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BRL Abstracts Database |
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Your search for ultrasound produced 3296 results. Page 185 out of 330
| Title |
Non-thermal effects of 2 MHz ultrasound on the growth and cytology of Vicia faba roots. |
| Author |
Gregory WD, Miller MW, Carstensen EL, Cataldo FL, Reddy MM. |
| Journal |
Br J Radiol |
| Volume |
|
| Year |
1974 |
| Abstract |
The effect of 2 MHz ultrasound at intensity levels from 1 to 20 W/cm2 on growth rate, lateral root formation, mitotic index and chromosome morphology was studied. The ultrasound produced an immediate reduction in growth rate on the first post-exposure day followed by recovery to control value after ten days. Ultrasound reduced lateral root formation and mitotic index. Intensity and time dependent relations were found for growth rate reduction and lateral root formation. No ?classical? chromosome aberrations were found but chromosomal anomalies - bridged prophases and metaphases and agglomerated metaphases - of another nature were observed after sonication: these anomalies were quantitated into a damage index. |
| Title |
Nonablative minimally invasive thermal therapies in the treatment of symptomatic benign prostatic hyperplasia. |
| Author |
d'Ancona FC. |
| Journal |
Curr Opin Urol |
| Volume |
|
| Year |
2008 |
| Abstract |
PURPOSE OF REVIEW: As all new treatment modalities nonablative thermal therapy for minimal invasive treatment of benign prostatic hyperplasia should be critically analyzed. This review discusses the literature to identify the merits of these so-called minimally invasive treatments and the place they should take in the armamentarium of benign prostatic hyperplasia therapy options. RECENT FINDINGS: In this review we analyze the different techniques and clinical studies of hot water induced thermotherapy, transurethral microwave thermotherapy, transurethral needle ablation and high intensity focused ultrasound. The high intensity focused ultrasound treatment is noninvasive, but due to the poor clinical results in benign prostatic hyperplasia and its need for anesthesia, this therapeutic option shifted towards the selective ablation of prostate cancer. The transurethral needle ablation treatment can be performed in an outpatient setting although most centers do not. The treatment is not suitable for the bigger prostates and therefore narrows its indication. Water induced thermotherapy is a very promising therapy, although without comparative studies a justified positioning remains difficult. SUMMARY: Of all nonablative thermal therapies, transurethral microwave thermotherapy is the best documented and with several randomized studies comparing transurethral microwave thermotherapy to surgical treatments of the prostate, this therapy definitively found its place as a serious alternative to the ablative surgical treatment options. |
| Title |
Nondestructive subharmonic imaging. |
| Author |
Chomas J, Dayton P, May D, Ferrara K. |
| Journal |
IEEE Trans UFFC |
| Volume |
|
| Year |
2002 |
| Abstract |
Ultrasound contrast agent microbubbles are intravascular agents that can be used to estimate blood perfusion. Blood perfusion may be estimated by destroying the bubbles in a vascular bed and observing the refresh of contrast agents back into the vascular bed. Contrast agents can be readily destroyed by traditional imaging techniques. The design of a nondestructive imaging technique is necessary for the accurate quantification of contrast agent refresh. In this work, subharmonic imaging is investigated as a method for nondestructive imaging with the contrast agent microbubble MP1950 (Mallinckrodt, Inc., St. Louis, MO). Optical observation during insonation, in conjunction with a modified Rayleigh-Plesset (R-P) analysis, provides insight into the mechanisms of and parameters required for subharmonic frequency generation. Subharmonic imaging with a transmission frequency that is the same as the resonant frequency of the bubble is shown to require a minimum pressure of insonation that is greater than the experimentally-observed bubble destruction threshold. Subharmonic imaging with a transmission frequency that is twice the resonant frequency of the bubble produces a subharmonic frequency response while minimizing bubble instability. Optimization is performed using optical experimental analysis and R-P analysis. |
| Title |
Noninvasive determination of carotid artery operability by Doppler ultrasound. |
| Author |
Barnes RW, Rittgers SE, Thornhill B, Nix L, Putney W. |
| Journal |
Va Med |
| Volume |
|
| Year |
1979 |
| Abstract |
