PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Computer Graphics”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 397 records · Page 22Linked to original sources
PubMed1992

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↗
PubMed1992

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↗
PubMedDate not supplied

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↗
PubMed1996

Investigating shape-from-shading illusions using solid objects.

Recent growth in the shape-from-shading psychophysics literature has been paralleled by an increasing availability of computer graphics hardware and software, to the extent that most psychophysical studies in this area now employ computer lighting algorithms. The most widely used of these algorithms in shape-from-shading psychophysics is the Phong lighting model. This model, and other shading models of its genre, produce readily interpretable images of three-dimensional scenes. However, such algorithms are only approximations of how light interacts with real objects in the natural environment. Nevertheless, the results from psychophysical experiments using these techniques have been used to infer the processes underlying the perception of shape-from-shading in natural environments. It is important to establish whether this substitution is ever valid. We report a series of experiments investigating whether two recently reported illusions seen in computer-generated, Phong shaded images occur for solid objects under real illuminants. The two illusions investigated are three-dimensional curvature contrast and the illuminant-position effect on perceived curvature. We show that both effects do occur for solid objects, and that the magnitude of these effects are equivalent regardless of whether subjects are presented with ray traced or solid objects.

Algorithms↗
PubMed1995

[Computerized three-dimensional reconstruction of human embryos and their organs using the "NIH image" software].

Three-dimensional structures of human embryos and their internal organs were reconstructed on a CRT from their serial histological sections using a free computer software system "NIH Image." It was possible to rotate the computer images on CRT and to make cut models on any desired plane. In addition, various developmental changes could be animated by artificial "morphing" between the models at different stages. Computer graphic modeling should be of great value in the study of normal and abnormal morphogenesis. The "NIH Image" software is freely available via computer networks and has a lot of advantages over previously developed software programs used for three-dimensional reconstruction.

Computer Graphics↗
PubMed1992

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↗
PubMed1995

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↗
PubMedDate not supplied

Imaging and graphics in medicine: concept of an object-oriented platform for clinical research.

We present a workstation-based research platform with two major components. A turnkey application system provides a functionality kernel for a broad community of clinical users with an interest in digital imaging. A development toolbox allows efficient implementation of research ideas and consistent integration of new applications with the common framework of the turnkey system. The platform is based on an elaborate object class structure describing objects for image processing, computer graphics, study handling and user interface control. Thus expertise of computer scientists familiar with this application domain is brought into the hospital and can be readily used by clinical researchers.

Computer Graphics↗
PubMed1990

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↗
PubMedDate not supplied

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↗
PubMed1996

The structure of the transitional and aganglionic zones of Auerbach's plexus in patients with Hirschsprung's disease: a computer-assisted three-dimensional reconstruction study.

Intestines resected from two patients with Hirschsprung's disease, both aged 6 months, were submitted to serial sectioning and three-dimensional reconstruction to visualize the overall structure of Auerbach's plexus and correlate its changes with functional abnormalities. Reconstruction was made possible by using a graphics computer system. In normal intestines taken from an autopsy case, both large and small, the plexus was shown extending along the intermuscular septum as a regular network. But in the large intestine, the density of the network was apparently higher and the individual bundles thicker than in the small intestines. This neural network was absent in the aganglionic zone in Hirschsprung's disease, as expected, where only hypertrophic extrinsic nerves were running in the septum. The "transitional zone" of Hirschsprung's disease was clearly definable as an area extending over a certain length, where the network meshes grow more irregular and the bundles taper more, toward the aganglionic zone. This finding was considered to be of profound significance in the design of a surgical strategy to prevent postoperative bowel dysfunction. In determining the range of resection, one must consider not only the presence or absence of nerve cells but also the grade of plexus hypoplasia.

Biopsy↗
PubMed1989

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↗
PubMedDate not supplied

Congenital apnea with medullary and olivary hypoplasia: a pathologic study with computer reconstructions.

We report a three-month-old infant with congenital central apnea who was ventilator-dependent throughout his brief life. At autopsy the most significant findings were localized to the medulla and included severe tegmental necrosis involving respiratory-related sites and olivary hypoplasia. Golgi impregnations of the cerebellum demonstrated several Purkinje cells with changes consistent with experimental olivary ablation. The majority of Purkinje cells, however, were normal; this observation suggests that in an early and subtotal olivary lesion, the incomplete complement of olivary neurons maintains sufficient collateral axonal branches to compensate for decreased cell number. Computer graphics enabled us to dissect the components of the complex medullary pathology and examine them individually and in selected combinations in three dimensions. Computer reconstruction aided the identification and dating of a malformative lesion (first trimester) from a later (second/third trimester), superimposed destructive lesion. This report suggests that the synthesis of complex morphologic data in human neuropathology into meaningful three-dimensional visual displays by computer reconstruction facilitates their comprehension. Computer reconstruction is especially valuable in the elucidation of 3-D topographic relationships in functionally and architecturally complex regions such as the brain stem.

