[Isotopic study of calcium metabolism in 10 subjects with 3-compartment methods. II. Comparison of graphic and computer analyses].
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Results for “Computer Graphics”
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Psyclops: an exploratory graphical system for clinical research and education.
We present Psyclops, an interactive computer graphic system designed to help address a growing information dilemma in the examination of individual psychiatric cases. Ever more information is needed to better understand conscious experience, interpersonal behavior, and the formation of psychiatric signs and symptoms, yet the information load already exceeds our usual methods of handling it. Psyclops consists of a suite of software modules, manual sections, and standards that have been developed according to guiding concepts intended to help one collect, organize, access, and explore complex data about a single subject for research, education, and ultimately, clinical care purposes. This document provides background in clinical information science and a description of the system; the reader interested in its application in clinical research theory development is referred to the companion paper in this issue (Horowitz et al., Pathological Grief: An Intensive Case Study).
Arousal↗
The modelling of nucleophilic and electrophilic additions to organometallic complexes using molecular graphics techniques.
A new formalism has been developed in order to evaluate intermolecular interaction energies for inorganic and organometallic complexes in the framework of the extended Hückel method. In order to provide the shortest possible response time on an interactive computer graphics facility, this model should require the minimum amount of computer time, which explains why approximate procedures are used to evaluate electrostatic, charge transfer and exchange repulsion components. When applying this model to typical examples of electrophilic addition reactions to organometallic complexes, it is found that it is essential to take account of charge transfer interactions, the electrostatic component alone being not sufficient, even qualitatively, for a proper description of the reaction mechanism. The results, presented as color-coded dot molecular surfaces, show a very good agreement with experiment as to the site of attack, namely (i) on metal for the electrophilic attack on Fe(cp)2, Fe(CO)5 and X(cp)(CO)2, X = Co, Rh; (ii) on the cp ligand for the nucleophilic attack on Co(cp)2+ and Rh(cp)2+; (iii) on bz for the nucleophilic attack on Fe(cp)(bz)+. Finally, modellizations of the nucleophilic attack on a coordinated olefin and of the relation between structure and acidic properties of zeolites are presented and discussed.
Computer Graphics↗
A veterinary digital anatomical database.
This paper describes the Veterinary Digital Anatomical Database Project. The purpose of the project is to investigate the construction and use of digitally stored anatomical models. We will be discussing the overall project goals and the results to date. Digital anatomical models are 3 dimensional, solid model representations of normal anatomy. The digital representations are electronically stored and can be manipulated and displayed on a computer graphics workstation. A digital database of anatomical structures can be used in conjunction with gross dissection in teaching normal anatomy to first year students in the professional curriculum. The computer model gives students the opportunity to "discover" relationships between anatomical structures that may have been destroyed or may not be obvious in the gross dissection. By using a digital database, the student will have the ability to view and manipulate anatomical structures in ways that are not available through interactive video disk (IVD). IVD constrains the student to preselected views and sections stored on the disk.
Anatomy, Veterinary↗
Using greyscale voxel databases for improved shading and segmentation.
Many different data representations are possible in computer graphics. Originally, in the medical field, simplified methods were used in order to reduce computation times on small computer systems. Currently a wider range of techniques is developing as costs of hardware continue to fall. In this paper we review a number of possible representations and explain the advantage of one that is greyscale, volumetric and random access. Different segmentation techniques can be used, as well as shading algorithms that give greatly improved appearances. A quantitative analysis of shading methods is derived in terms of the degree of sampling of the 'pseudo-normal' vectors that estimate the direction of the tangent to a surface. The application to a study of multiple sclerosis lesions in the brain using nuclear magnetic resonance data is shown.
Brain↗
Designing a user interface and computer screens for instruction: some considerations.
Computer-assisted instruction and interactive videodisc are being used more often in allied health sciences education and medical training. Because computer graphics screens can enhance both legibility and readability, an effective computer interface for instruction is basic to the design and development of both. This article discusses guidelines on legibility, which includes the use of graphics, type and text, contrast, and color.
Color↗
Sculpting proteins interactively: continual energy minimization embedded in a graphical modeling system.