Indirect periorbital screening techniques may detect obstruction of the extracranial internal carotid artery, but they do not distinguish operable stenosis from inoperable occlusion. In an attempt to overcome this limitation, direct interrogation of carotid artery flow velocity by Doppler ultrasound was added to periorbital screening of 97 arteries in 53 patients. Analysis of results suggests that this assessment can improve diagnostic accuracy and distinguish stenosis from occlusion of the internal carotid arteries in stroke-prone patients. |
| Title |
Noninvasive determination of in situ heating rate using kHz acoustic emissions and focused ultrasound. |
| Author |
Anand A, Kaczkowski PJ. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
2009 |
| Abstract |
For high-intensity focused ultrasound (HIFU) to be widely applicable in the clinic, robust methods of treatment planning, guidance and delivery need to be developed. These technologies would greatly benefit if patient specific tissue parameters could be provided as inputs so that the treatment planning and monitoring schemes are customized and tailored on a case by case basis. A noninvasive method of estimating the local in situ acoustic heating rate using the heat transfer equation (HTE) and applying novel signal processing techniques is presented in this article. The heating rate is obtained by experimentally measuring the time required to raise the temperature of the therapeutic focus from a baseline temperature to boiling (here assumed to be 100°C for aqueous media) and then solving the heat transfer equation iteratively to find the heating rate that results in the onset of boiling. The onset of boiling is noninvasively detected by measuring the time instant of onset of acoustic emissions in the audible frequency range due to violent collapse of bubbles. In vitro experiments performed in a tissue mimicking alginate phantom and excised turkey breast muscle tissue demonstrate that the noninvasive estimates of heating rate are in good agreement with those obtained independently using established methods. The results show potential for the applicability of these techniques in therapy planning and monitoring for therapeutic dose optimization using real-time acoustic feedback. (E-mail: ajay.anand@philips.com)© 2009 World Federation for Ultrasound in Medicine and Biology.
Key Words:Thermal ablation,HIFU,FUS,Ultrasound treatment monitoring,Tissue characterization, Therapy planning. |
| Title |
Noninvasive diagnosis of nonalcoholic fatty liver disease and quantification of liver fat using a new quantitative ultrasound technique |
| Author |
Lin SC, Heba E, Wolfson T, Ang B, Gamst A, Han A, Erdman JW Jr., O'Brien WD Jr., Andre MP, Sirlin CB, Loomba R |
| Journal |
Clin Gastroenterol Hepatol |
| Volume |
|
| Year |
2015 |
| Abstract |
BACKGROUND & AIMS: Liver biopsy analysis is the standard method used to diagnose nonalcoholic fatty liver disease (NAFLD). Advanced magnetic resonance imaging is a noninvasive procedure that can accurately diagnose and quantify steatosis, but is expensive. Conventional ultrasound is more accessible but identifies steatosis with low levels of sensitivity, specificity, and quantitative accuracy, and results vary among technicians. A new quantitative ultrasound (QUS) technique can identify steatosis in animal models. We assessed the accuracy of QUS in the diagnosis and quantification of hepatic steatosis, comparing findings with those from magnetic resonance imaging proton density fat fraction (MRI-PDFF) analysis as a reference.
METHODS: We performed a prospective, cross-sectional analysis of a cohort of adults (N [ 204) with NAFLD (MRI-PDFF, ‡5%) and without NAFLD (controls). Subjects underwent MRI-PDFF and QUS analyses of the liver on the same day at the University of California, San Diego, from February 2012 through March 2014. QUS parameters and backscatter coefficient (BSC) values were calculated. Patients were assigned randomly to training (n [ 102; mean age, 51 – 17 y; mean
body mass index, 31 – 7 kg/m2) and validation (n[102; mean age, 49 – 17 y; body mass index, 30 – 6 kg/m2) groups; 69% of patients in each group had NAFLD.
RESULTS: BSC (range, 0.00005–0.25 1/cm-sr) correlated with MRI-PDFF (Spearman r [ 0.80; P < .0001). In the training group, the BSC analysis identified patients with NAFLD with an area under the curve value of 0.98 (95% confidence interval, 0.95–1.00; P < .0001). The optimal BSC cut-off value identified patients with NAFLD in the training and validation groups with 93% and 87% sensitivity, 97% and 91% specificity, 86% and 76% negative predictive values, and 99% and 95% positive predictive values, respectively.
