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At least 559 records · Page 31Linked to original sources
PubMed2004

[Computer-assisted surgical navigation technique].

Surgical navigation system is a system that processes medical images by computer graphics and image processing technique, reconstructs 2D or 3D medical image models. It builds a real-time loop among the eyes of doctor, the surgical device and the head of patient by several of space localization technique, so that to realize displaying the localization of surgical devices real-time. The history and research status of surgical navigation system is summarized and the system configuration and the key techniques are expatiated emphatically in this paper. The key techniques include localization in space, image processing and displaying technique, system registration technique and head location technique. At last the progress direction of navigation systems is given.

Computer Graphics↗
PubMed1992

Computerized Arden grating technique for the measurement of the contrast sensitivity function.

We developed a computerized contrast sensitivity function (CSF) measurement technique using a computer graphics board to reproduce Arden grating type stimuli. The reliability of the procedure was examined by evaluating the standard deviation of repeated test differences. The validity of the procedure was tested by comparison with both a manual method of adjustment technique and with Regan low contrast letter charts. The procedure has been performed at a number of exposure speeds to account for the effect of reaction time and attention of the results. The optimum exposure time for the procedure has been found to be greater than or equal to 22 s. As a result of the benefits of automation the test is quick, produces test-retest correlation coefficients for the five spatial frequencies tested which are similar to those for the method of adjustment procedure (0.76 to 0.91 for the computerized test, 0.66 to 0.88 for the signal generator measurements), and produces values which correspond closely with the method of adjustment measurement. It has the advantages of utilizing hardware already available in many computer systems, having a constant mean luminance across the screen, and having a constant and optimized presentation time.

Adult↗
PubMed1990

[Development of the method of ultrasound topometry of the thyroid gland and computer programs in the planning of radioactive iodine therapy].

The paper is concerned with the problem of stereological volumenometry applied to the problems of ultrasound topometry of the thyroid. The organ surfaces are tightened on the basis of information obtained from echotomographic films using a method of cubic spline-interpolation, parametric function setting and methods of computer graphics. Images of sections can be obtained with an arbitrary step and an angle of inclination to the organ longitudinal axis. The main sources of errors of the method were estimated, and their numeric values were given.

Algorithms↗
PubMedDate not supplied

Investigation and modification of molecular structures with the nanoManipulator.

The nanoManipulator system adds a virtual reality interface to an atomic force microscope (AFM), thus providing a tool that enables the user not only to image but also to manipulate nanometer-sized molecular structures. As the AFM tip scans the surface of these structures, the tip-sample interaction forces are monitored, which in turn provide information about the frictional, mechanical, and topological properties of the sample. Computer graphics are used to reconstruct the surface for the user, with color or contours overlaid to indicate additional data sets. Moreover, by means of a force-feedback pen, which is connected to the scanning tip via software, the user can touch the surface under investigation to feel it and to manipulate objects on it. This system has been used to investigate carbon nanotubes, fibrin, DNA, adenovirus, and tobacco mosaic virus. Nanotubes have been bent, translated, and rotated to understand their mechanical properties and to investigate friction on the molecular level. AFM lithography is being combined with the nanoManipulator to investigate the electromechanical properties of carbon nanotubes. The rupture forces of fibrin and DNA have been measured. This article discusses how some of the graphics and interface features of the nanoManipulator made these novel investigations possible. Visitors have used the system to examine chromosomes, bacterial pili fibers, and nanochain aggregates (NCAs). Investigators are invited to apply to use the system as described on the web at http:@www.cs.unc.edu/Research/nano/doc/biovis it.html.

Adenoviridae↗
PubMed1993

Extracting prototypical facial images from exemplars.

A computer graphic method for extracting a natural image of an individual's facial prototype, or average appearance, from a number of different images of that individual is presented. The process improves upon previous photographic and computational techniques. Synthesis of a person's average expression and pose from a sample of images is derived in an automatic and quantitative way. Possible uses of composite faces produced in this manner in psychological investigations of facial qualities (eg attractiveness) and in applied areas such as telecommunication are pointed out.

