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At least 865 records · Page 48Linked to original sources

PubMed2001

Evaluation of an ossifying fibroma using three-dimensional computed tomography.

We describe the appearance of a mandibular ossifying fibroma in spiral computed tomography-based multiplanar (MPR) and three-dimensional (3D) reconstruction using computer graphics. The usefulness of the interactive reconstructed images, especially using a vascular protocol, for qualitative and quantitative analyses is demonstrated. This technique is an important adjunct to evaluation with conventional axial CT.

Adolescent↗

PubMed1977

Spatiotemporal mapping of scalp potentials.

Computerized analysis and display techniques are applied to the problem of identifying the origins of visually evoked scalped potentials (VESP's). A new stimulus for VESP work, white noise, is being incorporated in the solution of this problem. VESP's for white-noise stimulation exhibit time domain behavior similar to the classical response for flash stimuli but with certain significant differences. Contour mapping algorithms are used to display the time behavior of equipotential surfaces on the scalp during the VESP. The electrical and geometrical parameters of the head are modeled. Electrical fields closely matching those obtained experimentally are generated on the surface of the model head by optimally selecting the location and strength parameters of one or two dipole current sources contained within the model. Computer graphics are used to display as a movie the actual and model scalp potential field and the parameters of the dipole generators whithin the model head during the time course of the VESP. These techniques are currently used to study retinotopic mapping, fusion, and texture perception in the human.

Acoustic Stimulation↗

PubMed2004

Frequency domain formulation of active parametric deformable models.

Active deformable models are simple tools, very popular in computer vision and computer graphics, for solving ill-posed problems or mimic real physical systems. The classical formulation is given in the spatial domain, the motor of the procedure is a second-order linear system, and rigidity and elasticity are the basic parameters for its characterization. This paper proposes a novel formulation based on a frequency-domain analysis: The internal energy functional and the Lagrange minimization are performed entirely in the frequency domain, which leads to a simple formulation and design. The frequency-based implementation offers important computational savings in comparison to the original one, a feature that is improved by the efficient hardware and software computation of the FFT algorithm. This new formulation focuses on the stiffness spectrum, allowing the possibility of constructing deformable models apart from the elasticity and rigidity-based original formulation. Simulation examples validate the theoretical results.

Journal Article↗

PubMed1980

Measurement in jejunal biopsies by computer-aided microscopy.

A method of morphometric analysis of jejunal mucosa using computer-aided microscopy is described. It is based on the technique of interactive computer graphics with definition by the observer of areas and lengths for measurement, but it also includes automatic measurements based on grey-level segmentation. The analyses are performed rapidly and efficiently. The technique is applicable to the analysis of biopsy tissue from many sites.

Adult↗

PubMed1985

Digital image processing to handle neuroanatomical information and neurophysiological data.

An application of computer graphics technology to functional stereotactic neurosurgery is presented. Neuroanatomical images derived from a stereotactic atlas and information retrieved from a neurophysiological data base are drawn on a graphic monitor. The pictures are oriented and scaled according to appropriate landmarks. The aim of this work is to add confidence in the surgeon's selection of the probe trajectory and to improve the knowledge of sensory and motor organization within the thalamus.

Brain↗

PubMed1990

Current problems in the evaluation of chemical safety.

Current problems in the safety evaluation of chemicals, including species differences in chemical toxicity, the difficulty in predicting whether metabolism will result in detoxication or activation, the different metabolic roles of tissue cytochromes P-450, and the significance of oxygen radical formation, are reviewed. A number of specific chemical problems are discussed, including the safety evaluation of benzene, methylene dichloride, DDT, dieldrin, TCDD, the PCBs, and the hepatotoxic drugs: benoxaprofen and tienilic acid. Two novel methods for the prospective evaluation of chemical toxicity are described, namely (i) computer optimized parametric analysis for chemical toxicity (COMPACT) based on the computer graphic determination of chemical structure and its relationship to specific cytochromes P-450 and hence toxicity, and (ii) enzyme activation in chemical toxicity (ENACT) based on the induction of specific cytochromes P-450 by the chemical, from which toxicity can be predicted.

