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.

Page 37 out of 330

Title An investigation of a spread energy method.for medical ultrasound systems. Part one: theory and investigation.
Author Takeuchi Y.
Journal Ultrasonics
Volume
Year 1979
Abstract A medical ultrasound device using a Golay code is proposed and investigated.theoretically. The code enables the spread energy method to be used to help.overcome the restraints of the parameters of resolution, peak power and.penetration.


Title An investigation of the effects of intense noncavitating ultrasound on selected enzymes.
Author Macleod RM.
Journal Thesis(PhD): Univ of Illinois
Volume
Year 1966
Abstract No abstract available.


Title An investigation of the flow dependence of temperature gradients near large vessels during steady state and transient tissue heating.
Author Kolios MC, Worthington AE, Holdsworth DW, Sherar MD, Hunt JW.
Journal Phys Med Biol
Volume
Year 1999
Abstract Temperature distributions measured during thermal therapy are a major prognostic factor of the efficacy and success of the procedure. Thermal models are used to predict the temperature elevation of tissues during heating. Theoretical work has shown that blood flow through large blood vessels plays an important role in determining temperature profiles of heated tissues. In this paper, an experimental investigation of the effects of large vessels on the temperature distribution of heated tissue is performed. The blood flow dependence of steady state and transient temperature profiles created by a cylindrical conductive heat source and an ultrasound transducer were examined using a fixed porcine kidney as a flow model. In the transient experiments, a 20 s pulse of hot water, 30 degrees C above ambient, heated the tissues. Temperatures were measured at selected locations in steps of 0.1 mm. It was observed that vessels could either heat or cool tissues depending on the orientation of the vascular geometry with respect to the heat source and that these effects are a function of flow rate through the vessels. Temperature gradients of 6 degrees C mm(-1) close to large vessels were routinely measured. Furthermore, it was observed that the temperature gradients caused by large vessels depended on whether the heating source was highly localized (i.e. a hot needle) or more distributed (i.e. external ultrasound). The gradients measured near large vessels during localized heating were between two and three times greater than the gradients measured during ultrasound heating at the same location, for comparable flows. Moreover, these gradients were more sensitive to flow variations for the localized needle heating. X-ray computed tomography data of the kidney vasculature were in good spatial agreement with the locations of all of the temperature variations measured. The three dimensional vessel path observed could account for the complex features of the temperature profiles. The flow dependences of the transient temperature profiles near large vessels during the pulsed experiments were consistent with the temperature distributions measured in the steady state experiments and provided unique insights into the process of convective heat transfer in tissues. Finally, it was shown that even for very short treatment times (3-20 s), large vessels had significant effects on the tissue temperature distributions.


Title An investigation of the mutagenic potential of pulsed ultrasound.
Author Barnett SB Bonin A Mitchell G Meher-Homji KM Baker RSU.
Journal Br J Radiol
Volume
Year 1982
Abstract The possible mutagenic effect of microsecond pulses of ultrasound was investigated using 3 MHz ultrasound at diagnostic dosages, and also under conditions of increased pulse repetition frequency and acoustic power output. The first part of the study involved 5 strains of Salmonella typhimurium bacteria in which mutagenicity and viability were assessed using the Ames test, while functional competence was evaluated from microscopic observations of motility. No changes were observed in survival, in the incidence of mutants, or in microbial motility following irradiation with ultrasound intensities of 4.5 W/cm2 at temperatures ranging from 37 degrees to 43 degrees C. In the second part of this study, the frequency of sister chromatid exchange (SCE) in Chinese hamster ovary (CHO) cells, treated with similar ultrasound dosages, remained unaltered when cells were irradiated at temperatures up to 41 degrees C. At 43 degrees C and above, cell division was arrested by hyperthermia, an effect unrelated to ultrasound.


