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BRL Abstracts Database |
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Your search for ultrasound produced 3296 results. Page 321 out of 330
| Title |
Ultrasound-induced encapsulated microbubble phenomena. |
| Author |
Postema M,van Wamel A,Lancée CT,de Jong N. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
2004 |
| Abstract |
When encapsulated microbubbles are subjected to high-amplitude ultrasound, the following phenomena have been reported: oscillation, translation, coalescence, fragmentation, sonic cracking and jetting. In this paper, we explain these phenomena, based on theories that were validated for relatively big, free (not encapsulated) gas bubbles. These theories are compared with high-speed optical observations of insonified contrast agent microbubbles. Furthermore, the potential clinical applications of the bubble-ultrasound interaction are explored. We conclude that most of the results obtained are consistent with free gas bubble theory. Similar to cavitation theory, the number of fragments after bubble fission is in agreement with the dominant spherical harmonic oscillation mode. Remarkable are our observations of jetting through contrast agent microbubbles. The pressure at the tip of a jet is high enough to penetrate any human cell. Hence, liquid jets may act as remote-controlled microsyringes, delivering a drug to a region-of-interest. Encapsulated microbubbles have (potential) clinical applications in both diagnostics and therapeutics. |
| Title |
Ultrasound-induced heart rate decrease: Role of the Vagus Nerve |
| Author |
Coiado AC, Buiochi EB, O'Brien WD Jr. |
| Journal |
IEEE Trans UFFC |
| Volume |
|
| Year |
2015 |
| Abstract |
The goal of this study is to investigate the role of the vagus nerve (VN) in the ultrasound (US)-induced negative chronotropic effect (deceased heart rate). One of the functions of the VN is to mediate lowering of the heart rate. A previous study showed a decrease of ~20% in the heart rate but the mechanism of the effect was not investigated. Sprague Dawley rats (n = 20) were exposed transthoracically to ultrasonic pulses at an approximate duty factor of 1% with sequentially 2.0, 2.5, and 3.0 MPa peak rarefactional pressure amplitudes (PRPAs). The ultrasonic exposure parameters herein were chosen to match those of the previous study to have confidence that an ultrasound-induced negative chronotropic effect would occur. For each of the three PRPA sequences, the pulse repetition frequency (PRF) started slightly greater than the rat’s heart rate and then was decreased sequentially in 1-Hz steps every 10 s (i.e., 6, 5, and 4 Hz for a total duration of 30 s). The experiments were organized in a standard (2 × 2) factorial design with VN (cut versus intact) as one factor and US (on versus off) as another factor. VN (intact/cut) and US (on/off) groups were divided into four groups each consisting of 5 animals: 1) VN intact-US off, 2) VN intact-US on, 3) VN cut-US off, and 4) VN cut-US on. Two-way analysis of variance for repeated measures was used to compare heart rate, cardiac output, systolic volume, ejection fraction, end-diastolic volume, end-systolic volume, respiratory rate, and arterial pressure before and after ultrasound stimulation. In this study, the heart rate decreased ~4% for the non-vagotomy and vagotomy groups. The ultrasound effect was significant for heart rate (p = 0.02) and cardiac output (p = 0.005) at 3 min post US exposure; the vagotomy effect was not significant. For heart rate, the Bonferroni test showed no differences between the four groups. The vagotomy group showed similar ultrasound-induced cardiac effects compared with the non-vagotomy group, suggesting that the vagus nerve is not influenced by the ultrasound exposure procedures. The US application caused a negative chronotropic effect of the rat heart without affecting the hemodynamic conditions. The results at this point are suggestive for an alternative cardiac pacing capability. |
| Title |
Ultrasound-induced heart rate decrease: Role of the Vagus Nerve |
| Author |
Coiado OC, Buiochi EB, O'Brien WD Jr. |
| Journal |
IEEE Trans UFFC |
| Volume |
|
| Year |
2015 |
| Abstract |
