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BRL Abstracts Database |
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Your search for ultrasound produced 3296 results. Page 293 out of 330
| Title |
Ultrasonic measurement of the aortic arch, right pulmonary artery, and left atrium. |
| Author |
Goldberg BB. |
| Journal |
Radiology |
| Volume |
|
| Year |
1971 |
| Abstract |
Ultrasound successfully measured the aortic arch, right pulmonary artery, and left atrium in 130 out of 138 patients. The transducer was positioned in the suprasternal notch and the ultrasonic beam directed caudad. Clinical experiments established the identity of the sources of the echoes recorded. The diameters obtained by ultrasound were compared not only with angiocardiographic measurements in the same patients, but also with independent radiographic measurements. In all cases there was close correlation between the ultrasonic and angiocardiographic mean diameters. The motion of the echoes during the cardiac cycle was also analyzed. |
| Title |
Ultrasonic microstreaming and related phenomena. |
| Author |
Nyborg WL. |
| Journal |
Br J Cancer Suppl |
| Volume |
|
| Year |
1982 |
| Abstract |
It has been shown in recent work that biological cells and tissues are affected.by low intensity ultrasound in the lower megahertz frequency range if small.gas-filled channels or pores are present, with dimensions in the range of a few.microns. When these gas bodies pulsate in response to the ultrasound they act.on surrounding media by unique forms of radiation pressure, forces and.torque; in liquids small-scale eddying is generated, known as microstreaming..It is probably by combinations of these phenomena that biological effects are.produced. |
| Title |
Ultrasonic modification of experimental bruising in the guinea-pig pinna. |
| Author |
Hustler JE, Zarod AP, Williams AR. |
| Journal |
Ultrasonics |
| Volume |
|
| Year |
1978 |
| Abstract |
Both pinnae of anaesthetized male guinea-pigs were contused in a reproducible manner and one immediately treated with 0.75 MHz ultrasound at an average therapeutic intensity of 0.61 W cm-2 for a period of 2 min. The lividity and rate of resorption of the rusultant bruises were measured by a photometric method. The results fell into two distinct classes. In the majority of cases, the bruises formed on the insonated pinnae were significantly less intense and were resorbed at the same rate as their corresponding controls. In the remaining cases, ultrasonic irradiation resulted in an increased initial lividity and a significantly greater rate of resorption. |
| Title |
Ultrasonic pelvimetry. |
| Author |
Kratochwila A, Zeibekisa N. |
| Journal |
Obstet Gynecol |
| Volume |
|
| Year |
1972 |
| Abstract |
In recent years a high accuracy in measuring the biparietal diameter by ultrasonography has been achieved. As this is only one parameter in forecasting cephalo-pelvic disproportion a study was made to determine whether the true conjugate can be measured by utrasound with approximately the same reliability as the biparietal diameter. First, one-dimensional ultrasound studies were compared with X-ray measurements. Later, equipment was used which allows simultaneous display on two oscilloscopes of the B-scan for orientation and the A-mode trace for exact measurement. To exclude disproportion in the mid-pelvis a vaginal / rectal probe was constructed. In longitudinal scans, information about the form of the birth canal is obtainable. Transverse scans performed at the level of the symphysis provide information on the pelvic entrance. To evaluate ultrasonic pelvimetry the outcome of labour in 246 cases was analysed. The study demonstrates that ultrasonic pelvimetry can be an invaluable supplementary aid to X-ray diagnosis of cephalo-pelvic-disproportion especially in cases of breech presentation. Because it is often possible to diagnose cephalo-pelvic disproportion conclusively by using ultrasonic pelvimetry, X-ray examination can be restricted to borderline cases. In this manner it is possible therefore to reduce radiation dosage. |
| Title |
Ultrasonic phased array controller for hyperthermia applications. |
| Author |
Benkeser PJ, Pao TL, Yoon YJ. |
| Journal |
Ultrasonics |
| Volume |
|
| Year |
1991 |
| Abstract |
Multiple and mechanically scanned ultrasound transducer systems have demonstrated the efficacy of using ultrasound to produce deep localized hyperthermia. The use of ultrasonic phased arrays has been proposed as an alternative to these systems. A phased array offers a more flexible approach to heating tumours in that the size, shape, and position of its focal region can be altered during the course of treatment in order to achieve the desired temperature distribution. This added.flexibility comes at the cost of increased complexity of the hardware necessary to drive the transducer because each element requires its own amplifer with both phase and amplitude control. In order for phased arrays with large numbers of elements to be feasible for hyperthermia applications, the complexity of this circuitry must be minimized. This paper describes a circuit design which simplifies the electronics required to control a phased array transducer system for hyperthermia applications. The design is capable of controlling virtually any type of phased array transducer operating at frequencies less than 2 MHz. The system performance was verified through beam profile measurements using a 48-element tapered phased array transducer. |
| Title |
Ultrasonic phased array design for reduced crosstalk. |
| Author |
Dodson J, Crosh K. |
| Journal |
J Acoust Soc Am |
| Volume |
|
| Year |
1998 |
| Abstract |