Animals↗

PubMed1990

[Three-dimensional image display of the kidney from X-ray CT scan utilizing the 3DCT method].

Stereographic reproduction of human organs, now under development as an application of computer graphics, aims at delineating the three-dimensional spread of a lesion, simulating an operation and drawing up a radiotherapeutic plan. We are currently attempting to obtain a stereo display of the kidney using a 3DCT method based on X-ray CT data obtained by scanning a 4 mm slice in cases of bilateral renal calculus of the template type, renal bleeding and renal carcinoma. This 3DCT method was capable of displaying a stereo image of the kidneys relatively with ease since it made analysis possible, using a computer built inside the X-ray CT device. The development of a software program capable of stereographically displaying many organs on the same screen is an awaited future project.

Humans↗

PubMed1981

Three-dimensional computer reconstruction from surface contours for head CT examinations.

A three-dimensional surface reconstruction algorithm based on contour information from anatomic sites as identified on computed tomography examinations is presented. This algorithm efficiently reconstructs the surfaces between the contours using a triangular "tiling" method. A three-dimensional perspective view of the reconstructed surfaces is provided by a gray scale cathode-ray tube computer graphics system. Volume and surface area estimations are provided as a direct results of the surface reconstruction algorithm. Three cases are presented to illustrate the three-dimensional surface reconstruction algorithm.

Brain Neoplasms↗

PubMed1989

The three-dimensional spatial relationship between the collagen fibrils and the inorganic calcium-phosphate crystals of pickerel and herring fish bone.

High-voltage (1.0 mega-volt) electron stereomicroscopy has been used to examine the spatial relationship between the inorganic crystals and the collagen fibrils of pickerel and herring bone. Stereomicrographs of cross sections of the collagen fibrils encompassing regions of initial to full mineralization showed that the calcium phosphate crystals are located within the collagen fibrils. In all stages of mineralization, calcium-phosphate deposits were not observed associated or within membrane-bound structures. Serial cross sections of the fully mineralized collagen fibrils were three-dimensionally reconstructed using the computer graphic imaging process. Findings from this study suggest that there exist a local "bulging" along the fibrils corresponding to the 680 A periodicity in which additional mass of minerals were observed to be accommodated within the collagen fibril structure at this sites.

Animals↗

PubMed1996

Reproducibility of Bayesian belief network assessment of breast fine needle aspirates.

OBJECTIVE: To assess the consistency of diagnosis of fine needle aspiration biopsies of breast lesions by three experienced and five less experienced pathologists using conventional means and applying a Bayesian belief network (BBN) to 10 diagnostic features to support diagnostic decision making. STUDY DESIGN: Forty fine needle aspiration biopsies, previously assessed by one of the experienced pathologists both conventionally and using a BBN, were assessed by two further experienced pathologists and five less experienced pathologists. RESULTS: Using the BBN, the experienced pathologists arrived at diagnoses in agreement with an established consensus at a slightly lower rate than by conventional means. The less experienced pathologists arrived at the correct diagnoses no more frequently with the help of the BBN than conventionally. CONCLUSION: As used in this study, the BBN did not help less experienced pathologists to interpret their observations but did not enable less experienced pathologists to identify how their observations differed and affected their diagnoses. The prototype system used in this study has since been upgraded by providing computer graphic displays of the features to be observed so that a more uniform mental image can be held by the participating pathologists. This will be tested with the same study design.

Biopsy, Needle↗

PubMed1995

Molecular orbital-generated QSARs in a homologous series of alkoxyresorufins and studies of their interactive docking with P450s.

