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BRL Abstracts Database |
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Your search for ultrasound produced 3296 results. Page 159 out of 330
| Title |
Introduction to computed ultrasound tomography. |
| Author |
Grenleaf JF, Johnson SA, Bahn RC, Rajagopalan B, Kenue S. |
| Journal |
Proc Conf Comput Aided Tomogr Ultrason Med - Haifa |
| Volume |
|
| Year |
1978 |
| Abstract |
The application of computerized tomography (CT) to the field of transmission acoustic tomographic imaging is described and a preliminary study of the efficacy of acoustic speed CT images for the detection of cancer in a series of women who were subsequently scheduled for biopsy is reported. |
| Title |
Inverse imaging of the breast with a material classification technique. |
| Author |
Manry CW Jr, Broschat SL. |
| Journal |
J Acoust Soc Am |
| Volume |
|
| Year |
1998 |
| Abstract |
In recent publications [Chew et al., IEEE Trans Biomed Eng BME-9, 218-225 (1990); Borup et al., Ultrason Imaging 14, 69-85 (1992)] the inverse imaging problem has been solved by means of a two-step iterative method. In this paper, a third step is introduced for ultrasound imaging of the breast. In this step, which is based on statistical pattern recognition, classification of tissue types and a priori knowledge of the anatomy of the breast are integrated into the iterative method. Use of this material classification technique results in more rapid convergence to the inverse solution - approximately 40% fewer iterations are required - as well as greater accuracy. In addition, tumors are detected early in the reconstruction process. Results for reconstructions of a simple two-dimensional model of the human breast are presented. These reconstructions are extremely accurate when system noise and variations in tissue parameters are not too great. However, for the algorithm used, degradation of the reconstructions and divergence from the correct solution occur when system noise and variations in parameters exceed threshold values. Even in this case, however, tumors are still identified within a few iterations. |
| Title |
Inverse problems in two-dimensional acoustic media: A linear imaging model. |
| Author |
Goutsias JI, Mendel JM. |
| Journal |
J Acoust Soc Am |
| Volume |
|
| Year |
1987 |
| Abstract |
A fundamental problem in reflection seismology and ultrasound medicine is to identify the spatially variant parameters of the Earth or human tissue (e.g., the density and velocity profiles) from reflection and transmission wave-field data. This is known as the inverse scattering problem, or the diffraction tomography problem. Computer technology, and especially the development of supercomputing capabilities, revolutionized seismic and medical imaging. Various techniques have been developed for imaging the Earth's interior, as well as obtaining tomographic images of the interior of the human body, from measured backscattered wave-field data. Although these techniques try first to model the underlying forward scattering mechanisms, an accurate model for these mechanisms has not been available yet. The main contribution of this article is the development of a linear image formation system for modeling the traveling of waves through, and the scattering of waves from, a two-dimensional acoustic medium, that allows us to view the medium identification problem as an image restoration problem. A two-dimensional imaging model, characterizing the wave motion inside an inhomogeneous, isotropic, acoustic medium is described. A Born-series expansion of the wave field is employed and a linear two- dimensional imaging system is obtained. The higher-order scattering terms are incorporated in this model by approximating them, thus resulting in a more accurate scattering model. A variable background reference medium is used. It is argued that accurate acoustic imaging can be performed by developing a recursive downward continuation/image restoration procedure. The properties of this procedure are examined.
