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 Local hyperthermia by ultrasound for cancer therapy.
Author Lele PP.
Journal Book Chapter
Volume
Year 1985
Abstract No abstract available.


Title Localized harmonic motion imaging: Theory, simulations and experiments.
Author Konofagou EE, Hynynen K.
Journal Ultrasound Med Biol
Volume
Year 2003
Abstract Several techniques have been developed in an effort to estimate mechanical properties of tissues. These techniques typically estimate static or harmonic motion resulting from an externally or internally applied mechanical stimulus. In this paper, we discuss the advantages of utilizing a new technique that performs radiofrequency (RF) signal tracking to estimate the localized oscillatory motion resulting from the harmonic radiation force produced by two focused ultrasound (US) transducer elements with overlapping beams oscillating at distinct frequencies. Finite-element and Monte-Carlo simulations were performed to characterize the range of oscillatory displacements produced by a harmonic radiation force. In the experimental verification, three transducers were used: two single-element focused transducers and one lead zirconate-titanate (PZT) composite 16-element probe. Four agar gels were utilized to determine the effect of stiffness on the motion amplitude. Estimates of the displacement relative to the initial position (i.e., at the onset of the application of the radiation force) were obtained during the application of the radiation force that oscillated at frequencies ranging between 200 Hz and 800 Hz. In the simulations, the estimated oscillatory displacement spanned from −800 to 600 m and the frequencies of excitation could easily be estimated from the temporal variation of the displacement. In addition, a frequency upshift (on the order of tens of Hz) was estimated with stiffness increase. Furthermore, an exponential decrease of the displacement amplitude with stiffness was observed at all frequencies investigated. An M-mode version to depict both the spatial and temporal variations of the locally induced displacement was used. In experiments with gels of different stiffness, the resulting amplitude of the harmonic displacement estimated oscillated at the same frequencies and ranged from −300 to 250 m. An exponential decrease of the displacement amplitude with the gel stiffness was also observed. In tissue experiments, the results showed that the method is feasible in tissues and that focused US surgery (FUS) ablation can be detected. These preliminary results demonstrate the feasibility of imaging localized harmonic motion as induced by an oscillatory US radiation force. Due to the highly localized and harmonic nature of the estimated response, this technique may be proven to be highly suitable for simple and accurate estimation of the elastic modulus variation in tissues due to disease.


Title Localized tissue destruction by high-intensity focused ultrasound.
Author Linke CA, Carstensen EL, Frizzell LA, Elbadawi A, Fridd CW.
Journal Arch Surg
Volume
Year 1973
Abstract Rat liver and kidney were exposed to focused ultrasound of 312 w/sq cm (rat) and 900 w/sq cm (rabbit) by direct application of the ultrasound transducer to the surface of the organ exposed. A discrete, narrow, cylindrical zone of tissue necrosis to a depth of approximately 2 cm could be induced in the tissue exposed to the ultrasound. Lesions thus produced were well tolerated and tended to be resorbed over a period of several weeks without evidence of hemorrhage, infection, or adverse systemic effect. In rabbit liver, a linear zone of necrosis was induced by linear movement of the transducer. Development of the use of local high-intensity ultrasound may broaden the clinical scope of thermal destruction of cancer beyond that accomplished by electrocoagulation or cryosurgery.


Title Locally adaptive Nakagami-based ultrasound similarity measures.
Author Wachinger C, Klein T, Navab N.
Journal Ultrasonics
Volume
Year 2012
Abstract The derivation of statistically optimal similarity measures for intensity-based registration is possible by modeling the underlying image noise distribution. The parameters of these distributions are, however, commonly set heuristically across all images. In this article, we show that the estimation of the parameters on the present images largely improves the registration, which is a consequence of the more accurate characterization of the image noise. More precisely, instead of having constant parameters over the entire image domain, we estimate them on patches, leading to a local adaptation of the similarity measure. While this basic idea of creating locally adaptive metrics is interesting for various fields of application, we present the derivation for ultrasound imaging. The domain of ultrasound is particularly appealing for this approach, due to the inherent contamination with speckle noise. Furthermore, there exist detailed analyses of suitable noise distributions in the literature. We present experiments for applying a bivariate Nakagami distribution that facilitates modeling of several scattering scenarios prominent in medical ultrasound. Depending on the number of scatterers per resolution cell and the presence of coherent structures, different Nakagami parameters are required to obtain a valid approximation of the intensity statistics and to account for distributional locality. Our registration results on radio-frequency ultrasound data confirm the theoretical necessity for a spatial adaptation of similarity metrics.


Title Looking into teeth with ultrasound.
Author Lees S, Barber FE.
Journal Science
Volume
Year 1968
Abstract Ultrasound is readily conducted across a boundary when the specific acoustic impedances of the two media are about equal. The specific acoustic impedance of dental enamel is about that of aluminum. A longitudinal sonic pulse, less than 250 nanoseconds in duration, conducted to the tooth through an aluminum rod, has positively detected the enamel-dentin junction as well as the dentin-pulp interface.


