Bioacoustics Research Lab
University of Illinois at Urbana-Champaign | Department of Electrical and Computer Engineering | Department of Bioengineering
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Your search for ultrasound produced 3296 results.

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Title A study of streaming in plant tissue induced by a Doppler fetal heart detector.
Author Martin CJ, Gemmell HG, Watmough DJ.
Journal Ultrasound Med Biol
Volume
Year 1978
Abstract A study has been made of acoustic microstreaming in leaves of Elodea and in sections of the primary root tip of Vicia faba placed in a standing wave field produced by a Doppler fetal heart detector. The transducer frequency was 2.1 MHz and the total power output 7.0 mW which gave an effective intensity of 43 mW/cm2 at the centre of the ultrasound beam. The microstreaming was observed by light microscopy and took the form of the rotation of chloroplasts and other organelles. It was only found in association with channels of intercellular gas, and is thought to result from the acoustically stimulated pulsation of these channels. Quantitative observations of rotation speeds, threshold intensities and the variation in acoustic activity with time were made.


Title A study of synthetic-aperture imaging with virtual source elements in b-mode ultrasound imaging systems.
Author Bae MH, Jeong MK.
Journal IEEE Trans UFFC
Volume
Year 2000
Abstract We propose an all point transmit and receive focusing method based on transmit synthetic focusing combined with receive dynamic focusing in a linear array transducer. In the method, on transmit, a virtual source element is assumed to be. located at the transmit focal depth of conventional B-mode imaging systems, and transmit synthetic focusing is used in two half planes, one before and the other after the transmit focal depth, using the rf data of each scanline, together with. all other relevant rf scanline data previously stored. The proposed new method uses the same data acquisition scheme as the conventional focusing method while maintaining the same frame rate via high-speed signal processing, but it is. not suitable for imaging moving objects. It improves upon the lateral resolution and sidelobe level at all imaging depths. Also, it increases the transmit power and image signal-to-noise ratio (SNR), due to transmit field synthesis, and. extends the image penetration depth as well. Evaluations with simulation and experimental data show much improvement in resolution and SNR at all imaging depths.


Title A study of the biological action of focussed mechanical waves (focussed ultrasound).
Author Pond JB.
Journal Thesis(PhD): Univ of London
Volume
Year 1968
Abstract The interaction of mechanical waves with living tissues are complex and the dose may be widely varied. A division of possible primary mechanisms and a formalisation for the dosage and condition of treated tissues are therefore specified. The nature of ultrasound in its major bio-medical uses is briefly discussed in the light of this formalisation...Focal beam apparatus capable of a wide range of dose types has been built and used to irradiate tissues, chiefly the brains of rats. These were stained and examined under the light microscope. Doses, of various types, corresponding to a threshold (vanishing to focus centre) alteration of the tissue were determined...A mathematical approximation has been derived and tabulated. This allows the calculation of the history of excess temperature induced at the focus centre. Such temperature cycles have been checked with the aid of microthermocouples...To estimate the effect of temperature alone, resistance wire, introduced into the living brain, has been subjected to short pulses of electric current to produce, at various radii from the wire, temperature cycles approximating to those resulting from the absorption of the beam...The thermal conductivity of living rat brain was measured using a small thermistor, mounted on glass capillary and inserted into the brain. Experiments were performed with and without interruption of blood flow...Microthermocouples were used to measure the temperatures at the focus cetre under a variety of irradiation conditions. ..At higher intensities, a non-thermal involvement was found in tissue alteration, together with a time dependent increase of wave absorption. These effects, and various non-thermal mechanisms, are discusses and suggestions for future inquiry made..Frequencies of 1, 2, 3, 4, 5, and 6 MegaHertz were used. Most of the work was done at 3 MHz. Intensities of up to 4000 watts per cm squared and pulse width times down to 200 microseconds were used..


Title A study of the effect of ultrasound on the sympathico-adrenal system of workers.
Author Gerasimova EY.
Journal Gig Sanit
Volume
Year 1976
Abstract No abstract available.


Title A study of the effects of intense non-cavitating ultrasound on frog skin.
Author Coble AJ.
Journal Thesis(PhD): Univ of Illinois
Volume
Year 1973
Abstract The purpose of this study is to investigate the effects of intense ultrasound on the electrical parameters of biological membranes, particularly frog skin. The authors of similar studies at low ultrasonic intensities concluded that heating the tissue duplicated the effects of ultrasound completely, but evidence from central nervous system studies and studies utilizing cavitating ultrasound implicate a non-thermal causal agent for the propagation of ultrasound damage in biological tissue. In this study an attempt will be made to characterize the frog skin response to ultrasound within the framework currently used in explaining the membrane potential and short circuit current in frog skin. The extensive from skin literature is currently being reevaluated to include the new interpretations of data derived from the application of nonequilibrium thermodynamics, statistical mechanics, solid state physics and physical techniques such as NMR to an extent equaled only in the study of biological energy storage mechanisms. This circumstance does not facilitate the purpose of this study since the nature of ion transport in the skin is still open. The relation between the electrical parameters, membrane potential, short circuit current and membrane resistance, however, will be discussed in the same formalism, e.g. the electric equivalent circuit, as previously. The first section of this report reviews the basic physics of acoustic phenomena, i.e., a sound wave propagated in an ideal medium, followed by descriptions of mechanisms by which acoustic energy may be lost to the medium. The summary of the biological effects of ultrasound includes the rationale utilized in the choice of frog skin as the experimental membrane for this study. The experimental materials, equipment and techniques are described separately from the presentation of the rsults. The now classic representation of the membrane equivalent circuit is used in the discussion of the results.


