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At least 55 records · Page 3Linked to original sources
PubMed1981

[Basic studies on ultrasonic surgery. II. Studies on the stability after ultrasonic osteosynthesis in various forms of fractures in vitro].

Investigations on the load capacity of an ultrasonic weld in transverse fractures, oblique fractures, and multiple fragment fractures by means of homologous bone fragments and Fimomed were taken up in vitro on 84 human femur diaphyses. It was possible to demonstrate the essential influence of the form of the fracture on the stability of the weld. The mechanical density was the highest in transverse fractures, small in oblique fractures, and the smallest in multiple fragment fractures. Conclusions were drawn up for the clinical use.

Acrylates↗
PubMed1994

Measurement of thermal diffusivity of biomaterials by focused ultrasonic beams (thermal pulse decay method by focused ultrasonic beams).

This study propose a new simple method of measuring the thermal diffusivity of living tissue by thermal pulse decay technique with focused ultrasonic beam, which does not require the accurate knowledge of Gaussian variance within the focal region. The measurement of temperatures at two different locations outside the focal region replaces the elaborate measurement of the size of the focal region and gives a thermal diffusivity with reasonable accuracy and automatically avoids the artifact due to beam-thermocouple interaction. The focused ultrasound was generated by the bowl-shaped ceramic piezoelectric transducer with the diameter of 30 mm. The focal lengths of transducer were 40 mm and 60 mm and the frequencies 1.7 and 3.6 MHz. The values of thermal diffusivity of biological tissues obtained in this method are fairly close to the previously published values and are also compared to the values obtained by heated thermistor method.

Animals↗
PubMed2005

Coupling an ultrasonic propagation code with a model of the heterogeneity of multipass welds to simulate ultrasonic testing.

The knowledge of the anisotropic and heterogeneous behaviour of the material is the key point for understanding ultrasonic testing. In the case of austenitic stainless steel multipass welds, there was no exact knowledge. The succession of passes and complex solidification processes makes the modelling of the resulting grain orientation difficult. The MINA model allows such a description. Coupling this model with the new propagation code ATHENA permits a very good understanding of the propagation of elastic waves in this kind of complex media. After discussing the existing models of grains orientations for multipass welds, we show how the new MINA model allows to simulate the anisotropic heterogeneous structure in a more realistic manner. We introduce the simulated grains structure and the real one, obtained by macrographs, into the ATHENA propagation code. We obtain a very good correlation between the two simulated propagations. A first experimental application is also successful. We show in a quantitative and qualitative way that the modelling results are close to the experimental measurements on a thick austenitic weld.

Journal Article↗
PubMed2002

The measurement of the spatial average temporal average intensity I(sata) and ultrasonic power W in composite ultrasonic transducers for medical application.

Two possible methods to determine the spatial average temporal average intensity I(sata) and ultrasonic power W in composite ltrasonic transducers for medical application are described. Results showed that integrals using one method will yield accurate results but a vast amount of computational effort is required. On the other hand, using an alternative method these integrals may readily be solved at the expense of the accuracy of the results deduced.

Models, Theoretical↗
PubMed2002

Ultrasonic spectrum-analysis and neural-network classification as a basis for ultrasonic imaging to target brachytherapy of prostate cancer.

Conventional B-mode ultrasound is the standard means of imaging the prostate for guiding prostate biopsies and planning brachytherapy of prostate cancer. Yet B-mode images do not allow adequate visualization of cancerous lesions of the prostate. Ultrasonic tissue-typing imaging based on spectrum analysis of radiofrequency echo signals has shown promise for overcoming the limitations of B-mode imaging for visualizing prostate tumors. Tissue typing based on radiofrequency spectrum analysis uses nonlinear methods, such as neural networks, to classify tissue by using spectral-parameter and clinical-variable values. Two- and three-dimensional images based on these methods show potential for improving the guidance of prostate biopsies and the targeting of radiotherapy of prostate cancer. Two-dimensional images have been imported into instrumentation for real-time biopsy guidance and into commercial dose-planning software for brachytherapy planning. Three-dimensional renderings seem to be capable of depicting locations and volumes of cancer foci.

Brachytherapy↗
PubMed1986

Accurate ultrasonic estimation of fetal weight. Prospective analysis of new ultrasonic formulas.

Five new ultrasonic weight formulae incorporating head circumference, fetal femur length, and a correction for oligohydramnios were prospectively analyzed in a group of 198 unselected patients scanned within 72 hours of birth. Comparison with the Shepard formula showed that inclusion of these parameters slightly, but significantly, improved the random error of weight estimation. The best-fit formula was: Log(10) BW = .04355HC + .05394AC - .0008582HC X AC + 1.2594 (FL/AC) - 2.0661.

Birth Weight↗
PubMed1978

The ultrasonic and computed tomographic appearance of splenic lobulations: a consideration in the ultrasonic differential of masses adjacent to the left kidney.

A splenic lobulation interposed between the tail of the pancreas and the left kidney is not uncommon. On prone ultrasonic scans, this variant of splenic configuration must be considered in the differentiation of anterior masses adjacent to the left kidney and masses originating in the tail of the pancreas. Computed tomography is the most sensitive method to use in making this distinction.

Humans↗
PubMedDate not supplied

Evaluation of cross-circulation through circle of Willis using an ultrasonic Doppler technique. Part I. Comparison between blood flow velocity by ultrasonic Doppler flowmetry and angiogram.

In 24 patients with cerebrovascular disease and 6 without organic brain lesions, the increased velocity of blood flow in both the internal carotid and vertebral arteries during a contralateral carotid compression was compared with the angiographic appearance of the circle of Willis. The flow velocity was measured using ultrasonic Doppler flowmetry. It was not possible to investigate fully the relationship between the increase of velocity of blood flow in the internal carotid artery and the anatomical variations of the circle of Willis, specifically the anterior cerebral and communicating arteries. The velocity of flow in the patients with an aplastic proximal portion of the anterior cerebral artery showed no increase. There were no differences in the increase of velocity of flow in the vertebral artery in patients with hypoplastic, normal and fetal posterior communicating arteries. It is considered that although anatomical variations of the circle vessels influence the cross-circulation via the circle of Willis, peripheral vascular factors distal to the circle also play an important role in the quantity of cross-circulation through the circle.

Adolescent↗