Attention↗
PubMed1994

Computer-assisted restriction mapping: an integrated approach to handling experimental uncertainty.

Building a map of restriction sites from double-digest gel data can be a complex and frustrating task, especially when many DNA fragments are detected or when the gel results are ambiguous. 'Double Digester' is an interactive, graphical computer program which helps researchers understand and resolve such data. It explicitly represents the experimental data, the associated uncertainties, the researcher's hypotheses and possible map interpretations. Alternative solutions are frequently possible, and the differences between them may help determine which additional experiments might resolve ambiguities. Initial use has confirmed the benefits of this approach, and has suggested ways in which it can be refined and extended. Double Digester meets the need for a practical tool to help build restriction maps, and also illustrates how a computer-based tool can confront experimental uncertainty in an integrated fashion.

Algorithms↗
PubMedDate not supplied

Image analysis and quantification of atherosclerosis using MRI.

This paper describes an image processing, pattern recognition, and computer graphics system for the noninvasive identification and evaluation of atherosclerosis using multidimensional Magnetic Resonance Imaging (MRI). Particular emphasis has been placed on the problem of developing a pattern recognition system for noninvasively identifying the different plaque classes involved in atherosclerosis using minimal a priori information. This pattern recognition technique involves an extension of the ISODATA clustering algorithm to include an information theoretic criterion (Consistent Akaike Information Criterion) to provide a measure of the fit of the cluster composition at a particular iteration to the actual data. A rapid 3-D display system is also described for the simultaneous display of multiple data classes resulting from the tissue identification process. This work demonstrates the feasibility of developing a "high information content" display which will aid in the diagnosis and analysis of the atherosclerotic disease process. Such capability will permit detailed and quantitative studies to assess the effectiveness of therapies, such as drug, exercise, and dietary regimens.

Algorithms↗
PubMedDate not supplied

3D distance fields: a survey of techniques and applications.

A distance field is a representation where, at each point within the field, we know the distance from that point to the closest point on any object within the domain. In addition to distance, other properties may be derived from the distance field, such as the direction to the surface, and when the distance field is signed, we may also determine if the point is internal or external to objects within the domain. The distance field has been found to be a useful construction within the areas of computer vision, physics, and computer graphics. This paper serves as an exposition of methods for the production of distance fields, and a review of alternative representations and applications of distance fields. In the course of this paper, we present various methods from all three of the above areas, and we answer pertinent questions such as How accurate are these methods compared to each other? How simple are they to implement?, and What is the complexity and runtime of such methods?

Algorithms↗
PubMed1990

Medicinal chemistry: a support or a driving force in drug research?

The foregoing has demonstrated most emphatically the significant and central role which chemistry plays in modern and future drug research. It does not mean to diminish the important role of biology but it does serve to show that chemistry is not merely a support for the needs of biology but is a powerful driving force in itself. The two disciplines are essentially interdependent and each relies on the other for success in drug design, discovery and eventual delivery of a useful medicament to the patient. Finally, the medicinal chemist today is faced with as many if not more formidable challenges in medicinal research as his counterpart of a generation ago. The sciences of genetics, molecular biology, neuro-pharmacology and electrophysiology have expanded the knowledge base of cellular function many fold. This new knowledge when coupled with the fundamental role of biochemistry in outlining in chemical terms both normal and abnormal cellular events offers the researcher a much more sophisticated appreciation of the cause of disease states. Knowing which enzymes or receptors are involved is a crucial step towards correcting the malfunctioning cellular conditions. With powerful new methods for determining the three-dimensional structure of molecules and computer graphics which give insight on rational drug design and modification, the medicinal chemist can explore with greater confidence than ever before the road to new drugs. The new biology, the new physical methodology and the computer have enhanced the role of chemistry in modern drug research and have given the medicinal chemist a more profound grasp of cellular aberrations leading to disease. This knowledge is a golden rod in the hands of an imaginative chemist in the search of innovative drugs.

