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PubMedDate not supplied

Volumetric 3-D imaging of computerized tomography scans.

Contiguous transaxial high resolution CT scans of more than 100 patients with craniofacial deformities and orthopedic disorders were obtained. The CT scan examinations were used diagnostically in determining the need for surgery and for planning therapy. The serial section data was reconstructed in a three-dimensional form with surface and transparent volumetric computer graphics processing techniques. Real time sequences showing the presence of internal abnormalities in these patients were produced and recorded on video tape. This study demonstrates the feasibility and technical requirements of three-dimensional volumetric visualization for diagnostic evaluation of patients with craniofacial and orthopedic disorders.

Adult↗
PubMed1994

A three-dimensional representation of an athletic female knee joint using magnetic resonance imaging.

Intense interest in knee joint mechanics has resulted in the development of numerous models to predict forces acting at the knee. However, few models have accounted for the unique geometric characteristics of the knee joint's articular surfaces when predicting the mechanical response of the joint. The purpose of this study was to stimulate accurately the complex geometric characteristics of the tibiofemoral joint for input into a finite element model representing the knee joint of athletic females. The right knee of an athletic female with no history of knee joint trauma was imaged using a 0.5 T magnetic resonance imaging (MRI) unit. Twelve cross-sectional slices of the knee were scanned in each of three orthogonal planes (coronal, sagittal and axial) at slice intervals of 6 mm, 7 m, and 8 mm respectively. A scan plan (two coronal images and an axial image) was also generated to enable calculation of the orthogonal scans with respect to one another. Select anatomical reference points representing cancellous and compact bone, major ligament attachment areas, and articular cartilage of the distal femur and proximal tibia were digitized from the processed shadowgraphs. The processed digitized data were input into a computer graphics program which was the pre- and post-processing software for the finite element analysis package. Contours of the cancellous and compact bone of the tibial and femoral condyles were generated using beta and cubic spline curves. Bezier quadratic and cubic polynomials were used to reconstruct the tibial and femoral shafts.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Cardiology education using hypermedia and digital imagery.

A computer-based educational system for the study of cardiovascular imaging is described. This system, based on HyperCard * and a standard Macintosh II, integrates hypertext retrieval, computer graphics, sound, and medical images into a single interactive environment stored on a standard hard disk. This 'hypermedia' approach allows arbitrary complexity coupled with direct, immediate, easy traversal of the images and related text, which provides the opportunity for students to move at their own pace, choose their own direction through the material and repeat as often as desired. Storage on magnetic medium allows for easy updating with new studies and material in order to keep pace with advances in medical imaging technology. The system could be mastered onto CD-ROM for ease of distribution if so desired. The system includes a tutorial on the basics of digital image representation and example studies from cineangiography, nuclear medicine, echocardiography and magnetic resonance imaging of the heart. Quantitative techniques for evaluation of left ventricular function are explained using computer graphics overlays on the original medical images. Color encoded functional images are also included as an aid to visualization of ventricular performance data. The system has proven useful as a primer for digital imaging in cardiology prior to specific case study in a traditional mentor relationship.

CD-ROM↗
PubMed1993

A computational fluid mechanical study of blood flow in a variety of asymmetric arterial bifurcations.

In the present study, the results of an attempt to estimate the flow field at arterial bifurcations are shown and discussed with respect to the pathogenesis of vascular disorders. The Navier-Stokes equations for incompressible Newtonian fluid flow were solved using a finite volume method with a body-fitted coordinate (BFC) system. The arterial models had various branching angles and mother-daughter diameter ratios. The boundary conditions specified are: steady and pulsatile fully developed flow at the inflow cross-section and a non-slip condition at the rigid wall. Results obtained were displayed using color computer graphics and an animation technique. Complex vortices were always found at the bifurcation regardless of the branching angle. At the proximal region of the bifurcation, where the early atherosclerotic plaque usually develops, strong unsteady vortices were found to access the wall in the diastolic phase. Therefore it is necessary to take them into account when discussing the development of atherosclerosis.

Arteries↗
PubMed1995

Computer-aided human modelling programs for workstation design.

