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At least 307 records · Page 17Linked to original sources
PubMed1995

Computer-assisted geometric design of cerebral aneurysms for surgical simulation.

This report presents conceptual aspects and the clinical implications of a computer-assisted geometric design of a cerebral aneurysm and surrounding structures. The technique is based on the approximation power of the parametric spline function, which achieves interpolation and surface fitting of the arterial information obtained by conventional angiography. Computer graphic transformations including shifting, scaling, rotation, and putting different colors in different intensities make it possible to obtain the surgical simulation of a cerebral aneurysm. To our knowledge, this is the first report in which the computer graphic simulation of the surgical view of a cerebral aneurysm is made with a personal computer. Using our method, it may be possible to obtain the surgical simulation of a more complicated view by introducing a navigation system of a new style for conventional open neurosurgery. Concepts and the technical details of the method are described.

Basilar Artery↗
PubMed1983

Three-dimensional surface descriptions from sensed data.

Computer graphics are being employed in several fields to display images of objects that have never been seen by human eyes. The information collected by CAT scanners, ultrasound sensing systems, and other automatic measuring devices is typically not in a displayable form. This paper surveys several techniques for constructing three-dimensional descriptions of these sensed objects in forms suitable for manipulation by computer graphics display programs.

Computers↗
PubMed1988

Model of a complex between the tetrahemic cytochrome c3 and the ferredoxin I from Desulfovibrio desulfuricans (Norway strain).

A three-dimensional model of an electron-transfer complex between the tetrahemic cytochrome c3 and the ferredoxin I from the sulfate-reducing bacterium Desulfovibrio desulfuricans (Norway strain) has been generated through computer graphics methods. The model is based on the known X-ray structure of the cytochrome and on a model of the ferredoxin that has been derived through computer graphics modeling and energy minimization methods, from the X-ray structure of the homologous ferredoxin from Peptococcus aerogenes. Four possible models of interaction between the two molecules were examined by bringing in close proximity each of the four hemes and the redox center (4Fe-4S) of the ferredoxin and by optimizing the ion pairs interactions. One of these models shows by far the "best" structure in terms of charges, interactions, and complementarity of the topology of the contact surfaces. In this complex, the distance between the iron atoms of the ferredoxin redox center and the hemic iron atom is 11.8 A, which compares well with those found between redox centers in other complexes. The contact surface area between the two molecules is 170 A2.

Amino Acid Sequence↗
PubMed1995

Ophthalmic microsurgical robot and associated virtual environment.

An ophthalmic virtual environment has been developed as part of a teleoperated microsurgical robot built to perform surgery on the eye. The virtual environment is unique in that it incorporates a detailed continuum model of the anatomical structures of the eye, its mechanics and optical properties, together with a less detailed geometric-mechanical model of the face. In addition to providing a realistic visual display of the eye being operated on, the virtual environment simulates tissue properties during manipulation and cutting and the forces involved are determined by solving a mechanical finite element model of the tissue. These forces are then fed back to the operator via a force reflecting master and so the surgeon can experience both the visual and mechanical sensations associated with performing surgery. The virtual environment can be used to enhance the images produced by the camera on the microsurgical slave robot during surgery and as a surgical simulator in which it replaces these images with computer graphics generated from the eye model.

Computer Graphics↗
PubMed1988

Computerized three-dimensional reconstruction of the crypt system of the palatine tonsil.

The purpose of the present study is to note the three-dimensional structure of the tonsillar crypt using computer graphics methods. The tonsils used herein were human tonsils obtained from the surgical operation, and were cut in serial sections according to ordinary procedures. The crypt contours obtained from the serial sections were used as inputs to the computer (PC-9801 VM) through the image-scanner (PC-IN 502). The three-dimensional structure of the human tonsillar crypt revealed by computer graphics, showed that the crypts had not only branches but also anastomosis, and that they could divide into two types, a simple unbranched crypt and a complicated branched one. Generally, the simple type of crypt was located in the peripheral zone of the tonsils and the complicated type in the central zone. These findings are discussed briefly and with reference to previous reports.

Child↗
PubMed1989

Imaging workstations for computer-aided primatology: promises and pitfalls.

