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BRL Abstracts Database |
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Your search for ultrasound produced 3296 results. Page 224 out of 330
| Title |
Scattering properties of encapsulated gas bubbles at high ultrasound pressures. |
| Author |
Frinking PJA, de Jong N, Céspedes EI. |
| Journal |
J Acoust Soc Am |
| Volume |
|
| Year |
1999 |
| Abstract |
Encapsulated types of contrast agents possess a specific acoustical signature. When the applied acoustic pressure exceeds a specific threshold, the scattering level increases abruptly for a short time. A "dualistic" character of the encapsulated gas bubbles explains this signature, observed for Quantison TM (air bubbles encapsulated by a shell of human albumin). For acoustic pressures below a threshold, the bubbles act as encapsulated gas bubbles and are stable linear or nonlinear scatterers, depending on the applied acoustic pressure. For acoustic pressures above the threshold, the bubbles rupture and release the contained gas, subsequently acting as free-gas bubbles. The effect is transient and lasts until the released free-gas bubbles are dissolved in the surrounding liquid. This explanation was investigated experimentally and evaluated by theoretical models. A 15–20-dB increase in scattering, the appearance of higher harmonics, and a finite duration of the effect could be measured and agreed with corresponding theory. Therefore, ultrasound in combination with this dualistic character suggests that encapsulated gas bubbles can be construed as a robust vehicle for localized delivery of free-gas bubbles, the ultimate ultrasound contrast agent. |
| Title |
Scattering techniques: Tissue characterization by ultrasonic frequency-dependent attenuation and scattering. |
| Author |
Lele PP, Mansfield AB, Murphy AI, Namery J, Senapati N. |
| Journal |
Proc Semin Ultrason Tissue Character - Gaithersburg |
| Volume |
|
| Year |
1975 |
| Abstract |
Studies to explore the feasibility of utilizing acoustic impedance, attenuation, and scattering characteristics of tissues for enhancing the diagnostic capabilities of ultrasound are described. Frequency-dependent ultrasonic attenuation is found to be sufficiently greater in infarcted or otherwise necrotized tissues than in normal controls to permit their positive identification. Superficial and internal scattering properties of tissues hold the promise of being significant for diagnostic applications. The difficulties to be overcome to utilize these properties successfully are discussed. |
| Title |
Schallkopfe von Ultraschallgeraten und ihre Eigenschaften. (Maximum sound from ultrasound equipment and their properties.) Article is in German. |
| Author |
Obraz J. |
| Journal |
Wiss Z Humboldt Univ Berl |
| Volume |
|
| Year |
1965 |
| Abstract |
No abstract available. |
| Title |
Scientifically based safety criteria for ultrasonography. |
| Author |
Nyborg WL. |
| Journal |
J Ultrasound Med |
| Volume |
|
| Year |
1992 |
| Abstract |
One of the major contributions of E. L. Carstensen to medical ultrasonography lies in the research studies by him and his colleagues on biophysical mechanisms for biological effects. These studies have done much to provide a basis for predicting conditions under which ultrasound will affect living systems. The scientific information that now exists makes possible an improved approach to decisions on safety for diagnostic ultrasonography. In particular, estimates of the maximum temperature produced in a sonographic examination provide an index that can be used to ensure safety from thermal hazards. |
| Title |
Scintigraphic control of bone-fracture healing under ultrasonic stimulation: An animal experimental study. |
| Author |
Klug W, Franke W-G, Knoch H-G. |
| Journal |
Eur J Nucl Med |
| Volume |
|
| Year |
1986 |
| Abstract |
In a model of closed lower-leg fracture in rabbits and of secondary bone-fracture healing, scintigraphic control until biological healing was performed. Biological fracture healing was assumed for a region of interest (ROI)-activity ratio close to 1.0. After application of 99mTc-HEDP, 151 examinations were performed. ROI activity increased significantly until day 14 p.i. and reached the maximum value (Q=6.44) on day 14 postfracture. Sixty-one lower leg fractures were treated by ultrasound from days 14–28 postfracture. These stimulated fractures were biologically healed on day 168 postfracture. The fractures that were not treated by ultrasound could not be detected by scanning after day 203 postfracture. |
| Title |
Search for biochemical effects in cells and tissues of ultrasonic irradiation of mice and of the in vitro irradiation of mouse peritoneal and human amniotic cells. |
| Author |
Glick D, Adamovics A, Edmonds PD, Taenzer JC. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1979 |
| Abstract |
Cyclic AMP, cyclic GMP, and histamine concentrations were determined in skin, lung, and peritoneal cells of untreated, sham-treated, and treated mice in vivo (2MHz continuous wave, 1 W/cm2, 100 and 200 sec, 34 C). The mice were killed and samples were taken 2 - 120 min after exposure. Similar experiments, including some on liver, were performed with focused-beam exposures (8.4 W/cm2, 2 x 100 sec; 10 W/cm2, 12 sec) of specific areas of the mouse. In addition, wide-beam exposures in vitro of the peritoneal cells and of humon amniotic cells were included. In all of the work, no significant positive effect of the exposures was observed based on numbers of samples and respective means and distributions in comparison with the controls. Furthermore, the percentages of dead peritoneal and amniotic cells present were not affected by the exposures. These results may depend on maintenance of the integrity of cell membrane structures during the exposures, in spite of damage to other cell structures. |
