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BRL Abstracts Database |
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Your search for ultrasound produced 3296 results. Page 209 out of 330
| Title |
Quantitative assessment of cartilage surface roughness in osteoarthritis using high frequency ultrasound. |
| Author |
Adler RS, Dedrick DK, Laing TJ, Chiang EH, Meyer CR, Bland PH, Rubin JM. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1992 |
| Abstract |
Osteoarthritis (OA) is a common disease which affects nearly 50% of people over age 60. Histologic evaluation suggests that fibrillations ~20-150 [mu]m are among the earliest changes in the articular cartilage. We propose a technique to quantify these surface fibrillatory changes in osteoarthritic articular cartilage by considering the angular distribution of the envelope-detected backscattered pressure field from an incident 30-MHz focused transducer. The angular distribution of the scattered acoustic field from an insonifying source will directly relate to the distribution of surface fibrillatory changes. Data are presented for three different grades (400, 500 and 600 grit) of commercially available emory paper and three samples of osteoarthritic femoral head articular cartilage, which were visually assessed as having smooth, intermediate and rough surfaces, respectively. Our preliminary results indicate a probable monotonic relationship between articular cartilage roughening and the degree of broadening in the angle-dependent pressure amplitude. When applied to the emory paper, the technique indicates sensitivity to differences as small as ~5-10 [mu]m in mean roughness. This procedure may provide an extremely sensitive and reproducible means of quantifying and following the cartilage changes observed in early osteoarthritis. |
| Title |
Quantitative assessment of surface roughness using backscattered ultrasound: The effects of finite surface curvature. |
| Author |
Chiang EH, Adler RS, Meyer CR, Rubin JM, Dedrick DK, Laing TJ. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1994 |
| Abstract |
We have previously described a technique to quantify surface fibrillatory changes in osteoarthritic articular cartilage. In that study, the angular distribution of the scattered acoustic field from an insonifying source directly related to the distribution of surface fibrillatory changes. In the current study, we demonstrate a more sensitive method to quantify surface roughness,the effect of global surface curvature in estimating surface roughness and the utility of using focused transducers in circumventing this potential problem for in vivo work. Phantoms composed of acrylic rods with and without sandpaper grit (about 15 to 72 microns, mean particle size) applied to the surface were scanned. A more robust angular scattering technique to measure the angle dependent data was employed, in which the integrated squared pressure amplitude over a finite time window (mean power) was measured as a function of incident acoustic angle for varying surface roughnesses and radii of curvature. We show that the potential dynamic range for making roughness discriminations diminishes with decreasing radius of curvature of the acrylic rod phantoms using an unfocused transducer. This effect is minimized with use of a focused transducer. Roughness effects are most evident at sufficiently large angles where incoherent scattering dominates. We conclude that the roughness of cylindrically curved surfaces can be quantitatively assessed using a focused ultrasound beam atsufficiently large incident angles, given that the focal spot size is sufficiently smaller than the radius of curvature of the surface. |
| Title |
Quantitative assessment of the germicidal efficacy of ultrasonic energy. |
| Author |
Scherba G, Weigel RM, O'Brien WD Jr. |
| Journal |
Appl Environ Microbiol |
| Volume |
|
| Year |
1991 |
| Abstract |
Propagated (free-field) ultrasonic energy at a frequency of 26 kHz was used to expose aqueous suspensions of bacteria (Escherichia coli, Staphylococcus aureus, Bacillus subtilis, and Pseudomonas aeruginosa), fungus (Trichophyton mentagrophytes), and viruses (feline herpesvirus type 1 and feline calicivirus) to evaluate the germicidal efficacy of ultrasound. There was a significant effect of time for all four bacteria, with percent killed increasing with increased duration of exposure, and a significant effect of intensity for all bacteria except E. coli, with percent killed increasing with increased intensity level. There was a significant reduction in fungal growth compared with that in the controls, with decreased growth with increased ultrasound intensity. There was a significant reduction for feline herpesvirus with intensity, but there was no apparent effect of ultrasound on feline calicivirus. These results suggest that ultrasound in the low-kilohertz frequency range is capable to some degree of inactivating certain disease agents that may reside in water. The physical mechanism of inactivation appears to be transient cavitation. |
| Title |
Quantitative bone ultrasound measurements in young females 14-23 years of age. |
| Author |
Klentrou P, Ludwa IA. |
| Journal |
J Womens Health |
| Volume |
|
| Year |
2011 |
| Abstract |
AIM:
This study examined how transaxial quantitative ultrasound (QUS) measurements differed in young females between 14 and 23 years of age and if body composition and behavioral factors, namely, oral contraceptive (OC) use, physical activity, and calcium intake, influenced these measurements.