In this paper, the application of biomedical imaging workstations to primatology will be explained and evaluated. The technological basis, computer hardware and software aspects, and the various uses of several types of workstations will all be discussed. The types of workstations include: (1) Simple - these display-only workstations, which function as electronic light boxes, have applications as terminals to picture archiving and communication (PAC) systems. (2) Diagnostic reporting - image-processing workstations that include the ability to perform straightforward manipulations of gray scale and raw data values will be considered for operations such as histogram equalization (whether adaptive or global), gradient edge finders, contour generation, and region of interest, as well as other related functions. (3) Manipulation systems - three-dimensional modeling and computer graphics with application to radiation therapy treatment planning, and surgical planning and evaluation will be considered. A technology of prime importance in the function of these workstations lies in communications and networking. The hierarchical organization of an electronic computer network and workstation environment with the interrelationship of simple, diagnostic reporting, and manipulation workstations to a coaxial or fiber optic network will be analyzed.

Animals↗
PubMed1986

Modification of paradoxical sleep following transections of the reticular formation at the pontomedullary junction.

A retractable wire knife was employed to transect the reticular formation at the pontomedullary junction in order to assess the respective importance of pontine and medullary reticular neurons and their pathways in paradoxical sleep. Thirteen cats were implanted with a standard array of electrodes for polygraphic recording of sleep-wakefulness states during 3 days in baseline condition and during 21 days after transections. Average electroencephalographic (EEG) amplitude, average electromyographic (EMG) amplitude, and ponto-geniculo-occipital (PGO) spike rate were measured per 1-min epoch for each day. A trivariate computer graphics display of 1 day's data revealed three major clusters of points that corresponded to wakefulness, slow wave sleep, and paradoxical sleep in baseline. (a) After transections through the entire reticular formation at the pontomedullary junction, paradoxical sleep was no longer evident in the trivariate computer graphics or polygraphic record, either by the presence of a high PGO spike rate or by that of muscle atonia in association with a low-amplitude EEG. These results indicated that the reticular fibers that pass through the pontomedullary junction and interconnect the pontine tegmentum and the medullary reticular formation are necessary for generating the cluster of electrographic variables that normally characterizes paradoxical sleep. (b) After transections through the dorsal half of the reticular formation, paradoxical sleep was still evident, though with a reduced PGO spike rate, and muscle atonia was normal. These results indicated that the descending noradrenaline locus coeruleus fibers and the "longitudinal catecholamine bundle," which course through the dorsal tegmentum, are not necessary for the generation of muscle atonia or the state of paradoxical sleep. (c) After transections through the ventral half of the reticular formation, paradoxical sleep was still apparent by the association of a moderate, though reduced, rate of PGO spiking in association with low-amplitude EEG activity and a high-amplitude EMG, indicating a loss of muscle atonia. The duration of the PS episodes, however, was greatly reduced. These results indicated that the descending "tegmentoreticular" and ascending reticulotegmental pathways, which course ventrally through the pontomedullary junction and interconnect the dorsolateral pontine tegmentum and the ventromedial medullary reticular formation, are essential for the muscle atonia of paradoxical sleep and important for the normal cyclic generation and maintenance of the state of paradoxical sleep.

Animals↗
PubMed1991

HAMOG: molecular graphics program for chemistry, biochemistry, molecular biology and enzyme research.

HAMOG is a computer graphics program written in C for personal computers. Clear menus and a context-sensitive help option make the program easy to operate for occasional users. HAMOG provides a flexible environment for displaying and manipulating molecules and molecular systems. Special functions allow the investigation of structure-activity relationships of biologically active molecules. These include the calculation of molecular electrostatic potentials and fields, the superposition of molecules and the calculation of steric accessibilities. The visualization and manipulation of protein structures immediately readable from the Brookhaven Protein Data Bank files are also possible using HAMOG. The construction of any peptide or protein structure is very simple.

Chemical Phenomena↗
PubMed1991

Computer- and robot-assisted resection of thalamic astrocytomas in children.

Six children ranging in age from 2 to 10 years who harbored deep benign astrocytomas were operated upon using a computer- and robot-assisted system. A radical excision was achieved in all cases with no significant morbidity nor any mortality. The system consists of an interactive, three-dimensional display of computed tomographic image contours and digitized cerebral angiograms taken using the Brown-Roberts-Wells stereotactic frame. The surgical retractor is held and manipulated using a PUMA 200 robot. The position and orientation of the surgical retractor is displayed on the three-dimensional display. Preoperative planning and simulation are important features of this system. Movement of the brain after removal of the tumor and cerebrospinal fluid is substantial, so the tumor removal is based on visually defined margins. Enhanced computer graphics and robotic devices are important adjuncts to neurosurgical procedures and will find increasing use in the future.

