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BRL Abstracts Database |
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Your search for ultrasound produced 3296 results. Page 171 out of 330
| Title |
Measurement of the ultrasonic properties of vascular tissues and blood from 35-65 MHz. |
| Author |
Lockwood GR, Ryan LK, Hunt JW, Foster FS. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1991 |
| Abstract |
A 50 MHz ultrasound backscatter microscope has been built to measure the acoustic properties of vascular tissues and blood over the frequency range from 35–65 MHz. High resolution (45 μm) ultrasound backscatter microscope images of nine femoral and eight common carotid human artery samples were made and compared with corresponding histological sections. Individual tissue layers were selected using these images for quantitative measurement of the frequency dependent backscatter. Backscatter measurements were made in each layer of an artery at two different angles of incidence: along the axis of the artery (axial direction) and at 90 degrees to this measurement radially out from the center of the artery (radial direction). Scattering was found to be higher in elastic arteries (carotid) than in the muscular arteries (femoral). The largest difference was found in the media where the average scatter (measured in the radial direction at 50 MHz) increased from 0.002 sr−1 mm−1 in muscular arteries to 0.4 sr−1 mm−1 in elastic arteries. Large differences in scattering between measurements made in the axial and radial direction were also found. Again, the largest differences were found in the media where scattering (at 50 MHz) in carotid arteries increased from 0.003 sr −1 mm−1 measured in the axial direction to 0.4 sr−1 mm−1 measured in the radial direction. The speed of sound and attenuation in the artery wall of each sample were measured. Speed of sound measurements were found to range between 1579–1628 ms−1. The average attenuation in the artery wall increased from 4 dB mm−1 at 30 MHz to 10 dB mm−1 at 60 MHz. This is higher than the attenuation measured in blood which increased from 1.6 dB mm−1 to 5 dB mm−1 over the same frequency range. The backscatter coefficient for flowing blood was measured for flow velocities up to 36 cms−1. At flow velocities below 18 cms−1 a level of scattering of 0.0005 sr−1 mm−1 (at 50 MHz) was found. An increase in scattering of 1.6 times was measured when the flow velocity was increased to 36 cms−1. All measurements were made at 37°C. The relevance of these results to clinical imaging and image interpretation is discussed. |
| Title |
Measurement of the velocity of ultrasound in human cortical bone and.its potential clinical importance. An in vivo preliminary study. |
| Author |
Craven JD, Costantini MA, Greenfield MA, Stern R. |
| Journal |
Invest Radiol |
| Volume |
|
| Year |
1973 |
| Abstract |
The velocity of ultrasound in human cortical bone has been measured in vivo by a pulse echo technique. The velocity is reduced in a small group of older females, compared with a small group of young males. It is suggested that this change results from a proportionately greater decrease in the elastic constant of the bone, compared with its density. This method measures a new combination of physical properties of bone, which may have important clinical significance in the assessment of the diagnosis and course of osteoporosis. |
| Title |
Measurement of thermal properties of perfused biological tissue by transient heating with focused ultrasound. |
| Author |
Newman WH, Lele PP. |
| Journal |
Proc Ultrason Symp IEEE |
| Volume |
|
| Year |
1985 |
| Abstract |
Recent interest in therapeutic hyperthermia as a cancer treatment modality have shown the need for accurate tissue thermal property values for therapy planning, optimization and evaluation. Here a transient thermal pulse technique using a focused ultrasound beam as a heat source is described for the measurement of the thermal properties of perfused and nonperfused tissues, in vivo and in vitro. Thermal diffusivity measurements were made in a variety of biological tissues, under perfused and nonperfused conditions, and found to concur with tabulated values; in addition it is shown that by proper choice of experimental parameters the effect of perfusion may be minimized to obtain intrinsic property values in the presence of perfusion.. |
| Title |
Measurement of tissue mechanical properties. |
| Author |
Chen EJ, Shin M, Novakofski J, O'Brien WD Jr. |
| Journal |
Rep Univ Ill - Urbana/Champaign Beckman Inst |
| Volume |
|
| Year |
1995 |
| Abstract |
Information about tissue mechanical properties is potentially useful for medical imaging such as in cancer or hard tumor detection and for commercial applications such as maintaining objective measurements for quality control in food science. The goal of this paper is to develop a method to non-invasively measure tissue mechanical properties using ultrasound and to compare these measurements with independent mechanical measurements to verify accuracy. Ultrasound provides several advantages including real time imaging, high safety, low cost and non-invasive measurements. |
