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BRL Abstracts Database |
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Your search for ultrasound produced 3296 results. Page 59 out of 330
| Title |
Cardiopulmonary function in rats with lung hemorrhage induced by pulsed ultrasound exposure. |
| Author |
Kramer JM, Waldrop TG, Frizzell LA, Zachary JF, O'Brien WD Jr. |
| Journal |
J Ultrasound Med |
| Volume |
|
| Year |
2001 |
| Abstract |
OBJECTIVE: To assess cardiopulmonary function in rats exposed to pulsed ultrasound using superthreshold exposure conditions known to produce significant lung hemorrhage.
METHODS: In 1 group of 9 anesthetized Sprague-Dawley rats, 5 foci of ultrasound-induced hemorrhage were produced in the left lung of each rat. In a second group of 6 rats, 5 foci of ultrasound-induced hemorrhage were produced in the left and right lungs of each rat. Each lesion was induced using superthreshold pulsed ultrasound exposure conditions (3.1-MHz center frequency, 1.7-kHz pulse repetition frequency, 1.3-micro-second pulse duration, 60-second exposure duration, 39-MPa in situ peak compressional pressure, and 17-MPa in situ peak rarefactional pressure). After exposure, the lungs were fixed in formalin and assessed histologically. The total lesion volume was calculated for each lesion in each lung lobe. Measurements of cardiopulmonary function included assessment of pulsatile arterial pressure, heart rate, end-tidal carbon dioxide, respiratory rate, and arterial blood gases (PCO2 and PO2). Functional data were quantified before (baseline) and 30 minutes after exposure to ultrasound. RESULTS: In the 9 rats that had lesions in only the left lung, the mean (SEM) lesion volume was 97 (13) mm3 and represented about 3.4% of the total lung volume. In the 6 rats that had lesions in both the left and right lungs, the left, right, and total mean lesion volumes, respectively, were 102 (16), 114 (11), and 216 (18) mm3 and represented about 3.7%, 4.2%, and 7.9% of the total lung volume. There were no statistically significant differences in cardiopulmonary measurements between baseline values and values obtained after exposure to ultrasound in the 9 rats exposed on the left lung only. The 6 rats exposed bilaterally had statistically significant differences in arterial pressure (134 +/- 4 versus 113 +/- 9 mm Hg; P= .047) and arterial PO2 (70 +/- 5 versus 58 +/- 4 mm Hg; P = .024) between baseline values and values obtained after exposure to ultrasound.
CONCLUSIONS: The severity of ultrasound-induced lesions produced in 1 lung did not affect measurements of cardiopulmonary function because of the functional respiratory reserve in the unexposed lung. However, when both the left and right lungs had ultrasound-induced lesions, the functional respiratory reserve was decreased to a point at which rats were unable to maintain systemic arterial pressure or resting levels of arterial PO2. |
| Title |
Carotid plaque typing by multiple-parameter ultrasonic tissue characterization. |
| Author |
Noritomi T, Sigel B, Swami V, Justin J, Gahtan V, Chen X, Feleppa EJ, Roberts AB, Shirouzu K. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1997 |
| Abstract |
We evaluated the ability of ultrasonic tissue characterization (UTC), based on backscattered echo signals, to distinguish among the components of advanced carotid plaques. We performed spectral analysis of echo signals acquired from human carotid endarterectomy specimens in vitro to calculate three parameters of the calibrated power spectrum: slope, intercept and total power for fibrous, lipid pool and thrombus constituents of plaque. Plaque constituents were identified histologically. We evaluated classification efficacy by discriminant function analysis. Slope and intercept parameters alone provided correct classification in 92.5%, 57.6% and 72.4% of fibrous, lipid pool and thrombus plaque components, respectively. Slope, intercept and total power used in combination improved classification of the three tissue types to 93.0%, 69.7% and 81.0%. The overall proportion of correctly classified tissue regions increased from 84.5% to 88.0% by the combined use of the three parameters. The improvement in classification that occurred when we included total power as a third parameter suggests that ultrasound plaque components may not consist solely of small, randomly distributed isotropic scatterers. Our ability to identify plaque thrombi provides motivation for future studies of parameter-based imaging methods for identifying such plaque that presents an increased risk of embolic neurologic ischemic events. |
| Title |
Cataract production by ultrasound. |
| Author |
Torchia RT, Purnell EW, Sokollu A. |
| Journal |
Am J Ophthalmol |
| Volume |
|
| Year |
1967 |
| Abstract |
That the lens is susceptible to injury by ultrasound has been known since early work of Zeiss, Donn, Moore, and Lavine. Recently, in view of the proposed use of high energy ultrasound for retinal detachment repair, tumor destruction and cyclodiathermy, it appeared advisable to investigate this cataractogenic effect quantitatively. We were interested in three parameters of cataract production: energy density, pulse duration and pulse sound. |
| Title |
Catheter-based ultrasound devices and MR thermal monitoring for conformal prostate thermal therapy |
