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BRL Abstracts Database |
Your search for ultrasound produced 3296 results. Page 218 out of 330
Title |
Relationship between collagen and ultrasonic backscatter in myocardial tissue. |
Author |
O'Donnell M, Mimbs JW, Miller JG. |
Journal |
J Acoust Soc Am |
Volume |
|
Year |
1981 |
Abstract |
The relationship between ultrasonic backscatter and collagen concentration estimated on the basis of hydroxyproline concentration was examined in hearts from normal dogs and in hearts from dogs subjected to ischemic injury by coronary.occlusion as an approach toward elucidating the physical mechanisms underlying the scattering of ultrasound by soft tissue. Ultrasonic backscatter was found to increase significantly in regions of ischemic injury studied 5--17 weeks following.occlusion. The average backscatter coefficient was six time larger in regions of infarct studied 8--10 weeks after occlusion than that in regions of infarct studied 5--6 weeks after occlusion. In contrast, the average hydroxyproline concentration, a.quantitative index of molecular collagen content, for regions of infarct was only about 25% larger at 8--10 weeks compared with that at 5--6 weeks after occlusion. These results may suggest that the magnitude of ultrasonic scattering in regions of.remote myocardial infarct is sensitive not only to the concentration of molecular collagen but also to the organizational state of this structural protein. In addition, the results of this study may indicate that scattering represents a small fraction of the total attenuation coefficient in a biological system exhibiting either low collagen concentration (normal myocardium) or significant collagen concentration (scarred myocardium). |
Title |
Relationship between intensity of ultrasound and induction of chromosome aberrations. |
Author |
Macintosh IJC, Davey DA. |
Journal |
Br J Radiol |
Volume |
|
Year |
1972 |
Abstract |
Studies have been made of the effect of varying the intensity of ultrasound, at a frequency of 2 MHz for one hour, on chromosome aberration induction in human leucocyte cultures. A dose/response curve has been found with a threshold intensity of ultrasound of 8.2 mW/cm(^-2) below which no visible chromosome damage was detected under the experimental conditions described. |
Title |
Relationship between speed of sound in and density of normal and diseased rat livers. |
Author |
Hachiya H, Ohtsuki S, Tanaka M. |
Journal |
Jpn J Appl Phys |
Volume |
|
Year |
1994 |
Abstract |
Speed of sound is an important acoustic parameter for quantitative characterization of living tissues. In this paper, the relationship between speed of sound in and density of rat liver tissues are investigated. The speed of sound was measured by the nondeformable technique based on frequency-time analysis of a 3.5 MHz pulse response. The speed of sound in normal livers varied minimally between individuals and was not related to body weight or age. In liver tissues which were administered CC14, the speed of sound was lower than the speed of sound in normal tissues. The relationship between speed of sound and density in normal, fatty and cirrhotic livers can be fitted well on the line which is estimated using the immiscible liquid model assuming a mixture of normal liver and fat tissues. For 3.5 MHz ultrasound, it is considered that the speed of sound in fresh liver with fatty degeneration is responsible for the fat content and is not strongly dependent on the degree of fibrosis. |
Title |
Reliability of Doppler and impedance techniques for the diagnosis of thrombophlebitis. |
Author |
Salles-Cunha SX, Bernhard VM, Imray TJ. |
Journal |
Med Instrum |
Volume |
|
Year |
1978 |
Abstract |
The accuracy of Doppler ultrasound and impedance diagnostic techniques for identifying deep venous thrombosis was determined by comparison with patient venograms. Those patients suspected of having deep venous thrombosis were tested by ultrasound, impedance, and venography, with venography the standard for establishing the accuracy of the noninvasive methods. The deep inspiration, the Valsalva and abdominal pressure maneuvers, and the pneumatic cuff technique were employed with the impedance tests. The incidence of false negative and false positive results were determined for each noninvasive method separately and for both methods used concurrently. When both methods were considered, the number of false positives was high; however, all cases with major thrombosis were detected in the group of patients examined. A positive result with ultrasound or impedance tests should be considered an indication to perform venography, or if venography is contraindicated, to perform other noninvasive tests. |
Title |
Reliability of ocular and orbital diagnosis with B-scan ultrasound. 1. Ocular diagnosis. |
Author |
Coleman DJ. |
Journal |
Am J Ophthalmol |
Volume |
|
Year |
1972 |
Abstract |
No abstract available. |
Title |
Reliability of ocular and orbital diagnosis with B-scan ultrasound. 2. Orbital diagnosis. |
Author |
Coleman DJ. |
Journal |
Am J Ophthalmol |
Volume |
|
Year |
1972 |
Abstract |
No abstract available. |
Title |
Remnants of Albunex? nucleate acoustic cavitation. |
Author |
Dalecki D, Raeman CH, Child SZ, Penney DP, Carstensen EL. |
Journal |
Ultrasound Med Biol |
Volume |
|
Year |
1997 |
Abstract |
Mice were injected with 0.1 mL Albunex? and exposed to 200 pulses from a piezoelectric lithotripter at times ranging from 5 min to 24 h following injection. Each pulse was approximately 1.5 sinusoidal oscillations at a fundamental frequency of approximately 0.1 MHz with pressure amplitude of approximately 2 MPa. Although the contrast agent ceases to be an effective scatterer of diagnostic ultrasound after a few minutes in the circulation, the modest lithotripter exposures.caused significant hemorrhaging in bladder, mesentery and intestine for periods of up to 4 h after injection. The results demonstrate either that highly stable bubbles much smaller than resonance size or air-containing fragments of the shells of Albunex? serve as effective nuclei for acoustic cavitation. |
Title |
Renal ultrasound using parametric imaging techniques to detect changes in microstructure and function. |
Author |
Insana MF, Hall TJ, Wood JG, Yan ZY. |
Journal |
Invest Radiol |
Volume |
|
Year |
1993 |
Abstract |
Abstract
RATIONALE AND OBJECTIVES:
Signal processing techniques have been used to generate parametric ultrasound images that describe properties of tissue microstructure.
