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BRL Abstracts Database |
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Your search for ultrasound produced 3296 results. Page 26 out of 330
| Title |
Accuracy evaluation in ultrasonic-doppler-based measurement of small vibrations for acoustical diagnosis of the aortic wall. |
| Author |
Kawabe K, Kanai H, Chubachi N. |
| Journal |
Electron Lett |
| Volume |
|
| Year |
1993 |
| Abstract |
To diagnose atherosclerosis based on the acoustic characteristics of the aortic wall, it is necessary to detect vibration signals from various parts of the aortic wall near the heart. It is, however, difficult to obtain such small vibrations using previously proposed ultrasonic diagnostic methods or systems because the small vibrations are superimposed on the motion with large amplitude due to the heartbeat. The authors developed a new method for overcoming this problem and accurately measuring small vibrations of the aortic wall using ultrasound. The Letter describes the accuracy of evaluation using this new method by simulation experiments using a system which simulates small vibrations of the aortic wall near the heart. |
| Title |
Accuracy of grey-scale ultrasonography of liver and spleen in hodgkin's disease and the other lymphomas compared with isotope scans. |
| Author |
Glees JP, Taylor KJW, Gazet JC, Peckham MJ, McCready VR. |
| Journal |
Clin Radiol |
| Volume |
|
| Year |
1977 |
| Abstract |
Complementary techniques to laparotomy are required to monitor patients with lymphomas both before and after treatment. Our preliminary experience with grey-scale ultrasonography is presented. Fifty-two patients, the majority with Hodgkin's disease or other lymphomas, were examined with ultrasound equipment which was custom built. The essential difference between grey-scale equipment and conventional machines is the ability to display the internal consistency of soft organs. Of 20 spleens examined prior to splenectomy, the ultrasonic scan was considered suggestive of involvement in seven of nine that showed histological evidence of Hodgkin's disease. Three of 11 histologically negative on the scan contained histological disease. Fifty livers were examined with ultrasound. Of seven patients with histological involvement four were read as positive and three as negative and six of 43 patients with no macroscopic or microscopic evidence of liver infiltration were also considered to have a positive ultrasonic scan. Ultrasonic scanning has proved useful for demonstrating enlarged lymph nodes in the porta hepatis, upper para-aortic lymph nodes and bulky mesenteric nodes. On the basis of these preliminary observations the potential value and application of the technique is discussed. |
| Title |
Accurate diagnosis of nonalcoholic fatty liver disease in human participants via quantitative ultrasound |
| Author |
Andre MP, Han A, Heba E, Hooker J, Loomba R, Sirlin CB, Erdman JW Jr, O'Brien WD Jr. |
| Journal |
IEEE Int Ultrasonics Symp Proc |
| Volume |
|
| Year |
2014 |
| Abstract |
Nonalcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease in the United States, affects 30% of adult Americans, may progress to nonalcoholic steatohepatitis (NASH) and end-stage liver disease, and is a risk factor for diabetes and cardiovascular disease. The diagnosis, grading, and staging of NAFLD currently is based on liver biopsy examination with histologic assessment. Noninvasive image-based methods to evaluate the liver in adults with
NAFLD are urgently needed. We developed a quantitative ultrasound (QUS) method that in animal studies shows promise for detection and quantification of liver fat content. The current study’s contribution is to extend the work to human participants by assessing the accuracy of backscatter coefficient and attenuation
coefficient for detection of hepatic steatosis in a cohort of adult participants with NAFLD and non-NAFLD controls. QUS parameters measured using routine
clinical US scanners show promise for detecting and perhaps grading NAFLD. |
| Title |
Accurate histological techniques to evaluate critical temperature thresholds for prostate in vivo. |
| Author |
Bronskill M, Chopra R, Boyes A, Tang K, Sugar L. |
| Journal |
AIP Conf Proc |
| Volume |
|
| Year |
2007 |
| Abstract |
Various histological techniques have been compared to evaluate the boundaries of thermal damage produced by ultrasound in vivo in a canine model. When all images are accurately co-registered, H&E stained micrographs provide the best assessment of acute cellular damage. Estimates of the boundaries of 100% and 0% cell killing correspond to maximum temperature thresholds of 54.6 +/- 1.7°C and 51.5 +/- 1.9°C, respectively.
