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At least 109 records · Page 6Linked to original sources
PubMed1983

[Soft- and hardware support for the setup for computer tracking of radiation teletherapy].

A hard and soft ware computer assisted complex has been worked out for gamma-beam therapy. The complex included all radiotherapeutic units, including a Siemens program controlled betatron with an energy of 42 MEV computer ES-1022, a Medigraf system of the processing of graphic information, a Mars-256 system for control over the homogeneity of distribution of dose rate on the field of irradiation and a package of mathematical programs to select a plan of irradiation of various tumor sites. The prospects of the utilization of such complexes in the dosimetric support of radiation therapy are discussed.

Computers↗
PubMed1981

CT of soft-tissue tumors.

Computed tomography was performed on 52 patients with soft-tissue tumors, 36 malignant and 16 benign. Major advantages with CT include the possibility of differentiating between lipoma and other tumors and the ability to demonstrate the transverse location of a lesion (intra- or extracompartmental). It was not possible to relate attenuation values to histologic type or grade of malignancy. CT was found superior to conventional radiography in demonstrating additional bony destruction of the pelvis and spine. The risk of overestimating the size of high grade malignant tumors because of accompanying edema is discussed. CT should precede angiography in the investigation of soft-tissue tumors, and angiography may primarily be reserved for those lesions where vascular relationships are not adequately demonstrated by CT.

Adolescent↗
PubMed1982

Volume averaging limitations of computed tomography.

A simple volume averaging model was shown to be inadequate for predicting effective computed tomographic attenuation values of mixtures of bone or air with soft tissue. Computed tomographic values derived from scanning stratified sub-slice thickness objects were shown theoretically and experimentally to have a non-linear dependency on relative fractional content and a surprisingly large dependency on spatial extent of the stratified substances. The mode was applied to the problem of computed tomographic values in thin, flat structures such as pools of blood in the subarachnoid space. The results show only small deviations from simple volume averaging theory for layers of low contrast substances such as blood and soft tissue, but potentially large deviations for layers of substances with high contrast differences such as bone, air, and tissue. This phenomenon explains certain artifacts and demonstrates rather fundamental problems in the accuracy of analytic reconstruction techniques. It may justify postprocessing correction or iterative approaches.

Mathematics↗
PubMed2000

Evaluation of an iterative reconstruction method for quantitative elastography.

This paper describes an inverse reconstruction technique based on a modified Newton Raphson iterative scheme and the finite element method, which has been developed for computing the spatial distribution of Young's modulus from within soft tissues. Computer simulations were conducted to determine the relative merits of reconstructing tissue elasticity using knowledge of (a) known displacement boundary conditions (DBC), and (b) known stress boundary conditions (SBC). The results demonstrated that computing Young's modulus using knowledge of SBC allows accurate quantification of Young's modulus. However, the quality of the images produced using this reconstruction approach was dependent on the Young's modulus distribution assumed at the start of the reconstruction procedure. Computing Young's modulus from known DBC provided relative estimates of tissue elasticity which, despite the disadvantage of not being able to accurately quantify Young's modulus, formed images that were generally superior in quality to those produced using the known SBC, and were not affected by the trial solution. The results of preliminary experiments on phantoms demonstrated that this reconstruction technique is capable in practice of improving the fidelity of tissue elasticity images, reducing the artefacts otherwise present in strain images, and recovering Young's modulus images that possess excellent spatial and contrast resolution.

Computer Simulation↗
PubMed1996

Subtle pulmonary disease: detection with computed radiography versus conventional chest radiography.

PURPOSE: To determine the diagnostic efficacy of hard- and soft-copy computed radiographic (CR) images versus conventional screen-film images of the chest in the detection of subtle pulmonary abnormalities. MATERIALS AND METHODS: Twenty observes compared 87 hard-copy and soft-copy CR images with hard-copy screen-film images. Of 87 test images, 45 (including two identical sets of 12 images to test intra-observer variability) were abnormal and 42 (including two identical sets of 12 images) were normal. Of the 45 abnormal images, 15 (including two sets of four identical images) showed subtle abnormalities, 15 (including two sets of four identical images) showed mild abnormalities, and 15 (including two sets of four identical images) showed obvious abnormalities. Soft-copy viewing provided three differently processed images of every radiograph. RESULTS: No statistically significant differences in receiver operating characteristic analyses were found among hard-copy screen-film images, hard-copy CR images, and soft-copy CR images, even in the group with subtle interstitial abnormalities. CONCLUSION: Hard-copy and soft-copy chest CR images are acceptable and available in place of screen-film images for primary interpretation of subtle interstitial lung diseases.

Adult↗
PubMed1985

Limitations of computed tomography following excisional biopsy of soft tissue sarcomas.

