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PubMed2003

Data representation for joint kinematics simulation of the lower limb within an educational context.

Three-dimensional (3D) visualization is becoming increasingly frequent in both qualitative and quantitative biomechanical studies of anatomical structures involving multiple data sources (e.g. morphological data and kinematics data). For many years, this kind of experiment was limited to the use of bi-dimensional images due to a lack of accurate 3D data. However, recent progress in medical imaging and computer graphics has forged new perspectives. Indeed, new techniques allow the development of an interactive interface for the simulation of human motions combining data from both medical imaging (i.e., morphology) and biomechanical studies (i.e., kinematics). Fields of application include medical education, biomechanical research and clinical research. This paper presents an experimental protocol for the development of anatomically realistic joint simulation within a pedagogical context. Results are shown for the lower limb. Extension to other joints is straightforward. This work is part of the Virtual Animation of the Kinematics of the Human project (VAKHUM) (http://www.ulb.ac.be/project/vakhum).

Arthrography↗

PubMed1987

Connections between pyramidal neurons in layer 5 of cat visual cortex (area 17).

The structural features of two physiologically-characterised pyramidal neurons (PC1 and PC2) closely situated in layer 5b in the visual cortex (area 17) of a single cat were studied using a combination of electrophysiological and anatomical techniques. Both PC1 and PC2 had exceptionally large somata (30-40 microns in diameter). On the basis of this and other morphological features cell PC1 was classified as a Meynert cell. PC1 possessed a very large (2.75 degrees X 4.50 degrees) binocularly driven standard complex receptive field. PC2 was also binocularly driven with a small, B-type receptive field. Both cells had the same preference for the direction and orientation of visual stimuli. PC1 and PC2 could be antidromically activated from stimulating electrodes positioned above the dorsal lateral geniculate nucleus with a response latency indicating that these cells probably innervated the visual tectum or pretectum. In addition to corticoefferent axons, the two neurons possessed extensive intracortical axon arbors that ramified extensively in layers 5 and 6 of the medial and lateral banks of the lateral gyrus in area 17. Axon collaterals from both PC1 and PC2 also innervated a small common target region in area 18. A total of 313 boutons from the axonal arbors of PC1 and PC2 were examined in the electron microscope. All of the identified synaptic junctions were found to establish Gray type 1 asymmetrical contacts. The combined ultrastructural data for both neurons indicated that 80% of boutons were onto dendritic spine heads, with 14%, 6%, and 1% onto small-, medium-, and large-calibre dendritic shafts, respectively. The spectrum of postsynaptic targets showed little variation with respect to lamina, distance from somata, or cortical area. Other large pyramidal neurons in layer 5 and spiny neurons in layer 6 were identified as receiving synaptic input from either PC1 or PC2. Using a computer graphics system, rotations of the bouton distributions revealed the existence of a clustered innervation of layers 5 and 6 in areas 17 and 18 derived from the two identified neurons. The bouton distributions strongly resembled the tangential pattern described previously for the functional slab-like organisation of the cortex. The results provide a morphological basis for the clustered intrinsic connectivity of pyramidal cells in layers 5 and 6 of the cat visual cortex. Furthermore, the results indicate the widespread excitatory influence of large pyramidal neurons on other cells projecting subcortically to sites dealing with visually guided behavior.

Animals↗

PubMed2005

Double-step registration of in vivo stereophotogrammetry with both in vitro 6-DOFs electrogoniometry and CT medical imaging.