In recent years, therapeutic ultrasound has received increased attention as a treatment modality for cancer therapy (hyperthermia) and heart arrythmia (ablation surgery). Ultrasonic phased arrays offer the benefit of noninvasive treatment with the flexibility of variable focus and beam steering. In designing and building these arrays, electromechanical isolation is extremely important as interelement crosstalk will degrade array performance. However, manufacturability and cost, constraints which may conflict with the goal of reduced crosstalk, must also be a consideration. Efficient numerical methods present a useful design tool for array design and allow the investigation of structural acoustic phenomena in general. In this paper, a two‐dimensional finite‐element model for an ultrasonic phased array in contact with the human body is used to study array design. The effects of material selection and geometry for matching layer(s) and interelement structural matrix are examined for their impact on radiation pattern, power input to the fluid domain, and deleterious effect on the electromechanical behavior of the transducers. Finally, design guidelines are formulated and, if possible, compared to experimental results. |
| Title |
Ultrasonic power and intensities produced by diagnostic ultrasound equipment. |
| Author |
Carson PL Fischella PR Oughton TV. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1978 |
| Abstract |
The ultrasonic radiation force on an absorber was measured with a feedback microbalance to determine the ultrasonic power emitted into water by 26 diagnostic ultrasound instruments. Included in the measurements were pulse echo scanners, echocardiographic units, ophthalmic units, Doppler fetal heart detectors, fetal monitors, and continuous and pulsed Doppler units for peripheral vascular studies. The temporal and spatial average intensity at the transducer was calculated for those instruments by dividing the total power by the nominal area of the radiating surface. Estimates of the spatial maximum intensity in water, both temporal average and temporal peak, were made by measurements with miniature hydrophones normalized to the power measurements. Hydrophone measurements only were performed on linearly-scanned real time arrays. For transducers with single element transmitters, the maximum obtainable power ranged from 60μW to 37 mW, and maximum obtainable intensity at the transducer face ranged from 1 to 1700 W/m2. A much smaller range of power and intensity was encountered among systems designed for a given set of applications and providing similar performance in those applications. The temporal average and temporal peak intensities at the focal point of focused transducers employed frequently in the last few years for general purpose scanning were somewhat higher than previously quoted values because of the increased focusing. |
| Title |
Ultrasonic production of reversible changes in the electrical parameters of isolated frog skin. |
| Author |
Coble AJ, Dunn F. |
| Journal |
J Acoust Soc Am |
| Volume |
|
| Year |
1976 |
| Abstract |
Isolated frog skin was irradiated with 1-MHz noncavitating focused ultrasound, intensity range 1-100 W/cm2, in an adaptation of the Ussing chamber providing continuous perfusion of the specimen. The electrical parameters of the skin, viz., the membrane potential (MP) and the short circuit current (SCC), were monitored continuously before, during, and after the acoustic exposure. The magnitudes of the ultrasonically induced changes, in both parameters, were proportional to the acoustic intensity, though the MP decreased while the SCC increased. Unlinking of the two electrical parameters occurs in that their time courses in response to the ultrasound differ, i.e., the SCC increases continuously for exposures of 0.5 sec and longer while the MP reaches its maximum within 0.5 sec and is not altered with increased duration of exposure. |
| Title |
Ultrasonic propagation in the heterodispersive media of the eye. |
| Author |
Greguss P. |
| Journal |
Ultrasonics |
| Volume |
|
| Year |
1964 |
| Abstract |
Although the geometry of the eye is well plotted, ultrasonic examination is complicated by the fact that the fluids in the eye are not homogenous. Differences in the velocity of ultrasound in different parts can introduce errors of up to 4 mm in the measured positions of interfaces. The author shows how these errors can be calculated and also suggests that the hydrodynamic flow away from the transducer could be used to repair retinal detachments. |
| Title |
Ultrasonic propagation properties of articular cartilage at 100 MHz. |
| Author |
Agemura DH, O'Brien WD Jr, Olerud JE, Chun LE, Eyre DR. |
| Journal |
J Acoust Soc Am |
| Volume |
|
| Year |
1990 |
| Abstract |
A pilot study on articular cartilage assessed the contributions of individual matrix components to ultrasound propagation. The influence of collagen fibril orientation and collagen cross linking was also assessed. Sections of adult bovine articular cartilage cut both parallel and perpendicular to the articular surface were examined using the scanning laser acoustic microscope (SLAM) operating at an ultrasonic frequency of 100 MHz. A set of samples was evaluated that had been sequentially treated by enzymes to (1) remove 85% of the chondroitin sulfate; (2) remove remaining glycosaminoglycans, glycoproteins, and other noncollagen proteins, leaving only the collagen fibril network; and (3) disrupt the collagen intermolecular cross links. Two striking observations were made: a profound effect of the ``preferred'' collagen fibril orientation on ultrasonic speed and a marked increase in attenuation coefficient when intermolecular cross links were broken in the collagen. |
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