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BRL Abstracts Database |
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Your search for ultrasound produced 3296 results. Page 83 out of 330
| Title |
Detection of lines and boundaries in speckle images-Application to medical ultrasound. |
| Author |
Czerwinski RN, Jones DL, O'Brien WD Jr. |
| Journal |
IEEE Trans Med Imaging |
| Volume |
|
| Year |
1999 |
| Abstract |
Describes an approach to boundary detection in ultrasound speckle based on an image enhancement technique. The enhancement algorithm works by filtering the image with “sticks”, short line segments which are varied in orientation to achieve the maximum projected value at each point. In this paper, we present three significant extensions to improve the performance of the basic method. First, we investigate the effect of varying the size and shape of the sticks. We show that these variations affect the performance of the algorithm in very fundamental ways, for example by making it more or less sensitive to thinner or more tightly curving boundaries. Second, we present a means of improving the performance of this technique by estimating the distribution function of the orientation of the line passing through each point. Finally, we show that images can be “stained” for easier visual interpretation by applying to each pixel a false color whose hue is related to the orientation of the most prominent line segment at that point. Examples are given to illustrate the performance of the different settings on a single image. |
| Title |
Detection of microbubble ultrasound contrast agent destruction applied to definity. |
| Author |
Haak A, O'Brien WD Jr. |
| Journal |
Proc Int Cong Ultrasonics |
| Volume |
|
| Year |
2007 |
| Abstract |
For different applications such as imaging, drug delivery and tissue perfusion measurement, it is necessary to know the inertial cavitation (IC) threshold of ultrasonic contrast agent (UCA) microbubbles. The IC threshold for Definity
was determined using a passive cavitation detection (PCD) system. The IC threshold criterion was rebound. The incident ultrasonic field at a constant pulse repetition frequency of 10 Hz was varied with frequency (0.9, 2.8, 4.6 and 7.1 MHz), pulse duration (3, 5, and 7 cycles), and pressure level (ranging from 0.4 to 8.7 MPa). The transmit transducer excited the contrast agent while the 13-MHz receive transducer (mounted confocal to the transmitter) simultaneously received acoustic emissions from the microbubbles. The concentration of Definity
R was chosen so that statistically only one microbubble was in this focal volume.
Simulation results showed that a collapsing microbubble emits a characteristic broadband signal that was used to determine IC events. In order to classify the data, five different classes were created: Noise, Oscillation, Collapse, Multiple Bubbles and Not Classified. The peak rarefactional pressure thresholds of IC
events were determined for three of the four frequencies (e.g., 1.6, 0.8, and 2.6 MPa for 0.9, 2.8, and 4.6 MHz, respectively). It was not possible to determine a threshold pressure at 7.1 MHz. |
| Title |
Detection of small breast cancers. |
| Author |
Jellins J, Kossoff G, Reeve TS. |
| Journal |
J Fr Echogr |
| Volume |
|
| Year |
1984 |
| Abstract |
The assessment of breast disease with ultrasonic imaging provides the clinician with diagnostic information on the morphology of breast tissues. Improvements in scanning equipment and better appreciation of the ultrasonic appearance of disease processes have provided the ability to detect early changes in tissues due to benign and malignant conditions (1, 2, 3,). In a series of 3937 patients examined since 1972 at the Royal North Shore Hospital, ultrasound has been evaluated in the detection of 177 cancers greater than 5 mm in cross-section. Analysis of the results show that the technique has a sensitivity of 84% and a specificity of 96% (4). |
| Title |
Detection of spatially nonuniform ultrasonic radiation with phase sensitive (piezoelectric) and phase insensitive (acoustoelectric) receivers. |
| Author |
Busse LJ, Miller JG. |
| Journal |
J Acoust Soc Am |
| Volume |
|
| Year |
1981 |
| Abstract |
An analysis is present of the responses of a phase sensitive and a phase insensitive ultrasound receiver detecting a spatially nonuniform pressure distribution. The predicted output of each type of receiver is obtained numerically using a model of wave propagation based upon diffraction theory. Experimental verification of these predictions is obtained using a piezoelectric and an acoustoelectric receiver as a phase sensitive and a phase insensitive detector, respectively. Results are illustrated for transmission measurements of the frequency-dependent attenuation of an irregular plastic plate and for scattering measurements of the observed angular and spatial dependence of scattering from a pair of brass rods. |