We describe a new paradigm for modeling proteins in interactive computer graphics systems--continual maintenance of a physically valid representation, combined with direct user control and visualization. This is achieved by a fast algorithm for energy minimization, capable of real-time performance on all atoms of a small protein, plus graphically specified user tugs. The modeling system, called Sculpt, rigidly constrains bond lengths, bond angles, and planar groups (similar to existing interactive modeling programs), while it applies elastic restraints to minimize the potential energy due to torsions, hydrogen bonds, and van der Waals and electrostatic interactions (similar to existing batch minimization programs), and user-specified springs. The graphical interface can show bad and/or favorable contacts, and individual energy terms can be turned on or off to determine their effects and interactions. Sculpt finds a local minimum of the total energy that satisfies all the constraints using an augmented Lagrange-multiplier method; calculation time increases only linearly with the number of atoms because the matrix of constraint gradients is sparse and banded. On a 100-MHz MIPS R4000 processor (Silicon Graphics Indigo), Sculpt achieves 11 updates per second on a 20-residue fragment and 2 updates per second on an 80-residue protein, using all atoms except non-H-bonding hydrogens, and without electrostatic interactions. Applications of Sculpt are described: to reverse the direction of bundle packing in a designed 4-helix bundle protein, to fold up a 2-stranded beta-ribbon into an approximate beta-barrel, and to design the sequence and conformation of a 30-residue peptide that mimics one partner of a protein subunit interaction. Computer models that are both interactive and physically realistic (within the limitations of a given force field) have 2 significant advantages: (1) they make feasible the modeling of very large changes (such as needed for de novo design), and (2) they help the user understand how different energy terms interact to stabilize a given conformation. The Sculpt paradigm combines many of the best features of interactive graphical modeling, energy minimization, and actual physical models, and we propose it as an especially productive way to use current and future increases in computer speed.
Amino Acid Sequence↗
Efficiency of graphical perception.
The term graphical perception refers to the part played by visual perception in analyzing graphs. Computer graphics have stimulated interest in the perceptual pros and cons of different formats for displaying data. One way of evaluating the effectiveness of a display is to measure the efficiency (as defined by signal-detection theory) with which an observer extracts information from the graph. We measured observers' efficiencies in detecting differences in the means or variances of pairs of data sets sampled from Gaussian distributions. Sample size ranged from 1 to 20 for viewing times of 0.3 or 1 sec. The samples were displayed in three formats: numerical tables, scatterplots, and luminance-coded displays. Efficiency was highest for the scatterplots (approximately equal to 60% for both means and variances) and was only weakly dependent on sample size and exposure time. The pattern of results suggests parallel perceptual computation in which a constant proportion of the available information is used. Efficiency was lowest for the numerical tables and depended more strongly on sample size and viewing time. The results suggest serial processing in which a fixed amount of the available information is processed in a given time.
Attention↗
A graphics-based software system to develop and analyze models of musculoskeletal structures.
We have created a graphics-based software system that enables users to develop and analyze musculoskeletal models without programming. To define a model using this system one specifies the surfaces of the bones, the kinematics of the joints and the lines of action and force-generating parameters of the muscles. Once a model is defined, the function of each muscle can be analyzed by computing its length, moment arms, force and joint moments. The software has been implemented on a computer graphics workstation so that users can view the model from any perspective and graphically manipulate the joint kinematics and musculoskeletal geometry. Models can also be animated to visualize the results of motion analysis experiments. Since the software can be used to study models of many different musculoskeletal structures, it can enhance the productivity of investigators working on diverse problems in biomechanics.
Algorithms↗
Linear models of surface and illuminant spectra.
We describe procedures for creating efficient spectral representations for color. The representations generalize conventional tristimulus representations, which are based on the peripheral encoding by the human eye. We use low-dimensional linear models to approximate the spectral properties of surfaces and illuminants with respect to a collection of sensing devices. We choose the linear-model basis functions by minimizing the error in approximating sensor responses for collections of surfaces and illuminants. These linear models offer some conceptual simplifications for applications such as printer calibration; they also perform substantially better than principal-components approximations for computer-graphics applications.
Algorithms↗
Computerized three-dimensional reconstruction: a method to study pulpal vessels and nerves.
This study describes a method of computerized three-dimensional reconstruction of the main neurovascular pulpal bundle of human teeth, using serial cross paraffin sections, digital image processing, and three-dimensional computer graphics.
Adolescent↗
Computer-based multimedia in plastic surgery education.
Rapid developments in communications networks (cellular telephone, direct-link satellite, and international high-speed computer nets) and the continued success of affordable powerful personal computers (desktop, laptop and soon "palmtop" devices) have set the stage for educational materials accessible by electronic means. Computer-based multimedia are sophisticated audiovisual teaching materials built from digitized illustrations, photographs, audio and video recordings viewed by display on a computer screen. The computer interface allows interactive access to information, and connectivity to other sources of information. Computer programmability allows presentation of a single collection of information at different levels of sophistication (the "patient", "medical student" or "surgeon trainee" level, for example), to appeal to different viewer needs. The information may be electronically updated or changed whenever appropriate. This desktop exhibit demonstrates multimedia plastic surgery teaching materials with full-fidelity digital sound, three-dimensional computer graphics, and "picture-in-picture" video capabilities that we have developed since 1989. We have used these materials at St. Louis University for patient informed consent, and the education of medical students and surgical trainees. We are excited that similar multimedia teaching materials are now becoming commercially available in other fields of medical education, attesting to broadening interest among educators and publishers.