In designing a workstation, computer-aided human modelling programs can be used advantageously to analyse human-fit to the workstation components. The analysis is performed within a three-dimensional computer graphics environment. To illustrate the current state of development, six representative programs were selected: CYBERMAN, COMBIMAN, CREW CHIEF, JACK, SAMMIE, and MANNEQUIN. The programs differ considerably in terms of system requirement, operating characteristics, applicability and the various ergonomic evaluation functions available in the human modelling programs. The comparative analysis of the programs will aid the user to select the appropriate program for a particular workstation design.

Anthropometry↗
PubMedDate not supplied

Three-dimensional visualization of computerized tomography and laser scan data for the simulation of maxillo-facial surgery.

A system has been developed for the three-dimensional (3D) visualization of the face and skull using data obtained from a purpose-built no-contact laser scanning system and from a series of scans produced by X-ray computerized tomography. Features developed allow the simulation, planning and prediction of maxillo-facial surgery. Realistic skeletal and facial images with a solid 3D appearance are produced from these two datasets using computer graphics techniques. The images can be sectioned for diagnostic purposes or parts can be repositioned for the simulation of surgery. 3D measurements can be made on the images for pre- and post-surgical analysis. An example of the clinical use of the system in the planning of surgery and the prediction of post-surgical facial appearance is given.

Computer Graphics↗
PubMed1995

Molecular modelling of glycoproteins by homology with non-glycosylated protein domains, computer simulated glycosylation and molecular dynamics.

OBJECTIVES: This study aims to visualise glycoproteins by computer graphics molecular modelling in order to research the dynamics of the oligosaccharide chains, determine their affects on protein conformation, antigenicity and function and to characterise oligosaccharide recognition determinants. With respect to the last, the modelling included the sialylpolylactosamine of thymocyte Thy-l and the sialyl Le(x)/Le(a) determinant present on brain Thy-l. METHODS: The following techniques were used: 1) database searching for homologies with non-glycosylated protein domains; 2) protein modelling on the basis of homology and secondary structure prediction techniques; 3) oligosaccharide construction using a simulated annealing approach utilising the AMBER forcefield with appropriate parameters in the Biosyn software environment; 4) creation of glycoprotein conjugates for further investigation by energy minimisation and molecular dynamics. RESULTS: This approach was successful in providing models of Thy-l and the carboxy terminus 27.5 kD of HIV-1 gp 120, by homology with immunoglobulin light chain folds and in one case (Thy-l) adding the oligosaccharide chains, phosphatidylinositol glycan anchor and lipid membrane and, in the other, adding additional highly glycosylated domains, and domains which folded by molecular dynamics. Significant affects on protein conformation were shown in the presence or absence of the lipid anchor and simulated membrane, but not by the N-linked oligosaccharide chains. CONCLUSIONS: The highly glycosylated molecules Thy-l and gp120, which are not expected to crystallise in their native state, were modelled by computer graphics simulated annealing or molecular dynamics from which interactions could be predicted which agree with experimental data on antibody binding and in vitro activity.

Carbohydrate Conformation↗
PubMed1990

Long-term arterial pressure control: an analysis from animal experiments and computer and graphic models.

Long-term arterial pressure control is very different from acute control, because many of the acute control systems are overridden by a single long-term mechanism that has little to do with short-term control. This is the renal fluid volume mechanism for pressure control. It is based on a simple functional property of the kidney: as the arterial pressure rises, the kidney output of water and electrolytes increases dramatically. When the output rises above the net intake of water and electrolytes, negative body fluid balance occurs, causing both the body fluid volume and the pressure to decrease. This decrease continues until the kidney fluid output exactly balances the net fluid intake. Conversely, if the pressure falls below the exact level for balance, intake becomes greater than output; then fluid builds up in the body and the pressure rises until intake and output again exactly balance each other. This fluid mechanism for pressure control has been known from the beginning of blood pressure research. However, its overpowering importance was not appreciated until a mathematical computer analysis in 1966 demonstrated the renal-fluid feedback mechanism to have infinite feedback gain for long-term pressure control. This is the principal topic of the present review.

Animals↗
PubMed1988

[Computer aided design of anticancer drugs].

