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BRL Abstracts Database |
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Your search for ultrasound produced 3296 results. Page 77 out of 330
| Title |
Critical parameters in pulsed ultrasound exposures. |
| Author |
Barnett SB. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1986 |
| Abstract |
Repeatable in vivo bioeffects have only been observed in mammalian tissue where the exposure produces hyperthermia and agreement exists between the measured temperature increase and that predicted from the temporal average intensity and time of exposure to ultrasound.
However, some nonthermal in vitro studies have shown that for equivalent average intensities pulsed ultrasound is more effective than continuous wave in producing the biological change (see Tables 10?12).
In vitro studies with cell suspensions utilizing stable cavitation mechanisms have shown the extent of platelet aggregation around acoustically active bubbles to be most strongly dependent on pulse duration.
Conditions during the pulse are particularly important where cavitation is the main underlying mechanism, and studies of mortality in Drosophila larvae caused by exposure to microsecond pulses have shown the temporal peak intensity to be a better predictor of the bioeffect than the SPTA intensity parameters. |
| Title |
Cross-imaging platform comparison of ultrasonic backscatter coefficient measurements of live rat tumors. |
| Author |
Wirtzfeld LA, Ghoshal G, Hafez ZT, Nam K, Labyed Y, Anderson JJ, Herd MT, Haak A, He Z, Miller RJ, Sarwate S, Simpson DG, Zagzebski JA, Bigelow TA, Oelze ML, Hall TJ, O'Brien WD Jr. |
| Journal |
J Ultrasound Med |
| Volume |
|
| Year |
2010 |
| Abstract |
OBJECTIVE: To translate quantitative ultrasound (QUS) from the laboratory into the clinic, it is necessary to demonstrate that the measurements are platform independent. Because the backscatter coefficient (BSC) is the fundamental estimate from which additional QUS estimates are calculated, agreement between BSC results using different systems must be demonstrated. This study was an intercomparison of BSCs from in vivo spontaneous rat mammary tumors acquired by different groups using 3 clinical array systems and a single-element laboratory scanner system. METHODS: Radio frequency data spanning the 1- to 14-MHz frequency range were acquired in 3 dimensions from all animals using each system. Each group processed their radio frequency data independently, and the resulting BSCs were compared. The rat tumors were diagnosed as either carcinoma or fibroadenoma. RESULTS: Carcinoma BSC results exhibited small variations between the multiple slices acquired with each transducer, with similar slopes of BSC versus frequency for all systems. Somewhat larger variations were observed in fibroadenomas, although BSC variations between slices of the same tumor were of comparable magnitude to variations between transducers and systems. The root mean squared (RMS) errors between different transducers and imaging platforms were highly variable. The lowest RMS errors were observed for the fibroadenomas between 4 and 5 MHz, with an average RMS error of 4 x 10(-5) cm(-1)Sr(-1) and an average BSC value of 7.1 x 10(-4) cm(-1)Sr(-1), or approximately 5% error. The highest errors were observed for the carcinoma between 7 and 8 MHz, with an RMS error of 1.1 x 10(-1) cm(-1)Sr(-1) and an average BSC value of 3.5 x 10(-2) cm(-1)Sr(-1), or approximately 300% error. CONCLUSIONS: This technical advance shows the potential for QUS technology to function with different imaging platforms. |
| Title |
Cross-imaging system comparison of backscatter coefficient estimates from a tissue-mimicking material |
| Author |
Nam K, Rosado-Mendez IM, Wirtzfeld LA, Kumar V, Madsen EL, Ghoshal G, Pawlicki AD, Oelze ML, Lavarello RJ, Zagzebski JA, O'Brien WD Jr., Hall TJ |
| Journal |
J Acoust Soc Am |
| Volume |
|
| Year |
2012 |
| Abstract |
A key step toward implementing quantitative ultrasound techniques in a clinical setting is demonstrating that parameters such as the ultrasonic backscatter coefficient (BSC) can be accurately estimated independent of the clinical imaging system used. In previous studies, agreement in BSC estimates for well characterized phantoms was demonstrated across different laboratory systems.
The goal of this study was to compare the BSC estimates of a tissue mimicking sample measured using four clinical scanners, each providing RF echo data in the 1-15 MHz frequency range. The sample was previously described and characterized with single-element transducer systems. Using a reference phantom for analysis, excellent quantitative agreement was observed across the four array-based imaging systems for BSC estimates. Additionally, the estimates from data acquired with the clinical systems agreed with theoretical predictions and with estimates from laboratory measurements using single-element transducers. |
| Title |
Cross-imaging system comparison of backscatter coefficient estimates from a tissue-mimicking material |
| Author |
Nam K, Rosado-Mendez IM, Wirtzfeld LA, Kumar V, Madsen EL, Ghoshal G, Pawlicki AD, Oelze ML, Lavarello RJ, Zagzebski JA, O'Brien WD Jr., Hall TJ |
| Journal |
J Acoust Soc Am |
| Volume |
|
| Year |
2012 |
| Abstract |
A key step toward implementing quantitative ultrasound techniques in a clinical setting is demonstrating that parameters such as the ultrasonic backscatter coefficient (BSC) can be accurately estimated independent of the clinical imaging system used. In previous studies, agreement in BSC estimates for well characterized phantoms was demonstrated across different laboratory systems.