| Author |
Diederich CJ, Nau WH, Kinsey A, Ross T, Wootton J, Juang T, Butts-Pauly K, Rieke V, Chen J, Bouley DM, Sommer G. |
| Journal |
Conf Proc IEEE Eng Med Biol Soc |
| Volume |
|
| Year |
2008 |
| Abstract |
Catheter-based ultrasound applicators have been developed for delivering hyperthermia or high-temperature thermal ablation of cancer and benign disease of the prostate. These devices allow for control of heating along the length and angular expanse during therapy delivery. Four types of transurethral applicators were devised for thermal treatment of prostate combined with MR thermal monitoring: sectored tubular transducer devices with directional heating patterns and rotation; planar and curvilinear devices with narrow heating patterns and rotation; and multi-sectored tubular devices capable of dynamic angular control without applicator movement. Interstitial devices (2.4 mm OD) have been developed for percutaneous implantation with directional or dynamic angular control. In vivo experiments in canine prostate under MR temperature imaging were used to evaluate these devices and develop treatment delivery strategies. MR thermal imaging was used to monitor temperature and thermal dose in multiple slices through the target volume. Multi-sectored transurethral applicators can dynamically control the angular heating profile and target large regions of the gland in short treatment times without applicator manipulation. The sectored tubular, planar, and curvilinear transurethral devices produce directional coagulation zones, extending 15-20 mm radial distance to the outer prostate capsule. Sequential rotation under motor control and modulated dwell time can be used to tightly conform thermal ablation to selected regions. Interstitial implants with directional devices can be used to effectively ablate targeted regions of the gland while protecting the rectum. The MR derived 52 degrees C and lethal thermal dose contours (t43=240 min) effectively defined the extent of thermal damage and provided a means for real-time control of the applicators. Catheter-based ultrasound devices, combined with MR thermal monitoring, can produce relatively fast (5-40 min) and precise thermal ablation of prostate. |
| Title |
Catheter-delivered high intensity, low.frequency ultrasound induces.vasodilation in vivo. |
| Author |
Steffen W, Cumberland D, Gaines P, Luo H, Nita H, Maurer G, Fishbein MC, Siegel RJ. |
| Journal |
Eur Heart J |
| Volume |
|
| Year |
1994 |
| Abstract |
This study investigated the effect of intravascular high intensity, low frequency catheter-delivered ultrasound on vasomotor behaviour in vivo. Catheter-delivered therapeutic ultrasound induces endothelium-independent vasodilation in vitro. To study this effect in vivo we analysed the angiograms of canine coronaries and human femoropopliteal arteries before and after ultrasound exposure. Vasomotor behaviour was studied using a computer edge detection program. We analysed the angiograms of: (1) eight canine left coronary arteries before and after ultrasound; (2) eight canine left coronaries only subjected to serial angiograms, and three canine left coronary arteries of two dogs after passing the unactivated ultrasound probe down the coronary artery infusing saline at a rate of 10-20 ml.min-1, which served as controls, and (3) eight angiographically normal human arterial sites proximal to occlusions in eight femoropopliteal arteries of patients undergoing ultrasound.angioplasty for peripheral vascular disease. Vessel diameter of canine coronaries after ultrasound exposure increased from 2.3 +/- 0.3 mm to 2.8 +/- 0.3 mm (21 +/- 2.3%) (P < 0.01). There was no change in vascular diameter in controls after multiple angiograms (2.4 +/- 0.3 mm vs 2.5 +/- 0.2 mm (4.2 +/- 0.2%) (P = ns). Average vessel diameter after passage of the unactivated probe with saline infusion.decreased in the left anterior descending coronary artery from 3.66 mm to 3.13 mm, and in the left circumflex coronary artery from 2.88 mm to 2.62 mm. Vessel diameter in human femoropopliteal arteries increased from 3.2 +/- 0.2 mm to 3.6 +/- 0.5 mm or by 14.3 +/- 2.9% respectively (P < 0.01) after exposure to ultrasound energy. .. |
| Title |
Catheter-delivered ultrasound potentiates in vitro thrombolysis. |
| Author |
Shlansky-Goldberg RD, Cines DB, Sehgal CM. |
| Journal |
J Vasc Interven Radiol |
| Volume |
|
| Year |
1996 |
| Abstract |
PURPOSE:
To develop a catheter-directed method to enhance urokinase- mediated thrombolysis with use of ultrasound.
MATERIALS AND METHODS:
A prototype catheter was constructed by using a 9-F piezoelectric crystal capable of producing 640-kHz pulsed ultrasound energy. Clots formed in vitro from whole blood were trace-labeled with iodine-125 fibrinogen, and the release of radiolabeled fibrin degradation products was measured in the presence of urokinase, ultrasound, or a combination of urokinase and ultrasound.
RESULTS:
By 30 minutes, clot lysis was more complete with urokinase plus ultrasound (78.7% +/- 5.3 [mean +/- SD]) than with ultrasound alone (19.3% +/- 10.0) or urokinase alone (47.9% +/- 10.0) (P < .001 for ultrasound and urokinase vs either alone). The time to 50% clot lysis was shortened by 46% on average with the application of urokinase and ultrasound compared with urokinase alone (P < .03).
