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At least 631 records · Page 35Linked to original sources
PubMed2004

The role of viscosity in the impulse diffraction field of elastic waves induced by the acoustic radiation force.

Several ultrasound-based techniques for the estimation of soft tissue elasticity are currently being investigated. Most of them study the medium response to dynamic excitations. Such responses are usually modeled in a purely elastic medium using a Green's function solution of the motion equation. However, elasticity by itself is not necessarily a discriminant parameter for malignancy diagnosis. Modeling viscous properties of tissues could also be of great interest for tumor characterization. We report in this paper an explicit derivation of the Green's function in a viscous and elastic medium taking into account shear, bulk, and coupling waves. From this theoretical calculation, 3D simulations of mechanical waves in viscoelastic soft tissues are presented. The relevance of the viscoelastic Green's function is validated by comparing simulations with experimental data. The experiments were conducted using the supersonic shear imaging (SSI) technique which dynamically and remotely excites tissues using acoustic radiation force. We show that transient shear waves generated with SSI are modeled very precisely by the Green's function formalism. The combined influences of out-of-plane diffraction, beam shape, and shear viscosity on the shape of transient waves are carefully studied as they represent a major issue in ultrasound-based viscoelasticity imaging techniques.

Acoustics↗
PubMedDate not supplied

[Costa's acrokerato-elastoidosis. Ultrastructural study (author's transl)].

Acrokerato-elastoidosis described by Costa is characterized by numerous little keratotic points and translucent horny wheals on the dorsal aspect of hands and (or) feets. The ultrastructural study shows lesions of the elastic tissue which is very rarefied with an abnormal structure, but also demonstrates alterations of the fibroblasts that contain dense granules at the periphery of their cytoplasm without elastic extracellular fibers, suggesting a trouble in the secretion or the excretion of the elastic material.

Acrodermatitis↗
PubMedDate not supplied

[Costa's acrokerato-elastoidosis. Ultrastructural study (author's transl)].

Acrokerato-elastoidosis described by Costa is characterized by numerous little keratotic points and translucent horny wheals on the dorsal aspect of hands and (or) feet. The ultrastructural study shows lesions of the elastic tissue which is very rarefied with an abnormal structure, but also demonstrates alterations of the fibroblasts that contain dense granules at the periphery of their cytoplasm without elastic extracellular fibers, suggesting a trouble in the secretion or the excretion of the elastic material.

Acrodermatitis↗
PubMed1984

Amyloid P component in human thyroid.

The distribution of amyloid P component in the adult human thyroid was studied by direct immunofluorescence on frozen sections of surgically removed tissue. Amyloid P component shows a striking fibrillary and broken linear distribution in the interfollicular areas. This pattern corresponds to that of reticulin fibres. Amyloid P is also localised to the small amount of elastic tissue in blood vessels but is not demonstrable within cells or in acinar basement membranes.

Amyloid↗
PubMed1972

Chronic actinic keratopathy--a condition associated with conjunctival elastosis (pingueculae) and typified by characteristic extracellular concretions.

Morphologic observations on a peculiar type of corneal reaction with a predisposition for the superficial stroma of the interpalpebral portion of the cornea are reviewed. Histochemical evidence is provided which indicates that the corneal concretions, though not homogenous, are proteinaceous in nature and contain amino acids not normally detectable in the cornea. The corneal concretions were associated with conjunctival elastosis (pingueculae) in all 22 instances in which the eyes were sectioned in the horizontal plane. Identical concretions were identified within these associated pingueculae, as well as in a large percentage of other pingueculae and cutaneous lesions with actinic elastosis. The findings suggest that the abnormal material arises in the pericorneal conjunctival connective tissue from whence it diffuses into, and deposits in, the superficial corneal stroma. The data also raise the possibility that the concretions may be derived, at least in part, from altered elastic tissue. Morphologic and epidemiologic observations on the condition taken together strongly suggest that this unique reaction is a sequel to the cumulative effect of chronic actinic irradiation. Further observations on this keratopathy are needed to establish whether this unique response can be provoked by other noxious stimuli.

Adult↗
PubMed1980

Staining myelin, elastic fibers and nuclei with iron hematoxylin.

Two iron hematoxylin staining procedures were developed. Both use stable stock solutions and can be prepared volumetrically. The nuclear stain is progressive but differentiation is required for myelin sheath and elastic tissue staining. Histochemical procedures demonstrated that acid, hydroxyl, and aldehyde groups play no role in the staining but amine groups are essential. With both types of stains neither electrostatic bonding nor hydrogen bonding is essential but the nature of the union between tissue and the iron hematoxylin complex was not determined.