The recent advances in computer science and technology enabled us to use computer for drug-design. Calculation of structural features of drugs and modeling of biomacromolecules by means of 3D-computer graphics afford a new approach to comprehend a molecular interaction which is important for drug action. As target molecules for anticancer drug, DNA structure can be elucidated and drug-DNA complex model can be constructed to give further insight for drug design. For example, complex of DNA double helix and bleomycin was built and by conjunction with other complex model such as mitomycin C, anthramycin, and netropsin it would be able to design a base sequence specific DNA-groove binding molecule. In addition, DNA is also a target molecule for antibiotics which intercalate between base pairs. Rational design of intercalator and groove binder thus would lead a novel anticancer drug. On the other hand, combination of the fruitful results of molecular biology and gene engineering with computer technology, will give a detail of protein structure which is one of most desired information for designing novel drugs.

Antineoplastic Agents↗
PubMed1981

A computer-generated three-dimensional model of the B chain of bovine alpha-thrombin.

A computer graphic molecular display system has been used to construct a three-dimensional model of the B chain of bovine thrombin. The model is derived from the bovine alpha-chymotrypsin structure as determined by X-ray crystallographic studies. The amino acid sequence of bovine thrombin has been substituted for that of alpha-chymotrypsin, preserving the beta-barrel structure and maximizing homology of the amino acid sequence of the two proteins. With the exception of an area in the vicinity of the specificity binding pocket, most of the changes observed in thrombin occur on the surface of the molecule. The most notable changes observed in the model are the increases on the surface of positively charged (arginine and lysine) and negatively charged (glutamate and aspartate) residues. A glutamate replaces methionine 192 near the entrance to the specificity binding pocket. The nature of this site was further altered by the substitution of an aspartate for serine 189 and an alanine for serine 190. The structure of the resulting specificity binding pocket is consistent with that of serine proteases, which have trypsin-like substrate specificity. The computer graphics molecular display system has been used to insert models of synthetic thrombin inhibitors into the active site of the thrombin B chain model. With the model, it has been possible to correlate the interaction of thrombin with the observed binding constants of two inhibitors of trypsin-like serine proteases, p-amidinophenylmethylsulfonylfluoride (Ki = 1.27 x 10(-6) M) and m-[m-(trifluoromethyl)phenoxypropoxy]benzamidine (KD = 2.9 x 10(-6) M).

Amino Acids↗
PubMed1992

The structural mimicry of membrane sterols by tamoxifen: evidence from cholesterol coefficients and molecular-modelling for its action as a membrane anti-oxidant and an anti-cancer agent.

The anti-cancer drug tamoxifen is a potent inhibitor of lipid peroxidation induced by Fe(III)-ascorbate in ox-brain phospholipid liposomes. Similar anti-oxidant effects, but with varying potencies, are also shown by 4-hydroxy-tamoxifen, cholesterol, ergosterol and 17-beta-oestradiol. We now describe a computer-graphic fitting technique that demonstrates a structural similarity between the five compounds. In addition, we have quantified the differences (relative to cholesterol) between the anti-oxidant activities of the compounds in terms of a novel expression referred to here as the cholesterol coefficient (Cc) Finally, we discuss how the inhibitory effect of tamoxifen on lipid peroxidation may result from a membrane stabilization that is associated with a decrease in membrane fluidity. This action may be related to the anti-proliferative effect exerted by tamoxifen on cancer and fungal cells.

Antifungal Agents↗
PubMed1988

The Escherichia coli 30S ribosomal subunit; an optimized three-dimensional fit between the ribosomal proteins and the 16S RNA.

We have generated a computerized fit between the 3-dimensional map of the E.coli 30S ribosomal proteins, as determined by neutron scattering, and the recently published 3-dimensional model for the 16S RNA. To achieve this, the framework of coordinates for RNA-protein cross-link sites on the phosphate backbone in the RNA model was related to the corresponding framework of coordinates for the mass centres of the proteins by a least squares fitting procedure. The resulting structure, displayed on a computer graphics system, gives the first complete picture of the E.coli 30S ribosomal subunit showing both the proteins and the double-helical regions of the RNA. The root mean square distance between cross-link sites and protein centres is 32 A. The position of the mass centre of the combined double-helical regions was calculated from the model and compared with the position of the mass centre of the complete set of proteins. The two centres are displaced relative to one another by 20 A in the model structure, in good agreement with the experimental value of 25 A found by neutron scattering.