Biochemical Phenomena↗
PubMedDate not supplied

Fabrication of total-contact burn masks by use of human body topography and computer-aided design and manufacturing.

Total-contact burn masks are used to treat scar tissue hypertrophy of the face. The mask should conform very closely to the contours of the face and provide evenly distributed pressure. The mask is worn continually throughout wound maturation. Lack of fit because of an inability to obtain exact facial contours by use of an alginate material diminishes the effectiveness of the mask. A multidisciplinary team representing physical therapy, CAD/CAM (computer-aided design and computer-aided manufacturing), biomedical engineering, and prosthetics has advanced the method of developing total-contact burn masks by use of human body electronic imaging, computer graphics, and numerically controlled milling processes. High-resolution surface scanning and CAD/CAM have been used successfully to accurately fabricate three such masks. The methodology and preliminary results from use of these state-of-the-art techniques are described in this article.

Burns↗
PubMed1998

The application of volume deformation to three-dimensional facial reconstruction: a comparison with previous techniques.

Facial reconstruction has been widely criticised for its subjective nature and is thus often viewed as a last resort. Recent computer-aided reconstructions, which claim to be objective, may be subject to similar errors. To date, both manual reconstructions and computer-aided techniques have been limited to using the same tissue depth data reference tables. We propose that it is not solely the accuracy of the soft tissue depth data, but the sparsity of landmarks, which contributes to a lack of understanding of how soft tissue changes between the landmarks. The authors feel that a new approach to facial reconstruction using a computer graphics technique known as volume deformation addresses some of the problems encountered in the past. A review of previous methods is provided with discussion of the strengths and limitations of these techniques. In addition, areas are highlighted where the new deformation-based approach may offer possible solutions.

Computer Graphics↗
PubMed1988

A model for hormone receptor binding to the mouse mammary tumour virus regulatory element based on hydroxyl radical footprinting.

The mouse mammary tumour virus long terminal repeat region contains regulatory sequences able to mediate transcriptional induction by different steroid hormones. Two clusters of binding sites for the glucocorticoid and the progesterone receptors have been identified in the region between -70 and -190, the so called hormone responsive or regulatory element. To understand the molecular details of the interaction between the receptors and the DNA we have used the high resolution technique of hydroxyl radical footprinting. Both in the promoter distal site and in the promoter proximal cluster additional contacts between the proteins and the double helix are detected by this technique, outside of the region identified by methylation protection. The pattern of contacts in the promoter distal region is compatible with a model involving the interaction of a receptor dimer with the major grooves of four subsequent turns of the double helix, each turn being contacted by a separate zinc finger. This model is illustrated by computer graphical methods and discussed in terms of sequence homologies with other hormone regulatory elements.

Animals↗
PubMed1999

Haptic rendering of isosurfaces directly from medical images.

Virtual environments for surgical training, planning and rehearsal have the potential to significantly enhance patient treatment and diagnosis. Haptic feedback devices provide forces to the physician through a manipulator, simulating palpation, scalpel cuts, or retraction of tissue. While haptics have been studied in other fields, medical applications of haptics remain in their infancy. We propose a method of haptically rendering isosurfaces (representing hard structures) directly from anatomical datasets rather than through traditional intermediate graphical representations such as polygons. Our algorithm determines an implicit surface representation of a volumetric isosurface on the fly, and renders the structure using standard haptic algorithms to calculate the forces felt by the user. This approach has the advantage of providing easy access to the rich volume dataset containing the actual anatomy. By relating Hounsfield units to density, haptic rendering has the ability to provide different resistances based on the tissue type being rendered. We developed and tested our algorithm using a quadric implicit surface, a common primitive in computer graphics, and have applied it to a variety of anatomical image datasets. Our paper describes the algorithm in sufficient detail to facilitate reproduction by others.

Algorithms↗
PubMed1993

Computer-generated slide graphics: an exciting advancement or a problem?