CONCLUSIONS:
Catheter-based ultrasound enhances enzymatic thrombolysis in vitro and may be a practical means to reduce the dose of enzyme and the time needed to achieve clot lysis in vivo. |
| Title |
Cavitation as a mechanism for the biological effects of ultrasound on plant roots. |
| Author |
Carstensen EL, Child SZ, Law WK, Horowitz DR, Miller MW. |
| Journal |
J Acoust Soc Am |
| Volume |
|
| Year |
1979 |
| Abstract |
The growth rate of roots is reduced by exposure to ultrasound at 10 W/cm2 for 1 min. The reduction is somewhat greater at 1 MHz than at 5 MHz. A hydrostatic pressure of 30 atm reduced, but did not eliminate, the effect of ultrasound on growth. The frequency and pressure dependence taken together with earlier observations support the postulate that a cavitationlike mechanism is at least partly responsible for the action of ultrasound on the growth of these developing plant tissues. |
| Title |
Cavitation dosimetry: Estimates for single bubbles in a rotating-tube exposure system. |
| Author |
Miller DL, Thomas RM. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1994 |
| Abstract |
Cell lysis and hydrogen peroxide production from cavitation in a 60 rpm rotating-tube exposure system were observed for 2.17 MHz ultrasound at 0.8 MPa peak negative pressure amplitude. Synchronized 10 ms burst mode exposure was utilized to emphasize the phenomenon of bubble cycling each half rotation. Low cell numbers and inhibition of H2O2-consuming enzymes allowed measurement of the residual hydrogen peroxide in exposed cell suspensions. Canine red blood cells (RBCs) or Chinese hamster ovary cells (CHO) suspended at 1 x 10(6) mL-1 in phosphate buffered saline were lysed.exponentially with the number of bursts. The CHO cells were lysed faster than RBCs. The H2O2 increased approximately in proportion to the number of bursts. Longer bursts (100 ms) or continuous exposure produced similar trends, but were less effective per unit of total on-time. The number of bubbles per 10 ms burst was estimated from a simple model to be about 7100. The faster lysis of the CHO cells could be explained mostly by the larger size of these cells, which makes them more likely to meet a bubble. The H2O2 production gave concentrations of about 93-155 fM per bubble per burst. Similar calculations gave estimates of 178 fM per bubble for 100 ms bursts and 150 fM per bubble for continuous exposure. The rate of H2O2 production was roughly 500 fmole s-1 while a bubble crossed the tube. This sonochemical yield could be biologically significant under favorable circumstances. |
| Title |
Cavitation effect in some erythrocyte suspensions. |
| Author |
Veress E. |
| Journal |
Arch Acoust |
| Volume |
|
| Year |
1984 |
| Abstract |
The destructive effects of ultrasound on cell suspensions depends on the parameters of the ultrasonic field and the experimental conditions. Erythrocytes of three origins were investigated: frog, chicken and rat. The frequency of the ultrasound was 1 MHz, with the intensity ranging from 0.4 to 1.2 Wcm/sup -2/. The volume concentrations of the samples were in the range 0.5-2 per cent. The investigation determined the volume concentration limit at which, at a sufficiently high field intensity, the destructive effect may be produced. In well defined conditions (at sufficiently low concentration) cavitation occurs, which has destructive effects (haemolysis). Haemolysis is produced at a well defined concentration in each case, depending on the physical, chemical and biological properties of the erythrocytes. The threshold concentration varies for different erythrocytes; thus the following values were obtained at 0.4 Wcm/sup -2/: chicken 0.5 per cent, frog 1 per cent, rat 2 per cent. At low intensities (J=0.4 Wcm/sup -2/), high frequency, short duration and diluted suspensions, cavitation plays a major role in the haemolysing action. |
| Title |
Cavitation induced by asymmetric distorted pulses of ultrasound: Theoretical predictions. |
| Author |
Ayme EJ, Carstensen EL. |
| Journal |
IEEE Trans UFFC |
| Volume |
|
| Year |
1989 |
| Abstract |
Prediction of the response of gas-filled microbubbles to ultrasonic waves is complicated by the finite-amplitude distortion associated with large-amplitude acoustic fields. Typical finite-amplitude pulses in medical applications consist of a sharp positive spike followed by a smaller slowly varying negative pressure. A suitable model for pressure waveforms that have these temporal characteristics is described, and the response of microbubbles to such sound fields is subsequently computed. A selection of descriptive parameters is considered to determine the characteristic features of the distorted pulse which are most important in generating bubble response. The results show that a) the peak-positive pressure is a very poor predicator of bubble response; b) the peak-negative pressure typically underestimates the bubble response; and c) a better predictor of bubble response is the pressure amplitude of the fundamental frequency in a Fourier series expansion of the distorted pulse. Theoretical thresholds for transient cavitation induced by a distorted pulse are presented for a range of frequencies and initial sizes of microbubbles. |
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