1. Molecular and electronic structural parameters have been determined, by molecular orbital (MO) calculations, for a homologous series of 8 alkoxyresorufins (methoxy- to octoxy-). 2. Quantitative structure-activity relationships (QSARs) between these structural parameters and the rates of metabolism of the alkoxyresorufins in hepatic microsomes from the 3-methylcholanthrene (MC)-, and phenobarbital (PB)-pretreated mouse, and the beta-naphthoflavone (beta NF)-pretreated rat have been established. 3. The most significant single relationship is between beta NF-induction of cytochrome P4501 (CYP1A) and the total nucleophilic superdelocalizability (sigma SN) for the eight compounds in the series. 4. For double regressions, the electronic charge on the alkoxy oxygen, Q(O), or alpha-carbon Q(C), is important when combined with the hydrophobic substituent constant (pi). 5. These findings indicate that the rates of metabolism of these alkoxyresorufins are dependent upon their ability to cross cellular membranes, to fit the relevant CYP1A binding site, and on their ability to accept electrons from a donor nucleophilic species. 6. A different set of parameters correlated with CYP2B activity, namely, parameters of overall shape, which indicates that the way in which the alkoxyresorufins fit the CYP2B site, determines their differences in specificity. 7. Computer graphic interactive docking studies of the alkoxyresorufins with their affinity-specific cytochromes P450, namely, methoxy- with CYP1A2; ethoxy- with CYP1A1; pentoxy- with CYP2B1; and benzyloxy- with CYP3A, have also been undertaken to show the specific interactions of the alkoxyresorufins with the binding sites of the individual P450s.

Amino Acid Sequence↗

PubMed1995

Semi-automatic data acquisition for quantitative neuroanatomy. MicroTrace--computer programme for recording of the spatial distribution of neuronal populations.

We present a computer programme, MicroTrace, designed for user-guided digitisation of objects in biological sections. The programme is optimised for recording the spatial distribution of neuronal structures, such as large populations of tracer-labelled cell bodies or axonal plexuses, regional borders, and surfaces. System requirements are a PC running Microsoft Windows, a microscope equipped with stepping motors, and a drawing tube. A computer generated drawing area, surrounded by menus and icons, is projected into the microscope field of view via the drawing tube. Different 'object' icons are assigned to individual object categories (cell types, surfaces, etc.). Digitisation is performed by pointing the cursor at objects in the section. Computer graphical symbols are superimposed on the digitised objects. All object categories are digitised, before moving the stage to other fields of view by manipulating the joystick or scroll bars. Movement of the microscope stage is accompanied by a translation of the graphical image, so that continuous feedback on the progress of the digitisation is provided. MicroTrace can readily be adapted to the specific needs of the user. We show its use in different experimental neuroanatomical techniques. Two-dimensional images and three-dimensional reconstructions of neuronal distribution and surfaces are demonstrated.

Animals↗

PubMed2000

A study of orientation in a zero gravity environment by means of virtual reality simulation.

When the International Space Station (ISS) is completed and starts its operation, crew members will be stationed for three months or more in orbit aboard the ISS. As they stay longer in the space environment, "habitability" for them will become most important in the design of the interior space. One of the problems about habitability in a zero gravity (0 G) environment is disorientation. Crew members have difficulty in discriminating between "up" and "down" and more serious disorientations may cause space motion sickness. Crew members rely on visual perception to orient themselves because they can't use their sense of equilibrium in a 0 G environment. Although color and the direction of equipment of Space Shuttles or modules has been considered, no systematic study has been conducted on interior space. This study intended to clarify how people acquire visual information and recognize their orientation in a 0 G environment by an experiment in which a subject wears a head-mounted display (HMD) and enters a virtual weightless state represented by computer graphics (CG). Visual information of a room and the degree-of-freedom of motion were varied to examine the influence of the conditions on such a simple task as movement through several connected modules, and the performance and the behavior of each subject were investigated.

Humans↗

PubMed1982

X-ray crystallographic analysis of 3-(2'-phenyl-2,4'-bithiazole-4-carboxamido) propyldimethylsulphonium iodide, an analogue of the DNA-binding portion of bleomycin A2.