Animals↗
PubMed1979

"Lumpy-bumpy" elastic fibers in the skin and lungs of a patient with a penicillamine-induced elastosis perforans serpiginosa.

Penicillamine-induced cutaneous elastosis perforans serpiginosa associated with a large air-cyst in the right lung is described in a 29-year-old female patient with Wilson disease. Identical light and electron-microscopic changes were present in both dermal and pulmonary elastic tissue, suggesting a disseminated drug-induced cutaneo-visceral elastosis. Lung cysts have not been previously reported in association with long term penicillamine treatment. The electron-microscopic morphology of the elastic fibers was found to be "specific" enough to allow separation of penicillamine-induced elastosis perforans serpiginosa from other forms of this disease.

Adult↗
PubMed1995

Magnetic-resonance imaging techniques for detection of elasticity variation.

The relative success of manual palpation in the detection of breast cancer would suggest that a method for remote palpation resulting in a measurement of tissue elasticity could provide a diagnostic tool for detecting cancerous lesions deeper within the breast. This presumption is based in part on the excellent contrast between neoplastic and normal tissue due to the large (orders of magnitude) relative variation in the shear elastic modulus. By comparison, the bulk deformational modulus maintains the same value to within 20% for most soft tissues. A specific method of magnetic-resonance imaging (MRI) which measures tissue displacements has been used in experiments with a phantom containing regions of increased Young's modulus as a demonstration. The spatial modulation of magnetization technique uses the displacement of a spatial grid pattern caused by spin saturation to track regional motion. Mathematical reconstruction of the distribution of elastic moduli is shown for select examples. Any modality, e.g., MRI, ultrasound, etc., which can detect local tissue motion with sufficient spatial resolution can be used and therefore the results presented here should give an indication of the utility of such motion tracking techniques to future measurement of tissue elasticity.

Biophysical Phenomena↗
PubMed2000

Computerized endopharyngeal myotonometry (CEM): a new method to evaluate the tissue tone of the soft palate in patients with obstructive sleep apnoea syndrome.

This study compared the tissue tone of the soft palate in nonsnoring subjects and patients with obstructive sleep apnoea syndrome (OSAS) during wakefulness. Here, tissue tone means the biomechanical property of the tissue which can be characterized by two main parameters: stiffness and elasticity. Tissue tone includes both structural and neural components. A new method to evaluate the tissue tone of the soft palate was used - computerized endopharyngeal myotonometry (CEM). This method records and analyses the response of the soft palate tissues to a brief mechanical impact. The method enabled us to evaluate the most important parameters of tissue tone: stiffness, which is expressed as a frequency; and elasticity, expressed as a logarithmic decrement of the damped oscillation. First, a self-reported questionnaire was completed about the medical history of the subjects. Subjects then underwent a physical examination of the oropharynx and polysomnography with overnight pulse oximetry. The results of the CEM method indicated that patients with OSAS show an increased stiffness of the soft palate tissues (20.3, SD 4.7 Hz) compared with nonsnoring subjects (12.2, SD 1.8 Hz). In patients with sleep apnoea, elasticity is not increased in a similar way to stiffness. Thus, the disproportion between tissue stiffness and elasticity of the soft palate is a measure of the pathological changes in patients with sleep apnoea.

Adult↗
PubMed1965

Bronchiolar emphysema (diffuse bronchiolectasis)--so-called muscular cirrhosis of the lungs.

Eleven autopsied cases of bronchiolar emphysema are reported. In all, both lungs were involved. Their pleural surfaces were finely bosselated, presenting an appearance resembling that of the liver in Laennec's cirrhosis. The lungs were firm, they cut with increased fibrous resistance, and the cut surfaces were honeycombed with cysts.Microscopically, the cysts originated in terminal bronchioles. Their walls were thickened with fibrous tissue, elastic fibres and prominent smooth muscle. Areas of lung parenchyma were replaced by fibrous tissue rich in elastic fibres.The etiology of this disease is unknown. Inherent weakness of the myoelastic wall of the respiratory bronchiole, hypoplasia of the distal segment of the respiratory unit, and superimposed recurrent respiratory infections probably are essential in its pathogenesis. The pulmonary changes cause interference with hemorespiratory gaseous exchange.Death was due to respiratory failure in seven cases, to cardiac failure in three and to superimposed staphylococcal pneumonia in one.

Adult↗
PubMed1990

Elastogenesis in the wall of the human thoracic aorta.

