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BRL Abstracts Database |
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Your search for ultrasound produced 3296 results. Page 275 out of 330
| Title |
Three-dimensional quantitative ultrasound to guide pathologists towards metastatic foci in lymph nodes |
| Author |
Mamou J, Saegusa-Beecroft E, Coron A, Laugier P, Feleppa EJ |
| Journal |
34th Annual International Conference of the IEEE EMBS |
| Volume |
|
| Year |
2012 |
| Abstract |
The detection of metastases in freshly-excised
lymph nodes from cancer patients during lymphadenectomy is
critically important for cancer staging, treatment, and optimal
patient management. Currently, conventional histologic methods
suffer a high rate of false-negative determinations because
pathologists cannot evaluate each excised lymph nodes in its
entirety. Therefore, lymph nodes are undersampled and and
small but clinically relevant metastatic regions can be missed.
In this study, quantitative ultrasound (QUS) methods using
high-frequency transducers (i.e., > 20 MHz) were developed
and evaluated for their ability to detect and guide pathologists
towards suspicious regions in lymph nodes. A custom laboratory
scanning system was used to acquire radio-frequency
(RF) data in 3D from excised lymph nodes using a 26-MHz
center-frequency transducer. Overlapping 1-mm cylindrical
regions-of-interest (ROIs) of the RF data were processed
to yield 13 QUS estimates quantifying tissue microstructure
and organization. These QUS methods were applied to more
than 260 nodes from more than 160 colorectal-, gastric-,
and breast-cancer patients. Cancer-detection performance was
assessed for individual estimates and linear combinations of
estimates. ROC results demonstrated excellent classification.
For colorectal- and gastric-cancer nodes, the areas under the
ROC curves (AUCs) were greater than 0.95. Slightly poorer
results (AUC=0.85) were obtained for breast-cancer nodes.
Images based on QUS parameters also permitted localization
of cancer foci in some micrometastatic cases. |
| Title |
Three-dimensional spatial and temporal temperature imaging in gel phantoms using backscattered ultrasound. |
| Author |
Anand A, Savery D, Hall C. |
| Journal |
IEEE Trans UFFC |
| Volume |
|
| Year |
2007 |
| Abstract |
Thermal therapies such as radio frequency, heated saline, and high-intensity focused ultrasound ablations are often performed suboptimally due to the inability to monitor the spatial and temporal distribution of delivered heat and the extent of tissue necrosis. Ultrasound-based temperature imaging recently was proposed as a means to measure noninvasively the deposition of heat by tracking the echo arrival time shifts in the ultrasound backscatter caused by changes in speed of sound and tissue thermal expansion. However, the clinical applicability of these techniques has been hampered by the two-dimensional (2-D) nature of traditional ultrasound imaging, and the complexity of the temperature dependence of sound speed for biological tissues. In this paper, we present methodology, results, and validation of a 3-D spatial and temporal ultrasound temperature estimation technique in an alginate-based gel phantom to track the evolution of heat deposition over a treatment volume. The technique was experimentally validated for temperature rises up to ~10degC by comparison with measurements from thermocouples that were embedded in the gel. Good agreement (rms difference=0.12degC, maximum difference=0.24degC) was observed between the noninvasive ultrasound temperature estimates and thermocouple measurements. Based on the results obtained for the temperature range studied in this paper, the technique demonstrates potential for applicability in image guidance of thermal therapy for determining the location of the therapeutic focal spot and assessing the extent of the heated region at subablative intensities. |
| Title |
Three-dimensional ultrasound imaging. |
| Author |
Nelson TR, Pretorius DH. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1998 |
| Abstract |
The objective of this article is to provide scientists, engineers and clinicians with an up-to-date overview on the current state of development in the area of three-dimensional ultrasound (3-DUS) and to serve as a reference for individuals who wish to learn more about 3-DUS imaging. The sections will review the state of the art with respect to 3-DUS imaging, methods of data acquisition, analysis and display approaches. Clinical sections summarize patient research study results to date with discussion of applications by organ system. The basic algorithms and approaches to visualization of 3-D and 4-D ultrasound data are reviewed, including issues related to interactivity and user interfaces. The implications of recent developments for future ultrasound imaging/visualization systems are considered. Ultimately, an improved understanding of ultrasound data offered by 3-DUS may make it easier for primary care physicians to understand complex patient anatomy. Tertiary care physicians specializing in ultrasound can further enhance the quality of patient care by using high-speed networks to review volume ultrasound data at specialization centers. Access to volume data and expertise at specialization centers affords more sophisticated analysis and review, further augmenting patient diagnosis and treatment. |