Title A study of the heating capabilities of diagnostic ultrasound beams.
Author Duck FA, Starritt HC.
Journal Ultrasound Med Biol
Volume
Year 1994
Abstract A simple device for the experimental study of the heating capabilities of diagnostic ultrasound beams is described. Some results are reported that demonstrate the manner in which the device may be used to explore the heating potential of any particular commercial transducer, operating over the full range of output conditions. The heat generated in the base of a polyethylene container, filled with water, was measured using a fine-wire thermocouple, attached externally. The majority of measurements were carried out in beams generated by a curved array operating with a modern commercial scanner (Doppler, 2.5 MHz: imaging 3 MHz). A temperature rise in excess of 30?C was generated by a pulsed Doppler beam, when the water path and scanner controls were set appropriately. Comparable temperatures were measured at comparable intensities generated by Doppler beams of other scanners. Of the imaging beams studied, the greatest temperature rise observed was less than 2?C, when the highest frame rate and line density were selected. The greatest temperature rise in colour Doppler mode was 7.8?C. It was observed that the position of the fixed (nonelectronic) focus was significant in controlling the heating profile with depth, for scanned beams. As expected, there was a strong dependence of temperature rise on axial time-average intensity. A weak dependence on -6 dB beam area was observed over a range of beam area of about 7 to 70 mm2. A strong dependence on finite amplitude effects was observed, resulting from energy loss associated with acoustic shock propagation.


Title A study of the production of haemorrhagic injury and paraplegia in rat spinal cord by pulsed ultrasound of low megaHertz frequencies in the context of the safety for clinical usage.
Author Taylor KJ, Pond JB.
Journal Br J Radiol
Volume
Year 1972
Abstract The spinal cords of adult rats were irradiated with ultrasound using peak intensities of 25 or 50 W/cm(^2) at frequencies of 0.5 to 6 MHz. Delivery of energy was pulsed to avoid thermal effects. In most experiments, 10 ms pulses were separated by intervals of 100 ms. Such treatment resulted in paraplegia and/or gross haemorrhage into the cord. The appearance of haemorrhage was found to be a more consistent occurrence and this was used to compare the effects of ultrasound of varying parameters. Damaging ability was maximal at the lowest frequency employed (0.5 MHz) - it decreased with increasing frequency to 5 MHz, at which frequency neither paraplegia nor haemorrhage could be produced. The same method was used to investigate the effects of hypoxia when it was found that an arterial partial pressure of oxygen of 50 mm rendered the tissue more vulnerable to ultrasonic damage by a factor of 40 per cent. The effects of changing the duty cycle were similarly investigated. It was found that haemorrhage occurred whenever an accumulated dose-time had been received which time was characteristic of each frequency and independent of the changed time-averaged intensity resulting from the changed duty cycle. The results are discussed in terms of the known effects of ultrasound, indicating possible action mechanisms. Also considered are the possible relevance of the results to present and future applications of ultrasound in medicine.


Title A study of the relationship between mechanical and ultrasonic properties of dystrophic and normal skeletal muscle.
Author Hete B, Shung KK.
Journal Ultrasound Med Biol
Volume
Year 1995
Abstract A study has been made of the application of radio frequency (RF) ultrasound to the detection of muscular dystrophy by monitoring passively stretched skeletal muscle. The tests included detection of integrated backscatter changes in response to both static loading, in which muscle samples were stretched and allowed to relax, and stress relaxation. In both static and step strain loading conditions, the dystrophic muscle was found to exhibit little change in backscatter power while normal muscle responded to loading with significant changes in integrated backscatter. The backscatter response is compared with mechanical properties of the tissue (time constants and stress-strain constants). Both mechanical and ultrasonic time constants of relaxation are not significantly different between normal and dystrophic tissue, but stress-strain constants do differ. The difference in response of dystrophic and normal tissue appears to be due to a repression of motion of the constituent anatomy of dystrophic muscle which is responsible for the change of echogenicity with passive stretch.


Title A study of the specificity of ultrasound in concentrating an antimetabolite in mice.
Author Landgraff T.
Journal Thesis(MS): Catholic Univ of America
Volume
Year 1963
Abstract No abstract available.


Title A study of ultrasonic cavitation in biological tissues and its possible damaging effects.
Author Nagabhusan S.
Journal Thesis(PhD): Massachusetts Institute of Technology
Volume
Year 1973
Abstract Cavitation in tissues is believed to be one of the possible mechanisms of tissue destruction due to intense ultrasound. Scattering of a detecting beam of ultrasound at the focal zone of a focused field of ultrasound in prepared liquids was found to be a possible method of detecting cavitation in the medium. This method was, however, not adequately sensitive for detecting ultrasonic cavitation in tissues. Presence of subharmonic frequencies, essentially centered around the half-harmonic frequency, in the acoustic emission-spectra indicated occurrence of cavitation in tissues during their ultrasonic irradiation. The subharmonic power of the acoustic emission defined as the "Cavitation Power" was found to be a good quantitative criterion of ultrasonic cavitation in air-saturated water, blood plasma and the central nervous system (C.N.S.) of the cat. The cavitation power was found to be independent of pulse durations between 0.1 to 5 seconds but increased almost exponentially withthe irradiation power...The spatial distribution of cavitation intensity was correlated with the irradiation intensity. A mathematical models was developed to describe the stress process due to cavitation, as a random, zero-mean, Gaussian stress with the center frequency equal to the half-harmonic frequency of irradiating ultrasound. From the considerations of various possible mechanisms of mechanical failure cumulative damage due to random stress fatigue was found to be the most likely mechanism of the mechanical damage of structurally homogenous tissues like the C.N.S. of cats. The extent of damage computed from such a model of cavitation damage was compared with the empirical data. The predicted size of tissue damage was found to be smaller than the empirical values in contrast to the prediction of the thermal model of tissue damage which is quite accurate..


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