Standard registration techniques of bone morphology to motion analysis data often lead to unsatisfactory motion simulation because of discrepancies during the location of anatomical landmarks in the datasets. This paper describes an iterative registration method of a three-dimensional (3D) skeletal model with both 6 degrees-of-freedom joint kinematics and standard motion analysis data. The method is demonstrated in this paper on the lower limb. The method includes two steps. A primary registration allowed synchronization of in vitro kinematics of the knee and ankle joints using flexion/extension angles from in vivo gait analysis. Results from primary registration were then improved by a so-called advanced registration, which integrated external constraints obtained from experimental gait pre-knowledge. One cadaver specimen was analyzed to obtain both joint kinematics of knee and ankle joints using 3D electrogoniometry, and 3D bone morphology from medical imaging data. These data were registered with motion analysis data from a volunteer during the execution of locomotor tasks. Computer graphics output was implemented to visualize the results for a motion of sitting on a chair. Final registration results allowed the observation of both in vivo motion data and joint kinematics from the synchronized specimen data. The method improved interpretation of gait analysis data, thanks to the combination of realistic 3D bone models and joint mechanism. This method should be of interest both for research in gait analysis and medical education. Validation of the overall method was performed using RMS of the differences between bone poses estimated after registration and original data from motion analysis.

Aged, 80 and over↗

PubMed1982

Computer-aided prediction of RNA secondary structures.

A brief survey of computer algorithms that have been developed to generate predictions of the secondary structures of RNA molecules is presented. Two particular methods are described in some detail. The first utilizes a thermodynamic energy minimization algorithm that takes into account the likelihood that short-range folding tends to be favored over long-range interactions. The second utilizes an interactive computer graphic modelling algorithm that enables the user to consider thermodynamic criteria as well as structural data obtained by nuclease susceptibility, chemical reactivity and phylogenetic studies. Examples of structures for prokaryotic 16S and 23S ribosomal RNAs, several eukaryotic 5S ribosomal RNAs and rabbit beta-globin messenger RNA are presented as case studies in order to describe the two techniques. Anm argument is made for integrating the two approaches presented in this paper, enabling the user to generate proposed structures using thermodynamic criteria, allowing interactive refinement of these structures through the application of experimentally derived data.

Animals↗

PubMed1991

CAD/CAM in dentistry.

The advent of computers and interactive computer graphics laid the groundwork for a revolution in dentistry. Dental CAD/CAM systems can at least match the quality of cast restorations. With the automation, consistency in quality is also provided. The dental CAD/CAM system can simplify the effort required to produce a restoration. With new technologies for fabrication (like milling and edm), a whole array of new materials, which were historically difficult or impossible to manipulate, suddenly become viable possibilities. When used in the dental office, many of the systems eliminate the need for impressions and can produce a restoration while the patient waits. A dental revolution is underway, providing exciting possibilities for restorative dentistry.

Crowns↗

PubMed1993

[Current status and future prospects of the radiation oncology treatment planning system].

Treatment planning is the most essential radiation oncology practice and has been developing owing to various technological innovations such as faster computing speed, advanced computer graphics and enormous data storage capacity. Treatment planning consists of CT data retrieval, target input, selection of treatment techniques and dose calculation, evaluation of dose distribution, and data transfer to the accelerator, each of which has been progressing quite rapidly. In particular, ongoing topics in treatment planning include multi-leaf conformation, non-coplanar technique, CT scanner dedicated to treatment planning and data transfer through LAN. Target delineation using PACS, and megavoltage verification imaging represented by portal imaging, are also useful. Higher local control rates as well as lower complication probabilities are expected with the sophisticated treatment planning system.

Forecasting↗

PubMed2005

A video database of moving faces and people.

We describe a database of static images and video clips of human faces and people that is useful for testing algorithms for face and person recognition, head/eye tracking, and computer graphics modeling of natural human motions. For each person there are nine static "facial mug shots" and a series of video streams. The videos include a "moving facial mug shot," a facial speech clip, one or more dynamic facial expression clips, two gait videos, and a conversation video taken at a moderate distance from the camera. Complete data sets are available for 284 subjects and duplicate data sets, taken subsequent to the original set, are available for 229 subjects.

Adult↗

PubMed2003

A comparison of primate prefrontal and inferior temporal cortices during visual categorization.