Computer Graphics↗
PubMed1998

The effects of computer simulated facial plastic surgery on social perception by others.

Previous studies have demonstrated the remarkable impact of facial plastic surgery on the perception of facial features. However, pre- and postoperative differences other than the surgically changed features such as facial expression, hairstyle, make-up etc., have influenced the results of previous studies. To exclude these visual cues a computer composite photograph of the changed feature mounted upon the preoperative photograph, instead of the standard postoperative photograph, was presented to observers in this study. Computer graphic technology was used to superimpose the postoperative, surgically changed facial features such as the nose, ear and chin of 16 patients on standardized preoperative photographs. The randomized preoperative photographs and the 'postoperative' composed images were presented to 67 subjects, using a person-perception questionnaire. Multivariate analysis demonstrated a more favourable postoperative judgement in only two patients (12.5%). The exclusive effect of facial plastic surgery on the social perception of patients by others when excluding visual cues, such as facial expression, hairstyle, make-up etc, is limited. It is tentatively assumed that the role played by facial plastic surgery is one of initiating a positive cycle by changing the patient's self-perception rather than one of direct social impact from the changed features.

Adolescent↗
PubMed1983

A computer graphic-based angiographic model for normal left ventricular contraction in man and its application to the detection of abnormalities in regional wall motion.

Analyzing the digitized left ventricular cineangiograms of 70 patients with no demonstrable heart disease (NDHD), we derived an angiographic model for normal contraction in the intact heart as viewed in the 30 degree right anterior oblique projection. This model was verified statistically by comparing the predicted regional stroke volumes with the measured volumes for the NDHD group. A wall motion system based on this model was compared with four other systems by examining the ventriculograms of 141 patients, all suffering from coronary artery disease but with normal volumes and ejection fractions (greater than 0.61). Of these, 60 had normally contracting ventricles and 81 exhibited mild regional abnormalities according to two experienced angiographers. Using Cochrane's Q test, we found significant differences among the five methods (Q = 29.5;p less than .001). The new approach showed significantly better agreement with the subjective assessment than the next best method (Q = 5.3;p less than .05). On a regional basis, overall sensitivity was 87.5% and specificity was 97.9%.

Adult↗
PubMed1989

Assessment of feature size abnormalities using receiver operating characteristic analysis.

The ability of an observer to detect variations in size of a geometrical image feature have been investigated using receiver operating characteristic (ROC) analysis. Three types of image were constructed using computer graphics: disc-shaped targets of variable radius, model chest radiographs showing a variable heart diameter and model arterial angiograms with variable vessel width. Five factors were investigated: observer experience, variation of detectability with theoretical signal-to-noise ratio, the prior probability of the presence of an abnormality, viewing distance, and uncertainty in the location of an abnormality. In all but one experiment, excellent agreement was found between measured detectabilities and the predictions of signal detection theory, providing an initial practice session was included for each observer. No significant variation in detectability was found using six different prior probabilities and two different viewing distances, and the reduction in detectability for a four-alternative location task was in good agreement with theoretical predictions. The high statistical efficiencies found for the detection of geometrical signals suggest that the levels of observer "internal" noise arising from decision-making processes during an ROC experiment are very low.

Computer Graphics↗
PubMed1988

Crystal structure of p-hydroxybenzoate hydroxylase complexed with its reaction product 3,4-dihydroxybenzoate.

