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BRL Abstracts Database |
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Your search for ultrasound produced 3296 results. Page 186 out of 330
| Title |
Noninvasive localized delivery of Herceptin to the mouse brain by MRI-guided focused ultrasound-induced blood-brain barrier disruption. |
| Author |
Kinoshita M, McDannold N, Jolesz FA, Hynynen K. |
| Journal |
Proc Natl Acad Sci USA |
| Volume |
|
| Year |
2006 |
| Abstract |
Antibody-based anticancer agents are promising chemotherapeutic agents. Among these agents, Herceptin (trastuzumab), a humanized anti-human epidermal growth factor receptor 2 (HER2/c-erbB2) monoclonal antibody, has been used successfully in patients with breast cancer. However, in patients with brain metastasis, the blood-brain barrier limits its use, and a different delivery method is needed to treat these patients. Here, we report that Herceptin can be delivered locally and noninvasively into the mouse central nervous system through the blood-brain barrier under image guidance by using an MRI-guided focused ultrasound blood-brain barrier disruption technique. The amount of Herceptin delivered to the target tissue was correlated with the extent of the MRI-monitored barrier opening, making it possible to estimate indirectly the amount of Herceptin delivered. Histological changes attributable to this procedure were minimal. This method may represent a powerful technique for the delivery of macromolecular agents such as antibodies to treat patients with diseases of the central nervous system. |
| Title |
Noninvasive measurement of the stiffness of tissue in the above-knee amputation limb. |
| Author |
Malinauskas M Krouskop TA, Barry PA. |
| Journal |
J Rehabil Res Dev |
| Volume |
|
| Year |
1989 |
| Abstract |
In order to characterize the mechanical properties of the soft tissue in above-knee amputations, nine subjects were measured with a Doppler ultrasound system. Measurements were made at four locations: anterior, posterior, lateral, and medial. The characterizations included tissues up to 2.5 cm deep. The average posterior moduli are significantly greater than the anterior and lateral parameters. No significant difference was found among moduli from the medial zone compared to other areas. Superficial tissue had a significantly higher modulus than the tissue beneath. A simple method for transducer placement produced repeatable results. The present technique proved to be useful with patients in good health, and with no severe residual limb complications. The information generated with the ultrasonic device may aid in prosthesis fitting and will be used ina Computer-Aided Design (CAD) system as well as in other clinical applications. |
| Title |
Noninvasive MR imaging-guided focal opening of the blood-brain barrier in rabbits. |
| Author |
Hynynen K, McDannold N, Vykhodtseva N, Jolesz FA. |
| Journal |
Radiology |
| Volume |
|
| Year |
2001 |
| Abstract |
PURPOSE: To determine if focused ultrasound beams can be used to locally open the blood-brain barrier without damage to surrounding brain tissue and if magnetic resonance (MR) imaging can be used to monitor this procedure.
MATERIALS AND METHODS: The brains of 18 rabbits were sonicated (pulsed sonication) in four to six locations, with temporal peak acoustic power ranging from 0.2 to 11.5 W. Prior to each sonication, a bolus of ultrasonographic (US) contrast agent was injected into the ear vein of the rabbit. A series of fast or spoiled gradient-echo MR images were obtained during the sonications to monitor the temperature elevation and potential tissue changes. Contrast material?enhanced MR images obtained minutes after sonications and repeated 1?48 hours later were used to depict blood-brain barrier opening. Whole brain histologic evaluation was performed.
RESULTS: Opening of the blood-brain barrier was confirmed with detection of MR imaging contrast agent at the targeted locations. The lowest power levels used produced blood-brain barrier opening without damage to the surrounding neurons. Contrast enhancement correlated with the focal signal intensity changes in the magnitude fast spoiled gradient-echo MR images.
CONCLUSION: The blood-brain barrier can be consistently opened with focused ultrasound exposures in the presence of a US contrast agent. MR imaging signal intensity changes may be useful in the detection of blood-brain barrier opening during sonication.