Previous studies have suggested that both the prefrontal cortex (PFC) and inferior temporal cortex (ITC) are involved in high-level visual processing and categorization, but their respective roles are not known. To address this, we trained monkeys to categorize a continuous set of visual stimuli into two categories, "cats" and "dogs." The stimuli were parametrically generated using a computer graphics morphing system (Sheltonelton, 2000) that allowed precise control over stimulus shape. After training, we recorded neural activity from the PFC and the ITC of monkeys while they performed a category-matching task. We found that the PFC and the ITC play distinct roles in category-based behaviors: the ITC seems more involved in the analysis of currently viewed shapes, whereas the PFC showed stronger category signals, memory effects, and a greater tendency to encode information in terms of its behavioral meaning.

Analysis of Variance↗

PubMed2004

An XML standard for the dissemination of annotated 2D gel electrophoresis data complemented with mass spectrometry results.

BACKGROUND: Many proteomics initiatives require a seamless bioinformatics integration of a range of analytical steps between sample collection and systems modeling immediately assessable to the participants involved in the process. Proteomics profiling by 2D gel electrophoresis to the putative identification of differentially expressed proteins by comparison of mass spectrometry results with reference databases, includes many components of sample processing, not just analysis and interpretation, are regularly revisited and updated. In order for such updates and dissemination of data, a suitable data structure is needed. However, there are no such data structures currently available for the storing of data for multiple gels generated through a single proteomic experiments in a single XML file. This paper proposes a data structure based on XML standards to fill the void that exists between data generated by proteomics experiments and storing of data. RESULTS: In order to address the resulting procedural fluidity we have adopted and implemented a data model centered on the concept of annotated gel (AG) as the format for delivery and management of 2D Gel electrophoresis results. An eXtensible Markup Language (XML) schema is proposed to manage, analyze and disseminate annotated 2D Gel electrophoresis results. The structure of AG objects is formally represented using XML, resulting in the definition of the AGML syntax presented here. CONCLUSION: The proposed schema accommodates data on the electrophoresis results as well as the mass-spectrometry analysis of selected gel spots. A web-based software library is being developed to handle data storage, analysis and graphic representation. Computational tools described will be made available at http://bioinformatics.musc.edu/agml. Our development of AGML provides a simple data structure for storing 2D gel electrophoresis data.

Computational Biology↗

PubMed2004

Hominin brain evolution--new century, new directions.

The study of hominin brain evolution focuses on the interiors of fossilized braincases. Applications of recent three-dimensional computed tomography (CT) and magnetic resonance imaging (MRI) techniques for visualizing and measuring >>virtual endocasts<< from braincases in combination with advances in computer graphics and software for acquiring relevant data are transforming the way in which fossil skulls are analyzed, and improving the quality of paleoneurological investigations. Although CT imaging is preferred for fossil skulls, a novel method that combines high-resolution MRI of physical endocasts, electronic reconstruction of their missing parts, and warping of the resulting virtual endocasts is currently being developed and has great potential for future studies of hominin brain evolution. Applications of CT and MR techniques have already resulted in surprising new findings, which are briefly outlined. Exciting revelations about hominin brain evolution are expected as the 21st century unfolds.

Animals↗

PubMed1993

Structure design: an artificial intelligence-based method for the design of molecules under geometrical constraints.

This study presents an algorithm that implements artificial-intelligence techniques for automated, and site-directed drug design. The aim of the method is to link two or more predetermined functional groups into a sensible molecular structure. The proposed designing process mimics the classical manual design method, in which the drug designer sits in front of the computer screen and with the aid of computer graphics attempts to design the new drug. Therefore, the key principle of the algorithm is the parameterization of some criteria that affect the decision-making process carried out by the drug designer. This parameterization is based on the generation of weighting factors that reflect the knowledge and knowledge-based intuition of the drug designer, and thus add further rationalization to the drug design process. The proposed algorithm has been shown to yield a large variety of different structures, of which the drug designer may choose the most sensible. Performance tests indicate that with the proper set of parameters, the method generates a new structure within a short time.

Algorithms↗

PubMed1991

Methods of three dimensional analysis of patients with asymmetry of the face.