Title An investigation of the use of transmission ultrasound to measure acoustic attenuation changes in thermal therapy.
Author Parmar N, Kolios MC.
Journal Med Biol Eng Comput
Volume
Year 2006
Abstract The potential of using a commercial ultrasound transmission imaging system to quantitatively monitor tissue attenuation changes after thermal therapy was investigated. The ultrasound transmission imaging system used, the AcoustoCam (Imperium Inc., MD) allows ultrasonic images to be captured using principles similar to that of a CCD-type camera that collects light. Ultrasound energy is focused onto a piezoelectric array by an acoustic lens system, creating a gray scale acoustic image. In this work, the pixel values from the acoustic images were assigned acoustic attenuation values by imaging polyacrylamide phantoms of varying known attenuation. After the calibration procedure, data from heated polyacrylamide/bovine serum albumin (BSA) based tissue-mimicking (TM) phantoms and porcine livers were acquired. Samples were heated in water at temperatures of 35, 45, 55, 65, and 75 degrees C for 1 h. Regions of interest were chosen in the images and acoustic attenuation values before and after heating were compared. An increase in ultrasound attenuation was found in phantoms containing BSA and in porcine liver. In the presence of BSA, attenuation in the TM phantom increased by a factor of 1.5, while without BSA no significant changes were observed. The attenuation of the porcine liver increased by up to a factor of 2.4, consistent with previously reported studies. The study demonstrates the feasibility of using a quantitative ultrasound transmission imaging system for monitoring thermal therapy.


Title An overview of ultrasound: Theory, measurement, medical applications, and biological effects.
Author Stewart HF, Stratmeyer ME.
Journal Rep U S Dept HHS
Volume
Year 1982
Abstract This document examines medical ultrasound in the United States. The first part of this report provides background information on characteristics and interaction of ultrasound with matter, measurement of ultrasound fields, and medical applications of ultrasound. The second part of this report emphasizes the potential biological effects of ultrasound in humans and experimental animals and the possible mechanisms for producing these effects. The potential risk to public health is evaluated and recommendations are made for the safe use of this modality. Recommendations are also made for further research to help clarify the potential biological risk associated with this rapidly growing modality.


Title An ultrasonic attenuation parameter for investigating the holding power of non-threaded fixation pins in canine femur (in vitro).
Author Dickens JR, Bray DE, Palmer RH.
Journal Ultrasonics
Volume
Year 1994
Abstract External skeletal fixation (ESF) is a widely used method of fracture treatment but often produces medical complications in the patient. The most serious complication, pin loosening, may lead to pain, poor limb usage, pin tract infection, fracture instability and non-union. Studies of pin loosening are based primarily on pin extraction force measurements, which are destructive in nature. This paper will introduce a method for estimating the extraction force of non-threaded fixation pins based on three related parameters obtained from an ultrasonic pulse introduced into the pin. The ultrasonic test takes advantage of the inherent acoustic absorption across the bone-pin interface. A strong interlock between bone and pin results in increased transmission of ultrasound across the bone-pin interface. This is manifested as heavy signal attenuation, whereas a poor interlock results in considerably less attenuation. The parameters proposed in this paper are intended to quantify attenuation resulting from bone-pin interface interactions. One probe-parameter combination in particular showed considerable sensitivity to the conditions of the bone-pin interface (R2 = 0.79). Further research is suggested and may lead to an operational process for non-invasively evaluating pin security.


Title An ultrasonic dosage study: Functional endpoint.
Author Dunn F, Fry WJ.(Kelly E, ed.)
Journal Ultrasound Biol Med
Volume
Year 1957
Abstract No abstract available.


Title An ultrasonic method for outlining the cerebral ventricles.
Author Hueter TF, Bolt RH.
Journal J Acoust Soc Am
Volume
Year 1951
Abstract This paper discusses the general physical problems underlying the portrayal of ventricular geometry by ultrasonic techniques. This offers another means somewhat analogous to x-ray ventriculography for the detection of brain tumors. Progress is reported on studies of ultrasound propagation properties in the tissues involved. Preliminary conclusions on safety thresholds of pain and damage are discussed. The most promising method to date is straight-through transcranial transmission (not echo ranging) utilizing changes in attenuation owing to different amounts of ventricle along the transmission path. The optimum compromise frequency appears to be about 2.5 megacycles for which frequency results are reported on a studies of receiver sensitivity and dynamic range, resolution shielding transducers and presentation problems.


Title An ultrasound image conversion system for non destructive testing biological research.
Author Unknown.
Journal Rep James Electronics Inc
Volume
Year Unknown
Abstract No abstract available.


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