| Journal |
Rep Univ Rochester Dept Elect Eng |
| Volume |
|
| Year |
1975 |
| Abstract |
Ultrasonic heating of tissue was investigated with two purposes in mind. Firstly, to determine if a thermal mechanism would explain the destruction of tissues other than brain at intensities below 200 w/cm(^2). Secondly, to examine localized heating observed at impedance discontinuities in tissue. .To determine the mode of action of the ultrasound for intensities in the range of interest further data on the absorption coefficient of ultrasound in liver tissue were obtained. The intensity-time thresholds for lesion production in rabbit liver, kidney and testicle were then measured at 2 and 6 MHz and single pulse exposures of 5, 15, and 60 seconds duration. These data were compared to similar data on brain tissue that had been reported by other investigators. IT was found that the differences between tissues could be explained on the basis of a thermal model for the action of ultrasound on tissue. .It was hypothesized that mode conversion to shear waves at impedance discontinuities and subsequent absorption of these waves in a very small distance was the explanation for localized heating at these interfaces. To test this hypothesis rough measurements of the shear acoustic properties of soft tissues at low megahertz frequencies were made. At these frequencies soft tissues are viscosity dominated, but the viscosities are orders of magnitude below those reported at lower frequencies. The low viscosities result in low velocities and extremely high absorption coefficients for shear waves in tissue. A mathematical model for mode conversion at a plane interface between two viscoelastic media was developed. Longitudinal and shear properties of tissue then used to calculate the amount of mode conversion at muscle ? air, muscle ? water, muscle ? cholesteryl linoleate and muscle ? bone interfaces. Although, on the basis of this study, it was agreed that shear waves in bone are important, shear waves in muscles and second media other than bone gave negligible contributions to heating at the interfaces examined. .Ultrasonic heating at tissue ? air and tissue ? water interfaces was investigated further including analysis of possible contributions from surface waves, non-linear effects and superposition of the incident and reflected beams. It was found that consideration of changing beam profile, absorption and superposition of incident and reflected beams could explain the heating pattern observed at these interfaces. |
| Title |
Ultrasonic heating of Vicia faba roots. |
| Author |
Eames FA, Carstensen EL, Miller MW, Li M. |
| Journal |
J Acoust Soc Am |
| Volume |
|
| Year |
1975 |
| Abstract |
Irradiation of Vicia faba root tips with 2.3-MHz ultrasound at 10 W/cm2 causes a small but measurable heating of the tips and an immediate reduction in root growth rate. Roots exposed to comparable temperature increments without ultrasound show no reduction in growth, thus leading to the conclusion that the mechanism responsible for the biological effects of ultrasound on roots is nonthermal. From the time course of ultrasonic heating of the roots it appears that the thermal conductivity of the root material is comparable to that of water, and the acoustic absorption coefficient of the root tissue is higher than that of mammalian tissues. |
| Title |
Ultrasonic hyperthermia and radiation in the management of intraocular malignant melanoma. |
| Author |
Coleman DJ, Lizzi FL, Burgess SEP, Silverman RH, Smith ME, Driller J, Rosado A, Ellsworth RM, Haik BG, Abramson DH, McCormick B. |
| Journal |
Am J Ophthalmol |
| Volume |
|
| Year |
1986 |
| Abstract |
Hyperthermia and radiation were used in combination to treat four patients with choroidal malignant melanoma. This technique uses ultrasonically induced hyperthermia synergistically with radiation to destroy tumor cells. The lower levels of radiation used should avoid the late vascular and inflammatory complications seen in conventional radiation therapy. Tumors were scanned by a computerized diagnostic ultrasound system before treatment and assigned an acoustic tissue type on the basis of a statistical comparison of their ultrasound backscatter spectrum with spectra of tumors of known pathologic status. During the follow-up period, the longest of which was 15 months, all tumors demonstrated regression patterns consistent with choroidal tumors of the same acoustic tissue types treated with conventional radiation therapy. |
