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BRL Abstracts Database |
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Your search for ultrasound produced 3296 results. Page 133 out of 330
| Title |
Growth of air bubbles in tissue by rectified diffusion. |
| Author |
Crum LA, Hansen GM. |
| Journal |
Phys Med Biol |
| Volume |
|
| Year |
1982 |
| Abstract |
Introduction: Two recent reports (ter Haar and Daniels 1981, ter Haar et al 1982) have presented evidence for ultrasonically induced cavitation in vivo. In these experiments, guinea pig legs were irradiated with continuous ultrasound at spatial average intensities varying from 80 mW cm-2 to 680 mW cm-2. In addition, the leg was scanned with a pulse-echo ultrasonic imaging technique in order to detect both moving and stationary cavitation bubbles down to 10 ?m in diameter. The ultrasound was generated by a commercial ultrasonic therapy machine (Rank Sonacel Multiphon Mark III) at a frequency of 0.75 MHz and a spatial average to peak intensity ratio, at the position of the leg, of 1:3.
The results of their experiment were that air bubble of detectable size (that is, larger than 10 ?m in diameter) were generated in the guinea pig tissues at intensities as low as 80 mW cm-2, and that as intensity was increased to mW cm-2, then to 300 mW cm-2, and finally to 680 mW cm-2, progressively more events developed over the five minute irradiation time. The highest intensity produced several hundred such events.
This very important experiment has demonstrated that ultrasound systems driven in continuous modes and at relatively low intensities can initiate potentially hazardous side effects.
It is the purpose of this note to demonstrate that the observed production of stable cavitation bubbles in tissues, at the frequency and intensities used by ter Haar and Daniels, can be predicted on the basis of a presently available theory concerning the growth of bubbles by rectified diffusion.
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| Title |
Growth of pea roots exposed to pulsed ultrasound. |
| Author |
Child S, Carstensen EL, Miller MW. |
| Journal |
J Acoust Soc Am |
| Volume |
|
| Year |
1975 |
| Abstract |
Studies of the growth of pea roots after exposure to pulsed ultrasound (2.3 MHz, 10 W/cm2 peak intensity) support the postulate that a cavitation-like mechanism may be responsible in part for a decrease in the growth rate. There is a significant, although reduced, effect on growth at pulse lengths as short as 3 ?sec; this observation suggests that two nonthermal mechanisms may be involved. |
| Title |
Growth retardation in Chinese hamster V-79 cells exposed to 1 MHz ultrasound. |
| Author |
Kaufman GE, Miller MW. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1978 |
| Abstract |
Asynchronous Chinese hamster V-79 cells were exposed in suspension to continuous wave 1 MHz ultrasound for 1 min at an axial intensity of 2.5 W/cm2, then allowed to grow in monolayer culture. There was little if any growth, as determined by changes in the number of attached cells, for 24 hr after sonication, then a return to normal growth approximately 36 hr after sonication. The lack of growth during the first 24 hr appears to be due to an approximate balance between proliferation of viable cells and loss of non-viable cells into the medium. |
| Title |
Guidelines for journal of ultrasound in medicine authors and reviewers on measurement and reporting of acoustic output and exposure. |
| Author |
Edmonds PD, Abramowicz JS, Carson PL, Carstensen EL, Sandstrom KL. |
| Journal |
J Ultrasound Med |
| Volume |
|
| Year |
2005 |
| Abstract |
This report responds to a request from a deputy editor of the Journal of Ultrasound in Medicine (JUM) for guidelines for measurement and reporting of acoustic output and exposure. The request was addressed to the American Institute of Ultrasound in Medicine’s Technical Standards and Bioeffects Committees, which appointed a task group to draft a response. A basic premise of scientific reporting is the expectation that another investigator will wish to replicate a reported study. Therefore, it is essential that all pertinent information available or accessible to an investigator be reported. Methods and Guidelines. Rationales and checklists are presented to draw authors’ attention to aspects of experimental design and exposimetry that require consideration in project planning, execution, and reporting. Checklists are presented for use in 2 distinct categories of activity: (1) clinical settings in which a biophysical end point (bioeffect) is observed incidentally during another procedure; and (2) research projects specifically planned to investigate biophysical end points (bioeffects). Reportable parameters for the former are limited to essentials, whereas those for the latter are presented in detail. Certain basic information is recommended as mandatory for reports in both categories; certain additional parameters are designated as expected (at 3 levels of importance) when results of research are reported. Clinical investigators should comply with the short, first table (Table 1) and the last (Table 5) if applicable, but are encouraged to include additional data specified in other tables, as appropriate. Bioeffects experimenters should comply with Table 2 and such supplementary tables as are applicable to their study design. Table 3 is applicable if the study involved animal or human subjects. Table 4 is applicable if the study was on cells or in vitro. Table 5 is applicable if contrast agents were used in the study. Conclusions. We recommend that principal authors be required to certify to the JUM editors that they have reviewed the appropriate checklists and complied with indicated expectations. We recommend to reviewers that they consider individually adopting a mandatory requirement for reporting a basic set of parameters and/or descriptors of the equipment that are readily ascertainable by, or should be known to, a clinical user. |
| Title |
Haemolysis in vivo by therapeutic intensities of ultrasound. |
| Author |
Williams AR, Miller DL, Gross DR. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1986 |
| Abstract |