| Title |
Measurement of ultrasonic nonlinear parameter in excised fat tissues. |
| Author |
Errabolu RL, Sehgal CM, Bahn RC, Greenleaf JF. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1988 |
| Abstract |
This paper reports sound speed co, adiabatic acoustic nonlinear parameter B/A, and isothermal nonlinear parameter (B/A)' of 33 samples of excised human and animal fats and some simple mixtures, e.g., skim milk and powdered milk. Tissues were obtained from different parts of the body and the measurements were made in the temperature range of 20 degrees C to 37 degrees C. All the fats were highly nonlinear. Although there was a considerable overlap in the values of acoustic.nonlinearity of different body fats, in general their values followed the order: mesenteric fat greater than subcutaneous fat greater than omentum fat greater than breast fat. Temperature coefficients of co and B/A, and the difference between adiabatic and isothermal nonlinearity, correlated highly with water/fat content of tissues. A reciprocal relationship between B/A and co, similar to that proposed for liquids, was observed for soft tissues but not for solutions of powdered milk in skim milk. No significant correlation was observed between acoustic measurements and the age of human subjects from which fat tissues were obtained. |
| Title |
Measurement of ultrasonic pressure by heterodyne interferometry with a fiber-tip sensor. |
| Author |
Koch C. |
| Journal |
Appl Opt |
| Volume |
|
| Year |
1999 |
| Abstract |
A fiber-optic measurement system is described that allows ultrasound to be detected in fluids. It is based on a heterodyne interferometer, and the sensing element consists. of a metal-coated fiber tip. The heterodyne technique permits direct acquisition of the sound pressure. The required ac photodetection is carried out with wide bandwidth,. and the system provides high temporal and spatial resolution. For optimum performance the system parameters are matched to the sound-wave properties of the current. application with the aid of theoretical and numerical calculations. The fiber-optic sensor system was applied to two problems of ultrasonic exposimetry in which the. favorable features of the measurement technique were exploited. Shock waves from an electromagnetic lithotripter were investigated by use of the wide bandwidth of the. system, and the subharmonic in an ultrasonic cleaner was detected, which indicates cavitation. |
| Title |
Measurement of ultrasonic velocity in several biological tissues. |
| Author |
Frizzell LA, Gindorf JD. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1981 |
| Abstract |
The ultrasonic velocity at 100MHz and room temperature (23-26˚C) was measured in the fresh, excised mammalian liver, kidney, spleen, and pancreas and mouse kidney. The results show excellent agreement with measurements at low MHZ frequencies. A significant velocity difference is reported between kidney cortex and medulla, but no difference was observed between the exocrine and islets of Langerhans in the first measurements of velocity in the pancreas. |
| Title |
Measurement of ultrasound attenuation coefficient by a multifrequency echo technique - theory and basic experiments. |
| Author |
Hayakawa Y, Wagai T, Yosioka K, Inada T, Suzuki T, Yagami H, Fujii T. |
| Journal |
IEEE Trans UFFC |
| Volume |
|
| Year |
1986 |
| Abstract |
A theory for obtaining the attenuation coefficient a and its frequency dependence from strong echo signals is proposed. Experiments were conducted using caster oil, within which two planar reflectors were immersed. The experimentally obtained value of a was close to the published data of Mikhailov, supporting the theory. |
| Title |
Measurement of ultrasound velocity in human tissue. |
| Author |
Van Venrooij GEPM. |
| Journal |
Ultrasonics |
| Volume |
|
| Year |
1971 |
| Abstract |
This paper describes a method of measuring ultrasound velocity to high accuracy in small samples of reasonably homogenous substances. Results obtained with some body fluids and brain tumours are given. |
| Title |
Measurement of ultrasound velocity in tissues utilizing a microcomputer-based system. |
| Author |
Bronez MA, Shung KK, Heidary H, Hurwitz D. |
| Journal |
IEEE Trans Biomed Eng |
| Volume |
|
| Year |
1985 |
| Abstract |
The continued interest in diagnostic applications of ultrasound has led to a need for more detailed knowledge of the ultrasonic properties of biological tissues. This communication describes an experimental system based on a Z-80 microprocessor which communicates with other devices via an STD bus for measuring ultrasound velocity in biological tissues as a function of temperature. Data have been collected for bovine heart, kidney, liver, and blood over the temperature range of 10-45 C. |
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