| Title |
Ultrasonic hyperthermia for ophthalmic therapy. |
| Author |
Lizzi FL, Coleman DJ, Driller J, Ostromogilsky M, Chang S, Greenall P. |
| Journal |
IEEE Trans Sonics Ultrason |
| Volume |
|
| Year |
1984 |
| Abstract |
A theoretical model was developed to compute the spatiotemporal features of temperature rises induced in ocular tissue during exposure to high-intensity focused ultrasound. The model incorporates damage integral evaluation to predict the occurrence and dimensions of thermally induced lesions. Experimental data confirmed the accuracy of computed lesion dimensions for scieral and chorioretinal lesions. Computed results also are in agreement with measured threshold exposure levels needed to produce minimal chorioretinal lesions. The model is being improved to account for blood-flow cooling effects during long-term hyperthermia. Data were collected using this long-term mode on Greene's melanoma implanted in the rabbit choroid, and these data indicate that tumor regression can be achieved at levels that are consistent with damage integral predictions. |
| Title |
Ultrasonic hysteresis in biological media. |
| Author |
Johnston RL, Dunn F. |
| Journal |
Radiat Environ Biophys |
| Volume |
|
| Year |
1981 |
| Abstract |
Non-linear mechanical response of viscoelastic strain responding media to high amplitude stress-strain is examined from a.phenomenological point of view and found to lead to results compatible with empirical observations of high intensity ultrasound.irradiation of brain, liver, and eye lens tissues. The proposed hysteresis model provides for most of the observed dependencies.such as an intensity dependent absorption coefficient, an absorption coefficient increasing linearly with frequency, and a.dispersionless velocity of ultrasound in soft tissues (excluding lung). The non-linear compliance of tissues further predicts.production of half-harmonic signals even in the absence of cavitation. |
| Title |
Ultrasonic imaging of tumor angiogenesis using contrast microbubbles targeted via the tumor-binding peptide arginine-arginine-leucine. |
| Author |
Weller GER,Wong MKK,Modzelewski RA,Lu E,Klibanov AL,Wagner WR,Villanueva FS. |
| Journal |
Cancer Res |
| Volume |
|
| Year |
2005 |
| Abstract |
Endothelial cells (EC) of angiogenic tumor vasculature are characterized by altered expression of molecular markers on their surface. Numerous peptides have been identified that specifically bind tumor angiogenic endothelium, including the tripeptide arginine-arginine-leucine (RRL). We hypothesized that ultrasound contrast microbubbles (MB) targeted via linkage with RRL would specifically adhere to tumor angiogenic endothelium versus normal myocardium, and that this selective adhesion could be detected ultrasonically. Microbubbles were conjugated to cyclic peptides containing either RRL (RRL-MB) or a glycine control sequence (control-MB). As measured in a parallel plate flow chamber, in vitro adhesion of RRL-MBs was three times greater to cultured tumor-derived ECs than to normal ECs (P < 0.01), demonstrating selective binding of RRL-MBs to tumor endothelium. Mice bearing s.c. Clone C or PC3 tumors were given i.v. injections of fluorescent RRL to show in vivo localization to tumor vasculature or were ultrasonically imaged following i.v. injections of targeted contrast MBs. Ultrasound images showed strong RRL-MB contrast enhancement within the tumors but not the control tissue myocardium. Control-MBs caused minimal enhancement in either tissue. Quantitative acoustic videointensity was significantly greater for the tumors than the hearts (5 +/- 1 versus 0.5 +/- 1 intensity units; P = 0.001). These data show that ultrasound contrast MBs targeted to tumor vasculature via RRL preferentially adhere to tumor versus normal vasculature and that this selective adherence can be detected with ultrasound. Targeted microbubbles may thus offer a noninvasive contrast-enhanced ultrasound imaging technique for the functional imaging of tumor neovascularization, and may have further implications for therapeutic tumor targeting. |
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