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| Title |
Investigation into the possible genetic effects of.diagnostic ultrasound. |
| Author |
Wegner RD, Meyenburg M. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1983 |
| Abstract |
The mutagenic effect of DUS (diagnostic ultrasound) was examined using two.generators emitting continuous waves and pulsed waves, respectively. Three different.test systems for mutagenic activity were employed in this study. 1. The frequency of.sister chromatid exchanges (SCEs) was determined in metaphase chromosomes of.human lymphocytes and of Chinese hamster ovary (CHO) cells sonicated at different.stages of the cell cycle. 2. The induction of DNA single strand breaks was tested in.CHO cells treated with continuous wave ultrasound. Following sonication an.endonuclease was introduced into the cells converting single strand breaks to.chromosomal aberrations scorable in the following metaphase. 3. The influence of.DUS on the number of point mutations was evaluated in the Ames test. A tester strain.of Salmonella typhimurium indicating base substitutions was sonicated. At the.present stage, all results proved to be completely negative and could thus not support.the view of any mutagenic activity of diagnostic ultrasound. |
| Title |
Investigation of abdominal masses by pulsed ultrasound. |
| Author |
Donald I, MacVicar J, Brown TG. |
| Journal |
Lancet |
| Volume |
|
| Year |
1958 |
| Abstract |
Large intro-abdominal masses, including the gravid uterus, pelvic tumours, and ascites, have been investigated by the echo patterns obtainable by pulsed ultrasound. Masses containing fluid are easily but crudely demonstrated. The possible identification of structures within the abdomen by their sonic properties is discussed. A scanning mechanism is described whereby cross-sectional views of the abdomen are obtained, and illustrative examples are given. The possible harmful effects of diagnostic ultrasound are discussed; they appear to be negligible. The limitations of the technique so far developed in practical diagnosis are described, but further refinements in technique may provide a useful diagnostic weapon in cases in which radiological diagnosis with ionizing radiations is either impracticable or undesirable. |
| Title |
Investigation of cellular and molecular responses to pulsed focused ultrasound in a mouse model. |
| Author |
Burks SR, Ziadloo A, Hancock HA, Chaudhry A, Dean DD, Lewis BK, Frenkel V, Frank JA. |
| Journal |
PLoS One |
| Volume |
|
| Year |
2011 |
| Abstract |
Continuous focused ultrasound (cFUS) has been widely used for thermal ablation of tissues, relying on continuous exposures to generate temperatures necessary to induce coagulative necrosis. Pulsed FUS (pFUS) employs non-continuous exposures that lower the rate of energy deposition and allow cooling to occur between pulses, thereby minimizing thermal effects and emphasizing effects created by non-thermal mechanisms of FUS (i.e., acoustic radiation forces and acoustic cavitation). pFUS has shown promise for a variety of applications including drug and nanoparticle delivery; however, little is understood about the effects these exposures have on tissue, especially with regard to cellular pro-homing factors (growth factors, cytokines, and cell adhesion molecules). We examined changes in murine hamstring muscle following pFUS or cFUS and demonstrate that pFUS, unlike cFUS, has little effect on the histological integrity of muscle and does not induce cell death. Infiltration of macrophages was observed 3 and 8 days following pFUS or cFUS exposures. pFUS increased expression of several cytokines (e.g., IL-1α, IL-1β, TNFα, INFγ, MIP-1α, MCP-1, and GMCSF) creating a local cytokine gradient on days 0 and 1 post-pFUS that returns to baseline levels by day 3 post-pFUS. pFUS exposures induced upregulation of other signaling molecules (e.g., VEGF, FGF, PlGF, HGF, and SDF-1α) and cell adhesion molecules (e.g., ICAM-1 and VCAM-1) on muscle vasculature. The observed molecular changes in muscle following pFUS may be utilized to target cellular therapies by increasing homing to areas of pathology. |
| Title |
Investigation of HIFU-induced anti-tumor immunity in a murine tumor model. |
| Author |
Hu Z, Yang XY, Liu Y, Sankin GN, Pua EC, Morse MA, Lyerly HK, Clay TM, Zhong P. |
| Journal |
J Transl Med |
| Volume |
|
| Year |
2007 |
| Abstract |
BACKGROUND:
High intensity focused ultrasound (HIFU) is an emerging non-invasive treatment modality for localized treatment of cancers. While current clinical strategies employ HIFU exclusively for thermal ablation of the target sites, biological responses associated with both thermal and mechanical damage from focused ultrasound have not been thoroughly investigated. In particular, endogenous danger signals from HIFU-damaged tumor cells may trigger the activation of dendritic cells. This response may play a critical role in a HIFU-elicited anti-tumor immune response which can be harnessed for more effective treatment.
METHODS:
Mice bearing MC-38 colon adenocarcinoma tumors were treated with thermal and mechanical HIFU exposure settings in order to independently observe HIFU-induced effects on the host's immunological response. In vivo dendritic cell activity was assessed along with the host's response to challenge tumor growth.
