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BRL Abstracts Database |
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Your search for ultrasound produced 3296 results. Page 95 out of 330
| Title |
Dynamic cardiac imaging using a focused, phased-array ultrasound system. |
| Author |
Kisslo JA, vonRamm OT, Thurstone FL. |
| Journal |
Am J Med |
| Volume |
|
| Year |
1977 |
| Abstract |
A two-dimensional ultrasound imaging system capable of producing high resolution, cross-sectional images of the heart in real-time has been developed. This system relies upon phased-array principles to rapidly steer and focus the ultrasound beam through the cardiac structures under investigation. A hand-held, linear array of 24 transducers is manipulated on the anterior chest wall to image various cardiac structures. Images of high line density are presented in selectable sector arcs to a maximum of 90 degrees. This imaging system has proved particularly useful for the detection of a variety of left ventricular and cardiac valvular disease. |
| Title |
Dynamic measurement of the internal solid displacement in articular cartilage using ultrasound backscatter. |
| Author |
Fortin M, Buschmann MD, Bertrand MJ, Foster FS, Ophir J. |
| Journal |
J Biomech |
| Volume |
|
| Year |
2003 |
| Abstract |
Mechanics of articular cartilage can be represented using poroelastic theories where fluid and solid displacements are viscously coupled to create a time-dependent spatially heterogeneous behavior. IN recent models of this tissue, finite element methods have been used to predict tissue deformation as a function of time for adult articular cartilage bearing a characteristic depth-dependent structure and composition. However, current experimental methods are limited in providing verification of these predictions. The current study presents an apparatus for imaging the radial displacement profile of cartilage in unconfined compression using an ultrasound technique called elastography. We acquired ultrasound A-scans across the lateral diameter of full-thickness cartilage disks containing a thin layer of underlying bone, during axial compression. Elastography was then applied to correlate temporally sequential A-scans to estimate the solid radial displacement profile in articular cartilage while it undergoes compression and stress-relaxation. Both time-dependent and depth-dependent solid radial displacement profiles were obtained with a precision better than 0.2 um. The results generally agree with predictions of poroelastic models, demonstrating lateral expansion with an effective Poisson?s ratio just after completion of the compression phase of the mechanical tests reaching values from 0.18 to 0.4 (depending on compression speed) followed by contraction to lower values. A more restricted movement was observed at both the articular surface and near to the subchondral bone than at regions midway between these two locations. |
| Title |
Dynamic three-dimensional freehand echocardiography using raw digital ultrasound data. |
| Author |
Berg S, Torp H, Martens D, Steen E, Samstad S, Hoivik I, Olstad B. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1999 |
| Abstract |
In this paper, we present a new method for simple acquisition of dynamic three-dimensional (3-D) ultrasound data. We used a magnetic position sensor device attached to the ultrasound probe for spatial location of the probe, which was slowly tilted in the transthoracic scanning position. The 3-D data were recorded in 10-20 s, and the analysis was performed on an external PC within 2 min after transferring the raw digital ultrasound data directly from the scanner. The spatial and temporal resolutions of the reconstruction were evaluated, and were superior to video-based 3-D systems. Examples of volume reconstructions with better than 7 ms temporal resolution are given. The raw data with Doppler measurements were used to reconstruct both blood and tissue velocity volumes. The velocity estimates were available for optimal visualization and for quantitative analysis. The freehand data reconstruction accuracy was tested by volume estimation of balloon phantoms, giving high correlation with true volumes. Results show in vivo 3-D reconstruction and visualization of mitral and aortic valve morphology and blood flow, and myocardial tissue velocity. We conclude that it was possible to construct multimodality 3-D data in a limited region of the human heart within one respiration cycle, with reconstruction errors smaller than the resolution of the original ultrasound beam, and with a temporal resolution of up to 150 frames per second. |
| Title |
Dynamics of therapeutic ultrasound contrast agents. |
| Author |
Allen JS, May DJ, Ferrara KW. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
2002 |
| Abstract |
Novel therapeutic contrast agents offer great potential for localized drug delivery. Localized delivery should significantly improve the efficacy of drug delivery and reduce any toxic exposure to the healthy tissue. This work describes a preliminary theoretical description of agents, such as those developed by the ImaRx Corporation, enclosed by a relatively thick fluid shell. A theoretical extension is made to a generalized Rayleigh-Plesset formulation that allows it to be solved for an encapsulating liquid shell of arbitrary thickness and density. The equation is used to investigate the role of shell thickness, density and viscosity on the radial dynamics and velocity of the inner and outer radii. Comparisons are made with experimental measurements of the maximum radial expansions for agents with triacetin shells. For a seven-cycle driving acoustic pulse with a center frequency of 1.5 MHz and peak amplitude of 1.6 MPa, the equation predicts maximum expansions from 5.5 to 1.3 times the initial radius for agents 1 to 10 µm, respectively, in initial radius with a 500-nm (28.0 cP) encapsulating shell. These predictions have reasonable agreement with the maximum radial expansions obtained from optical experimental data of fragmenting and intact agents. Approximate agreement between theory and experiment for a similar range of agent sizes is also demonstrated for a pulse with the same pressure amplitude at 2.5 MHz. At 2.5 MHz, smaller radial expansion amplitudes from 1.1 to 4.1 times the initial radius were found for agents 1 to 10 µm in initial radius, respectively. Discrepancies are attributed to shape instabilities and their associated fragmentation effects not incorporated in the equation. A significant difference in the inner and outer wall velocities is predicted for agents with a 500-nm triacetin shell. A 2.5 µm initial radius agent driven with a seven-cycle pulse at 2.5 MHz and 1.6 MPa achieves a maximum negative inner wall velocity of 364 m/s and outer wall velocity of 63 m/s. For parameters that correspond to large differences between the inner and outer wall velocities, fragmentation is typically observed experimentally.