|
| Title |
Noninvasive real-time multipoint temperature control for ultrasound phased array treatments. |
| Author |
Seip R, VanBaren P, Cain CA, Ebbini ES. |
| Journal |
IEEE Trans UFFC |
| Volume |
|
| Year |
1996 |
| Abstract |
A method for noninvasively estimating spatiotemporal temperature changes in samples using diagnostic ultrasound, and using these as inputs to a multipoint ultrasound phased array temperature controller, is presented in this paper. This method is based on a linear relationship between the apparent tissue echo pattern displacements and temperature, as seen along A-lines acquired with diagnostic ultrasound when the sample is heated by external heating fields. The proportionality constant between echo displacement and temperature is determined by the local change in speed of sound due to temperature and the linear coefficient of thermal expansion of the material. Accurate estimation of the displacements and proportionality constant yields accurate calibrated high-resolution (1 mm spatial, sub-°C) noninvasive sample temperature estimates. These are used as inputs to a multipoint temperature controller, capable of controlling ultrasound phased array treatments in real-time. Phantom and in vitro results show that the noninvasively estimated temperature values can effectively be used to control ultrasound hyperthermia treatments, almost replacing invasive thermocouple measurements. The mathematical background and assumptions of the noninvasive temperature estimator and the controller are presented in this paper, together with experimental results showing estimator and controller performance and limitations. To the best of our knowledge, this paper presents the first demonstration of real-time treatment control based entirely on noninvasive temperature estimates. |
| Title |
Noninvasive surgery of prostate tissue by high intensity focused ultrasound: An updated report. |
| Author |
Sanghvi NT, Foster RS, Bihrle R, Casey R, Uchida T, Phillips MH, Syrus J, Zaitsev AV, Marich KW, Fry FJ. |
| Journal |
Euro J Ultrasound |
| Volume |
|
| Year |
1999 |
| Abstract |
Objective: To establish clinical efficacy and safety of High Intensity Focused Ultrasound (HIFU) for the treatment of benign prostatic hyperplasia (BPH) in a multiple site clinical study. Methods: Seven clinical sites were set up for these studies, five in the USA, one in Canada and one in Japan respectively. Sixty two patients were enrolled in these three studies. Transrectal ultrasound probes made to produce sufficient acoustic power required for focused ultrasound surgery of the prostate as well as to perform imaging of the prostate, were employed in the study. The probes were made of 2.5, 3.0, 3.5, 4.0 and 4.5 cm focal length transducers to treat varying prostate sizes and shapes and operated at 4 MHz freqnecy for both imaging and treatment. The employed ultrasound device produced both transverse and longitudinal images of the prostate on the same display. The images were used for selection of tissue volume, treatment planning and monitoring of the tissue during the HIFU treatment cycle. The patients in the USA and Canada were followed for two years and those in Japan were followed for one year on a regular interval. The results were evaluated for changes in the peak flow rate (Qmax in ml/s), quality of life (QOL) and International Prostate Symptom Score (IPSSS). Results: The average pre / post treatment results at 180 days were significantly different for Qmax, QOL and IPSS 8.5/14.2 (ml/s), 4.7/2.1 and 22/10 respectively. Conclusion: Under this protocol, HIFU was found safe and efficacious for the treatment of BPH. The HIFU atreatment produced statistically significant results for the parametners measured with least complications. Additionally, the HIFU treatment was found to be durable. |
| Title |
Noninvasive temperature estimation using sonographic digital images. |
| Author |
Abolhassani MD, Norouzy A, Takavar A, Ghanaati H. |
| Journal |
J Ultrasound Med |
| Volume |
|
| Year |
2007 |
| Abstract |
Objective:
The purpose of this study was to develop and evaluate a speckle-tracking method for tissue temperature estimation due to heating fields using digital sonographic images.
Methods:
The temperature change estimation method is based on the thermal dependence of the ultrasound speed and the thermal expansion of the medium. Local changes in the speed of sound due to changes in the temperature produce apparent displacement of the scatterers, and the expansion introduces physical displacement. In our study, a new technique has been introduced in which the axial physical displacements were obtained from digital sonographic images. The axial speckle pattern displacement was determined with a cross-correlation algorithm. The displacement data were then used for computing the temperature changes. To monitor the temperature in real time, the computational time was decreased by restricting the search region in the cross-correlation algorithm and carrying out the cross-correlation function in the frequency domain via a fast Fourier transform algorithm.
Results:
Experiments were performed on tissue-mimicking phantoms. The imaging probe was a commercial linear array working at 10 MHz. In addition, the temperature changes during heating were measured invasively by negative temperature coefficient thermistors. There was good agreement between ultrasonic temperature estimations and invasive temperature measurements.
