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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↗
PubMed2003

Curvature analysis of the mandibular condyle.

OBJECTIVE: To determine whether curvature analysis on high resolution CT images can be used as a tool for evaluation of mandibular condyle morphology. METHODS: Curvature analysis was performed on reconstructed oblique coronal CT images of 634 normal condyles from 317 patients (144 men and 173 women; age range 4-89 years) with inner or middle ear disease. The condyles were scanned with 1 mm collimation using helical CT. The CT images were analysed manually on a personal computer. RESULTS: The condyle CT images could be categorized into five curvature profile patterns: (1) bi-peak; (2) no peak; (3) tri-peak; (4) bi-peak with an intervening bottom above the base line (bi-peak with a col); and (5) bi-peak with an intervening negative phase. A separate evaluation using computer graphic condyle models indicated that these curvature patterns corresponded to flat (bi-peak), round (no peak), convex (bi-peak with a col), concave (bi-peak with a negative phase) and angled (tri-peak) contours of the condyle's superior surface. The curvature profiles were identical between bilateral condyles in 40% (126/317) of the patients. Gender-related differences in the incidence of the curvature profiles were also found, the bi-peak with a col profile being more frequently observed in women and the bi-peak with a negative phase profile being observed more frequently in men. CONCLUSION: Curvature analysis on CT images depicts condyle morphology effectively and may be an adjunctive tool for condyle morphometry.

Adolescent↗
PubMedDate not supplied

Binary-space-partitioned images for resolving image-based visibility.

We propose a novel 2D representation for 3D visibility sorting, the Binary-Space-Partitioned Image (BSPI), to accelerate real-time image-based rendering. BSPI is an efficient 2D realization of a 3D BSP tree, which is commonly used in computer graphics for time-critical visibility sorting. Since the overall structure of a BSP tree is encoded in a BSPI, traversing a BSPI is comparable to traversing the corresponding BSP tree. BSPI performs visibility sorting efficiently and accurately in the 2D image space by warping the reference image triangle-by-triangle instead of pixel-by-pixel. Multiple BSPIs can be combined to solve "disocclusion," when an occluded portion of the scene becomes visible at a novel viewpoint. Our method is highly automatic, including a tensor voting preprocessing step that generates candidate image partition lines for BSPIs, filters the noisy input data by rejecting outliers, and interpolates missing information. Our system has been applied to a variety of real data, including stereo, motion, and range images.

Algorithms↗
PubMedDate not supplied

Bilateral recovering of sharp edges on feature-insensitive sampled meshes.

A variety of computer graphics applications sample surfaces of 3D shapes in a regular grid without making the sampling rate adaptive to the surface curvature or sharp features. Triangular meshes that interpolate or approximate these samples usually exhibit relatively big error around the insensitive sampled sharp features. This paper presents a robust general approach conducting bilateral filters to recover sharp edges on such insensitive sampled triangular meshes. Motivated by the impressive results of bilateral filtering for mesh smoothing and denoising, we adopt it to govern the sharpening of triangular meshes. After recognizing the regions that embed sharp features, we recover the sharpness geometry through bilateral filtering, followed by iteratively modifying the given mesh's connectivity to form singlewide sharp edges that can be easily detected by their dihedral angles. We show that the proposed method can robustly reconstruct sharp edges on feature-insensitive sampled meshes.

Algorithms↗
PubMed2006

Walking from thought.

Online analysis and classification of single electroencephalogram (EEG) trials during motor imagery were used for navigation in the virtual environment (VE). The EEG was recorded bipolarly with electrode placement over the hand and foot representation areas. The aim of the study was to demonstrate for the first time that it is possible to move through a virtual street without muscular activity when the participant only imagines feet movements. This is achieved by exploiting a brain-computer interface (BCI) which transforms thought-modulated EEG signals into an output signal that controls events within the VE. The experiments were carried out in an immersive projection environment, commonly referred to as a "Cave" (Cruz-Neira, C., Sandin, D.J., DeFanti, T.A., Surround-screen projection-based virtual reality: the design and implementation of the CAVE. Proceedings of the 20th annual conference on Computer graphics and interactive techniques, ACM Press, 1993, pp. 135-142) where participants were able to move through a virtual street by foot imagery only. Prior to the final experiments in the Cave, the participants underwent an extensive BCI training.

Adult↗
PubMed1995

Three-dimensional analysis of the intrinsic cardiac ganglia in a young dog.

The intrinsic ganglia of the heart of a young dog were studied by computer graphic reconstruction to determine the accurate location. The heart was embedded in celloidin, and transverse sections were cut. Using every third 60 microns section, a series of 49 sections was mapped. Three-dimensional (3D) images were constructed by a personal computer. Numerous intrinsic ganglia, most of which were located in the epicardiun, were observed. The intrinsic ganglia were found in the base of the aorta and pulmonary vessels and from the base of the superior vena cava to the right atrium, i.e., the sinoatrial nodal region. Using the 3D reconstruction technique, the locations of the intrinsic ganglia could be accurately identified. Furthermore, it was demonstrated that these ganglia formed several groups which formed a continuity. This study suggested that it was necessary to consider the existence of the numerous intrinsic ganglia, when we studied the cardiac innervation.

Animals↗
PubMed2005

Quantitative evaluation of axial wall taper in prepared artificial teeth.