The results of this study dealing with the human thoracic foetal aorta testify that even in the middle of the fifth month of development the internal elastic membrane is not yet completely continuous. Furthermore they show that elastogenesis in the tunica media of the human thoracic aorta does not begin directly below the internal elastic membrane, as it does in the foetal aorta of the laboratory rat, but, as it can be seen in our material, somewhat deeper in the developing tunica media. A thin layer of less differentiated tunica media cells persists for a long time in the vicinity of the internal elastic membrane. In the middle of the fifth month, the fusing elastic membrane segments in the tunica media still consist of very immature elastic tissue with a large proportion of the microfibrillar component. The collagen fibrils in the intercellular spaces in the whole depth of the wall of the developing aorta do not become a part of the elastic membranes. Their bundles merely accompany all the elastic membranes in the wall of the thoracic aorta, including the internal elastic membrane.

Aorta, Thoracic↗
PubMed1977

[Dissecting aneurysm of the anterior cerebral artery and Guillain-Barré-syndrome during pregnancy (author's transl)].

In the 8th month of her second pregnancy a young woman fell ill with polyradiculitis. She suddenly died because of a massive abdominal hemorrhage, the cause of which remained obscure. Autopsy revealed typical morphological findings of polyradiculoneuritis and a dissecting aneurysm of the anterior cerebral artery and the recurrent artery of Heubner. The importance of elastic tissue degneration in intracranial dissecting aneurysms is stressed and similar reports in the literature are referred.

Adult↗
PubMed2004

A quantitative comparison of modulus images obtained using nanoindentation with strain elastograms.

Tissue stiffness is generally known to be associated with pathologic changes. Ultrasound (US) elastography, on the other hand, is capable of imaging tissue strain, which may or may not be well-correlated with tissue stiffness. Hence, a quantitative comparison between the elastographic tissue strain images and the corresponding tissue modulus images needed to be performed to evaluate the usefulness of elastography in imaging tissue stiffnesss properties. Simulations were performed to demonstrate and quantify the similarities between modulus images and strain elastograms. This was followed by comparing nanoindenter-based modulus images with strain elastograms of thin slices of tissue-mimicking phantoms. Finally, some beef slices, canine prostates, ovine kidneys and breast cancers grown in mice were used to demonstrate the qualitative correspondence between modulus images and strain elastograms. The simulations and the experiments indicated that it is feasible to perform quantitative comparisons between strain images (using elastography) and modulus images on certain tissue structures and geometries. A good quantitative correspondence (correlation values of greater than 0.8) between structures in the modulus and strain images could be obtained at scales equal to or larger than 20 Qlambda (where Q is the quality factor defined as the ratio of the center frequency over the band width and lambda is the wavelength of the US system) modulus contrasts larger than 5, applied strains between 0.5% and 3% and window lengths for computing strain elastograms between 3 Qlambda and 5 Qlambda. The gelatin-phantom experiments showed lower values of correlation (values around 0.5) than with theory and simulations. The decrease in correlation was attributed to the presence of measurement noise in both strain elastography and modulus imaging, an increase of dimensionality of the problem (from 2-D to 3-D), local anisotropy, heterogeneity and nonstationarity. Experiments on real tissue slices showed further decrease in the correlation to around 0.3, possibly due to additional confounding factors such as time-dependent mechanical properties and geometrical distortions in the tissue during imaging. The work presented in this paper demonstrates that there is an intrinsic relationship between strain elastograms and the actual distribution of soft tissue elastic moduli, and bodes well for continued work in the area of elastography.

Algorithms↗
PubMed1977

Elastosis perforans serpiginosa with widespread arterial lesions: a case report.

A case is presented of elastosis perforans serpiginosa (EPS) with unilateral dermal lesions, widespread arterial lesions with aortic rupture, and elastosis of the endocardium and bronchiolar walls. Other chronic skin disorders with lesions resembling EPS are discussed; and the arterial lesions compared with some arterial diseases. The findings support a concept of the disease as a focal affection of elastic tissue, not only in the skin, but also in arteries and other organs.

Adult↗
PubMed1987

Viability and morphology of aortic and pulmonary homografts. A comparative study.

In view of possible clinical use of the pulmonary homograft for right ventricular outflow tract reconstruction a comparative study with the aortic counterpart was performed. Samples of aortic and pulmonary walls from 10 cadaveric hearts were assessed for viability and morphologic characteristics before and after storage in nutrient-antibiotic solution. The viability, as evaluated by an autoradiographic technique, was similar in both aortic and pulmonary specimens at the time of dissection, after 2 weeks, and after 4 weeks of storage. The histologic examination showed no changes in the structure of the media in all samples up to 4 weeks of storage. The total calcium content per gram of tissue in the pulmonary media was on an average less than half of that in the aortic counterpart. We conclude that the pulmonary homograft is preserved the same as the aortic homograft and, accordingly, it becomes available for clinical application. Moreover, a lesser content of elastic tissue and a lower amount of total calcium may, in all likelihood, make the pulmonary wall less prone to calcification.

Adolescent↗