RESULTS:
Thermal and mechanical HIFU were found to increase CD11c+ cells 3.1-fold and 4-fold, respectively, as compared to 1.5-fold observed for DC injection alone. In addition, thermal and mechanical HIFU increased CFSE+ DC accumulation in draining lymph nodes 5-fold and 10-fold, respectively. Moreover, focused ultrasound treatments not only caused a reduction in the growth of primary tumors, with tumor volume decreasing by 85% for thermal HIFU and 43% for mechanical HIFU, but they also provided protection against subcutaneous tumor re-challenge. Further immunological assays confirmed an enhanced CTL activity and increased tumor-specific IFN-gamma-secreting cells in the mice treated by focused ultrasound, with cytotoxicity induced by mechanical HIFU reaching as high as 27% at a 10:1 effector:target ratio.
CONCLUSION:
These studies present initial encouraging results confirming that focused ultrasound treatment can elicit a systemic anti-tumor immune response, and they suggest that this immunity is closely related to dendritic cell activation. Because DC activation was more pronounced when tumor cells were mechanically lysed by focused ultrasound treatment, mechanical HIFU in particular may be employed as a potential strategy in combination with subsequent thermal ablations for increasing the efficacy of HIFU cancer treatment by enhancing the host's anti-tumor immunity. |
| Title |
Investigation of mechanisms of the action of ultrasound on biological media and objects. |
| Author |
Akopyan VB, Sarvazyan AP. |
| Journal |
Sov Phys Acoust |
| Volume |
|
| Year |
1979 |
| Abstract |
No abstract available. |
| Title |
Investigation of rotational isomers with ultrasound. |
| Author |
Karpovich J. |
| Journal |
J Chem Phys |
| Volume |
|
| Year |
1954 |
| Abstract |
Sound absorption measurements in organic liquids have revealed relaxation processes in some cyclohexane derivatives, cyclohexene, methyl formate, ethyl acetoacetate, acetic anhydride, and methyl benzoate. Additional absorption measurements have been made in the relaxation regions of formic acid, ethyl formate, methyl acetate, and ethyl acetate. A study of cyclohexane derivatives and other similar ring molecules has led to the identification of the mechanism responsible for the relaxations in these liquids. The relaxation phenomena are attributed to the disturbance by the sound wave of equilibria between rotational isomers. The restricted rotational occurs about the single bonds in the ring during the conversion from one chair configuration to another. The relaxation in cyclohexene is caused by the disturbance of the equilibrium between pseudochair and boat configurations, again involving rotation about single C-C bonds. The relaxations in esters of the carboxylic acids are attributed to rotational isomers which arise from rotation about C-O bonds. Infrared absorption bands at about 1160 and 1185 cm(-1) in the formates and acetates are identified with rotational isomers of the type postulated for the relaxations in these liquids. |
| Title |
Investigation of spatial sampling resolution of the real-time ultrasound pulse-echo BAI-mode imaging technique. |
| Author |
Yin X, Morris SA, O'Brien WD Jr. |
| Journal |
Proc Ultrason Symp IEEE |
| Volume |
|
| Year |
2001 |
| Abstract |
Hermetically-sealed flexible food packages require effective seal integrity tests for quality assurance purpose. 10 ?m-diameter channel defects can propagate microorganisms into food. The channel diameter limits of human inspection are about 50 ?m in transparent food packages. A reliable methodology is thus needed to detect 50 ?m-diameter and smaller channels. The pulse-echo Backscattered Amplitude Integral (BAI)-mode imaging technique [UFFC Trans, 45:30, 1998] has been developed and demonstrated by us to 100% reliably detect 38 ?m-diameter and larger channels in plastic films; tested using a static stop-and-go transducer scanning pattern. In this study, we examined experimentally the spatial sampling issue of the BAI-mode imaging technique with a new real-time transducer scanning protocol to simulate continuous package production line motion. A focused transducer (17.3 MHz, -6 dB pulse-echo focal beam diameter of 173 ?m) acquired RF data in a zigzag raster scanning pattern from plastic film samples bearing point reflectors arranged in a rectangular grid of varying spacings. The contrast-to-noise ratio (CNR) and the average BAI value difference (?BAI) between defected and background regions were assessed to quantitatively study image quality versus the varying grid size and the changing spatial scanning step sizes. For any given spatial grid size, the CNR and ?BAI values degraded as scanning step size in each spatial dimension increased. When the ?BAI dropped below 5% of the maximum BAI value, the point targets could not be separated in the image. |
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