The goal of this study is to investigate the role of the vagus nerve (VN) in the ultrasound (US)-induced negative chronotropic effect (deceased heart rate). One of the functions of the VN is to mediate lowering of the heart rate. A previous study showed a decrease of ~20% in the heart rate but the mechanism of the effect was not investigated. Sprague Dawley rats (n = 20) were exposed transthoracically to ultrasonic pulses at an approximate duty factor of 1% with sequentially 2.0, 2.5, and 3.0 MPa peak rarefactional pressure amplitudes
(PRPAs). The ultrasonic exposure parameters herein were chosen to match those of the previous study to have confidence that an ultrasound-induced negative chronotropic effect would occur. For each of the three PRPA sequences, the pulse repetition frequency (PRF) started slightly greater than the rat’s
heart rate and then was decreased sequentially in 1-Hz steps every 10 s (i.e., 6, 5, and 4 Hz for a total duration of 30 s). The experiments were organized in a standard (2 × 2) factorial design with VN (cut versus intact) as one factor and US (on versus off) as another factor. VN (intact/cut) and US (on/off)
groups were divided into four groups each consisting of 5 animals: 1) VN intact-US off, 2) VN intact-US on, 3) VN cut-US off, and 4) VN cut-US on. Two-way analysis of variance for repeated measures was used to compare heart rate, cardiac output, systolic volume, ejection fraction, end-diastolic volume,
end-systolic volume, respiratory rate, and arterial pressure before and after ultrasound stimulation. In this study, the heart rate decreased ~4% for the non-vagotomy and vagotomy groups. The ultrasound effect was significant for heart rate (p = 0.02) and cardiac output (p = 0.005) at 3 min post US exposure;
the vagotomy effect was not significant. For heart rate, the Bonferroni test showed no differences between the four groups. The vagotomy group showed similar ultrasound-induced cardiac effects compared with the non-vagotomy group,
suggesting that the vagus nerve is not influenced by the ultrasound exposure procedures. The US application caused a negative chronotropic effect of the rat heart without affecting the hemodynamic conditions. The results at this point are suggestive for an alternative cardiac pacing capability. |
| Title |
Ultrasound-induced hyperthermia for the treatment of human superficial tumors. |
| Author |
Corry PM, Barlogie B, Tilchen EJ, Armour EP. |
| Journal |
Int J Radiat Oncol Biol Phys |
| Volume |
|
| Year |
1982 |
| Abstract |
Ultrasonic systems were developed for the treatment of superficial human tumors, generating local tumor hyperthermia at tumor center temperatures ranging from 43 degrees to 50 degrees. Twenty-eight patients with disease of varying histology were evaluable for response, and demonstrated an overall response rate of 57% with a complete response rate of 18%. In 11 patients who had received definitive radiation therapy to the heat treated area, the response rate was 81%; there were no toxicities other than those noted for the overall study. As temperature was escalated a marked increase was observed both in response rates (from 53% (43-44 degrees C) to 83% (48-50 degrees C) and in duration of response (from 29 to 250 days for the same temperatures). Toxicities were minimal, consisting of superficial blistering in four patients and pain in six patients. Pain was usually associated with tumor involvement in the periostium. |
| Title |
Ultrasound-induced hyperthermia for the treatment of human superficial tumors. |
| Author |
Corry PM Barlogie B Tilchen EJ Armour EP. |
| Journal |
Int J Radiat Oncol Biol Phys |
| Volume |
|
| Year |
1982 |
| Abstract |
Ultrasonic systems were developed for the treatment of superficial human tumors, generating local tumor hyperthermia at tumor center temperatures ranging from 43 degrees to 50 degrees. Twenty-eight patients with disease of varying histology were evaluable for response, and demonstrated an overall response rate of 57% with a complete response rate of 18%. In 11 patients who had received definitive radiation therapy to the heat treated area, the response rate was 81%; there were no toxicities other than those noted for the overall study. As temperature was escalated a marked increase was observed both in response rates (from 53% (43-44 degrees C) to 83% (48-50 degrees C) and in duration of response (from 29 to 250 days for the same temperatures). Toxicities were minimal, consisting of superficial blistering in four patients and pain in six patients. Pain was usually associated with tumor involvement in the periostium. |