CONCLUSIONS: QUS measurements of BSC can accurately diagnose and quantify hepatic steatosis, based on a cross-sectional analysis that used MRI-PDFF as the reference. With further validation, QUS could be an inexpensive, widely available method to screen the general or at-risk population for NAFLD. |
| Title |
Noninvasive estimation of tissue temperature response to heating fields using diagnostic ultrasound. |
| Author |
Seip R, Ebbini ES. |
| Journal |
IEEE Trans Biomed Eng |
| Volume |
|
| Year |
1995 |
| Abstract |
A noninvasive technique for monitoring tissue temperature changes due to heating fields using diagnostic ultrasound is described in this paper. The approach is based on the discrete scattering model used in the tissue characterization literature and the observation that most biological tissues are semi-regular scattering lattices. It has been demonstrated by many researchers and verified by us that the spectrum of the backscattered radio frequency (RF) signal collected with a diagnostic ultrasound transducer from a semi-regular tissue sample exhibits harmonically related resonances at frequencies determined by the average spacing between scatterers along a segment of the A-line. It is shown theoretically and demonstrated experimentally (for phantom, in vitro, and in vivo media) that these resonances change with changes in the tissue temperature within the processing window. In fact, changes in the resonances (delta f) are linearly proportional to changes in the temperature (delta T), with the proportionality constant being determined by changes in the speed of sound with temperature and the linear coefficient of thermal expansion of the tissue. Autoregressive (AR) model-based methods aid in the estimation of delta f. It should be emphasized that this new technique is not a time of flight velocimetric one, so it represents a departure from previously used ultrasonic methods for tissue temperature estimation. |
| Title |
Noninvasive estimation of tissue temperature via high-resolution spectral analysis techniques. |
| Author |
Amini AN, Ebbini ES, Georgiou TT. |
| Journal |
IEEE Trans Biomed Eng |
| Volume |
|
| Year |
2005 |
| Abstract |
We address the noninvasive temperature estimation from pulse-echo radio frequency signals from standard diagnostic ultrasound imaging equipment. In particular, we investigate the use of a high-resolution spectral estimation method for tracking frequency shifts at two or more harmonic frequencies associated with temperature change. The new approach, employing generalized second-order statistics, is shown to produce superior frequency shift estimates when compared to conventional high-resolution spectral estimation methods Seip and Ebbini (1995). Furthermore, temperature estimates from the new algorithm are compared with results from the more commonly used echo shift method described in Simon et al. (1998). |
| Title |
Noninvasive in vivo clot dissolutio without a thrombolytic drug: recanalization of thrombosed iliofemoral arteries by transcutaneous ultrasound combined with intravenous infusion of microbubbles. |
| Author |
Birnbaum Y, Luo H, Nagai T, Fishbein MC, PetersonTM, Li S, Kricsfeld D, Porter TR, Siegel RJ. |
| Journal |
Circulation |
| Volume |
|
| Year |
1998 |
| Abstract |
BACKGROUND: Previous in vivo studies have shown that microbubbles not only enhance the effectiveness of thrombolytic agents in the presence of ultrasound but may also augment clot.dissolution without thrombolytic drugs. METHODS AND RESULTS: The objective of this study was to examine the efficacy of arterial clot disruption by a noninvasive, nonlytic approach with.intravenous administration of perfluorocarbon-exposed sonicated dextrose albumin (PESDA) and transcutaneous delivery of ultrasound alone. Pairs of iliofemoral arteries in 10 rabbits were.randomized to receive transcutaneous ultrasound treatment or no ultrasound treatment after an acute artery thrombotic occlusion and intravenous PESDA infusion. Five arteries from 3 additional rabbits.served as controls (ultrasound alone). All 10 iliofemoral arteries treated with PESDA + ultrasound were recanalized by angiography after ultrasound treatment. None of the 10 contralateral arteries.treated with PESDA alone and none of the 5 arteries treated with ultrasound alone were patent after 1 hour. D-Dimer levels did not change after intravenous PESDA + ultrasound-mediated reperfusion..CONCLUSIONS: In vivo arterial clot dissolution can be achieved with intravenous microbubbles and transcutaneous ultrasound delivery alone. This technique has potential for clinical application in.patients with acute arterial and venous thrombotic occlusions. |
| Title |
Noninvasive laser-induced photoacoustic tomography for structural and functional in vivo imaging of the brain. |
| Author |
Wang X, Pang Y, Ku G, Xie X, Stoica G, Wang LV. |
| Journal |
Nat Biotechnol |
| Volume |
|
| Year |
2003 |
| Abstract |
Imaging techniques based on optical contrast analysis can be used to visualize dynamic and functional properties of the nervous system via optical signals resulting from changes in blood volume, oxygen consumption and cellular swelling associated with brain physiology and pathology. Here we report in vivo noninvasive transdermal and transcranial imaging of the structure and function of rat brains by means of laser-induced photoacoustic tomography (PAT). The advantage of PAT over pure optical imaging is that it retains intrinsic optical contrast characteristics while taking advantage of the diffraction-limited high spatial resolution of ultrasound. We accurately mapped rat brain structures, with and without lesions, and functional cerebral hemodynamic changes in cortical blood vessels around the whisker-barrel cortex in response to whisker stimulation. We also imaged hyperoxia- and hypoxia-induced cerebral hemodynamic changes. This neuroimaging modality holds promise for applications in neurophysiology, neuropathology and neurotherapy. |
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