Apnea↗
PubMed1991

Early mineral deposition in calcifying tendon characterized by high voltage electron microscopy and three-dimensional graphic imaging.

Extracellular matrix organization and the spatial relationship between collagen fibrils, vesicular structures, and the first deposits of mineral in the calcifying leg tendon from the domestic turkey, Meleagris gallopavo, have been investigated by high voltage electron microscopy and three-dimensional computer graphic imaging of serial thick tissue sections. The work demonstrates that the tendon extracellular matrix is a complex assembly of somewhat flexible, highly aligned collagen fibrils with different diameters and occasionally opposite directionality. Smaller collagen fibrils appear to branch from larger fibrils or to aggregate to form those of greater size. While the matrices are dominated by fibrils, space exists between adjacent packed fibrils. The three-dimensional perspective indicates that approximately 60% of the total tendon volume is extrafibrillar over the regions examined. The first observable mineral in this tissue is extrafibrillar and appears to derive from vesicles. This view of three-dimensional matrix-mineral spatial relations supports earlier two-dimensional results that mineral is initially associated with membrane-invested vesicles and is deposited between collagen fibrils, but it is distinct in showing the mineral at different depths in the matrix rather than at a single depth as deduced from two-dimensional conventional electron microscopy. These results are important in the onset and development of tendon calcification in that they suggest, first, that collagen fibrils appear to be aligned three-dimensionally such that their hole zones are in contiguous arrangement. This situation may create channels or grooves within the collagen volume to accommodate extensive mineral deposition in association with the fibrils. Second, the results indicate that there are widely dispersed sites of vesicle-mediated mineralization in the tendon matrix, that the bulk of mineralization in this tissue is collagen-mediated, and that, while vesicles may possibly exert some local influence temporally on mineralization of neighboring collagen, vesicle- and collagen-mediated mineralization arise at spatially and structurally distinct sites by independent nucleation phenomena. Such concepts are fundamental in considerations of possible mechanisms of mineralization of tendon and potentially of other normally calcifying vertebrate tissues in general.

Animals↗
PubMed1995

Three computer methods to reconstruct pulpal blood vessels and nerves.

This study describes three methods 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. These methods are surface representation, representation by means of a stack of slices, and volume representation.

Adolescent↗
PubMed1988

Active site model of cytochrome P-450 LM2.

Based on (i) a detailed analysis of the physicochemical properties of selected benzphetamine derived substrates and (ii) the identification of Tyr-380 as active site residue trans to thiolate theoretical studies (computer aided molecular design) revealed a model of the substrate binding site of cytochrome P-450 LM2. The results indicate that substrates with a butterfly-like bulky conformation exhibit the highest intrinsic activity. Those substrates which preferably exist in an extended conformation are sterically hindered to intensively interact with the binding site which is demonstrated by computer graphics.

Benzphetamine↗
PubMed1995

Three-dimensional display of the pelvic structure of anorectal malformations based on CT and MR images.

Three-dimensional images of the pelvic structure of patients with anorectal malformation (ARM) were constructed by computer graphics based on radiographic computerized tomography (CT) and magnetic resonance (MR) images. Organ contour data from CT images and raw MR image data were transferred to a personal computer and to a graphic workstation respectively. On MR image processing, organs were extracted semiautomatically by thresholding enclosed areas. After several steps of image processing, three-dimensional anatomy of each anomaly was visualized with emphasis on position and shape of the muscle complex. In control patients without an anomaly, images showed that the rectum is supported by the levator muscle from behind and descends along with the urethra. In the male patient, the anal canal separates from the urethra and penetrates through the middle of the sphincter complex to reach the orifice. In those with low-type anomaly with a fistula opening to the perineum or the vestibule, images showed the fistula descending through the anterior portion of the sphincter complex. Images of those with a rectourethral fistula could show the muscle complex behind the rectum and at the region where the external sphincter should be. In those with cloacal anomalies, anatomical position and the shape of three different viscera were easily recognized, and the muscle complex was shown like that of rectourethral-type anomalies. This study is a new approach to the anomaly to facilitate understanding it and can assist a surgeon in planning a procedure. This kind of application would make it possible for a surgeon to consider the strategy on a display screen before the real surgery.

Anal Canal↗