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BRL Abstracts Database |
Your search for ultrasound produced 3296 results. Page 177 out of 330
Title |
Microstructure Characterization in Cement Paste using Backscattered Diffuse Ultrasound |
Author |
M. Goueygou, J. Popovics, K. Hall, M. Oelze, Z. Lafhaj |
Journal |
AIP Conf Proc |
Volume |
|
Year |
2009 |
Abstract |
In this paper, the quantitative ultrasound technique (QUS) technique is applied to characterize voids in cement paste. Experiments are conducted on two series of cement paste specimens: a pair of regular samples with two levels of capillary porosity and a pair of air entrained samples with two concentrations of bubbles. The specimens are placed in a water tank and scanned at 5 MHz in pulse‐echo mode. Velocity, attenuation, transmission coefficient and backscattering cross section are measured. Then, several models are used to estimate the parameters of the microstructure from the backscattered energy. Finally, the microstructure is analyzed from digital images. In the air‐entrained samples, the mean scatterer size is correctly estimated and a clear difference in the acoustic concentration is observed in both samples, although this difference is higher than expected. In regular cement paste, the ultrasonically estimated scatterer size is too high to correspond to capillary pores. In this case, the scattered energy may originate from clumps of flocculated cement paste. |
Title |
Microvascular remodeling and accelerated hyperemia blood flow restoration in arterially occluded skeletal muscle exposed to ultrasonic microbubble destruction. |
Author |
Song J,Cottler PS,Klibanov AL,Kaul S,Price RJ. |
Journal |
Am J Physiol Heart Circ Physiol |
Volume |
|
Year |
2004 |
Abstract |
Song, Ji, Patrick S. Cottler, Alexander L. Klibanov, Sanjiv 0Kaul, and Richard J. Price. Microvascular remodeling and accelerated hyperemia blood flow restoration in arterially occluded skeletal muscle exposed to ultrasonic microbubble destruction. Am J Physiol Heart Circ Physiol 287: H2754–H2761, 2004. First published August 19, 2004; doi:10.1152/ajpheart.00144.2004.—We showed previously that microbubble destruction with pulsed 1-MHz ultrasound creates a bioeffect that stimulates arteriogenesis and a chronic increase in hyperemia blood flow in normal rat muscle. Here we tested whether ultrasonic microbubble destruction can be used to create a microvascular remodeling response that restores hyperemia blood flow to rat skeletal muscle affected by arterial occlusion. Pulsed ultrasound (1 MHz) was applied to gracilis muscles in which the lateral feed artery was occluded but the medial feed artery was left intact. Control muscles were similarly occluded but did not receive ultrasound, microbubbles, or both. Hyperemia blood flow and number of smooth muscle (SM) α-actin-positive vessels, >30-μm arterioles, and capillaries per fiber were determined 7, 14, and 28 days after treatment. In ultrasound-microbubble-treated muscles, lateral region hyperemia blood flow was increased at all time points and restored to normal at day 28. The number of SM α-actin vessels per fiber was increased
over control in this region at days 7 and 14 but decreased by day 28, when larger-diameter arterioles became more prevalent in the medial region. The number of capillaries per fiber was increased over control only at day 7 in the lateral region and only at days 7 and 14 in the medial region, indicating that the angiogenesis response was transient and likely did not contribute significantly to flow restoration at day 28. We conclude that ultrasonic microbubble destruction can be tailored to stimulate an arteriogenesis response that restores hyperemia blood flow to skeletal muscle in a rat model of arterial occlusion.
revascularization; microcirculation; angiogenesis; ultrasonics; contrast media. |
Title |
Microwatt ultrasonic power determination using laser interferometry. |
Author |
Reibold R. |
Journal |
Ultrasound Med Biol |
Volume |
|
Year |
1982 |
Abstract |
A system using a water-immersed balance with laser interferometer for radiation force measurements has been developed which is capable of determining powers in the range of a few microwatts up to about 100 mW. High consistency of measuring values and low background noise levels are achieved by compensating thermal and atmospheric pressure drifts, shielding the balance system from convection currents and effective isolation from building vibrations. The sensitivity ascertained is 104 micrometer/mW or, expressed as interferometer steps (IS), 8740 IS/mW. The standard deviation for a power output of 100 mu W is less than 1% ; it increases to 11% for 3.5 mu W, the lowest value measured. |
Title |
Miniaturized ultrasound arrays for interstitial ablation and imaging. |
Author |
Makin IR, Mast TD, Faidi W, Runk MM, Barthe PG, Slayton MH. |
Journal |
Ultrasound Med Biol |
Volume |
|
Year |
2005 |
Abstract |
A potential alternative to extracorporeal, noninvasive HIFU therapy is minimally invasive intense ultrasound ablation that can be performed laparoscopically or percutaneously. An approach to minimally invasive ablation of soft tissue using miniaturized linear ultrasound arrays is presented here. Recently developed 32-element arrays with aperture 2.3 x 49 mm, therapy frequency 3.1 MHz, pulse-echo bandwidths >42% and surface acoustic energy density >80 W/cm2, are described. These arrays are integrated into a probe assembly, including a coupling balloon and piercing tip, suitable for interstitial ablation. An integrated electronic control system allows therapy planning and automated treatment guided by real-time interstitial B-scan imaging. Image quality, challenging because of limited probe dimensions and channel count, is aided by signal processing techniques that improve image definition and contrast, resulting in image quality comparable to typical transabdominal ultrasound imaging. Ablation results from ex vivo and in vivo experiments on mammalian liver tissue show that this approach is capable of ablation rates and volumes relevant to clinical applications of soft tissue ablation such as treatment of liver cancer. |