Therapeutic intensities of MHz ultrasound directed at the upper abdominal area of rats in vivo resulted in damage to the circulating red blood cells. This damage was detected as free haemoglobin in the plasma as well as microspheres and spherocytic cell fragments which are characteristically produced when blood is heated to more than 49 degrees C. The magnitude of this effect increased with increasing frequency of the ultrasound and was dependent upon the time-averaged intensity, even when the ultrasound was delivered as bursts of high spatial peak intensities. Thermal lesions were found above 10 W/cm2 SP at 1 MHz and above 3 W/cm2 SP at 3.4 MHz. These results show that the observed blood cell damage is primarily a thermal effect which occurs as the blood perfuses anatomical structures which are being heated by the ultrasound beam. |
| Title |
Hardware design of an ultrasound CT scanner. |
| Author |
Dick DE, Bay HP, Carson PL. |
| Journal |
Biomed Sci Instrum |
| Volume |
|
| Year |
1977 |
| Abstract |
No abstract available. |
| Title |
Harmonic imaging for microbubble contrast agent detection, |
| Author |
Chin CT, burns PN. |
| Journal |
J Acoust Soc Am |
| Volume |
|
| Year |
1998 |
| Abstract |
The detection of microbubble contrast agents in the vessels of the microcirculation is currently limited by the relatively low concentrations attainable without causing acoustic attenuation, set against the high clutter signal imposed by surrounding soft tissue. By inducing nonlinear resonant oscillation in a population of microbubbles in transit in the circulation, echoes at the second harmonic can be detected preferentially, thus segmenting the blood signal from that due to tissue. Real‐time harmonic imaging and Doppler have been implemented using a clinical array imaging system, and it is shown that with bubble agents it can detect flow in 40 μm vessels of the kidney. At higher incident peak pressures (above about 0.5 Mpa at about 3 MHz), some microbubble contrast agents are irreversibly disrupted by ultrasound. They then produce transient echoes which are high in amplitude and rich in harmonics. Furthermore, transient echoes can be obtained repeatedly over a period of milliseconds, allowing correlation imaging. Such ‘‘transient Doppler’’ imaging can demonstrate microcirculatory blood in the capillaries of the moving myocardium, a new development with significant clinical potential. |
| Title |
Harmonic motion imaging for focused ultrasound (HMIFU): A fully integrated technique for sonication and monitoring of thermal ablation in tissues. |
| Author |
Maleke C, Konofagou EE. |
| Journal |
Phys Med Biol |
| Volume |
|
| Year |
2008 |
| Abstract |
FUS (focused ultrasound), or HIFU (high-intensity-focused ultrasound) therapy, a minimally or non-invasive procedure that uses ultrasound to generate thermal necrosis, has been proven successful in several clinical applications. This paper discusses a method for monitoring thermal treatment at different sonication durations (10 s, 20 s and 30 s) using the amplitude-modulated (AM) harmonic motion imaging for focused ultrasound (HMIFU) technique in bovine liver samples in vitro. The feasibility of HMI for characterizing mechanical tissue properties has previously been demonstrated. Here, a confocal transducer, combining a 4.68 MHz therapy (FUS) and a 7.5 MHz diagnostic (pulse-echo) transducer, was used. The therapy transducer was driven by a low-frequency AM continuous signal at 25 Hz, producing a stable harmonic radiation force oscillating at the modulation frequency. A pulser/receiver was used to drive the pulse-echo transducer at a pulse repetition frequency (PRF) of 5.4 kHz. Radio-frequency (RF) signals were acquired using a standard pulse-echo technique. The temperature near the ablation region was simultaneously monitored. Both RF signals and temperature measurements were obtained before, during and after sonication. The resulting axial tissue displacement was estimated using one-dimensional cross correlation. When temperature at the focal zone was above 48 °C during heating, the coagulation necrosis occurred and tissue damage was irreversible. The HMI displacement profiles in relation to the temperature and sonication durations were analyzed. At the beginning of heating, the temperature at the focus increased sharply, while the tissue stiffness decreased resulting in higher HMI displacements. This was confirmed by an increase of 0.8 µm °C-1(r = 0.93, p < .005). After sustained heating, the tissue became irreversibly stiffer, followed by an associated decrease in the HMI displacement (-0.79 µm °C-1, r = -0.92, p < 0.001). Repeated experiments showed a reproducible pattern of the HMI displacement changes with a temperature at a slope equal to 0.8 ± 0.11 and - 0.79 ± 0.14 µm °C-1, prior to and after lesion formation in seven bovine liver samples, respectively. This technique was thus capable of following the protein-denatured lesion formation based on the variation of the HMI displacements. This method could, therefore, be applied for real-time monitoring of temperature-related stiffness changes of tissues during FUS, HIFU or other thermal therapies. |
| Title |
Has diagnostic ultrasound mutagenic effects? |
| Author |
Wegner RD, Obe G, Meyenburg M. |
| Journal |
Hum Genet |
| Volume |
|
| Year |
1980 |
| Abstract |
Chinese hamster ovary cells were treated with ultrasound from a fetal pulse detector (Eucotone, Siemens) operated at 10 mW/cm2 and 2.2 MHz. The frequencies of structural chromosomal aberrations and of sister chromatid exchanges were not.increased by the treatment. There was no indication of single-strand breaks induced by ultrasound in the G2 phase of the cell cycle. |
| Title |
Has diagnostic ultrasound mutagenic effects? |
| Author |
Wegner RD, Obe G, Meyenburg M. |
| Journal |
Hum Genet |
| Volume |
|
| Year |
1981 |
| Abstract |
Chinese hamster ovary cells were treated with ultrasound from a fetal pulse detector (Eucotone, Siemens) operated at 10 mW/cm2 and 2.2 MHz. The frequencies of structural chromosomal aberrations and of sister chromatid exchanges were not increased by the treatment. There was no indication of single-strand breaks induced by ultrasound in the G2 phase of the cell cycle. |
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