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BRL Abstracts Database |
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Your search for ultrasound produced 3296 results. Page 149 out of 330
| Title |
In vitro ultrasonic characterization of human cancellous femoral bone using transmission and backscatter measurements: Relationships to bone mineral density. |
| Author |
Jenson F, Padilla F, Bousson V, Bergo C, Laredo J-D, Laugier P. |
| Journal |
J Acoust Soc Am |
| Volume |
|
| Year |
2006 |
| Abstract |
Thirty-eight slices of pure trabecular bone 1-cm thickness were extracted from human proximal femurs. A pair of 1-MHz central frequency transducers was used to measure quantitative ultrasound (QUS) parameters in transmission [normalized broadband ultrasound attenuation (nBUA), speed of sound (SOS)] and in backscatter [broadband ultrasound backscatter (BUB)]. Bone mineral density (BMD) was measured using clinical x-ray quantitative computed tomography. Site-matched identical region of interest (ROIs) of 7?7 mm2 were positioned on QUS and QCT images. This procedure resulted in 605 ROIs for all the specimens data pooled together. The short-term precision of the technique expressed in terms of CV was found to be 2.3% for nBUA, 0.3% for SOS and 4.5% for BUB. Significant linear correlation between QUS and BMD were found for all the 605 ROIs pooled, with r2 values of 0.73, 0.77, and 0.58 for nBUA, SOS, and BUB, respectively (all p<0.05). For the BUB, the best regression was obtained with a polynomial fit of second order (r2=0.63). An analysis of measurements errors was developed. It showed that the residual variability of SOS is almost completely predicted by measurements errors, which is not the case for BUA and BUB, suggesting a role for micro-architecture in the determination of BUA and BUB. |
| Title |
In vitro ultrasonic heating of fetal bone. |
| Author |
Drewniak JL, Carnes KI, Dunn F. |
| Journal |
J Acoust Soc Am |
| Volume |
|
| Year |
1989 |
| Abstract |
The temperature increase measured in vitro in human fetal femurs exposed to 1 MHz, continuous wave ultrasound at 37 degrees C is reported. The temperature is measured with a thermocouple probe and is given for several gestational ages. The initial rate of the temperature increase in the specimens is evaluated and compared to known values of absorption in soft tissue. For example, the initial rate of temperature increase in the 108-day gestational age specimen resulting from exposure to ultrasound is 30 times greater in the fetal bone than that of soft tissue with an absorption coefficient of 0.05 cm-1. |
| Title |
In vivo acoustic attenuation in liver: Correlations with blood tests and histology. |
| Author |
Duerinckx A, Rosenberg K, Hoefs J, Aufrichtig D, Cole-Beuglet C, Kanel G, Lottenberg S, Ferrari LA. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1988 |
| Abstract |
Results of in vivo attenuation measurements in the liver have been obtained in 26 normal controls and in 51 patients with chronic diffuse liver disease. A modified real-time sector scanner was used for narrow-band amplitude attenuation examination. In the control group (people without apparent liver disease), a statistically significant correlation was found between acoustic attenuation in liver and two blood tests reflecting liver function: serum albumin (n = 24, r = 0.67, p = 0.002) and prothrombin time (n = 23, r = 0.63, p = 0.019). There was a statistically significant positive correlation between attenuation and fat for all biopsied patients (n = 51, r = 0.32, p = 0.023) and for patients with minimal fibrosis (n = 25, r = 0.45, p = 0.027). Although no correlation with fibrosis was found for all patients, in the group of patients with minimal fat there was a correlation with portal fibrosis (n = 33, r = 0.37, p = 0.035). This double blind prospective study shows that in the liver: (1) attenuation estimates appear correlated with clinical parameters (blood tests) in normal volunteers, and (2) large changes in fat affect narrow-band acoustic attenuation estimates to a greater degree than severe portal fibrosis in patients with chronic diffuse liver disease. Further research is needed before these estimates can become a clinical tool. |
| Title |
In vivo and in vitrio studies of application of ultrasonic visualization techniques for detection of breast cancer. |
| Author |
Kelly-Fry E, Gallager HS, Franklin T Jr. |
| Journal |
Ultrasound Symp |
| Volume |
|
| Year |
1971 |
| Abstract |
No abstract available. |
| Title |
In vivo biomicroscopy with ultrasound 2. |
| Author |
Santosh K, Tobocman W, Haacke EM, Boada F. |
| Journal |
Ultrasonics |
| Volume |
|
| Year |
1990 |
| Abstract |
In the first article of this series it was shown that the use of inverse scattering theory to analyse ultrasound reflections could provide high resolution images of the acoustic impedance profile of the retina. Unlike the retina, most tissue structures of interest, like small tumours and arterial plaque deposits, are shielded from view by intervening layers of tissue of appreciable acoustic impedance and attenuation. By analysing a one-dimensional model for a plaque deposit on the wall of a carotid artery embedded in a 5 cm thick layer of tissue, we demonstrate that a relatively high quality image can be recovered when compensation for the attenuation of the intervening tissue is made. We observe that because of the dearth of low frequency power in the recovered signal of ultrasound transducers, it is important that the field of view imaged is not taken to be too large. We compare the exact iterative distorted wave Born approximation inverse scattering method with the approximate but computationally faster plane wave Born approximation method and find that they give images of comparable quality for this model. .. |
| Title |
In vivo biomicroscopy with ultrasound. |
| Author |
Santosh K, Tobocman W, Haacke EM, Izen SH. |
| Journal |
Ultrasonics |
| Volume |
|
| Year |
1987 |
| Abstract |