The crystal and molecular structure of the title compound, an analogue of the DNA binding region of bleomycin A2, has been determined by X-ray crystallography. All the three independent molecules in an asymmetric unit are approximately planar with fully extended side chains. A computer graphics model-building study has shown that the phenyl group and the second thiazole ring can be intercalated between the base pairs of the double-stranded deoxydinucleoside phosphate d(CpG), and also that the sulphonium cation can interact with a backbone phosphate group. This model is in accord with NMR spectral data.

Bleomycin↗

PubMed1985

Three-dimensional computer reconstruction of the neuromuscular junction distribution in the human posterior cricoarytenoid muscle.

Recent studies have indicated that in a denervated muscle highly specific interactions occur between regenerating axons and the basal lamina of the myofiber precisely at the original synaptic sites. Since these findings suggest that synapse regeneration is facilitated at the original synaptic sites, a knowledge of the distribution of neuromuscular junctions in the human posterior cricoarytenoid (PCA) muscle may guide reinnervation procedures in this muscle. We, therefore, have used histochemical and computer graphics techniques to reconstruct the three-dimensional distribution of neuromuscular junctions in the human PCA taken fresh at autopsy. The results indicated a more localized pattern of neuromuscular junctions as compared to the human thyroarytenoid muscle. The results will be discussed with respect to their implications for procedures for reinnervation of the posterior cricoarytenoid muscle.

Computers↗

PubMed2005

[Three-dimensional reconstruction of human organs based on magnetic resonance imaging data].

OBJECTIVE: To build proper three-dimensional models of human organs for radiation dose calculation. METHOD: Human organ models were built by contour reconstruction algorithm conforming to 4 criteria. The contours of the organs were extracted based on the contours of the reconstructed organ surfaces, and the three-dimensional models with smooth surface, exact structure and good visibility were completed by computer graphic techniques such as lighting, smoothing, and normal average. RESULT AND CONCLUSION: Several organ models were successfully reconstructed, suggesting that this method is suitable for building three-dimensional digital human organ models which can meet the need for dose calculation.

Humans↗

PubMedDate not supplied

Three-dimensional structure, specificity and catalytic mechanism of renin.

Renin is an aspartyl proteinase that catalyses the first, and rate-limiting, step in the conversion of angiotensinogen to the hormone angiotensin II. The catalysis is highly specific, and plays an important physiological part in the regulation of blood pressure. For this reason inhibitors of renin are of potential value in the treatment of certain forms of hypertension. Although progress has been made in the design of inhibitors for clinical use by modification of angiotensinogen sequences, and as pepstatin analogues or with reduced peptide bonds, we have now provided the basis for a more rational approach by the use of interactive computer graphics techniques to build a three-dimensional model of renin. The model is based on the three-dimensional structure of endothia pepsin and the primary structure of mouse renin, which is very similar to that of the human enzyme. We show that renin may have a three-dimensional structure similar to that of other aspartyl proteinases.

Animals↗

PubMed2002

Significance of the dimensional view for visualizing relevant aspects of a production system in a co-operative planning process.

Pictorial visualization is expected to facilitate communication between industrial professionals when planning working environments and production systems. This hypothesis was investigated by studying how 24 participants including managers, supervisors, machine operators, and occupational health and safety officials, judged three types of computer animated visualization varying in dimensional view (scale and scope of a production line): shop floor view/survey of shop floor; production unit view/semi-survey of production unit; and workplace view/close-up of workplace, in relation to a set of planning issues. The participants participated in a controlled 2-day planning workshop, redesigning a fictitious manufacturing process by means of computer graphics, and then responded to a questionnaire. It can be concluded that shop floor view as well as production unit view are significant for survey planning issues, while all 3-dimensional views are significant for close-up planning issues. Analogously, all dimensional views are significant for technocentric planning issues, whereas only the workplace view is valuable for anthropocentric planning issues.

Communication↗