Crystals of the flavin-containing enzyme p-hydroxybenzoate hydroxylase (PHBHase) complexed with its reaction product were investigated in order to obtain insight into the catalytic cycle of this enzyme involving two substrates and two cofactors. PHBHase was crystallized initially with its substrate, p-hydroxybenzoate and the substrate was then converted into the product 3,4-dihydroxybenzoate by allowing the catalytic reaction to proceed in the crystals. In addition, crystals were soaked in mother liquor containing a high concentration of this product. Data up to 2.3 A (1 A = 0.1 nm) were collected by the oscillation method and the structure of the enzyme product complex was refined by alternate restrained least-squares procedures and model building by computer graphics techniques. A total of 273 solvent molecules could be located, four of them being presumably sulfate ions. The R-factor for 14,339 reflections between 6.0 A and 2.3 A is 19.3%. The 3-hydroxyl group of the product introduced by the enzyme is clearly visible in the electron density, showing unambiguously which carbon atom of the substrate is hydroxylated. A clear picture of the hydroxylation site is obtained. The plane of the product is rotated 21 degrees with respect to the plane of the substrate in the current model of enzyme-substrate complex. The 4-hydroxyl group of the product is hydrogen bonded to the hydroxyl group of Tyr201, its carboxyl group is interacting with the side-chains of Tyr222, Arg214 and Ser212, while the newly introduced 3-hydroxyl group makes a hydrogen bond with the backbone carbonyl oxygen of Pro293.

4-Hydroxybenzoate-3-Monooxygenase↗
PubMed1997

Development of a frameless and armless stereotactic neuronavigation system with ultrasonographic registration.

OBJECTIVE: We have developed a frameless stereotactic neuronavigation system that allows navigation during neurosurgical procedures through an image formed from integrating ultrasonography and preoperative magnetic resonance (MR) imaging and/or x-ray computed tomography. METHODS: The system consists of a ultrasound imaging scanner, a workstation with an image capture board, and an ultrasonic tracking sensor with a 5-MHz ultrasonographic transducer. The ultrasonic tracking sensor measures the position and orientation of the ultrasonographic transducer. The oblique plane of the MR/computed tomographic image corresponding to the ultrasound image is then displayed on the workstation monitor. A three-dimensional computer graphic representation of the integrated image is also reported as a preliminary test. For the patient-image registration, the coordinates of digitized and imaged markers on a specifically developed reference frame are used. The reference frame is noninvasive because it is not bolted but only fastened to the patient's head with silicon. RESULTS: Based on the findings from the clinical application of the system in three cases, the system was advantageous because of the surgical procedures could be controlled by intraoperative ultrasonography as well as by preoperative MR/computed tomographic images. Missing parts in the ultrasonogram were supplemented with preoperative MR/computed tomographic images. At other times, spatial positioning and visualization by ultrasonography were useful for identifying anatomical objects in the image. CONCLUSION: This preliminary study of the frameless integration of ultrasonography into stereotactic space demonstrated its clinical usefulness. We believe that the concept of pre- and intraoperative image-guided surgery presented here will find increasing use in the future.

Adolescent↗
PubMed1996

Interaction of human leukocyte elastase with a N-aryl azetidinone suicide substrate: Conformational analyses based on the mechanism of action of serine proteinases.

The three-dimensional interaction of the enzyme-activated (suicide) inhibitor AA 231-1 [N-(2-chloromethyl)-3, 3-difluoro-azetidin-2-one] with human leukocyte elastase has been studied using computer graphics and molecular mechanics. Systematic conformational analyses and energy minimizations have been performed for the inhibitor AA 231-1 and its presumed complexes formed during the enzymatic process of inactivation, i.e., the Michaelis complex, the acyl-enzyme, and the inactivated enzyme with the covalently bound inhibitor. The beta-lactam ring characteristics of modeled AA 231-1 were in agreement with crystallographic data of related structures. Lowest energy conformations were found when the angle between the planes of the beta-lactam ring and that of its phenyl substituent was about -60 or 60 degrees. To study the interaction with the enzyme, the enzyme-inhibitor complexes were constructed by docking the inhibitor in the active site using enzyme coordinates from an X-ray crystallographic structure. The whole enzyme structure was used for conformational analyses and energy mechanics. Favorable conformations for the Michaelis complex have been obtained in which the carbonyl oxygen of the inhibitor was located in the oxyanion hole and the hydroxyl of Ser195 was in position to interact with the beta-lactam carbonyl carbon on the alpha face of AA 231-1. Simulations of the approach of the benzylic carbon by the nucleophilic amino acid His40 or His57 through an SN2 displacement on the halomethyl group of AA 231-1 were performed. The results agreed with the alkylation of the imidazole nitrogen N epsilon 2 of His57 leading to the inactivated enzyme (bis-adduct form).

Azetidines↗