We propose the use of inverse scattering theory methods to analyse high frequency ultrasound reflection data to provide high resolution image of living tissue. Conventional ultrasound imaging uses the pulse-echo method which can only resolve structures which are large compared to the wavelength of the ultrasound. Inverse scattering analysis, on the other hand, can image details as small as a quarter wavelength. This makes possible a significant improvement in resolution and has many potential applications in the detection and study of disease. We report here results obtained using this method to produce images of the retina, where we were able to resolve details as small as 50 micron in a 300 micron layer. |
| Title |
In vivo choroidal thickness measurement. |
| Author |
Coleman DJ, Lizzi FL. |
| Journal |
Am J Ophthalmol |
| Volume |
|
| Year |
1979 |
| Abstract |
We developed a system that permits exceptionally accurate measurements of human choroidal thickness in vivo by means of ultrasound. With minicomputer techniques, the complementary functions of the time and spectral domains of reflected sound can be used to permit measurements accurate to less than 20 mu at 10 MHz center frequency. Even more accuracy can be obtained with higher center frequencies. Choroidal thickness has been found to exceed that previously reported, with typical values of 420 mu found at the posterior pole. Even greater values are seen in regions outside the macula. |
| Title |
In vivo detection of ultrasonically induced cavitation by a fibre-optic technique. |
| Author |
Huber P, Debus J, Peschke P, Hahn EW, Lorenz WJ. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1994 |
| Abstract |
The measurement of cavitation events in tissue in vivo would greatly assist us to better understand how pulsed high energy ultrasound (PHEUS) interacts with living tissues, especially with regard to cancer therapy. To accomplish this, we designed and built a fibre-optic hydrophone. The principle was to couple the light of a laser diode into a lightfibre and to register the ultrasound induced modification of the refractive index in tissue. In this manner, the cavitation event could be quantitatively investigated both in water and in vivo. The structure of the bubble dynamic is in reasonable agreement with theoretical predictions, and in vitro measurements. With the fibre-optic set-up, the pressure signal can also be detected. PHEUS was generated by an electromagnetic source adapted from a commercial lithotripter (Lithostar Siemens). As biological tissue we used the experimental R3327-AT1 Dunning prostate tumor growing subcutaneously in the thigh of male Copenhagen rats. The lifetime of the cavitation bubble in water increased with the energy level of the ultrasonic pulse from 250 microseconds at 13 kV capacitor voltage to 750 microseconds at 21 kV, while the lifetime inside the tumor tissue in vivo increased only from 100 microseconds at 13 kV to 220 microseconds at 21 kV capacitor voltage.
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| Title |
In vivo effect of ultrasound at human therapeutic doses on marrow cell chromosomes of golden hamster. |
| Author |
Levi S, Gustot P, Galperin-Lemaitre H. |
| Journal |
Humangenetik |
| Volume |
|
| Year |
1974 |
| Abstract |
Ultrasounds are widely used in therapy and diagnosis, particularly for obstetrical diagnosis. Studies of their biological effects were recently focused on chromosomes and the results were contradictory. Because of possible artefacts due to tissue culture stages, in vivo insonation of bone marrow cells has been performed at 1 and 1.5 W/cm2 and 0.87 MHz frequency for 2 to 5 min, at much higher doses than used for human fetus investigation. Colchicine was injected in vivo 1 hr before cell harvesting and chromosomes were examined immediately afterward. A study of 1503 mitoses from 20 animals was made. No statistically significant differences in aberration rate were observed between insonated and control cells. |
| Title |
In Vivo frequency dependent backscatter estimations in liver. |
| Author |
Wilson TA. |
| Journal |
Thesis(PhD): Univ of Wisconsin-Madison |
| Volume |
|
| Year |
2000 |
| Abstract |
The work presented in this thesis is a continuation of our research to develop and evaluate quantitative backscatter parameters for diagnosing diffuse and focal liver disease. Emphasis was placed on developing echo data acquisition hardware and software to digitize signals from clinical ultrasound scanners. A reference phantom method was employed to measure backscatter and attenuation coefficients of test samples. The method compares echo signals from a well calibrated tissue-mimicking phantom to those acquired form a test sample.
Bulk acoustic properties were studied in four animal models of diffuse liver disease to determine the usefulness of ultrasound in the early detection of these abnormal states. The changes observed in the backscatter and attenuation coefficients for these animal models were in good agreement with trends observe din human conditions of these diseases. Initial investigations into an animal model of focal disease in liver was also investigated, and variation in the dependence of scattering from the tumor from that of normal liver was observed.
A reference phantom method for the determination of the effective number of scatterers versus frequency was also developed in this work. Phantoms with sparse scatterer concentrations were used to verify the validity of this method. In addition to backscatter and attenuation results, effective scatterer number density estimates, Neff, in the models of diffuse liver disease in animals were obtained. The results showed Neff can be used as a parameter to quantify a difference between diffusely diseased liver from that of normal liver in these models.
Finally, initial research into the attenuation properties of ultrasound contrast agents is presented. A significant dependence on pressure amplitude in these agents was noted in the laboratory measurements, and initial clinical trials were based upon these results. A measurable change over time in the attenuation coefficient of three dogs livers were measured post administration of ultrasound contrast agent. The clinical results along with the significant pressure dependence of the agent on incident pressure amplitude of the ultrasound waves suggests the future possibility of measuring perfusion using ultrasound.
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