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BRL Abstracts Database |
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Your search for ultrasound produced 3296 results. Page 15 out of 330
| Title |
A real-time approach to detect seal defects in food packages using ultrasonic imaging. |
| Author |
Shah NN, Rooney PK, Ozguler A, Morris SA, O'Brien WD Jr. |
| Journal |
J Food Prot |
| Volume |
|
| Year |
2001 |
| Abstract |
The microbial integrity of many types of flexible food packages depends on a zero defect level in the fused seam seal. Human inspection for defects in these seals is marginal at best, and secondary incubation protocols are often used to spot packages with compromised integrity before releasing product for sale. A new type of inspection method has been developed and is being evaluated for robustness. The purpose of the study was to evaluate a new raster scanning geometry to simulate continuous motion, online ultrasonic inspection of the seal region in flexible food package seals. A principal engineering tradeoff of scanning inspection systems is between increased line speed that results from decreased spatial sampling (less acquired data to process) and decreased image quality. The previously developed pulse-echo Backscattered Amplitude Integral (BAI) mode imaging technique is used to form ultrasound images using the new scanning geometry. At an ultrasonic frequency of 22.9 MHz, 38- and 50-microm-diameter air-filled channel defects in all-plastic transparent trilaminate are evaluated. The contrast-to-noise ratio (CNR) of the processed BAI-mode image is used to quantify image quality as a function of spatial sampling. Results show seal defects (38- and 50-microm diameter) are still detectable for undersampled conditions, although image quality degrades as spatial sampling decreases. Further, it is concluded that the raster scanning geometry is feasible for online inspection. |
| Title |
A real-time integrated backscatter measurement system for quantitative cardiac tissue characterization. |
| Author |
Thomas LJ III, Wickline SA, Perez JE, Sobel BE, Miller JG. |
| Journal |
IEEE Trans UFFC |
| Volume |
|
| Year |
1986 |
| Abstract |
To quantify integrated backscatter of ultrasound for real-time tissue characterization of myocardium in vivo an analog system that is used in conjunction with a two-dimensional/M-mode echocardiographic imager was developed and evaluated. The system measures the energy contained in a portion of the received rf signal from a selected myocardial segment with a CdS acoustoelectric detector. A standard substitution technique is used to calibrate the system relative to a stainless steel reflector. Integrated backscatter is sampled at 5 ms intervals, its time-variation recorded and simultaneously integrated to yield the time-averaged integrated backscatter. Both time-varying and time-averaged integrated backscatter are displayed in real-time. Time-averaged integrated backscatter in five dogs was -54 ? 2.4 dB (SD). Cyclic variations during the cardiac cycle ranged from 5-10 dB. Both the time-averaged and time-varying features of integrated backscatter are consistent with values obtained with earlier measurement systems that required off-line analysis of data. The real-time data acquisition system developed should facilitate clinical tissue characterization with ultrasonic backscatter. |
| Title |
A real-time ultrasound time-domain correlation blood flowmeter. Part I.Theory and design. |
| Author |
Hein IA, Chen JT, Jenkins WK, O'Brien WD Jr. |
| Journal |
IEEE Trans UFFC |
| Volume |
|
| Year |
1993 |
| Abstract |
A real-time ultrasound time-domain correlation (UTDC) blood flowmeter has been developed. Real-time performance has been achieved through the implementation of a custom-designed high-speed residue-number system (RNS) hardware correlator. The flowmeter is interfaced to a commercial ultrasound imager and can produce one-dimensional velocity versus range graphs at a rate of three per second. It has been validated in a blood flow phantom under a variety of conditions along with in vivo measurements in the human carotid artery. The theory of the time-domain correlation technique, design and implementation of flowmeter hardware, and the important correlation parameters which affect the performance of the flowmeter are described. |
| Title |
A real-time ultrasound time-domain correlation blood flowmeter. Part II. Performance and experimental verification. |
| Author |
Hein IA, O'Brien WD Jr. |
| Journal |
IEEE Trans UFFC |
| Volume |
|
| Year |
1993 |
| Abstract |
For Part I, see ibid., vol.40, no.6, p.768-775 (1993). The performance of a real-time ultrasound time-domain correlation (UTDC) flowmeter employing a high-speed residue number system correlator under various flow conditions for different correlation parameter settings is evaluated. Previous work has incorporated a weighted-averaging scheme to estimate the flow velocity over a wide number of echo signal spacings. The present evaluation indicates that a linear averaging of 50 adjacent echo signal pairs produces equivalent accuracy and precision at real-time processing speed as compared to previous non-real time systems incorporating weighted averaging. |
| Title |
A reflection technique for measurement of high acoustic intensities. |
| Author |
Kossoff G, Carpenter DA. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1984 |
| Abstract |
A number of commercially available hydrophones having a uniform frequency response suitable for measurement of pulse echo waveforms overload at high acoustic intensities. A reflection technique which reduces the magnitude of this incident energy is described and permits these hydrophones to measure high intensities without distortion. |
| Title |
A relationship between ultrasonic intensity.and changes in myocardial mechanics. |
| Author |
Mortimer AJ, Roy OZ, Trollope BJ, McEwen JI, Taichman GC,.Forester GV, Keon WJ. |
| Journal |
Can J Physiol Pharmacol |
| Volume |