| Title |
Detection of tissue harmonic motion induced by ultrasonic radiation force using pulse-echo ultrasound and kalman filter. |
| Author |
Zheng Y, Chen S, Tan W, Kinnick R, Greenleaf JF. |
| Journal |
IEEE Trans UFFC |
| Volume |
|
| Year |
2007 |
| Abstract |
A method using pulse echo ultrasound and the Kalman filter is developed for detecting submicron harmonic motion induced by ultrasonic radiation force. The method estimates the amplitude and phase of the motion at desired locations within a tissue region with high sensitivity. The harmonic motion generated by the ultrasound radiation force is expressed as extremely small oscillatory Doppler frequency shifts in the fast time (A-line) of ultrasound echoes, which are difficult to estimate. In slow time (repetitive ultrasound echoes) of the echoes, the motion also is presented as oscillatory phase shifts, from which the amplitude and phase of the harmonic motion can be estimated with the least mean squared error by Kalman filter. This technique can be used to estimate the traveling speed of a harmonic shear wave by tracking its phase changes during propagation. The shear wave propagation speed can be used to solve for the elasticity and viscosity of tissue as reported in our earlier study. Validation and in vitro experiments indicate that the method provides excellent estimations for very small (submicron) harmonic vibrations and has potential for noninvasive and quantitative stiffness measurements of tissues such as artery. |
| Title |
Determination of acoustic power outputs in the microwatt-milliwatt range. |
| Author |
Rooney JA. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1973 |
| Abstract |
A system using an electrobalance for radiation pressure measurements has been developed capable of determining acoustic powers in the microwatt-milliwatt range. Low background "noise" levels are achieved by effective isolation of the balance from building vibrations and shielding the target from convection currents. The standard deviation for a power output of 1 mW is typically less than 1 percent. |
| Title |
Determination of alterations of phase angle of ultrasound transmitted through a malignant breast tumor: A preliminary investigation. |
| Author |
Fry EK, Sanghvi NT, Fry FJ, Gardner G, Gallager HS. |
| Journal |
Proc Twenty-second Annu Meet AIUM |
| Volume |
|
| Year |
1977 |
| Abstract |
No abstract available. |
| Title |
Determination of alterations of phase angle of ultrasound transmitted through a malignant breast tumor: A reliminary investigation. |
| Author |
Fry EK, Sanghvi NT, Fry FJ, Gardner G, Gallager HS. |
| Journal |
Ultrasound Med |
| Volume |
|
| Year |
1978 |
| Abstract |
No abstract available. |
| Title |
Determination of biomechanical properties in guinea pig esophagus by means of high frequency ultrasound and impedance planimetry. |
| Author |
Assentoft JE, Gregersen H, O'Brien WD Jr. |
| Journal |
Dig Dis Sci |
| Volume |
|
| Year |
2000 |
| Abstract |
Impedance planimetry and high-frequency ultrasound were used to determine circumferential stress and strain from measurements of luminal cross-sectional area and wall thickness during balloon distension of the guinea pig esophagus in vitro (N = 30). The excised esophagus was mounted on two plastic tubes in an organ bath containing oxygenated calcium-free Krebs-Ringer solution with 10–2 M MgCl2 to abolish smooth muscle contractile activity. One of the plastic tubes was movable in order to stretch the esophagus longitudinally by 15% (elongated state). The impedance planimetry probe was placed with the balloon inside the lumen of the esophagus. A 20-MHz ultrasound transducer was mounted above the esophagus and provided scans in the transverse and longitudinal directions. The luminal cross-sectional area at the highest applied pressure of 2.9 kPa was 13.3 ± 0.3 mm2 in the resting state. In the elongated state the luminal cross-sectional area at the highest pressure was 12.5 ± 0.1 mm2 (P < 0.02). The wall thickness decreased from 990 ± 21 mgrm at 0 kPa to 640 ± 9 mgrm at 2.9 kPa at in vitro length. In the elongated state, the values were 940 ± 32 mgrm to 480 ± 13 mgrm (P < 0.01). The stress–strain relation was exponential (sgr = agr(e betaepsi – 1), r 2 > 0.98, P < 0.01). The circumferential elastic modulus calculated at a Green strain of 0.95 was 44.5 ± 10.5 kPa in the in vitro state and 81.7 ± 13.1 kPa in the elongated state. The elastic modulus differed between the resting and elongated states (P < 0.02). |
| Title |
Determination of human gestational age by ultrasound. |
| Author |
Bartolucci L. |
| Journal |
Proc West Pharmacol Soc |
| Volume |
|
| Year |
1973 |
| Abstract |
No abstract available. |
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