| Title |
Threshold dosages for damage to mammalian liver by high intensity focused ultrasound. |
| Author |
Frizzell LA. |
| Journal |
IEEE Trans UFFC |
| Volume |
|
| Year |
1988 |
| Abstract |
The threshold dosages for high intensity focal lesion production were determined at 3 MHz in the cat liver for exposure durations covering the range 0.003-35 s. The liver threshold was found to parallel that for the brain over the range of exposure durations 0.1 to 10 s, but to be more than twice the intensity level, approximately following the relation IT(exp)(0.5) = (460 W)(cm2)(s(exp)0.5) where I is the peak intensity and T is the exposure duration. At shorter exposure durations the threshold curve deviates from this relation, probably due to a change to a transient cavitation mechanism of damage. |
| Title |
Threshold estimates and superthreshold behavior of ultrasound-induced lung hemorrhage in adult rats: Role of pulse duration. |
| Author |
O'Brien WD Jr, Simpson DG, Frizzel LA, Zachary JF. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
2003 |
| Abstract |
The study objective was to estimate the pressure threshold (ED05, effective dose, or in situ peak rarefactional pressure associated with 5% probability of lesions) of ultrasound (US)-induced lung hemorrhage as a function of pulse duration (PD) in adult rats. A total of 220 10- to 11-week-old 250-g female Sprague-Dawley rats (Harlan) were randomly divided into 20 ultrasonic exposure groups (10 rats/group) and one sham group (20 rats). The 20 ultrasonic exposure groups (2.8-MHz; 10-s exposure duration; 1-kHz PRF; −6-dB pulse-echo focal beam width of 470 μm) were divided into four PD groups (1.3, 4.4, 8.2 and 11.6 μs) and, for each PD group, there were five in situ peak rarefactional pressures (range between 4 and 9 MPa). Rats were weighed, anesthetized, depilated, exposed, and euthanized under anesthesia. The left lung was removed and scored for the occurrence of hemorrhage. If hemorrhage was present, the lesion surface area and depth were measured. Individuals involved in animal handling, exposure and lesion scoring were “blinded” to the exposure conditions. Logistic regression analysis was used to examine the dependence of the lesion occurrences, and Gaussian tobit regression analysis was used to examine the dependence of the lesion surface areas and depths on in situ peak rarefactional pressure and PD. Threshold results are reported in terms of ED05. For PDs of 1.3, 4.4, 8.2 and 11.6 μs, respectively, lesion occurrence ED05s were 3.1, 2.8, 2.3 and 2.0 MPa with standard errors around 0.6 MPa. Lesion size ED05s showed similar values. A mechanical index (MI) of 1.9, the US Food and Drug Administration (FDA) regulatory limit of diagnostic US equipment, is equivalent to the adult rat's in situ peak rarefactional pressure of 4.0 MPa. PDs of 8.2 and 11.6 μs had ED05s more than 2 standard errors below 4.0 MPa, indicating that the ED05s of these two PDs are statistically significantly different from 4.0 MPa. The ED05 threshold levels for a PD of 1.3 μs are consistent with previous US-induced lung hemorrhage studies. As the PD increases, the ED05 levels decrease, suggesting greater likelihood of lung damage as the PD increases. All of the ED05s are less than the FDA limit. |
| Title |
Threshold estimation and superthreshold behavior of ultrasound-induced lung hemorrhage in rats: Role of age dependency. |
| Author |
O'Brien WD Jr, Yang Y, Simpson DG. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
2009 |
| Abstract |
Age-dependent threshold and superthreshold behaviors of ultrasound-induced lung hemorrhage were investigated with one hundred ten 12.6 ± 0.8-d-old rats, one hundred ten 22.9 ± 0.8-d-old rats, and one hundred 57.7 ± 3.9-d-old rats. Exposure conditions were: 2.8 MHz, 10-s exposure duration, 1-kHz pulse repetition frequency and 1.3-μs pulse duration. The in situ (at the pleural surface) peak rarefactional pressure (pr(in situ)) ranged between 1.4 and 10.8 MPa for which there were either 9 or 10 acoustic pressure groups for each of the three rat ages (10 rats/exposure group). For each of the three rat ages there were also shams; there were no lesions in the shams. The pr(in situ) levels were randomized within each age group; rat age was not randomized. Individuals involved in animal handling, exposure and lesion scoring were blinded to the exposure condition. In addition, one hundred fifty-six 72-d-old rats were included from three completed studies (same experimental conditions) to provide a fourth age group for the analysis. Probit regression analysis was used to examine the dependence of the occurrence of lesions on pr(in situ) in the four age groups. Likewise, lesion depth and lesion root surface area were analyzed using Gaussian tobit regression analysis. Although pr(in situ) was a significant variable, no significant age dependence of the pr(in situ) effect was found. Furthermore, age had no significant effect on either the rate of occurrence or the depth of lesions. Given the occurrence of a lesion, a weak age dependence was found for the median surface area of the induced lesion (p-value = 0.037). |
| Title |
Threshold estimation of ultrasound-induced lung hemorrhage in adult rabbits and comparison of thresholds in mice, rats, rabbits and pigs. |
| Author |
