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BRL Abstracts Database |
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Your search for ultrasound produced 3296 results. Page 181 out of 330
| Title |
MRI-temperature mapping during ultrasound prostate ablation using fat for phase estimation. |
| Author |
Rieke V, Ross AB, Nau WH, Diederich CJ, Sommer G, Butts K. |
| Journal |
Conf Proc IEEE Eng Med Biol Soc |
| Volume |
|
| Year |
2004 |
| Abstract |
Referenceless proton resonance frequency (PRF) shift thermometry provides a means to measure temperature changes during minimally invasive thermotherapy that is inherently robust to motion and tissue displacement. In this study, the method is expanded to allow background phase estimation from fatty tissue. A correction scheme for temperature map distortions caused by the ultrasound applicator is developed. The method is tested during thermal ablation of canine prostate using a directional transurethral ultrasound applicator. |
| Title |
Multi-feature analysis for automated breast lesion classification from ultrasonic data. |
| Author |
Alam SK,Lizzi FL,Feleppa EJ,Liu T,Kalisz A. |
| Journal |
Proc IEEE Bioeng Conf |
| Volume |
|
| Year |
2002 |
| Abstract |
We have developed quantitative descriptors of lesions for reliable, operator-independent breast cancer identification using ultrasound. These include acoustic features as well as morphometric features related to lesion shape. Acoustic features include "echogenicity," "heterogeneity," and "shadowing," computed from radio-frequency (RF) spectral-parameter images of the lesion and surrounding tissue. Morphometric features were computed by geometric and fractal analysis of manually-traced lesion boundaries. Initial results show that no single parameter can precisely identify cancerous breast lesions and that the use of multiple features can substantially improve discrimination. Our analysis produced an ROC-curve area of 0.9164 ± 0.0346. |
| Title |
Multigated contrast-enhanced power doppler to measure blood flow in mice tumors. |
| Author |
Kamotani Y, Lee WMF, Arger PH, Cary TW, Sehgal CM. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
2003 |
| Abstract |
This study evaluated an image-gating method using contrast-enhanced power Doppler ultrasound (US) to estimate blood perfusion in mice tumors. A mathematical model that compensates for the effect of bubble destruction by US pulses was used to determine contrast flow through an image plane. Multigated power Doppler images were obtained following contrast injection. Contrast flow index (CFI) was determined by measuring the area under the color level vs. time curve for each gating frequency. CFI was compared with true flow. The method was first evaluated using a flow phantom with variable flow rates, and then verified in a mouse model with implanted tumors. Color levels in Doppler images were modulated with gating frequency due to variable destruction of microbubbles by US pulses. CFI measured from the images correlated strongly with true flow in the flow phantom (r2 = 0.87). The proposed method yielded reproducible CFI for mice tumors, suggesting that multigated contrast-enhanced power Doppler imaging may provide noninvasive measurements of tumor perfusion in mice. |
| Title |
Multiple crossed-beam ultrasound Doppler velocimetry. |
| Author |
Fox MD. |
| Journal |
IEEE Trans Sonics Ultrason |
| Volume |
|
| Year |
1978 |
| Abstract |
A new ultrasound Doppler technique for obtaining calibrated 3D flow velocity information is reported. Theoretical expressions are derived for the expected Doppler shift and the spectral spread under a variety of flow conditions. Experimental results using a revolving turntable demonstrated the linearity of velocity detection, the ability to resolve an arbitrary velocity vector, and confirmed the theoretical predictions of spectral spread. |
| Title |
Multiple malformations and exposure to therapeutic ultrasound during organogenesis. |
| Author |
McLeod DR, Fowlow SB. |
| Journal |
Am J Med Genet |
| Volume |
|
| Year |
1989 |
| Abstract |
We present a case of sacral agenesis, microcephaly, and developmental delay. The pregnancy with this child was complicated by left psoas bursitis that was treated by 18 applications of ultrasound between days 6 and 29 of gestation. |
| Title |
Multiple-focus ultrasound phased-array pattern synthesis: Optimal driving-signal distributions for hyperthermia. |
| Author |
Ebbini ES, Cain CA. |
| Journal |
IEEE Trans UFFC |
| Volume |
|
| Year |
1989 |
| Abstract |
A new method for computing array element amplitude and phase distributions for direct synthesis of multiple-focus field patterns using ultrasonic phased arrays is shown to be capable of producing desired field levels at a set of control points in the treatment volume. The complex pressure at any of these control points can be chosen to produce the desired power deposition at that point, including reducing the field level to avoid potential hot spots, thus providing a powerful tool for hyperthermia treatment planning. The method also allows the complex excitation vector to be weighted to reduce the dynamic range of the driving signals without disturbing the relative field levels at the control points allowing near maximum power transfer from the array into the treatment volume. |
| Title |
Murine ovulatory response to ultrasound exposure and its gynecological relevance. |
| Author |
Gates AH, Carstensen EL, Child SZ, Hall WJ, Maczynski CL. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1988 |
| Abstract |