Twenty-one patients were evaluated by computed tomography (CT) following complete or incomplete excisional biopsy of soft tissue sarcomas. Since the surgical margins were inadequate, additional treatment was required, and CT was intended to identify and delineate any residual tumor. Thirteen patients had no palpable mass in the operative area. In these, eleven CTs showed no tumor, but microscopic tumor was found in seven. The other two CTs showed masses, but both proved to be hematomas. Eight patients had palpable masses and seven proved to be residual tumor. Of these, two CTs failed to show the residual tumor. Five CTs correctly identified residual tumor, but two of them failed to show the entire tumor extent. Computed tomography did not correctly predict the presence or absence of microscopic residual tumor when there was no palpable mass, and was at least partly inaccurate in delineating residual tumor in four of eight patients with palpable masses.

Adolescent↗
PubMed1979

Computed tomography in bone and soft tissue pathology of the extremities.

Forty patients suffering from various pathological conditions of the extremities were examined by computed tomography (CT) and the results were correlated with conventional imaging techniques: plain radiography, conventional tomograms, angiograms, and radionuclide scanning. The patients' ages ranged from 4 to 80 years. The study included cases of osteomyelitis, benign and malignant bone and soft tissue tumors, metabolic disorders, and a case of pulmonary osteoarthropathy. We were able to follow progression and/or regression of osteomyelitis by recording the changes in the attenuation coefficient of the medullary cavity and also were able to determine the extent of the malignant infiltration of the marrow cavity. Contrast enhancement was valuable in demonstrating the vascularity of soft tissue tumors and in determining the extension of primary bone lesions.

Adolescent↗
PubMed2003

Mechanobiology of soft skeletal tissue differentiation--a computational approach of a fiber-reinforced poroelastic model based on homogeneous and isotropic simplifications.

The material properties of multipotent mesenchymal tissue change dramatically during the differentiation process associated with skeletal regeneration. Using a mechanobiological tissue differentiation concept, and homogeneous and isotropic simplifications of a fiber-reinforced poroelastic model of soft skeletal tissues, we have developed a mathematical approach for describing time-dependent material property changes during the formation of cartilage, fibrocartilage, and fibrous tissue under various loading histories. In this approach, intermittently imposed fluid pressure and tensile strain regulate proteoglycan synthesis and collagen fibrillogenesis, assembly, cross-linking, and alignment to cause changes in tissue permeability (k), compressive aggregate modulus (H(A)), and tensile elastic modulus (E). In our isotropic model, k represents the permeability in the least permeable direction (perpendicular to the fibers) and E represents the tensile elastic modulus in the stiffest direction (parallel to the fibers). Cyclic fluid pressure causes an increase in proteoglycan synthesis, resulting in a decrease in k and increase in H(A) caused by the hydrophilic nature and large size of the aggregating proteoglycans. It further causes a slight increase in E owing to the stiffness added by newly synthesized type II collagen. Tensile strain increases the density, size, alignment, and cross-linking of collagen fibers thereby increasing E while also decreasing k as a result of an increased flow path length. The Poisson's ratio of the solid matrix, nu(s), is assumed to remain constant (near zero) for all soft tissues. Implementing a computer algorithm based on these concepts, we simulate progressive changes in material properties for differentiating tissues. Beginning with initial values of E=0.05 MPa, H(A)=0 MPa, and k=1 x 10(-13) m(4)/Ns for multipotent mesenchymal tissue, we predict final values of E=11 MPa, H(A)=1 MPa, and k=4.8 x 10(-15) m(4)/Ns for articular cartilage, E=339 MPa, H(A)=1 MPa, and k=9.5 x 10(-16) m(4)/Ns for fibrocartilage, and E=1,000 MPa, H(A)=0 MPa, and k=7.5 x 10(-16) m(4)/Ns for fibrous tissue. These final values are consistent with the values reported by other investigators and the time-dependent acquisition of these values is consistent with current knowledge of the differentiation process.

Algorithms↗
PubMedDate not supplied

[Computed tomography in the diagnosis of soft tissue changes in patients with chronic osteomyelitis of the femur].

Computed tomography was used to study soft tissues of the femur in 78 patients with its chronic recurrent osteomyelitis and the studied parameters were estimated. The fibrous changes were found to be more pronounced in posttraumatic osteomyelitis; the thickening of the subcutaneous fat and its atrophy were equally marked; the density gradients between the intact muscle, infiltrated muscle tissue, and purulent leakage were calculated.

Adipose Tissue↗
PubMed1986

Computed tomography of hemangiomas and related soft-tissue lesions in children.

The varied computed tomographic (CT) appearances of 19 hemangiomas and related soft-tissue lesions in 17 children were assessed retrospectively. Good CT-tissue correlation was obtained in 11 patients in whom histology was available. Although most cutaneous vascular lesions can be diagnosed by their characteristic clinical features, their extent may be difficult to assess clinically and at surgery. CT is important in defining the extent of these lesions as a guide for the surgeon, and for conservative follow-up. The often characteristic CT appearances also help in the diagnosis of the few patients with unusual clinical presentations.

Adipose Tissue↗
PubMed1993

Computer-aided treatment design of a distal upper extremity soft tissue tumor with electron beam radiotherapy.