Title Low contrast detectability and contrast/detail analysis in medical ultrasound.
Author Smith SW, Wagner RF, Sandrik JM, Lopez H.
Journal IEEE Trans Sonics Ultrason
Volume
Year 1983
Abstract The first- and second-order statistics of envelope detected ultrasound (US) B-mode images for the case of a scattering phantom with many scatterers per resolution cell have been previously derived. These characteristics are integrated over the region of a simulated focal (disk) lesion and the signal-to-noise ratio (SNR) for lesion detectability is obtained. This SNR requires the average number of independent speckle cells over the lesion area (analogous to the number of x-ray photons over the lesion area in incoherent light or x-ray imaging). This number is obtained from our autocorrelation analysis (second-order statistics). By setting the SNR expression equal to the threshold value SNR(T) required to detect a lesion in the presence of speckle noise, the dependence of lesion contrast on lesion diameter at threshold is found, i.e., the contrast/detail function. This is a simple inverse relation for ideal observers of US B-scans. It is also found that the contrast-detail results for envelope detection in diagnostic ultrasound are almost identical with the results for square law detection (the usual laser case) with the latter serving as an upper limit for performance in lesion detection. Finally, the results of human observer performance using a contrast/detail phantom are compared with the predictions for optimal or ideal performance. The results are comparable with results for photon imaging systems, with values of the SNR at threshold in the neighborhood of 2-3.


Title Low intensity ultrasonic effects on yeast hexokinase.
Author Braginskaya FI, Zaitzeva EA, Zorina OM, Poltorak OM, Chukrai ES, Dunn F.
Journal Radiat Environ Biophys
Volume
Year 1990
Abstract The kinetics of yeast hexokinase activity exposed to 1 MHz ultrasound of therapeutic intensities 0.1-1.5 W/cm2 was studied using traditional physico-chemical methods and by the thermoinactivation approach. Analysis of the kinetic curves and the kinetic parameters, obtained by two independent methods, suggested specific perturbation processes provoked by the ultrasonic waves, viz., the mechanical breakdown of the contact site between monomer units and the subsequent sonochemical modification of the active enzyme site. Low intensity ultrasound also caused the destabilization of the molecular structure of hexokinase as revealed by the apparent thermolability of the sonicated enzyme.


Title Low-frequency sonophoresis: current status and future prospects.
Author Ogura M, Paliwal S, Mitragotri S.
Journal Adv Drug Deliv Rev
Volume
Year 2008
Abstract Application of ultrasound enhances skin permeability to drugs, a phenomenon referred to as sonophoresis. Significant strides have been made in sonophoresis research in recent years, especially under low-frequency conditions (20 kHz


Title Low-frequency ultrasound induces nonenzymatic thrombolysis in vitro.
Author Nedelmann M,Eicke M,Lierke EG,Heimann A,Kempski O,Hopf HC.
Journal J Ultrasound Med
Volume
Year 2002
Abstract To evaluate whether ultrasound, applied over a distance of several centimeters and in the absence of thrombolytic agents, may have a thrombolytic effect on blood clots. Methods. Lowfrequency (20 kHz) continuous wave ultrasound at different intensity levels (0.15–1.2 W/cm2) and exposure times (5, 10, and 20 minutes) was assessed for its potential to induce thrombolysis of fresh human blood clots. The ultrasound effect was also studied in combination with recombinant tissue-type plasminogen activator–mediated thrombolysis. Experiments were carried out in a flow model in degassed sodium phosphate buffer at 37°C at a distance of 3 cm from the ultrasonic probe to the blood clots. Regardless of ultrasound exposure times, blood clots in all experimental groups and the control group were left in the flow system for 20 minutes. Results. The use of ultrasound alone showed a significant thrombolytic effect compared with the control group, with a statistically significant effect at 0.15 W/cm2 and exposure of 10 minutes (P = .02). There was a clear correlation between the extent of weight loss and the chosen intensity level and exposure time. Complete disruption in 8 of 10 blood clots occurred at 1.2 W/cm2 within 10 min. Addition of ultrasound to recombinant tissue-type plasminogen activator–mediated thrombolysis significantly enhanced thrombolysis compared with application of recombinant tissue-type plasminogen activator or ultrasound alone (P = .0001), with the results pointing toward a purely additive, nonsynergistic effect of the 2 treatment modalities. Lysis was more effective in fresh thrombi. Conclusions. The use of low-frequency ultrasound alone, without addition of a thrombolytic drug, has the potential to induce thrombolysis over a distance. Combination of ultrasound with recombinant tissue-type plasminogen activator is superior to either treatment alone. Ultrasound is a promising tool for developing an alternative or additional treatment modality for acute cerebral vessel occlusion. Key Words: ultrasound • thrombolysis • fibrinolysis • tissue-type plasminogen activator • stroke


Title Low-intensity pulsed ultrasound enhances early healing of medial collateral ligament injuries in rats.
Author Takakura Y, Matsui N, Yoshiya S, Fujioka H, Muratsu H, Tsunoda M, Kurosaka M.
Journal J Ultrasound Med
Volume
Year 2002
Abstract OBJECTIVE: To investigate the effect of low-intensity pulsed ultrasound exposure on the healing of injured medial collateral ligaments. METHODS: Thirteen male Sprague Dawley rats were used in the study. After surgical transection of the bilateral medial collateral ligaments, the ligament of 1 knee received low-intensity pulsed ultrasound exposure (30 mW/cm2 for 20 minutes daily), whereas no ultrasound was applied to the contralateral knee (control side). Eight rats were killed at 12 days after surgery, and 5 rats were killed at 21 days. The bilateral knees of 5 rats were used for mechanical testing at each of the 2 periods, and 12-day specimens of the remaining 3 rats were prepared for the electron microscopic examination. The knees of 5 additional rats were used to obtain mechanical data of the normal uninjured medial collateral ligament. RESULTS: On the 12th day, the low-intensity pulsed ultrasound-treated side exhibited significantly superior mechanical properties when compared with the control side in ultimate load, stiffness, and energy absorption (P < .05). However, the treatment did not afford any mechanical advantage when tested on the 21st day. The mean diameter of the fibril was significantly larger on the treatment side than on the control side (P < .05). CONCLUSIONS: Low-intensity pulsed ultrasound exposure is effective for enhancing the early healing of medial collateral ligament injuries.


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