| Title |
Ultrasound-induced hyperthermia in the treatment of cutaneous leishmaniasis. |
| Author |
Aram H,Leibovici V. |
| Journal |
Cutis |
| Volume |
|
| Year |
1987 |
| Abstract |
Local hyperthermia induced by ultrasound was delivered by two to three weekly to twenty-eight lesions of acute cutaneous leishmaniasis in eighteen patients. Twenty-two lesions(78.5 percent) in thirteen patients resolved completely five to ten weeks after the start of treatment.Our results are explained by these thermo sensitivity of the parasite and its inability to survive at supranormal temperature. Ultrasound hyperthermia was tolerated by most of the patients. The results this study indicate than topical heat is safe and effective for the treatment of patients with acute cutaneous leishmaniasis. |
| Title |
Ultrasound-induced lung hemorrhage in the monkey. |
| Author |
Tarantal AF, Canfield DR. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1994 |
| Abstract |
Studies with the mouse have shown that lung hemorrhage can result from exposure to ultrasound at a peak pressure of approximately 1 MPa at 4 MHz (Mechanical Index [MI] approximately 0.5). In order to determine whether a comparable outcome could occur in a larger animal with characteristics similar to humans, studies were performed with monkeys using a clinical scanner under maximum output conditions (imaging + pulsed and color Doppler; derated pr of 3.7 MPa [4.5 MPa, measured in water], 4 MHz; MI approximately 1.8) (N =.57). Monkeys ranged in age from 1 day of life to 16 years with exposures limited to the right lung lobes (5 min cranial, 5 min caudal; N = 41 exposed, N = 12 sham-exposed controls, N = 4 colony controls). Results showed that animals ranging in age from 3 months to 5 years (mean age of 2.5 years) had a greater propensity for the occurrence of multiple well-demarcated circular hemorrhagic foci (0.1-1.0 cm), which were not observed in either control group. These lesions were characterized by marked congestion of alveolar capillaries with accumulation of red blood cells within the alveolar spaces, and were unassociated with major vessels or respiratory bronchioles. Further studies will be required in order to determine the relevance of these findings to the human, although it was concluded that ultrasound-induced lung hemorrhage in the monkey is of a significantly lesser degree when compared to the mouse. |
| Title |
Ultrasound-induced lung hemorrhage is not caused by inertial cavitation. |
| Author |
O'Brien WD Jr, Frizzell LA, Weigel RM, Zachary JF. |
| Journal |
J Acoust Soc Am |
| Volume |
|
| Year |
2000 |
| Abstract |
In animal experiments, the pathogenesis of lung hemorrhage due to exposure to clinical diagnostic levels of ultrasound has been attributed to an inertial cavitation mechanism. The purpose of this article is to report the results of two experiments that directly contradict the hypothesis that ultrasound-induced lung hemorrhage is caused by inertial. cavitation. Elevated hydrostatic pressure was used to suppress the involvement of inertial cavitation. In experiment one, 160 adult mice were equally divided into two hydrostatic. pressure groups (0.1 or 1.1 MPa), and were randomly exposed to pulsed ultrasound (2.8-MHz center frequency, 1-kHz PRF, 1.42-micros pulse duration, 10-s exposure. duration). For the two hydrostatic pressure groups (80 mice each), 8 in situ peak rarefactional pressure levels were used that ranged between 2.82 and 11.8 MPa (10. mice/group). No effect of hydrostatic pressure on the probability of hemorrhage was observed. These data lead to the conclusion that lung hemorrhage is not caused by inertial. cavitation. Also, the higher hydrostatic pressure enhanced rather than inhibited the impact of ultrasonic pressure on the severity (hemorrhage area, depth, and volume) of lesions.. These counterintuitive findings were confirmed in a second experiment using a 2 x 5 factorial design that consisted of two ultrasonic pressure levels and five hydrostatic pressure. levels (100 mice, 10 mice/group). If inertial cavitation were the mechanism responsible for lung hemorrhage, then elevated hydrostatic pressures should have resulted in less. rather than more tissue damage at each ultrasonic pressure level. This further supports the conclusion that the pathogenesis of ultrasound-induced lung hemorrhage is not caused. by inertial cavitation. |
