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BRL Abstracts Database |
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Your search for ultrasound produced 3296 results. Page 7 out of 330
| Title |
A cylindrical-section ultrasound phased-array applicator for hyperthermia cancer therapy. |
| Author |
Ebbini ES, Umemura S, Ibbini M, Cain CA. |
| Journal |
IEEE Trans UFFC |
| Volume |
|
| Year |
1988 |
| Abstract |
A new phased-array applicator geometry for deep localized hyperthermia is presented. The array consists of rectangular transducer elements forming a section of a cylinder that conforms to the body portals in the abdominal and pelvic regions. Focusing and scanning properties of the cylindrical-section array are investigated in homogeneous lossy media using appropriate computer simulations. The characteristic focus of this array is shown to be spatially limited in both transverse and longitudinal directions with intensity gain values suitable for deep hyperthermia applications. The ability of the cylindrical-section phased array to generate multiple foci using the field conjugation method is examined. The effect of the grating lobes on the power deposition pattern of the scanned field is shown to be minimal. Steady-state temperature distributions are simulated using a three-dimensional (3-D) thermal model of the normal tissue layers surrounding a tumor of typical volume. Finally, the advantages and the limitations of this array configuration are discussed. |
| Title |
A data acquisition system for ultrasonic tomography. |
| Author |
Chan K, Fish RM, O'Brien WD Jr. |
| Journal |
Thesis(MS): Univ of Illinois |
| Volume |
|
| Year |
1980 |
| Abstract |
Living tissues can be characterized by their interaction with ultrasound. Our research involves measuring the frequency dependent amplitude and time-of-flight of ultrasound after it passes through biological materials. This information is processed to produce tomographic images of the material being studied. This type of tomographic images yields resolutions of 0.5 cm in the low MHz ultrasonic frequency range. This paper describes the data acquisition circuitry used in these computerized tomography systems. A block diagram of the system is given in Figure 1. |
| Title |
A description of ultrasonically-induced chromosomal anomalies in Vicia faba. |
| Author |
Cataldo FL, Miller MW, Gregory WD. |
| Journal |
Radiat Bot |
| Volume |
|
| Year |
1973 |
| Abstract |
An investigation of the effect of 2.0 MHz ultrasound at 8.0 W/cm(^2) on chromosomes of Vicia faba root meristem cells. No "classical" chromosome aberrations were found, but chromosome damage in the form of bridged prophases and metaphases and agglomerated mitotics was observed during the first mitosis after sonication. |
| Title |
A device for the study of the effects of ultrasound on tissue growth in rabbits' ears. |
| Author |
Pond J, Dyson M. |
| Journal |
J Sci Instrum |
| Volume |
|
| Year |
1967 |
| Abstract |
A hand-held instrument has been developed to apply high intensity ultrasound to experimental wounds in the external ears of rabbits. The method allows accurate positioning, is convenient and avoids excessive heating of the tissues. |
| Title |
A digitized, direct contact B-scanner for ophthalmic application. |
| Author |
Holasek E, Sokollu A, Purnell EW. |
| Journal |
J Clin Ultrasound |
| Volume |
|
| Year |
1973 |
| Abstract |
This paper presents the principles of a portable compact instrument utilizing a digital control system and providing B-scan displays. The instrument is designed exclusively for ophthalmic applications. The system is comprised of a self-contained scanning head and a signal display unit. The entire unit can easily be rolled to the patient's bedside or into the operating room. A programmed pulse generator provides signals for incremental angular positioning of the transducer as well as signals for the formation of the display. The transducer is moved by a stepping motor to establish the incremental sector scan. Display sweeps are generated by digital-to-analog conversion to circumvent the use of mechanically-driven position sensors as used in conventional systems. |
| Title |
A discussion of procedures for ultrasonic intensity and power calculations from miniature hydrophone measurements. |
| Author |
Harris GR. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1985 |
| Abstract |
In this paper, some of the fundamental procedures for evaluating medical ultrasound fields using miniature hydrophones are discussed. Examples are considered for both static (fixed beam) and real-time (moving beam) ultrasound systems. Intensity and power quantities are calculated from hydrophone measurements using defintions contained in current standards, and where reasonable some simplified computational procedures are introduced. Assumptions implicit in common expressions for spatial average-temporal average intensity and ultrasonic power are identified, and in some cases illustrations of calculations using idealized pressure waveforms and beam shapes are given and compared with more exact results. Also, the adequacy of present guidelines for choosing the hydrophone size is evaluated using a simple time domain approach. This material is presented to augment and help clarify descriptions of procedures contained in existing standards, and to provide a basis for pursuing some of the more difficult problems associated with hydrophone measurements. |
| Title |
A dispersive model for the propagation of ultrasound in soft tissue. |
| Author |
Gurumurthy KV, Arthur RM. |
| Journal |
Ultrason Imaging |
| Volume |
|
| Year |
1982 |
| Abstract |
Although the dispersion of tissue is small and difficult to measure, it can be calculated from a knowledge of the tissue's attenuation. A minimum-phase function, which characterizes tissue dispersion was derived using the Hilbert transform. This function was incorporated into a tissue model which has a causal impulse response and from which accurate estimates of the slope of attenuation times path length can be extracted. Predictions of phase velocity closely match available dispersion measurements. The model suggests that phase velocity measurements must be much more accurate than attenuation measurements for a comparable description of tissue. |
| Title |
A facility for the investigation of the bioeffects of ultrasound. |
| Author |
Holzemer JF, Taenzer JC, Havlice JF, Ramsey SD Jr, Green PS. |
| Journal |
Rep Stanford Res Inst |
| Volume |
|
| Year |
Unknown |
| Abstract |
No abstract available. |
| Title |
A field conjugation method for direct synthesis of hyperthermia phased-array heating patterns. |
| Author |
Ibbini MS Cain CA. |
| Journal |
IEEE Trans UFFC |
| Volume |
|
| Year |
1989 |
| Abstract |
A phased-array field conjugation method is investigated as a means for synthesizing directly many ultrasound field patterns useful for tumor heating. For virtually any ultrasound phased array, the method permits the computation of element driving amplitude and phase distributions appropriate for synthesizing directly diffuse heating patterns without the need for mechanical or electrical scanning. Moreover, the proposed method offers the possibility of creating simultaneously, at different sites, more than one focus, which can then be scanned electronically. This attractive feature eliminates the need for operating at high spatial-peak temporal-peak focal intensities, a potential problem associated with conventional scanning, while achieving a desired heating pattern. The method is applied to two different applicator configurations: a concentric-ring and a square n?n array. Computer simulations of different heating patterns, synthesized using the field conjugation method, are presented. Important practical design parameters, such as the size and number of the array elements, are discussed. |
| Title |
A finite-element formulation for the study of ultrasonic NDT systems. |
| Author |
Ludwig R, Lord W. |
| Journal |
IEEE Trans UFFC |
| Volume |
|
| Year |
1988 |
| Abstract |
Analytical approaches to the modeling of elastic wave propagation in solids are difficult to apply in the case of ultrasonic non-destructive testing (NDT) systems, where one is interested in predicting realistic transducer signals from ultrasound interactions with complex defect shapes. The paper presents a finite element formulation for an overall ultrasonic NDT system including appropriate models for transmitter and receiver transducers. Results are given for two-dimensional (2-D) plane-strain geometry simulations that agree qualitatively with corresponding experimental measurements and show the potential of the method. |
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