Title |
Mitochondrial changes resulting from ultrasound irradiation. |
Author |
Stephens RJ, Torbit CA, Groth DG, Taenzer JC, Edmonds PD. |
Journal |
Proc Twenty-second Annu Meet AIUM |
Volume |
|
Year |
1977 |
Abstract |
No abstract available. |
Title |
Mitotic reduction in rat liver exposed to ultrasound. |
Author |
Kremkau FW, Witcofski RL. |
Journal |
J Clin Ultrasound |
Volume |
|
Year |
1974 |
Abstract |
Livers in anesthetized rats were exposed to 1.90 mHz, 60 mW/cm2 (spatial average) continuous wave ultrasound for five minutes. Subsequent mitotic activity was stimulated by partial hepatectomy. About thirty hours following stimulation (the time of peak mitotic activity in control animals), exposed animals had mean mitotic indices ranging from 20 to 80% of control values. |
Title |
Mode of action of ultrasound on the surface charge of mammalian cells in vitro. |
Author |
Joshi GP, Hill CR, Forrester JA. |
Journal |
Ultrasound Med Biol |
Volume |
|
Year |
1973 |
Abstract |
A reduction of cell surface charge has been found, from electrophoretic mobility measurements, in L5178Y mouse.lymphoma cells, following ultrasonic irradiation at 2 MHz and 10 W cm-2 peak intensity. The effect only occurs.in conditions conducive to cavitation, being inhibited by the employment of very short pulse durations or increased.ambient pressure during the irradiation. Reduction of mobility in an irradiated cell population is found to be .accompanied by an approximately proportional degree of cell disintegration but the surviving population is found.to be unaffected in its ability to proliferate, and its mobility returns to normal within 48 hr of irradiation. |
Title |
Mode scanning: heating pattern synthesis with ultrasound phased arrays. |
Author |
Mcgough RJ, Wang H, Ebbini ES, Cain CA. |
Journal |
Proc Ultrason Symp IEEE |
Volume |
|
Year |
1994 |
Abstract |
Modes, the characteristic symmetric focal patterns of an ultrasound phased array, prove especially useful for hyperthermia. Modes cancel the complex pressure fields exactly along the central axis, eliminating axial constructive interference both proximal and distal to the treatment volume. A simple calculation exploits planar or rotational array symmetry and produces the driving signals which generate modal focal patterns. Results show that temporal mode scanning improves heating patterns considerably, expanding the maximum treatable size of the tumour volume. |
Title |
Model studies of angular behaviour of acoustic backscatter. |
Author |
Braun M, Robinson DE. |
Journal |
Ultrasound Med Biol |
Volume |
|
Year |
1980 |
Abstract |
This note describes some studies of the relationship between filtered 1800 backscattered amplitude and rotation angle, which has been suggested as a means for tissue characterization. The studies include experimental measurements on simple linear and two-dimensional point targets, and theoretical computed results on both regular arrays and arrays with random displacement of the point scatters. .The studies were carried out on models under favorable conditions with only small amounts of irregularity. They show that in certain situations neither the disposition and spacing of peaks in the curve of backscattered amplitude versus angle, nor a cross-correlation algorithm designed to detect the optimum scatterer-spacing in the model gave a good estimate of average scatterer spacing. The implication of this finding to clinical application is discussed. |
Title |
Modeling the amplitude statisticas of ultrasonics images. |
Author |
Eltoft T. |
Journal |
IEEE Trans Med Imaging |
Volume |
|
Year |
2006 |
Abstract |
In this paper, a new statistical model for representing
the amplitude statistics of ultrasonic images is presented. The
model is called the Rician inverse Gaussian (RiIG) distribution,
due to the fact that it is constructed as a mixture of the Rice distribution
and the Inverse Gaussian distribution. The probability
density function (pdf) of the RiIG model is given in closed form
as a function of three parameters. Some theoretical background
on this new model is discussed, and an iterative algorithm for
estimating its parameters from data is given. Then, the appropriateness
of the RiIG distribution as a model for the amplitude
statistics of medical ultrasound images is experimentally studied.
It is shown that the new distribution can fit to the various shapes
of local histograms of linearly scaled ultrasound data better than
existing models. A log-likelihood cross-validation comparison of
the predictive performance of the RiIG, the K, and the generalized
Nakagami models turns out in favor of the new model. Furthermore,
a maximum a posteriori (MAP) filter is developed based on
the RiIG distribution. Experimental studies show that the RiIG
MAP filter has excellent filtering performance in the sense that
it smooths homogeneous regions, and at the same time preserves
details.
Index Terms—Compound distribution, generalized Nakagami
distribution, K distribution, maximum a posteriori speckle filter,
non-Gaussian statistics, non-Rayleigh amplitude statistics, speckle
filtering, ultrasound amplitude statistics, ultrasound imaging. |
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