|
| Title |
Acosutic saturation and output regulation. |
| Author |
Duck FA. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1999 |
| Abstract |
Acoustic saturation pressures are predicted for ultrasonic beams of a range of frequencies and focal depths. Using reasonable approximations, saturation values for mechanical index (MI) and derated spatial-peak, time-average and pulse-average intensities are calculated. These are compared with thresholds set for regulatory purposes by the U. S. Food and Drug Administration (FDA), and by the International Electrotechnical Commission (IEC). It is concluded that there are many conditions for which acoustic saturation in water prevents the values of MI and regulated intensities from exceeding thresholds set by the FDA. These conditions are particularly associated with higher frequencies and deeper focal lengths. The thresholds for action set by IEC 61157 are sufficiently low that similar problems do not arise. It is concluded that present regulations are not fully effective in limiting the output from diagnostic ultrasound equipment, and that some conditions exist that are not subject to output control. |
| Title |
Acoustic attenuation reconstruction from back-scattered ultrasound. |
| Author |
Duck FA, Hill CR. |
| Journal |
Comput Aided Tomogr Ultrason Med |
| Volume |
|
| Year |
1979 |
| Abstract |
A digital iterative approach has been investigated with the objective of mapping quantitatively the distribution of acoustic attenuation within human tissue, using as data multiple backscattered pulse intensities. It has been shown that the use of a simple iterative algorithm which corrects both attenuation and back-scatter values gives a convergent solution both in simulation studies and with input of pulse-echo data gathered from tissue. The effects of a variety of controls have been investigated, including threshold, iterative sequence and weighting. The behaviour of the technique with a limited angle of view has been investigated. |
| Title |
Acoustic backscatter and effective scatterer size estimates using a 2D CMUT transducer. |
| Author |
Liu W, Zagzebski JA, Hall TJ, Madsen EL, Varghese T, Kliewer MA, Panda S, Lowery C, Barnes S. |
| Journal |
Phys Med Biol |
| Volume |
|
| Year |
2008 |
| Abstract |
Compared to conventional piezoelectric transducers, new capacitive microfabricated ultrasonic transducer (CMUT) technology is expected to offer a broader bandwidth, higher resolution and advanced 3D/4D imaging inherent in a 2D array. For ultrasound scatterer size imaging, a broader frequency range provides more information on frequency-dependent backscatter, and therefore, generally more accurate size estimates. Elevational compounding, which can significantly reduce the large statistical fluctuations associated with parametric imaging, becomes readily available with a 2D array. In this work, we show phantom and in vivo breast tumor scatterer size image results using a prototype 2D CMUT transducer (9 MHz center frequency) attached to a clinical scanner. A uniform phantom with two 1 cm diameter spherical inclusions of slightly smaller scatterer size was submerged in oil and scanned by both the 2D CMUT and a conventional piezoelectric linear array transducer. The attenuation and scatterer sizes of the sample were estimated using a reference phantom method. RF correlation analysis was performed using the data acquired by both transducers. The 2D CMUT results indicate that at a 2 cm depth (near the transmit focus for both transducers) the correlation coefficient reduced to less than 1/e for 0.2 mm lateral or 0.25 mm elevational separation between acoustic scanlines. For the conventional array this level of decorrelation requires a 0.3 mm lateral or 0.75 mm elevational translation. Angular and/or elevational compounding is used to reduce the variance of scatterer size estimates. The 2D array transducer acquired RF signals from 140 planes over a 2.8 cm elevational direction. If no elevational compounding is used, the fractional standard deviation of the size estimates is about 12% of the mean size estimate for both the spherical inclusion and the background. Elevational compounding of 11 adjacent planes reduces it to 7% for both media. Using an experimentally estimated attenuation of 0.6 dB cm−1 MHz−1, scatterer size estimates for an in vivo breast tumor also demonstrate improvements using elevational compounding with data from the 2D CMUT transducer. |
| Title |
Acoustic cavitation and the safety of diagnostic ultrasound. |
| Author |
Carstensen EL. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1987 |
| Abstract |
A massive body of screening studies attests to the safety of diagnostic ultrasound. It appears that further progress in analysis of the safety question, will require mechanistic guidance. In theory, transient cavitation can occur under diagnostically relevant conditions if appropriate nuclei exist in the exposed medium. Low-temporal-average-intensity, pulsed ultrasound equivalent to that used in diagnosis has been shown to cause deleterious effects in lower organisms. All available evidence supports the conclusion that these effects are mediated by acoustic cavitation. It is impossible to extrapolate from these observations to human beings. However, all of the information available to us at the present time suggests that if transient cavitation occurs under diagnostic conditions, the events are rare, highly localized and probably would be of minor importance in almost any part of the body with the possible exception of the developing embryo or fetus. Transient cavitation is characterized by sharply defined thresholds. If future studies demonstrate the occurrence of cavitation related effects, they can be eliminated simply by keeping the maximum pressure amplitudes below those thresholds. |
| Title |
Acoustic cavitation and the safety of ultrasound. |
| Author |
Carstensen EL. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1987 |
| Abstract |
A massive body of screening studies attests to the safety of diagnostic ultrasound. It appears that further progress in analysis of the safety question, will require mechanistic guidance. In theory, transient cavitation can occur under diagnostically relevant conditions if appropriate nuclei exist in the exposed medium. Low-temporal-average-intensity, pulsed ultrasound equivalent to that used in diagnosis has been shown to cause deleterious effects in lower organisms. All available evidence supports the conclusion that these effects are mediated by acoustic cavitation. It is impossible to extrapolate from these observations to human beings. However, all of the information available to us at the present time suggests that if transient cavitation occurs under diagnostic conditions, the events are rare, highly localized and probably would be of minor importance in almost any part of the body with the possible exception of the developing embryo or fetus. Transient cavitation is characterized by sharply defined thresholds. If future studies demonstrate the occurrence of cavitation related effects, they can be eliminated simply by keeping the maximum pressure amplitudes below those thresholds. |
| Title |
Acoustic cavitation generated by an extracorporeal shockwave lithotripter. |
| Author |
Coleman AJ, Saunders JE, Crum LA, Dyson M. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1987 |
| Abstract |
Evidence is presented of acoustic cavitation generated by a Dornier extracorporeal shockwave lithotripter. Using x-ray film, thin aluminum sheets, and relatively thick metal plates as targets, evidence of liquid jet impacts associated with cavitation bubble collapse was observed. The jet impact was violent enough to puncture thin foils and deform metal plates. Furthermore, numerous jet impacts were generated over a volume of greater than 200 cm3. It is likely that such violent cavitation will also occur in tissue, and observed biological effects (e.g. renal calculus disintegration and tissue trauma) may be related to cavitation damage. |
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