| Title |
Second-trimester sonographic comparison of the lower uterine segment in pregnant women with and without a previous cesarean delivery. |
| Author |
Sambaziotis H, Conway C, Figueroa R, Elimian A, Garry D. |
| Journal |
J Ultrasound Med |
| Volume |
|
| Year |
2004 |
| Abstract |
Objective. To compare measurements of the lower uterine segment during a second-trimester sonographic examination in women with and without a previous cesarean delivery. Methods. Women undergoing second-trimester sonographic examination, 24 with a history of cesarean delivery and 30 control subjects with no history of cesarean delivery, were recruited for transvaginal sonographic evaluation of the lower uterine segment with a high-frequency probe. The uterine niche or previous cesarean scar site was defined as a small triangular anechoic defect in the anterior wall of the uterus. The uterine wall thickness was measured successively at the level where the bladder dome meets the lower uterine segment. Measurements were obtained with cursors at the interface of the urine?bladder and the amniotic fluid-decidua. The study was approved by the Institutional Review Board, and P< .05 was considered significant. Results. The uterine niche was identified in 14 (58% of 24 women with a previous cesarean delivery. The lower uterine segment was significantly thinner in women with a cesarean delivery compared with control subjects (mean +/- SD, 4.7 +/- 1.1 versus 6.6 +/- 2.0 mm; P < .001). In the previous cesarean group, the mean lower uterine segment thickness was small in the 5 women with 2 cesarean deliveries when compared with those with 1 cesarean delivery (4.6 +/- 1.0 versus 4.7 +/- 1.4 mm; P = .91). In a linear regression model, the only variable retaining significance in the prediction of the uterine wall thickness was previous cesarean delivery (P = .002). Maternal age, parity, number of previous cesarean deliveries, and gestational age did not attain significance in the model. Conclusions. The lower uterine segment during asecond-trimester sonographic examination is significantly thinner in women with a previous cesarean delivery. Identification of the scar niche is possible in most of these women. |
| Title |
Segment therapy: The effects of ultrasound and benzocaine spray in the treatment of contractures and spasticity. |
| Author |
Sonnen VG. |
| Journal |
J Alt Complement Med |
| Volume |
|
| Year |
1997 |
| Abstract |
According to Krusen?s Handbook of Physical Medicine and Rehabilitation, topical application of ultrasound exerts only an indirect and adjunctive effect as deep-heat treatment. In support of this idea the extensibility of an isolated tendon in a heated water bath is described. The significance of this experiment as a biological phenomenon has never been critically examined. In this article the existence of a segmental reflex is proposed. Such a segmental paradigm is in keeping with the segmental organization and evolution of the locomotor system. It is further suggested that ultrasound and related therapy, if applied segmentally, may have a curative effect. |
| Title |
Segmentation of high-frequency ultrasound images of atherosclerotic coronary arteries. |
| Author |
Bauer JM, Stein RA, McPherson DD. |
| Journal |
Comput Biol Med |
| Volume |
|
| Year |
1991 |
| Abstract |
High-frequency epicardial echocardiography (HFE) is an ultrasound imaging technique capable of visualizing coronary arteries in cross-section. Use of this imaging technique in the intra-operative setting can provide information about the structure of coronary arteries. As a result of time constraints imposed in this setting, here is a need for rapid, on-line analysis of HFE images. An algorithm for segmenting HFE images of coronary arteries into wall and luminal regions is described in this paper. The algorithm is more objective and time efficient than manual methods. A validation study with post-mortem human hearts demonstrated an excellent correlation (r=0.99 for luminal areas, r=0.99 for wall areas) between HFE images segmented with the algorithm and by manual methods, and a good correlation (r=0.99 for luminal areas, r=0.86 for wall areas) between HFE images segmented with the algorithm and manually segmented images of histological samples of the corresponding coronary arterial segments. Use of the algorithm for intra-operative HFE image segmentation may reduce the amount of time required for HFE image analysis and allow for an increased amount of data collection and analysis in the operating room. |
| Title |
Segmenting ultrasound images of the prostrate using neural networks. |
| Author |
Prater JS, Richard WD. |
| Journal |
Ultrason Imaging |
| Volume |
|
| Year |
1992 |
| Abstract |
Describes a method for segmenting transrectal ultrasound images of the prostate using feedforward neural networks. Segmenting two-dimensional images of the prostate into prostate and nonprostate regions is required when forming a three-dimensional image of the prostate from a set of parallel two-dimensional images. Three neural network architectures are presented as examples and discussed. Each of these networks was trained using a small portion of a training image segmented by an expert sonographer. The results of applying the trained networks to the entire training image and to adjacent images in the two-dimensional image set are presented and discussed. The final network architecture was also trained with additional data from two other images in the set. The results of applying this retrained network to each of the images in the set are presented and discussed. |
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