Computer-generated slide graphics have significantly altered the face of audiovisual presentations. However, it remains to be determined if dramatic effects enhance presentation clarity and increase information retrieval. This study compared color combination and print type graphics. Ninety medical students were shown a 29-minute, 45-slide presentation addressing aspects of plastic surgery. Each slide represented one of 15 color combinations and one of 3 fonts. The students studied each slide for 10 seconds and then in 25 seconds recorded all information they could recall. Statistical analysis (using ANOVA) revealed a significant difference in information retrieval among slides and a significant interaction between color and font. The "best" was orange block print on a raspberry background. The "worst" was yellow cursive print on a black background. This study demonstrated that (1) color influences information gleaned from a slide presentation and (2) font type simplicity may result in improved retention.

Audiovisual Aids↗
PubMed2004

Analysis on multiresolution mosaic images.

Image mosaicing is the act of combining two or more images and is used in many applications in computer vision, image processing, and computer graphics. It aims to combine images such that no obstructive boundaries exist around overlapped regions and to create a mosaic image that exhibits as little distortion as possible from the original images. In the proposed technique, the to-be-combined images are first projected into wavelet subspaces. The images projected into the same wavelet space are then blended. Our blending function is derived from an energy minimization model which balances the smoothness around the overlapped region and the fidelity of the blended image to the original images. Experiment results and subjective comparison with other methods are given.

Algorithms↗
PubMed1993

Quantitative three-dimensional assessment of face-lift with an optical facial surface scanner.

Three-dimensional computed tomographic scan images of facial deformities provide information that has been useful in planning and evaluating therapy. However, the benefits of computed tomographic imaging in cosmetic plastic surgery are often insufficient to justify exposing the patient to radiation. This report describes application of an optical, noncontact, three-dimensional surface digitizer with subsecond scanning time for 360-degree examination of the human head. The resultant three-dimensional surface data are suitable for computer graphics display and manipulation, and for noncontact skin surface measurement. The scanner provides accurate and complete coverage of complex facial surfaces. This system was applied to digitization of the human head in the planning and evaluation of facial plastic surgery. The results indicate that the resulting image is accurate enough to detect subtle dimensional changes resulting from surgery, including postoperative edema and surface changes due to face-lift. This type of scanning can assist in a number of tasks performed by plastic surgeons, including collecting anthropomorphic measurements, preoperative and postoperative assessment, volume monitoring, customizing of implants, and interactive planning.

Algorithms↗
PubMed2002

[Mathematical classification of root canal curvature of human teeth].

Endodontic research requires a mathematically based classification method of root canal forms. The aim of this study was to give a mathematical description of root canal forms using differential geometrical pattern analysis and computer graphics. The measurements of 433 extracted human roots were carried out on isometric radiographs taken from clinical view. Seven points of root canal axis of the same radiographs were approximated using fourth degree polynomial functions describing the imaginary axis of canals. The Schneider's angle of each root was also measured for grouping the samples according to this parameter. The classification of root canal form on the basis of Schneider's angle differs from the classification of geometrical pattern analysis. This type of classification of root canals is suitable for standardizing test specimens, including natural human teeth used for testing root forms: I (straight), J (apically curved), C (continuously curved) or S (multicurved).

Computer Graphics↗
PubMed1998

Virtual reality: preparation and execution of sinus surgery.

Endonasal sinus surgery requires a great deal of training before it can be performed adequately. Due to the complex and variable anatomy and the proximity of important structures, severe complications are possible, even for experienced surgeons. The nasal endoscopy simulator (NES) is an interactive training system for nasal endoscopy and endonasal sinus surgery that combines computer graphics and virtual reality (VR) techniques. This system consists of a graphics workstation, a tracking system for measuring the position of the endoscope and surgical instruments in space, a head model, image data sets of the nasal cavity and paranasal sinus area, and complementary software. The current NES is a visual and auditory VR system that provides both educational and planning options for sinus surgery. The usual resistance when touching relevant anatomical structures is not provided by this release. Therefore, a "force feedback system" is implemented that allows for such a response. VR simulation will become an important part of surgical education and planning for individual sinus surgery procedures. The ongoing development of the NES will lead to an improved educational environment for residents in training and practitioners.

Computer Graphics↗