One of the problems of patients with facial asymmetry is that two dimensional analysis of such patients does not give a satisfactory picture of the underlying problem. Various methods have been suggested to overcome this problem, such as stereophotogrammetry (Burke et al. 1983) and Moire fringes (Takasaki 1970, Xenofos and Jones 1979). These methods are time consuming and are not fully automated. At present no 3D method is available which provides a readily analysable, global description of change in the face due to the limitations of the techniques which have been used. The 3D changes in shape of the face which occur during growth and with surgical intervention remain undetermined, either qualitatively or quantitatively. Although the importance of such a development has been pointed out, no method of 3D analysis has been developed. (Cutting et al. 1986). Attempts at three dimensional (3D) measurement of the face for monitoring the growth of children with facial deformities usually use hazardous and invasive techniques of ionizing radiation and metallic implants to assess the growth of the skull. Over the past 10 years the Departments of Orthodontics and Medical Physics and Bio-Engineering at University College London have collaborated in the development of a computer graphics based 3D system for the simulation, planning and prediction of maxillo-facial surgery. The laser scanning system developed measures over 20,000 points over the surface of the face in 10 seconds using a non-invasive and completely non-hazardous technique (Arridge et al. 1985, Moss et al. 1987, Moss et al. 1988). The data acquired is accurate to approximately 0.5 mm. Analytical programmes have been developed to handle the enormous quantity of data produced. These programs form the basis of a practical, user-friendly, clinical system whose performance has been evaluated and is now in routine use (Moss et al. 1989).

Cephalometry↗

PubMed1981

Two-state analysis for allosteric properties of abnormal hemoglobins.

To shed light upon the understanding of structure and function relationship of hemoglobin, we determined the oxygen equilibrium curves of a series of alpha 1 beta 2 contact anomalous hemoglobins, low and high spin derivatives of valency hybrid hemoglobins and normal hemoglobin under various conditions comparable with each other using an automatic recording apparatus. The Hill plots of their curves were analyzed by a trial and error method without any assumptions using computer graphic display. The results deduced from these analyses are as follows. Anomaly in alpha 1 beta 2 contact region, weakening or rupture of the Bohr effect and Cl- dependent salt-bridges, small displacement of heme iron from porphyrin plane result in not only shifting the R--T equilibrium towards R but also raising the oxygen affinity of the T state to various extents. IHP binding can oppose these effects. A relation that the change in L strongly depends upon the change in c was newly discovered. These results suggest that the T state of individual Hb takes a single structure of many heterogeneous T quaternary structures depending on its function.

Allosteric Regulation↗

PubMed1993

Determination of the existence of hinge movements of the temporomandibular joint during normal opening by Cine-MRI and computer digital addition.

PURPOSE: The purpose of the first phase of this two-part investigation was to determine if the opening motion of the mandible could be illustrated and described using a dynamic imaging method. The purpose of the second phase of the investigation was to determine if a center of rotation would be discovered. MATERIALS AND METHODS: Five volunteer subjects, 2 female and 3 male, whose temporomandibular joints had previously been determined to be asymptomatic, were examined by magnetic resonance imaging (MRI) during opening from a standardized position. The serial static images were reconstructed by the MRI's computer in "cine mode" to simulate dynamic motion, similar to a motion picture. For the second phase, each patient's series of static images were digitally added and manipulated by a computer graphics program to locate the center of hinge motion. RESULTS: After reviewing the animated images recorded on videotape, three independent dentist observers confirmed that the opening movement of the mandible was initially rotational, followed by translation within the glenoid fossa. A center of rotation was calculated to be in the anatomic center of the condylar head of all of the subjects in this study. CONCLUSIONS: This study showed that opening dynamics of the mandibular condyle could be studied by cine-MRI and that an opening hinge axis appears to be located in the anatomic center of the condylar head.

Biomechanical Phenomena↗

PubMed1995

Design and implementation of a database and program for 3D reconstruction from serial sections: a data-driven approach.