METHODS:
Images of the average scatterer size (D) and integrated backscatter coefficient (IBC) for normal dog kidneys were examined.
RESULTS:
With parametric ultrasound the authors identified sources of cortical backscatter and observed microanatomical changes corresponding to ischemia. In particular, scatterer size images acquired in vitro and in vivo show it is possible to rapidly assess changes and differences in the average glomerular diameter and the average arteriolar cross-sectional diameter.
CONCLUSIONS:
A more direct interpretation of sonographic image data is possible with this new type of imaging. Parametric imaging may have a diagnostic role as a means to differentiate among conditions producing increased cortical echogenicity and to detect important structural indicators such as glomerular hypertrophy. |
Title |
Repeatibility and reproducibility of a clinically based QUS phantom study and methodologies |
Author |
Han A, Andre MP, Erdman J W Jr, O'Brien W D Jr. |
Journal |
IEE TUFFC |
Volume |
|
Year |
2017 |
Abstract |
The purpose of this study is to evaluate the repeatability and reproducibility (R&R) of quantitative ultrasound (QUS) estimates, specifically attenuation coefficient (AC) and backscatter coefficient (BSC), using the same Siemens
3000 clinical ultrasound scanner. Additionally, the purpose of this work is to detail the measurement and analysis methodology. Repeatability is closeness of agreement between measures obtained with the same method under same conditions (same sonographer and same transducer) and reproducibility is closeness of agreement between measures obtained with the same method under different conditions (different sonographers and/or different transducers). Calibrated phantoms were scanned by two sonographers using two transducers in each session for multiple sessions over a period of four months. The phantom scans occurred as part of a clinical QUS liver study in human research participants spanning a spectrum of obesity and liver disease severity. The scanner was adjusted in each participant to obtain the highest quality liver B-mode images prior to acquiring
data from the phantoms for which no scanner adjustments were made. The R&R were analyzed and estimated using the unweighted sums of squares ANOVA approach by applying two random effect models. The measurement variance caused by repeatability and reproducibility is small (AC: 2.4–3.2 × 10−4 [dB/cm-MHz]2; 10log10BSC: 0.23–0.27 dB2). The reproducibility variance is statistically significantly lower than the repeatability variance. The total R&R was not influenced by phantom properties over a wide range representing those found
in liver in vivo. |
Title |
Report from the conference on ultrasound-assisted liposuction safety and effects. |
Author |
Young VL, Schorr MW. |
Journal |
Clin Plast Surg |
Volume |
|
Year |
1999 |
Abstract |
The authors report on the Ultrasound-Assisted Liposuction (UAL) Safety and Effects conference held in St. Louis, Missouri, in November. 1998. The meeting was convened to discuss how internal UAL works (its physics and mechanisms of action), gain a basic knowledge of the. interaction between acoustic energy and tissue, identify safety concerns potentially related to thermal effects and free radical production, and. define future research questions. Those attending represented multiple scientific disciplines: plastic surgery, physics, lipid chemistry, cancer. biology, and medical biophysics. Participants agreed that scientists do not yet understand the mechanisms of UAL action, although multiple. mechanisms are probably involved, such as mechanical forces, cavitation, and thermal effects. Additional research has revealed that. long-term complications or negative bioeffects--including DNA damage and oxidation-free radical attack--are probably not serious safety. concerns with UAL. Several areas deserving future investigation were proposed. |
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