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| Title |
Early cancer diagnosis through ultrasonics. |
| Author |
Kikuchi Y, Uchida R, Tanaka K, Wagai T. |
| Journal |
J Acoust Soc Am |
| Volume |
|
| Year |
1957 |
| Abstract |
After various fundamental experiments, we succeeded in getting echoes from the human intercranial ventricle and brain tumor not only through dura mater during surgical operation, but also through the skull at preoperative and postoperative examination. In these experiments, we used 1-10 Mc ultrasound and A-scope indication. As a special finding, we would report that an echo from the ventricle wall pulsates slowly and rhythmically with synchronization to each heartbeat. .Furthermore, we succeeded in detecting echoes from various abdominal organs and tumors through the skin, and found that echoes, reflected from the bowel, move in correlation to bowel peristalsis. .As the echoes are so clearly perceptible, we are now engaged in developing ?ultrasono-tomography? for a horizontal section of the human head or abdomen by plan-position indication; such a tomography cannot be attained by any penetration method including X-ray. .In thoracic examination also, we attained some achievements not only in the ultrasonic diagnosis of breast tumor but also in detection of fluctuating echoes from the heart, which are considered valuable for studies of heart function. Regarding the lung, we found special echoes form lung tumors and also from pneumonia lungs..Another important finding is the decrease of ultrasonic attenuation in narcotized tissue. This finding will introduce a future possibility in qualitative measurement of the degree of anesthesia. . |
| Title |
Early detection of breast carcinoma by ultrasound. |
| Author |
Kobayashi T. |
| Journal |
Le J Fr Echogr |
| Volume |
|
| Year |
1985 |
| Abstract |
Breast ultrasonography in particular has high diagnostic accuracy because of recently developed gray scale image display. History of breast echography, technique of water-bag examination, demonstration of echograms of normal female breast, diagnostic criteria to differentiate breat carcinoma for other benign breast tumors, demonstration of typical echograms of benign cyst, fibroadenoma and breast carcinomas of various histological types, current status of diagnostic accuracy rates achieved in Japan and its international trends, ultrasonic tissue characterization of breast carcinoma, and application of ultrasound to the screening of breast carcinoma were presented. |
| Title |
Early diagnosis of hepatocellular carcinoma: Usefulness of ultrasonically guided fine-needle aspiration biopsy. |
| Author |
Tanaka S, Kitamura T, Kasugai H, Okano Y, Tatsuta M, Okuda S. |
| Journal |
J Clin Ultrasound |
| Volume |
|
| Year |
1986 |
| Abstract |
The results of various diagnostic procedures performed on six cases with solitary and minimal (less than 2 cm) hepatocellular carcinoma (HCC) that was later surgically resected were comparatively reviewed. The tumor was detected in 6/6 patients by ultrasonography, 1/6 by scintigraphy, 2/6 by CT, and 4/6 by angiography, and hepatocellular carcinoma was diagnosed in 3/6 by angiography and 6/6 by ultrasonically guided fine-needle aspiration biopsy. Since there are not a few HCCs that can be detected only by ultrasonography, fine-needle aspiration biopsy with ultrasound guidance is strongly recommended to confirm cases with a minimal lesion in the liver visualized only on a sonogram. |
| Title |
Early experience with high-intensity focused ultrasound for the treatment of benign prostatic hypertrophy. |
| Author |
Sullivan LD, McLoughlin MG, Goldenberg LG, Gleave ME, Marich KW. |
| Journal |
Br J Urol |
| Volume |
|
| Year |
1997 |
| Abstract |
To evaluate the safety and effectiveness of high-intensity focused ultrasound (HIFU) in patients with benign prostatic hypertrophy (BPH).
PATIENTS AND METHODS:
The study comprised 25 patients (mean age 67 years: range 47-84) with BPH treated using the Sonoblate HIFU device. Patients were evaluated before and after one treatment of HIFU using the American Urological Association (AUA) symptom score, peak urinary flow rate (Qmax) and a quality-of-life (QOL) score, and any complications were noted.