METHODS:
Participants (n = 595) were classified as nonusers or users of OC. QUS measurements were performed at the distal radius and midtibia, and the bone speed of sound (SOS) was recorded for each site. Body mass index (BMI) was calculated from body mass and height. Physical activity and dietary calcium intake were assessed using standardized questionnaires.
RESULTS:
Bone SOS increased significantly with increasing age (r(2) = 0.28 and 0.20 for radius and tibia, respectively, p < 0.05) but slower after age 18. OC use was not significantly associated with the QUS measurements, yet there was a significant age-by-OC use interaction (p < 0.05) for SOS of the tibia. For the nonusers of OC, age, BMI, and calcium intake were significant predictors of tibia SOS, explaining 24% of the variance in tibial SOS scores, whereas among the OC users, only age and BMI were significant predictors of tibial SOS, explaining 18% of the variance with no other variables entering in the model. Age was the only predictor of radius SOS in both groups. QUS scores increased steadily from 14 to 23 years of age in young females.
CONCLUSIONS:
OC use was associated with lower tibial SOS scores in early adulthood but not during adolescence, suggesting that OC use possibly may interfere with the bone development of the tibia. Furthermore, daily calcium intake demonstrated a positive relationship with the tibial SOS only in the nonusers of OC; however, this relationship was reversed for BMI irrespective of OC use. |
| Title |
Quantitative cross-sectional imaging of ultrasound parameters. |
| Author |
Greenleaf JF, Johnson SA, Bahn RC. |
| Journal |
Ultrasonics |
| Volume |
|
| Year |
1977 |
| Abstract |
No Abstract Available. |
| Title |
Quantitative echography: The basis of tissue differentiation. |
| Author |
Ossoinig KC. |
| Journal |
J Clin Ultrasound |
| Volume |
|
| Year |
1974 |
| Abstract |
Quantitative echography performed with a simple but optimally designed and standardized commercial A-scan instrument has become the basis of acoustic tissue differentiation in the examination of the eye, orbit and periorbital region. The reflectivity of a lesion is determined by comparing the signal intensities obtained from the lesion with "standard" signals. Two types of quantitative echography are applied: In Type I identical system sensitivities are used to display and compare the signal intensities from an unknown lesion and from known standards. If a high defined, comparable system sensitivity and a standardized A-scan unit are used, the display of the standard pattern is not necessary; it is then sufficient to measure the height of the lesion spikes and to determine its percentage of the display height. With Type I quantitative echography mass lesions such as tumors can be classified into five groups. Type I quantitative echography requires a special design of the A-scan instrument used (e.g., S-shaped amplifier characteristics, dynamic range of 36dB, calibration of system sensitivity in dB). In Type II quantitative echography identical intensities of both abnormal and "standard" signals are displayed by adjusting the system sensitivity at the proper levels. The difference between the two sensitivity settings indicates the reflectivity of the lesion. Type II quantitative echography is used for the evaluation of single surfaces (e.g., the surface of a tumor). This type of quantitative echography requires and A-scan instrument with a sensitivity control which is calibrated in dB and can be adjusted continuously. This technique can be any other region of the human body as well if high-frequency ultrasound (frequencies above 6mHz) can be used. |
| Title |
Quantitative evaluation of the use of microbubbles with transcranial focused ultrasound on blood-brain-barrier disruption. |
| Author |
Yang F-Y, Fu W-M, Chen W-S, Yeh W-L, Lin W-L. |
| Journal |
Ultrason Sonochem |
| Volume |
|
| Year |
2008 |
| Abstract |
It has been shown that focused ultrasound (FUS) can disrupt the blood–brain barrier (BBB) noninvasively and reversibly at target locations when applied in the presence of ultrasound contrast agent (UCA). In this study, the dose-dependent effects of UCA on BBB disruption were investigated in the brains of 16 male Wistar rats sonicated by 1.0-MHz transcranial FUS, with the UCA present at four doses. The BBB disruption was evaluated quantitatively based on the extravasation of Evans blue (EB). The amount of EB extravasation in the brain increased with the quantity of UCA injected into the femoral vein prior to sonication. Moreover, the use of a suitable dose of UCA resulted in the BBB disruption being concentrated in the focal region instead of the entire brain. Our results indicate that injecting an appropriate quantity of UCA effectively increases and localizes the BBB disruption induced by transcranial FUS sonications. |
| Title |
Quantitative imaging of temperature elevations in tissues due to thermal therapies |
| Author |
Kemmerer JP, Ghoshal G, Oelze ML |
| Journal |
IEEE Int Ultrasonics Symp Proc |
| Volume |
|
| Year |
2014 |
| Abstract |
Thermal ablation and hyperthermia remain as potent treatment options for cancer. However, the inability to closely monitor temperature elevations from thermal therapies in real time continues to limit clinical applicability. Therefore, the development of new imaging techniques capable of providing
feedback and temperature monitoring is highly medically significant. In this study, quantitative ultrasound imaging techniques based on spectral estimates were examined for their ability to monitor and map temperature elevations induced in tissues using either microwave ablation or high intensity focused
ultrasound (HIFU).