Conclusions:
The proposed method verifies the capability of the speckle-tracking algorithm for determining both the magnitude and direction of displacement. The average error was 0.2°C; the maximum error was 0.53°C; and the SD was 0.19°C. Therefore, the proposed algorithm is capable of extracting the temperature information from sonographic digital images. |
| Title |
Noninvasive transesophageal cardiac thermal ablation using a 2-D focused, ultrasound phased array: a simulation study. |
| Author |
Yin X, Epstein LM, Hynynen K. |
| Journal |
IEEE Trans UFFC |
| Volume |
|
| Year |
2006 |
| Abstract |
This simulation study proposes a noninvasive, transesophageal cardiac-thermal ablation using a planar ultrasound phased array (1 MHz, 60 x 10 mm2, 0.525 mm interelement spacing, 114 x 20 elements). Thirty-nine foci in cardiac muscle were defined at 20, 40, and 60-mm distances and at various angles from the transducer surface to simulate the accessible posterior left atrial wall through the esophageal wall window. The ultrasound pressure distribution and the resulting thermal effect in a volume of 60 x 80 x 80 mm3, including esophagus and cardiac muscle, were simulated for each focus. For 1, 10, and 20-s sonications with 60 degrees C and 70 degrees C peak temperatures in cardiac muscle and without thermal damage in esophageal wall, the transducer acoustic powers were 105-727, 28-117, 21-79 W and 151-1044, 40-167, 30-114 W, respectively. The simulated lesions (thermal dose in equivalent minutes at 43 degrees C > or = 240 minutes) at these foci had lengths of 1-6, 3-11, 3-13 mm and 3-15, 5-19, 6-23 mm, respectively, and widths of 1-4, 2-7, 3-9 mm and 3-9, 4-13, 4-17 mm, respectively. As a first step toward feasibility, controllable tissue coagulation in cardiac tissue without damage to the esophagus was demonstrated numerically. |
| Title |
Noninvasive, transcranial and localized opening of the blood-brain barrier using focused ultrasound in mice. |
| Author |
Choi JJ, Pernot M, Small SA, Konofagou EE. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
2007 |
| Abstract |
The feasibility of blood-brain barrier (BBB) opening in the hippocampus of wild-type mice using focused ultrasound (FUS) through the intact skull and skin was investigated. Needle hydrophone measurements through ex vivo skulls revealed minimal attenuation (not, vert, similar18% of the pressure amplitude), a well-focused beam pattern and minute focus displacement through the parietal bone. In experiments in vivo, the brains of three mice were sonicated transcranially. Pulsed ultrasound sonications at 1.5 MHz and acoustic pressures ranging from 0.8 to 2.7 MPa were used at 20% duty cycle. Before sonication, a bolus of 10 μL of an ultrasound contrast agents (Optison) was injected intravenously. Contrast-enhanced high-resolution magnetic resonance imaging (9.4 T) revealed BBB opening and allowed for the monitoring of the slow permeation of gadolinium in the hippocampus. The region of the brain where BBB opening occurred increased with the pressure amplitude. These findings thus demonstrated the feasibility of locally opening the BBB in mice using FUS through intact skull and skin and serve as the first step in determining and assessing feasibility of drug delivery to specific regions in the mouse brain using FUS. |
| Title |
Nonlinear and linear propagation of diagnostic ultrasound pulses. |
| Author |
Filipczynski L, Kujawska T, Tymkiewicz R, Wojcik J. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1999 |
| Abstract |
The effect of nonlinear propagation in fluid followed by soft tissue was studied both theoretically and experimentally for a most crucial case in obstetrical ultrasonography. For this purpose, short pressure pulses, with the duration time of 1.3 micros and a carrier frequency of 3 MHz, radiated by a concave transducer into water, with maximum intensities up to the value of 18 W/cm2, were computed and measured. The ultrasonic beam had the physical focus at the distance of 6.5 cm, where the highest focal intensity of I(SPPA) = 242 W/cm2 was obtained. In front of the transducer, at a distance of 7 cm, artificial tissue samples prepared on the basis of ground porcine kidney, with a thickness of 0.5, 1.5 and 3 cm, were placed in water. Pressure pulses and their spectral components were produced numerically and measured by means of a PVDF hydrophone in water before and after penetrating the tissue samples. The theoretical analysis and measurements were carried out, in every case, for two signal levels: for a high level assuring nonlinear propagation and for a low one where conditions of linear propagation were fulfilled. In this way, it was possible to compare directly the effects of nonlinear and linear propagation, in every case showing a good conformity of theoretical values with measured ones. A method of determination of the effective frequency response of the hydrophone was elaborated to enable quantitative comparisons of numerical and experimental results. The theoretical part of our study was based on a paper of Wojcik (1998), enabling us to compute the characteristic function of nonlinear increase of absorption. An agreement of up to 10% was obtained when comparing theoretical and measured values of these functions in the investigated beam in water and behind tissue samples. The results obtained showed that the recently given theory of nonlinear absorption, based on the spectral analysis and the elaborated numerical procedures, may be useful in various practical ultrasonic medical problems and also in technological applications. |
| Title |
Nonlinear behavior of a liquid containing uniform bubbles: Comparison between theory and experiments. |
| Author |
Wu J, Zhu Z, Du G. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1995 |
| Abstract |
Bubbles oscillating at resonance frequency dramatically enhance nonlinearity of a bubbly liquid. A second-order nonlinear wave equation taking account of bubble pulsation is solved. Numerical calculations based on the equation are compared favorably with experimental results. Possible biological significance of the highly nonlinear medium is also discussed. |
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