This paper describes a structural approach for a standard setup of a computer program for 3D reconstruction from serial sections. Three-dimensional reconstruction as a technique increases in importance as, along with modern immunohistochemical techniques, it is a tool in the understanding of three-dimensional development patterns. In order to apply 3D reconstruction technique in a standard laboratory setup, an attempt was made to streamline the input and the manipulation of the data such that results are obtained easily. One will find a combination of two approaches in this paper: the first is a strict ordering of the complex data, and the second is an ordering of the processes that one wishes to apply on the data (together, these two approaches constitute an information analysis); because it was observed that developmental biologists tend to work from simple lines to describe their observations, the contour model was chosen as the vehicle to build a reconstruction model from. Consequently, the data is ordered in a database that has to be manipulated to get the data out in the desired format. The most important output format is a display of the reconstructed contour stack on a graphical computer screen. Together with the other data manipulation processes, such as the input, the inspection, the revision (correction), and the reconstruction, all processes are described using the reconstruction of an 11 embryonic days (ED) rat embryo as an example. Finally, the merits of the program are illustrated with an example from the development of the human embryonic heart.

Animals↗

PubMed1996

Visualizing the pediatric airway: three-dimensional modeling of endoscopic images.

Three-dimensional reconstruction of medical images has emerged as an important visualization tool for studying complex anatomy. These tools have found important applications in neurology and plastic surgery using computed tomography (CT) and magnetic resonance imaging (MRI) data. However, CT and MRI do not sufficiently delineate lesions of the pediatric airway. Inspection through the rod lens telescope remains the standard diagnostic method. A video recording of an endoscopic procedure is essentially a sequence of two-dimensional images captured as the telescope traverses the airway lumen. Using digitized endoscopic video recordings and computer graphics reconstruction techniques, we have developed a preliminary three-dimensional modeling system for the pediatric airway. A series of normal and abnormal telescopic airway examinations were video recorded. Serial sections were obtained by digitizing the video images at uniform intervals as the scope traversed the airway lumen between the vocal folds and the carina. The digitized images were calibrated and used to reconstruct the airway lumen in three dimensions. Classifying airway abnormalities according to the minimal cross-sectional area or with descriptive terms can be subjective and dependent on the endoscopist's observational skills. We hope that this preliminary work will lead to more precise and understandable methods for representing complex airway lesions.

Child↗

PubMed1998

Design of a 3D workbench interface for training in dental implantology.

The recent technological advances in the area of image processing and interactive computer graphics have lead to many sophisticated systems which support clinical experts in diagnosis and treatment planning tasks. In dentistry, the treatment with implants becomes more and more important. Although in the near future there will be increased demand for dentists who are trained in dental implantology, little effort has been made to introduce technologically new teaching methods into the curriculum of dentists. This paper describes the design of a virtual implant treatment planning system which is based on the concept of a three-dimensional horizontal display. The system is utilizing different VR and multimedia techniques to achieve a highly interactive virtual workbench environment which is suited for class-room experimental education in dental implantology.

Computer-Assisted Instruction↗

PubMed2006

Soft-tissue balance evaluation system for total hip arthroplasty by intraoperative contact pressure measurement at the hip joint.

We developed a system for measurement of contact pressure at the hip joint surfaces that enables checking of the artificial hip joint condition during surgery. First, we constructed the pressure sensor that forms the artificial joint. We installed eight small pressure sensors to the spherical head component, a part of the ball-socket joint. Next, we developed software for recording and visualizing the detected pressures that were recorded every 1 ms. The pressure distribution was displayed with the 3D computer graphics in real-time. The system enabled intuitive recognition of pressure direction 3-dimensions. Next, using the system, we conducted measurements during total hip arthroplasty. Although it requires some improvements in its measurement accuracy, the system allows real-time acquisition of information on the artificial hip joint in real-time. Further improvements of the calibration method should enable more accurate measurements. As a complete system, it will be a useful tool for selecting an appropriate implant that fits a patient's hip joint or for estimating the risk of complications after surgery.

Arthroplasty, Replacement, Hip↗