Ex vivo liver samples were treated with microwave ablation while ultrasound image frames were recorded using a SonixTouch system and linear array (14L5). In vivo tumors in rats (MAT) were treated using a custom-built HIFU system while
concurrently imaged using a SonixRP scanner and linear array (14L5). The ultrasound scanners provided raw radio frequency (RF) data. From the RF data, the backscatter coefficient was calculated using the reference phantom technique. The backscatter coefficient was parameterized by estimating an
effective scatterer diameter (ESD) and effective acoustic concentration (EAC) assuming a spherical Gaussian model. Maps of the ESD and EAC were created for each acquired frame. Temperature was measured by placing a needle thermocouple in the samples during treatment and temperature changes were correlated with changes in the scattering parameters.
In the ex vivo liver samples, the ESD was observed to increase with temperature elevation while the EAC was observed to decrease with temperature elevation. Specifically, the mean ESD increased by 7 μm and EAC decreased by 1.5 dB as the
temperature increased from 18 to 42 °C. Conversely, in the in vivo tumor samples treated with HIFU, the EAC was observed to increase with increasing temperature, i.e., the EAC increased by 20 to 30% as the temperature increased from 37 °C to a range of 50 to 60 °C. When the HIFU was turned off, the EAC continued to track the decrease in temperature of the tumor. In the in vivo
studies, the tumors were grown on the chest wall of the rats and, therefore, large out of plane tissue motion occurred due to the breathing of the animal. In spite of this, the EAC parameter was capable of tracking temperature in the presence of large tissue motion. |
| Title |
Quantitative investigation of acoustic streaming in blood. |
| Author |
Shi X, Martin RW, Vaezy S, Crum LA. |
| Journal |
J Acoust Soc Am |
| Volume |
|
| Year |
2002 |
| Abstract |
Acoustic streaming may have practical utility in diagnostic medical ultrasound in distinguishing between stagnant blood and tissue as well as clotted and unclotted blood. This distinction can be difficult with conventional ultrasound but have high value in managing trauma patients with internal hemorrhage. Ultrasound energy applies a force to blood by momentum transfer, resulting in bulk streaming that is a function of the acoustic attenuation, sound speed, acoustic intensity, blood viscosity, and the boundary conditions posed by the geometry around the hematoma. A simple tubular model was studied analytically, by finite element simulation, and experimentally by in vitro measurement. The simulation agreed closely with measurements while the analytic solutions were found to be valid only for beam diameters approximating the diameter of the tubular channel. Experimentally, the acoustic streaming in blood decreased as the blood began to clot and the streaming flow was not detected in clotted blood. In contrast, the echogenicity of the same blood samples did not change appreciably from the unclotted to the clotted state for the stagnant blood studied. Streaming detection appears to offer a potential tool for improving hemorrhage diagnosis. |
| Title |
Quantitative particle characterization by scattered ultrasound. |
| Author |
Roy RA. |
| Journal |
Rep Yale Univ Dept Mech Eng |
| Volume |
|
| Year |
1987 |
| Abstract |
The topic of this thesis is an acoustic scattering technique for determining the compressibility and density of individual particles. The particles, which have diameters on the order of 10 ?m, are model as fluid spheres. Ultrasonic tone bursts of 2 ?sec duration and 30 MHz center frequency scatter from individual particles as they traverse the focal region of two confocally positioned transducers. One transducer acts as a receiver while the other both transmits and receives acoustic signals. The resulting scattered bursts are detected at 90? and at 180? (backscattered). Using either the long wavelength (Rayleigh) or the weak scatterer (Born) approximations, it is possible to determine the compressibility and density of the particle provided we possess a priori knowledge of the particle size and the host properties. The detected scattered signals are digitized and stored in computer memory. With this information we can compute the mean compressibility and density averaged over a population of particles (typically 1000 particles) or display histograms of scattered amplitude statistics. An experiment was run first to assess the feasibility of using polystyrene polymer microspheres to calibrate the instrument. A second study was performed on the buffy coat harvested from whole human blood. Finally, chinese hamster ovary cells which were subject to hyperthermia treatment were studied in order to see if the instrument could detect heat induced membrane blebbing. |
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