Computer Graphics↗
The influence of teeth on denture base processing accuracy.
The Michigan Computer Graphics Coordinate Measuring System was used to determine the influence of denture teeth on the accuracy of processed denture bases. Three different processing methods--compression molding, injection pressing, and vacuum-assisted resin pouring--were used. The presence of denture teeth was determined to affect the accuracy of the processed denture bases of all three techniques. For denture bases without teeth, the compression-molding technique demonstrated significant differences in accuracy; however, no significant differences were found in the injection-pressed or resin-poured denture bases.
Computer Graphics↗
Tek FRODO: a new version of FRODO for Tektronix graphics stations.
A new version of the molecular graphics program FRODO was developed to allow the range of Tektronix graphics stations to be used for molecular modeling and crystallographic applications. The work was divided into two parts: first, the universal molecular modeling graphic package (Tek_MMGP) was written to enable basic modeling operations for Tektronix stations. Second, all routines of FRODO involving computer graphics were modified to fit the new hardware environment, and linked with Tek_MMGP. The resulting package, Tek_FRODO, has been used successfully for crystallographic refinement in several projects. The program, written in FORTRAN, is ready to be ported to any of Tektronix 3D graphics stations; it is available from the authors on request.
Computer Graphics↗
SMART: a solvent-accessible triangulated surface generator for molecular graphics and boundary element applications.
An algorithm is presented for generating a representation of the solvent-accessible molecular surface as a smooth triangulated manifold. The algorithm, called SMART (SMooth moleculAR surface Triangulator), divides the contact and reentrant portions of the solvent-accessible molecular surface into curvilinear three-sided elements. In contrast to the author's earlier implementation of this general approach [Zauhar, R.J. and Morgan, R.S., J. Comput. Chem., 11 (1990) 603], the SMART algorithm defines elements directly on the appropriate geometric surface types (rather than using interpolation over cubic elements), and has special features to handle highly distorted regions which often appear in deep crevices and internal cavities. While the method is designed for use with boundary element techniques in continuum electrostatics, it can also be applied to the accurate computation of molecular surface areas and volumes, and the generation of shaded surfaces for display with interactive computer graphics.
Algorithms↗
A microcomputer-based system for measurement of ultrasound imaging.
A microcomputer-based imaging system for acquisition and analysis of ultrasound has become available. In order to fulfill the clinical demands, the more complete and detailed examinations required, the more sophisticated ultrasound instrumentation costs. This paper demonstrates the simplicity of a personal computer to provide an inexpensive method for measurement on video images from a real-time ultrasound scanner. The process data obtained on ATL 600 and found acoustic intensity histograms to be of value in differential diagnostic purposes. It includes spatial filtering, gray scale expansion, contrast enhancement, color index shifting and histogram analysis, etc. It allows the computer graphics to be superimposed on the ultrasound video images and permits subsequent analysis. To perform the manipulations and programming one of commercially available software and hardware are outlined and encouraged.
Computer Graphics↗
A data exchange format for neuroanatomy workstations.
The development of the microprocessor has enabled biomedical researchers to use powerful computers as single user workstations. Many such systems are now in use--some developed for use within individual laboratories, and others purchased commercially. These systems typically mix computer graphics and image processing capabilities. No standard exists that allows users of these workstations to exchange anatomical data in graphical or image form. This paper considers issues involved in designing a flexible format for exchanging digital anatomical data between laboratories.
Animals↗
Three-dimensional reconstruction of human limbs from tomographic views.
The recently developed medical imaging technique of tomography can be used with amazing success to learn about the interior of a human body. Each tomograph, however, is limited to only one section of the specific human limb. A series of tomographs taken at irregular intervals and various angles would provide three-dimensional information of the interior of the limb. Currently available 3-D surface display algorithms have limitations, particularly when applied to clinically important image data requiring fast and flexible interactive analysis. In addition to the problem of computation time is the cost of specialized hardware. A new algorithm has been designed for use with three-dimensional medical images which attempts to overcome these limitations. A computer graphics system is described which reconstructs three-dimensional images from tomographic sectional data. This 3-D surface algorithm can be exploited in planning reconstructive bone surgery. An example which illustrates the versatility and speed of the new algorithm is presented.
Algorithms↗