The goal of this study was to compare the BSC estimates of a tissue mimicking sample measured using four clinical scanners, each providing RF echo data in the 1-15 MHz frequency range. The sample was previously described and characterized with single-element transducer systems. Using a reference phantom for analysis, excellent quantitative agreement was observed across the four array-based imaging systems for BSC estimates. Additionally, the estimates from data acquired with the clinical systems agreed with theoretical predictions and with estimates from laboratory measurements using single-element transducers. |
| Title |
Crystallization in oil-in-water emulsions containing liquid and solid droplets. |
| Author |
Dickinson E, Kruizenga FJ, Povey MJ, van der Molen M |
| Journal |
Colloids Surfaces A: Physicochem Eng Aspects |
| Volume |
|
| Year |
1993 |
| Abstract |
The kinetics of crystallization of supercooled oil droplets in emulsions containing a mixture of solid and liquid n-hexadecane droplets has been monitored at constant temperature from time-dependent measurements of the velocity of ultrasound. In emulsions stabilized by non-ionic surfactant (Tween 20 or C12E8) or anionic surfactant (sodium dodecyl sulphate, SDS), crystallization is induced in liquid droplets when solid droplets are present; in the absence of solid droplets crystallization proceeds at a negligible rate. Increasing the aqueous phase surfactant concentration leads to a substantial increase in the crystallization rate in Tween 20 emulsions. Ionic strength has no significant effect on the rate in SDS emulsions. The mechanism of this crystallization probably involves crystals on solid droplets penetrating into supercooled liquid droplets during collisions and thereby acting as nucleation sites for crystal growth. The process is enhanced by aggregated surfactant molecules bridging between the colliding droplets. |
| Title |
Current applications of diagnostic ultrasound. |
| Author |
Taylor KJW, Carpenter DA. |
| Journal |
Guys Hosp Rep |
| Volume |
|
| Year |
1974 |
| Abstract |
Diagnostic ultrasound has been used for many years yet several technical limitations have not permitted its wider use in specialties other than obstetrics and cardiology. A new scanner is described which indicates the excellent resolution allowed by the method and the wide range of new applications now amenable to investigation by ultrasound. This range can be divided into three parts: the first relates to those situations in which, at the present state of the art, it appears that ultrasound produces unique information as a non-invasive technique. This includes applications in obstetrics, the investigation of solid and cystic tumours in kidney, the abdomen, enlarged lymph nodes, spleen, bladder, eye and testis. The second concerns situations in which ultrasound is the method of choice. This includes more general applications in obstetrics, the investigation of space occupying masses in liver, in particular in obstructive jaundice, and in relation to the heart. Thirdly, ultrasound can also give information which is supplementary to other investigations in nuclear medicine and radiology. With the commercial developments of similar scanners in other centres, it is apparent that the future scope of the method will rapidly increase and will assume a more important role in departments of diagnosis. |
| Title |
Current status of breast echography. |
| Author |
Kobayashi T. |
| Journal |
Prog Med Ultrasound |
| Volume |
|
| Year |
1980 |
| Abstract |
No abstract available. |
| Title |
Current status of breast echography. |
| Author |
Kobayashi T. |
| Journal |
Prog Med Ultrasound |
| Volume |
|
| Year |
1981 |
| Abstract |
No abstract available. |
| Title |
Current status of breast ultrasonography and ultrasound tissue characterization of breast cancer. |
| Author |
Kobayashi T. |
| Journal |
Proc Third World Conf Med Inform - Tokyo |
| Volume |
|
| Year |
1980 |
| Abstract |
For the clinical management of breast cancer, there is no doubt that the early detection is mandatory and correct differential diagnosis is an important determinant of prognosis. Breast ultrasonography has been highly appraised in the viewpoints of its high diagnostic accuracy, no physical hazard like radiological approach and non-invasive techniques. Its technical methods, diagnostic accuracy rates, expanded echography for the detection of early breast cancer and ultrasonic tissue characterization of breast cancer were presented. |
| Title |
Current status of research on biophysical effects of ultrasound. |
| Author |
Barnett SB, ter Haar GR, Ziskin MC, Nyborg WL, Maeda K, Bang J. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1994 |
| Abstract |
This overview of bioeffects of ultrasound presents some key aspects of selected papers dealing with biophysical end-points. Its purpose is to establish a basis for exposure and dosimetric standards for medical ultrasonic equipment. It is intended to provide essential background resource material for the medical/scientific community, and more specifically for scientific working groups. This document was prepared by members of the Safety Committee of the World Federation for Ultrasound in Medicine and Biology. It was produced as a resource document in response to a request for information by Working Group 12 (Ultrasound exposure parameters) of the International Electrotechnical Commission Technical Committee 87, Ultrasonics. IEC TC 87, WG12 is the working group responsible for generating international standards for the classification of equipment by its acoustic fields based on safety thresholds. Our paper is intended to update and supplement information on the thermal mechanism provided in the publication, "WFUMB Symposium on Safety and Standardisation in Medical Ultrasound: Issues and Recommendations Regarding Thermal Mechanisms for Biological Effects of Ultrasound" (WFUMB 1992). It also provides an overview of trends in research into nonthermal mechanisms as a preliminary to the next WFUMB Symposium on Safety of Medical Ultrasound when this subject will be examined in detail by a select group of international experts. The WFUMB-sponsored workshop will take place in Utsunomiya, Japan during 11-15th July, 1994. The purpose of the meeting is to evaluate the scientific literature and to formulate internationally accepted recommendations on the safe use of diagnostic ultrasound that may be endorsed as official policy of the WFUMB. It should be noted that the current publication is not intended for review or endorsement as an official WFUMB document. It is produced as a scientific paper by individuals who are members of the WFUMB Safety Committee, and it therefore represents the opinions of the authors. Nevertheless, during the preparation of this document, contributions were received from members of the International Electrotechnical Commission Technical Committee 87 as well as many other individual experts, and the authors sincerely acknowledge their support. |
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