We present here a novel approach for the planning and treatment of a distal upper extremity soft tissue tumor. Utilizing computed tomography (CT) based electron dose calculations, a customized compensating wax bolus was designed in order to deliver sufficient dose coverage to the tumor volume while sparing the draining lymphatics of the patient's hand and digits. A clinical case is presented as well as the design and construction of the compensator. Outcome and clinical implications are discussed.

Adult↗
PubMed1988

Wheat cultivar identification by a totally automatic soft-laser scanning densitometry and computer-aided analysis of protein electropherograms.

A computer-aided analysis based on soft-laser densitometry of electrophoretic patterns is described. The system has the potential to automatically identify wheat cultivars from normalized sodium dodecyl sulfate-polyacrylamide gel electropherograms. The principle encompasses autocalibration of the relative mobilities of components of the unknown pattern using standards of Mr that bracket each pattern on the pictures, automatic identification of peaks and baseline correction, and simplified estimation of the peak intensities. The algorithm provides a normalized array that can be automatically compared with a library of standard cultivar patterns in order to determine those having the highest similarity percentage. The outputs of the program are 1) relative similarity plots which show the percentage of similarity between the unknown cultivar to that of each of the common standard cultivars put in a pattern library, 2) the names of cultivars in the library having the most similar patterns and 3) computer-generated electrophoretic graphics of these cultivars. This system is not intended to identify closely related cultivars but it is particularly recommended for cultivar identification without well-trained personnel, familiar with band location and nomenclature.

Densitometry↗
PubMed2006

Mechanical characterization of anisotropic planar biological soft tissues using large indentation: a computational feasibility study.

Traditionally, the complex mechanical behavior of planar soft biological tissues is characterized by (multi)axial tensile testing. While uniaxial tests do not provide sufficient information for a full characterization of the material anisotropy, biaxial tensile tests are difficult to perform and tethering effects limit the analyses to a small central portion of the test sample. In both cases, determination of local mechanical properties is not trivial. Local mechanical characterization may be performed by indentation testing. Conventional indentation tests, however, often assume linear elastic and isotropic material properties, and therefore these tests are of limited use in characterizing the nonlinear, anisotropic material behavior typical for planar soft biological tissues. In this study, a spherical indentation experiment assuming large deformations is proposed. A finite element model of the aortic valve leaflet demonstrates that combining force and deformation gradient data, one single indentation test provides sufficient information to characterize the local material behavior. Parameter estimation is used to fit the computational model to simulated experimental data. The aortic valve leaflet is chosen as a typical example. However, the proposed method is expected to apply for the mechanical characterization of planar soft biological materials in general.

Animals↗
PubMed1996

Evaluation of soft-tissue foreign bodies: comparing conventional plain film radiography, computed radiography printed on film, and computed radiography displayed on a computer workstation.

OBJECTIVE: The study was performed to evaluate detection of soft-tissue foreign bodies using conventional radiography (film-screen radiography), computed radiography printed on films (computed radiography-hard copy), and computed radiography displayed on a computer workstation (computed radiography-soft copy). SUBJECTS AND METHODS: Fifteen foreign bodies of different size, shape, and composition were implanted at different locations in a fresh cadaveric hand, and images were obtained using three radiographic techniques. Images were evaluated by four board-certified radiologists to ascertain the conspicuity of the foreign bodies with the different techniques. A subjective grade was assigned to each image in an attempt to identify the relative conspicuity of foreign bodies when imaged with the three techniques. RESULTS: Computed radiography-soft copy is the preferred imaging technique for the detection of wood and plastic foreign bodies in soft tissue regardless of the size of the wood or the plastic. No significant differences in conspicuity among the three techniques were demonstrated with glass foreign bodies. CONCLUSION: Detection of soft-tissue foreign bodies is best done using computed radiography-soft copy instead of film-screen radiography and computed radiography-hard copy imaging.

Cadaver↗
PubMed1999

Accurate guidance for percutaneous access to a specific target in soft tissues: preclinical study of computer-assisted pericardiocentesis.

In the field of percutaneous access to soft tissues, our project was to improve classical pericardiocentesis by performing accurate guidance to a selected target, according to a model of the pericardial effusion acquired through three-dimensional (3D) data recording. Required hardware is an echocardiographic device and a needle, both linked to a 3D localizer, and a computer. After acquiring echographic data, a modeling procedure allows definition of the optimal puncture strategy, taking into consideration the mobility of the heart, by determining a stable region, whatever the period of the cardiac cycle. A passive guidance system is then used to reach the planned target accurately, generally a site in the middle of the stable region. After validation on a dynamic phantom and a feasibility study in dogs, an accuracy and reliability analysis protocol was realized on pigs with experimental pericardial effusion. Ten consecutive successful punctures using various trajectories were performed on eight pigs. Nonbloody liquid was collected from pericardial effusions in the stable region (5 to 9 mm wide) within 10 to 15 minutes from echographic acquisition to drainage. Accuracy of at least 2.5 mm was demonstrated. This study demonstrates the feasibility of computer-assisted pericardiocentesis. Beyond the simple improvement of the current technique, this method could be a new way to reach the heart or a new tool for percutaneous access and image-guided puncture of soft tissues. Further investigation will be necessary before routine human application.

Animals↗