| Title |
Ultrasound-induced lung hemorrhage: role of acoustic boundary conditions at the pleural surface. |
| Author |
O'Brien WD Jr, Kramer JM, Waldrop TG, Frizzell LA, Miller RJ, Blue JP, Zachary JF. |
| Journal |
J Acoust Soc Am |
| Volume |
|
| Year |
2002 |
| Abstract |
In a previous study [J. Acoust. Soc. Am. 108, 1290 (2000)] the acoustic impedance difference between intercostal tissue and lung was evaluated as a possible explanation for the enhanced lung damage with increased hydrostatic pressure, but the hydrostatic-pressure-dependent impedance difference alone could not explain the enhanced occurrence of hemorrhage. In that study, it was hypothesized that the animal's breathing pattern might be altered as a function of hydrostatic pressure, which in turn might affect the volume of air inspired and expired. The acoustic impedance difference between intercostal tissue and lung would be affected with altered lung inflation, thus altering the acoustic boundary conditions. In this study, 12 rats were exposed to 3 volumes of lung inflation (inflated: approximately tidal volume; half-deflated: half-tidal volume; deflated: lung volume at functional residual capacity), 6 rats at 8.6-MPa in situ peak rarefactional pressure (MI of 3.1) and 6 rats at 16-MPa in situ peak rarefactional pressure (MI of 5.8). Respiration was chemically inhibited and a ventilator was used to control lung volume and respiratory frequency. Superthreshold ultrasound exposures of the lungs were used (3.1-MHz, 1000-Hz PRF, 1.3-micros pulse duration, 10-s exposure duration) to produce lesions. Deflated lungs were more easily damaged than half-deflated lungs, and half-deflated lungs were more easily damaged than inflated lungs. In fact, there were no lesions observed in inflated lungs in any of the rats. The acoustic impedance difference between intercostal tissue and lung is much less for the deflated lung condition, suggesting that the extent of lung damage is related to the amount of acoustic energy that is propagated across the pleural surface boundary. |
| Title |
Ultrasound-induced orientation of discoid.platelets and simultaneous changes in light transmission: preliminary characterisation of the phenomenon. |
| Author |
Trenchard PM |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1987 |
| Abstract |
Discoid platelet suspensions were subjected to ultrasonic fields, in the 1-10.MHz frequency range and at estimated acoustic pressures in the range of.0.05-7.6 X 10(4) Pa. Absolute definition of the acoustic field/pressures was.precluded by the small dimensions, and internal reflective surfaces, of the.experimental configurations employed. Direct microscopy revealed platelet.flow, in patterns consistent with theory for ultrasonically induced streaming..This ultrasonic effect was presumed to be accompanied by platelet orientation.since it could be quantitated by simultaneous light transmission.measurements. The preliminary characterisation of this phenomenon, defined.as ultrasound induced light transmission change (USILTC) is reported, and.indicates that it may be readily quantitated in a reproducible manner, but.which shows a complex relationship both to pressure and frequency. In.addition, qualitative characteristics of the response traces are apparent under.certain conditions, particularly 5 MHz above 1 X 10(4) Pa, and may relate to.platelet viability. Preliminary evidence is provided and discussed, which.suggests that USILTC may be a useful model for studying certain ultrasound.bioeffects, and may be a useful tool for indirectly assessing platelet.morphology and viability for quality assurance purposes. |
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