RESULTS:
Five patients with large glands were withdrawn because the failure rate was high in these patients. The remaining 20 patients showed a mean improvements in the AUA symptom score (20.25 to 9.56), Qmax (9.2 to 13.7 mL/s) and QOL score (4.75 to 2.50). There were no major complications.
CONCLUSIONS:
HIFU is safe, produces minimal side-effects or complications and relieves the symptoms of prostatism. |
| Title |
Early identification with ultrasonic integrated backscatter of viable but stunned myocardium in dogs. |
| Author |
Milunski MR, Mohr GA, Wear KA, Sobel BE, Miller JG, Wickline SA. |
| Journal |
J Am Coll Cardiol |
| Volume |
|
| Year |
1989 |
| Abstract |
It has been shown that canine and human hearts exhibit a cardiac cycle-dependent variation of integrated backscatter (cyclic variation) that reflects intrinsic regional contractile performance. To determine whether ultrasound tissue characterization can identify viable though stunned myocardium before recovery of regional wall thickening, transient ischemic injury was produced in eight open chest dogs for 15 min followed by reperfusion for 2 h. Cyclic variation and wall thickening were measured before ischemia, at 15 min after the onset of ischemia and at selected intervals after the onset of reperfusion from multiple sites within the ischemic zone with a novel combined two-dimensional and M-mode acquisition system. Cyclic variation and wall thickening were computed from digitized M-mode integrated backscatter images with an algorithm developed and validated for this purpose. Magnitude and "delay" of cyclic variation and wall thickening were compared. Delay represents the degree of synchrony of regional cyclic variation or wall thickening with global ventricular mechanical systole. Baseline cyclic variation and wall thickening magnitudes were 3.8 +/- 0.2 dB and 37 +/- 1.4%, respectively. With ischemia, cyclic variation and wall thickening decreased to 1.7 +/- 0.2 dB and 17 +/- 2%, respectively (p less than 0.05, compared with baseline). Cyclic variation recovered to baseline levels within 20 min after reperfusion (3.3 +/- 0.4 dB, p = NS). Wall thickening remained depressed for 2 h after the onset of reperfusion (23 +/- 2%, p less than 0.05 compared with baseline). Delay of cyclic variation in a unitless ratio expressed as delay (in milliseconds) divided by the QT interval (in milliseconds) increased from 0.87 +/- 0.03 at baseline to 1.10 +/- 0.12 with ischemia, a change consistent with mild asynchrony, and returned to baseline (0.95 +/- 0.07, p = NS compared with baseline) within 20 min after reperfusion. Delay of wall thickening was 0.88 +/- 0.02 at baseline, increased to 1.23 +/- 0.09 with ischemia and remained significantly increased 2 h after reperfusion (1.07 +/- 0.05, p less than 0.05 compared with baseline). Recovery time constants for cyclic variation and wall thickening with reperfusion reflected earlier restoration of cyclic variation (8.1 min) than of wall thickening (420.5 min). Thus, cyclic variation recovers before wall thickening with reperfusion. Its analysis appears to provide a useful index of the presence of viable and potentially salvageable tissue in regions of stunned myocardium that is independent of wall thickening. |
| Title |
ECG-Gated, mechanical and electromechanical wave imaging of cardiovascular tissues in vivo. |
| Author |
Pernot M, Fujikura K, Fung-Kee-Fung SD, Konofagou EE. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
2007 |
| Abstract |
In simplistic terms, the motion of the heart can be summarized as an active contraction and passive relaxation of the myocardium. However, the local motion of cardiovascular tissues over the course of an entire cardiac cycle results from various transient events such as the valves closing/opening, sudden changes in blood pressure and electrical conduction of the myocardium. The transient motion generated by most of these events occurs within a very short time (on the order of 1 ms) and cannot be imaged correctly with conventional imaging systems, due to their limited temporal resolution. In this paper, we propose a method for imaging this rapid transient motion of tissues in cardiovascular applications. Our method is based on imaging tissues with ultrasound at high frame rates (up to 8000 fps) by synchronizing the two-dimensional (2D) image acquisition on the electrocardiogram (ECG) signals. In vivo feasibility is demonstrated in anesthetized mice. The propagation of several transient mechanical waves was imaged in different regions of the myocardium and the wave phase velocities were found to be between 0.44 m/s and 5 m/s. These waves may be generated by either a purely mechanical effects or through electromechanical coupling in the myocardium depending on the phase of the cardiac cycle, in which they occur. The abdominal aorta was also imaged using the same technique and the propagation of a mechanical pulse wave was imaged. The pulse wave velocity was measured and the Young’s modulus of the vessel wall was derived based on the Moens-Korteweg equation. This method could potentially be used for mapping the stiffness of the myocardium and the artery walls and may lead to the early diagnosis of cardiovascular diseases. |
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