|
| Year |
1980 |
| Abstract |
The effects of ultrasound on the mechanical properties of isometrically.contracting rat papillary muscle have been studied as a function of the.intensity of the ultrasonic irradiation. Each muscle was subjected to irradiation.at 1.1., 2.2, and 3.3 W/cm2 at a frequency of 2.3 MHz. Ultrasonic irradiation.caused heating in the vicinity of the muscle; thus it was necessary to separate.the pure thermal and ultrasonic effects. After irradiation the bath temperature.was increased so that the muscle reached the same temperature which.occurred during ultrasonic irradiation. The mechanical parameters measured.during the equivalent thermal procedure were compared with the parameters.during irradiation. There was a significant (p less than 0.05) decrease in.resting force which was significantly different from the equivalent thermal.intervention and could be related to the ultrasonic intensity. Thus, the effect of.ultrasound on rat papillary consists of two components, a thermal component.which affects all parameters studied and a nonthermal component which.affects only the diastolic force. |
| Title |
A research approach to visualization of breast tumor by ultrasound methods. |
| Author |
Kelly-Fry E, Gallager HS. |
| Journal |
BookChap |
| Volume |
|
| Year |
1978 |
| Abstract |
No abstract available. |
| Title |
A reusable perfusion supporting tissue-mimicking material for ultrasound hyperthermia phantoms. |
| Author |
Chin RB, Madsen EL, Zagzebski JA, Jadvar H, Wu XK, Frank GR. |
| Journal |
Med Phys |
| Volume |
|
| Year |
1990 |
| Abstract |
A new ultrasonically and thermodynamically tissue-mimicking material is reported. The material is well suited for use in phantoms for testing ultrasound hyperthermia systems or related predictive models. Controlled convective heat transfer effects, mimicking to some extent perfusive heat transfer in tissues, can be instituted in the material with appropriate fluid sources and sinks. The material consists of closely packed agar spheres varying in diameters from 0.3-3.6 mm. The interstitial space between spheres is filled with 10% n-propanol solution. The material has two practical advantages over the solid-gel-type tissue-mimicking materials. The first advantage is that it allows rapid return of a hyperthermia phantom to thermal equilibrium following a heating test by rapid circulation of the perfusion fluid. The second advantage is that the material is in a "liquid" form. It can be easily siphoned in and out of phantom containers of any geometric shape for different purposes without change in its physical properties. Methods for measuring ultrasonic and thermodynamic properties of the material and the results of the measurements are reported. The physical parameters measured are the intensity attenuation and absorption coefficients, the ultrasonic speed, the thermal conductivity, specific-heat capacity and the mass density. Temperature measurements in a hyperthermia phantom made of the material are also reported. |
| Title |
A review of in vitro bioeffects of inertial ultrasonic cavitation from a mechanistic perspective. |
| Author |
Miller MW, Miller DL, Brayman AA. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1996 |
| Abstract |
This selective review of the biological effects of ultrasound presents a synopsis of our current understanding of how cells insonated in vitro are affected by inertial cavitation from the standpoint of physical and chemical mechanisms. The focus of this review is on the physical and chemical mechanisms of action of inertial cavitation which appear to be effective in causing biological effects. There are several fundamental conditions which must be satisfied before cavitation-related bioeffects may arise. First, bubbles must be created and then brought into proximity to cells. Exposure methods are critical in this regard, and simple procedures such as rotation of a vessel containing the cells during exposure can drastically alter the results. Second, once association is achieved between bubbles and cells, the former must interact with the latter to produce a bioeffect. It is not certain that the inertial event is the prime mechanism by which cells are lysed; there is evidence that the turbulence associated with bubble translation may cause lysis. Additionally, there appear to be chemical and other physical mechanisms by which inertial cavitation may affect cells; these include the generation of biologically effective sonochemicals and the apparent emission of ultraviolet (UV) and soft X-rays. The evidence for inertial cavitation occurring within cells is critically reviewed. |
| Title |
A review of low intensity bioeffects and their relation to B-mode ultrasonic imaging. |
| Author |
Barnett SB, Kossoff G. |
| Journal |
Australas Radiol |
| Volume |
|
| Year |
1983 |
| Abstract |
Reports of biological effects following insonation with B-mode equipment are compared and put into perspective with respect to the dosage employed in diagnostic ultrasound examinations. Cellular changes have been observed in vitro following irradiation with diagnostic intensities, but where the duration of insonation of a fixed tissue target was extended. A small increase in the frequency of sister chromatid exchanges was reported after insonation for 7.5 minutes with a stationary real time transducer. In B-mode imaging the transducer scans the examined tissue and an equivalent single point exposure would be achieved by repeating 560 simple scans of the same plane. In similar studies by the authors this bioeffect occurred only at greatly increased total energy exposure, resulting from an increase in both the energy content within each pulse and the duration of insonation of a fixed target. Further research is required to determine whether the dosage relationship is linear producing the same effect if a constant total amount of energy is distributed in a varying time relationship. |
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