O'Brien WD Jr, Yang Y, Simpson DG, Frizzell LA, Miller RJ, Blue JP Jr, Zachary JF. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
2006 |
| Abstract |
The objective of this study was to assess the threshold and superthreshold behavior of ultrasound (US)-induced lung hemorrhage in adult rabbits to gain greater understanding about species dependency. A total of 99 76 +/- 7.6-d-old 2.4 +/- 0.14-kg New Zealand White rabbits were used. Exposure conditions were 5.6-MHz, 10-s exposure duration, 1-kHz PRF and 1.1-micros pulse duration. The in situ (at the pleural surface) peak rarefactional pressure, p(r(in situ)), ranged between 1.5 and 8.4 MPa, with nine acoustic US exposure groups plus a sham exposure group. Rabbits were assigned randomly to the 10 groups, each with 10 rabbits, except for one group that had nine rabbits. Rabbits were exposed bilaterally with the order of exposure (left then right lung, or right then left lung) and acoustic pressure both randomized. Individuals involved in animal handling, exposure and lesion scoring were blinded to the exposure condition. Probit regression analysis was used to examine the dependence of the lesion occurrence on in situ peak rarefactional pressure and order of exposure (first vs. second). Likewise, lesion depth and lesion root surface area were analyzed using Gaussian tobit regression analysis. Neither probability of a lesion nor lesion size measurements was found to be statistically dependent on the order of exposure after the effect of p(r(in situ)) was considered. Also, a significant correlation was not detected between the two exposed lung sides on the same rabbit in either lesion occurrence or size measures. The p(r(in situ)) threshold estimates (in MPa) were similar to each other across occurrence (3.54 +/- 0.78), depth (3.36 +/- 0.73) and surface area (3.43 +/- 0.77) of lesions. Using the same experimental techniques and statistical approach, great consistency of thresholds was demonstrated across three species (mouse, rat and rabbit). Further, there were no differences in the biologic mechanism of injury induced by US and US-induced lesions were similar in morphology in all species and age groups studied. The extent of US-induced lung damage and the ability of the lung to heal led to the conclusion that, although US can produce lung damage at clinical levels, the degree of damage does not appear to be a significant medical problem. |
| Title |
Threshold of fragmentation for ultrasonic contrast agents. |
| Author |
Chomas JE, Dayton P, May D, Ferrara K. |
| Journal |
J Biomed Opt |
| Volume |
|
| Year |
2001 |
| Abstract |
Ultrasound contrast agents are small microbubbles that can be readily destroyed with sufficient acoustic pressure, typically, at a frequency in the low megaHertz range. Microvascular flow rate may be estimated by destroying the contrast agent in a vascular bed, and estimating the rate of flow of contrast agents back into the vascular bed. Characterization of contrast agent destruction provides important information for the design of this technique. In this paper, high-speed optical observation of an ultrasound contrast agent during acoustic insonation is performed. The resting diameter is shown to be a significant parameter in the prediction of microbubble destruction, with smaller diameters typically correlated with destruction. Pressure, center frequency, and transmission phase are each shown to have a significant effect on the fragmentation threshold. A linear prediction for the fragmentation threshold as a function of pressure, when normalized by the resting diameter, has a rate of change of 300 kPa/microm for the range of pressures from 310 to 1200 kPa, and a two-cycle excitation pulse with a center frequency of 2.25 MHz. A linear prediction for the fragmentation threshold as a function of frequency, when normalized by the resting diameter, has a rate of change of -1.2 MHz/microm for a transmission pressure of 800 kPa, and a two-cycle excitation pulse with a range of frequencies from 1 to 5 MHz. |
| Title |
Threshold ultrasonic dosages for structural changes in the mammalian brain. |
| Author |
Fry FJ, Kossoff G, Eggleton RC, Dunn F. |
| Journal |
J Acoust Soc Am |
| Volume |
|
| Year |
1970 |
| Abstract |
The relationship between the acoustic intensity and the time duration of exposure, for a single pulse, necessary to produce a threshold lesion in the cat brain was studied. Focused ultrasound of 1, 3, and 4 MHz was employed with intensities ranging from 10(^2) to 2X10(^4) W/cm(^2) with the corresponding pulse durations from 7 to 2X10(^-4) sec, respectively. Three types of lesions were observed attending three regions. At the lower intensities and long time durations of exposure, the lesion is produced by a thermal mechanism. At the highest intensities and shortest time durations, cavitation is believed to be the mechanism responsible for the sometimes randomly appearing lesions. At intermediate dosages, the lesions are formed by a mechanical mechanism which is thus far not well understood. These results exhibit good agreement with that of other investigators on both the cat and the rat brain. |
| Title |
Thresholds and mechanisms of ultrasonic damage to "organized" animal tissues. |
| Author |
Lele PP. |
| Journal |
Proc Symp Biol Eff Character Ultrasound Sour |
| Volume |
|
| Year |
1977 |
| Abstract |
No abstract available. |
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