The purpose of this study was to quantitatively evaluate the axial wall taper of prepared artificial teeth using a non-contact three-dimensional shape measuring system. A total of 54 artificial teeth prepared by pre-clinical dental students for complete cast restorations were evaluated. For quantitative analysis, five cross sections were computer-graphically placed perpendicularly to the z-axis. The surface coordinate values (x, y, z) of each cross section were converted into polar coordinate values (r, theta), which were then graphically rendered to a two-dimensional plane. At four points, each 90 degrees from the distal center point of the cross section, the axial wall taper was quantitatively calculated using a formula based on the differences in radius between the highest and lowest positions of the cross sections of the prepared tooth. The average calculated taper was 5.8 degrees in the distal region, 21.7 degrees in the buccal region, 14.9 degrees in the mesial region and 12.5 degrees in the lingual region. These results suggest that the axial wall taper of prepared teeth can be quantitatively evaluated using this measuring system.

Computer Graphics↗
PubMed1994

Characterization of the glycosylation status of proteins.

Proteins are posttranslationally modified by a number of mechanisms, by far the most significant of which in terms of the molecular mass and functional diversity is glycosylation. The oligosaccharide chains added shortly after biosynthesis at the ribosome, and further modified while the protein is translocated through the intracellular membranes, have multiple affects on transport, localization, stability, plasma membrane expression activity, and antigenicity. Characterization of the glycosylation patterns at each site around the protein is essential for detailed understanding of structure/function relationships and the design of potential therapeutic agents. This can be achieved by a series of chromatographic and physicochemical procedures including HPLC, GC, MS, NMR, and computer graphics molecular modeling, which culminate in information on monosaccharide sequence and linkage, glycoprotein conformation, and oligosaccharide-to-protein interactions.

Carbohydrate Conformation↗
PubMed1994

DNurbs: DNA modeled with NURBS.

DNurbs (dee-in-urbs) are a small number of bicubic patches wrapping each base pair in complementary DNA. NURBS, the nonuniform rational B-spline surfaces now popular in computer graphics, are employed for the patches. Control points for the surface patches are generated from the molecular surface based on canonical base pairs.

Base Sequence↗
PubMed1988

Synthetic amphiphilic peptide models for protein ion channels.

Ion channel proteins are important for the conduction of ions across biological membranes. Recent analyses of their sequences have suggested that they are composed of bundles of alpha-helices that associate to form ion-conducting channels. To gain insight into the mechanisms by which alpha-helices can aggregate and conduct ions, three model peptides containing only leucine and serine residues were synthesized and characterized. A 21-residue peptide, H2N-(Leu-Ser-Ser-Leu-Leu-Ser-Leu)3-CONH2, which was designed to be a membrane-spanning amphiphilic alpha-helix, formed well-defined ion channels with ion permeability and lifetime characteristics resembling the acetylcholine receptor. In contrast, a 14-residue version of this peptide, which was too short to span the phospolipid bilayer as an alpha-helix, failed to form discrete, stable channels. A third peptide, H2N-(Leu-Ser-Leu-Leu-Leu-Ser-Leu)3-CONH2, in which one serine per heptad repeat was replaced by leucine, produced proton-selective channels. Computer graphics and energy minimization were used to create molecular models that were consistent with the observed properties of the channels.

Computer Graphics↗
PubMed1993

Human basal ganglia volume asymmetries on magnetic resonance images.

The brains of 19 healthy adults, ages 18-49, were imaged on a GE Signa 1.5 T MR scanner. Basal ganglia were circumscribed on sequential axial proton density-weighted images (TR 1700, TE 20) and submitted for 3-dimensional reconstruction and volumetric analysis at a computer graphics workstation. The 15 right-handed patients (12 men, 3 women) had significantly larger left total basal ganglia volumes, which included larger globus pallidus and lenticular nuclei on the left, but larger caudate nuclei on the right. In contrast, basal ganglia asymmetries were not seen in four left-handers. No sex differences were detected. The basal ganglia appear to belong to an increasing number of CNS structures that display anatomical hemispheric lateralization.

Adult↗
PubMed1987

Landmark identification in computerized posteroanterior cephalometrics.

A lack of cognition regarding the reliability of landmark identification in posteroanterior cephalometrics keeps the extracted data questionable. The present study was designed to analyze this problem for the purpose of providing certain insights. An interactive computer graphic package was developed. This package was called EA-PAX (Error Analysis of Postero-Anterior cephalometric X-ray films). A random sample of 40 clear posteroanterior cephalometric head plates was studied. The reliability of landmark identification was established. The skeletal landmarks seemed more reliable than the dental landmarks. The variation in the direction and magnitude of the error was determined for each landmark. Most landmarks had their own characteristic noncircular envelope of error. It is not the philosophy of the present authors to tell the orthodontists what to use. Rather, the philosophy is to be aware of the amount and direction of variation for a particular landmark. Taking this into consideration will enable the orthodontists to look on their cephalometric numbers with a mental awareness of the possible variations. Several clinical and research studies are suggested in the article.

Adolescent↗
PubMed2004

Adjustable typography: an approach to enhancing low vision text accessibility.

Millions of people have low vision, a disability condition caused by uncorrectable or partially correctable disorders of the eye. The primary goal of low vision rehabilitation is increasing access to printed material. This paper describes how adjustable typography, a computer graphic approach to enhancing text accessibility, can play a role in this process, by allowing visually-impaired users to customize fonts to maximize legibility according to their own visual needs. Prototype software and initial testing of the concept is described. The results show that visually-impaired users tend to produce a variety of very distinct fonts, and that the adjustment process results in greatly enhanced legibility. But this initial testing has not yet demonstrated increases in legibility over and above the legibility of highly legible standard fonts such as Times New Roman.

Adult↗