Ultrasonographic assessment of ovarian follicular maturity was reportedly associated with atypically early ovulation in women; related studies reported reduced litter sizes in rats. To confirm these findings, mice which were midway between ovulatory gonadotropin (LH or human chorionic gonadotropin) stimulation and ovulation, were sham- or ultrasound-treated periovarially for 5 min. Exposure was at a spatial average, temporal maximum intensity of 60 W/cm2. Carrier frequency in the pulse was 2.2 MHz, pulse length was 10 microseconds, and pulse repetition frequency was 200 Hz. Spatial average,.temporal average intensity was 0.12 W/cm2. At autopsy, ultrasound- and sham-treated groups responded similarly in proportions ovulating and in mean ova ovulated. Combined experiments had a 97% chance of detecting a significant (greater than 1 h) advance in ovulation time, had it occurred. Thus, our adequately sensitive mammalian ovulatory tests revealed no association of ultrasound with decrease in ovum number or acceleration in ovulation time (as reported in humans). |
| Title |
Mutagenicity of ultrasound in cultured mammalian cells. |
| Author |
Kaufman GE. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1985 |
| Abstract |
Chinese hamster V79 cells were exposed in suspension to 1 MHz continuous wave ultrasound at spatial peak intensities of 7 and 35 W/cm2. Exposure durations were from 10 to 180 sec, so as to encompass the first decade of decreased survival at each intensity. Exposure at 35 W/cm2 resulted in the induction of 6-thioguanine-resistant mutants. The mutation frequency was approximately one-tenth that induced by x rays at similar survival levels. No mutagenesis was.observed at 7 W/cm2. Results are consistent with free radical formation as the mechanism responsible for ultrasound-induced mutagenesis. |
| Title |
Myocardial elastography - A feasibility study in vivo. |
| Author |
Konofagou EE, D'Hooge J, Ophir J. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
2002 |
| Abstract |
Early detection of cardiovascular diseases has been a very active research area in the medical imaging field. Assessment of the local and global mechanical functions is one of the major goals of accurate diagnosis. In this study, we investigated the feasibility of elastography for estimation and imaging of the local cardiac muscle displacement and strain in a human heart in vivo. In its noninvasive applications, elastography has been typically used to determine local tissue strain through the use of externally applied compression. For our study, we utilized the cardiac muscle motion during a cardiac cycle as the mechanical stimulus, and acquired successive radiofrequency (RF) data frames of the septal and posterior walls over a few cardiac cycles in parasternal and apical views, respectively. High-quality ciné-loop elastograms were obtained due to high frame rates and the resulting low decorrelation noise. Furthermore, the strain contrast was higher in the parasternal case, when only the posterior wall was imaged, and strain estimation was more robust in the apical view. High repeatability of the results was observed through elastographic measurements over several cardiac cycles. Finally, an M-mode version of elastography was used to follow part of the interventricular septum or the posterior wall over the course of two cardiac cycles. Not only do these preliminary results show that elastography is feasible in cardiac applications in vivo, but also that it can provide new information regarding cardiac motion and mechanical function. Future prospects include assessment of the role of elastography in detection of ischemia and infarction. |
| Title |
Myocardial elastography at both high temporal and spatial resolution for the detection of infarcts. |
| Author |
Luo J, Fujikura K, Homma S, Konofagou EE. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
2007 |
| Abstract |
Myocardial elastography is a novel method for noninvasively assessing regional myocardial function, with the advantages of high spatial and temporal resolution and high signal-to-noise ratio (SNR). In this paper, in-vivo experiments were performed in anesthetized normal and infarcted mice (one day after left anterior descending coronary artery [LAD] ligation) using a high-resolution (30 MHz) ultrasound system (Vevo 770, VisualSonics Inc., Toronto, ON, Canada). Radiofrequency (RF) signals of the left ventricle (LV) in longitudinal (long-axis) view and the associated electrocardiogram (ECG) were simultaneously acquired. Using a retrospective ECG gating technique, 2-D full field-of-view RF frames were acquired at an extremely high frame rate (8 kHz) that resulted in high-quality incremental displacement and strain estimation of the myocardium. The incremental results were further accumulated to obtain the cumulative displacements and strains. Two-dimensional and M-mode displacement images and strain images (elastograms), as well as displacement and strain profiles as a function of time, were compared between normal and infarcted mice. Incremental results clearly depicted cardiac events including LV contraction, LV relaxation and isovolumetric phases in both normal and infarcted mice, and also evidently indicated reduced motion and deformation in the infarcted myocardium. The elastograms indicated that the infarcted regions underwent thinning during systole rather than thickening, as in the normal case. The cumulative elastograms were found to have higher elastographic SNR (SNRe) than the incremental elastograms (e.g., 10.6 vs. 4.7 in a normal myocardium, and 6.0 vs. 2.4 in an infarcted myocardium). Finally, preliminary statistical results from nine normal (m = 9) and seven infarcted (n = 7) mice indicated the capability of the cumulative strain in differentiating infracted from normal myocardia. In conclusion, myocardial elastography could provide regional strain information at simultaneously high temporal (≥0.125 ms) and spatial (not, vert, similar55 μm) resolution as well as high precision (not, vert, similar0.05 μm displacement). This technique was thus capable of accurately characterizing normal myocardial function throughout an entire cardiac cycle, at the same high resolution, and detecting and localizing myocardial infarction in vivo. |
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