Astrocytoma↗
PubMed1987

Motor end-plate distribution in the human interarytenoid muscle.

Histochemical and computer graphic techniques were used to determine the distribution of neuromuscular junctions in the human interarytenoid (IA) muscle. The motor end-plates of four IA specimens obtained from normal postmortem larynges were visualized using an acetylcholinesterase stain. The three-dimensional distribution of motor end-plates was later reconstructed using computer graphics. The motor end-plates in the IA were found to be distributed in an inverted "Y" configuration. A broad band of end-plates was found at the midpoint of the muscle fibers in the superior and middle aspect of the muscle. This band divided obliquely in a lateral direction toward the inferior border of the muscle. This pattern of motor end-plate distribution is possibly consistent with the bilateral innervation of the IA by the recurrent laryngeal nerves.

Adult↗
PubMed1990

On the development of an integrated computer system for cephalometric analyses.

This paper describes a microcomputer based system that integrates image processing and computer graphics techniques to automate the data extraction and storage process in cephalometric analyses. The system increases the consistency of measurements and improves the productivity of surgical and dental staff.

Cephalometry↗
PubMed1987

Automated data collection and processing for a cycle ergometer.

A system is described for collection and processing of data from a cycle ergometer. Cycle pedals, specially made to withstand the extremely high forces exerted during maximal power cycling, contain transducers to measure pedal angle relative to the crank and foot forces both perpendicular and parallel to the pedal surface. An additional transducer monitors crank position. Output signals are conditioned, amplified, digitized by a 12-bit analog-to-digital converter, fed into a computer at 100 Hz/channel, and mathematically smoothed to attenuate noise. For each sample interval, foot force components perpendicular and parallel to the crank arm are calculated. Power generated on each crank revolution is determined from transducer information. Computer graphics display pedaling parameters vs. crank angle in both rectangular and circular format. Data files containing variables descriptive of pedaling force curves are produced to enable computerized statistical analysis of cycling performance.

Computer Graphics↗
PubMedDate not supplied

Three-dimensional computer reconstruction of the distribution of neuromuscular junctions in the thyroarytenoid muscle.

Microinjections of botulinum toxin have recently been shown to be effective in the treatment of strabismus, and it has also been suggested that microinjections of this myoneural blocking agent might be of value in the treatment of spastic dysphonia. The success of such a microinjection technique would rely on a precise knowledge of the distribution of myoneural junctions in the thyroarytenoid muscle. In view of this potential application as well as the need for such information in reinnervation procedures, we have used computer graphics to reconstruct the three-dimensional distribution of motor end-plates in the thyroarytenoid muscle. Three cat and one human (fresh autopsy specimen) larynges were frozen and sectioned on a cryostat. Serial sections were then processed for the histochemical localization of acetylcholinesterase activity to demarcate the neuromuscular junctions. An X-Y digitizer was used to reference the position of the motor end-plates in each serial section, and the three-dimensional distribution of the neuromuscular junctions was reconstructed on a computer graphics terminal. The results are discussed in regard to their applicability to clinical treatment of spastic dysphonia and other disorders of phonation.

Animals↗
PubMedDate not supplied

Quantitative changes in fissure sealant six months after placement.

Earlier studies have reported extensive volumetric loss of fissure sealant shortly after placement. To determine the volume of fissure sealant lost at six months, we used a servohydraulic profilometric apparatus in combination with computer graphics. Twenty-two premolar teeth were selected, and baseline silicone impressions were made of each tooth. The teeth were sealed and the occlusion adjusted where necessary. Impressions were made immediately of sealed teeth and again at six months. Epoxy replicas were made from all impressions, and their surfaces digitized by sequential profilometry. Using a three-dimensional root mean square (RMS) goodness-of-fit computer program, before sealant, after sealant, and six months after sealant computer-graphic images were superimposed. The volume of sealant lost after six months for all premolar teeth was X = 0.23 mm3 (maxillary second premolar: N = 9, X = 0.29 mm3; maxillary first premolar: N = 5, X = 0.27 mm3; mandibular second premolar: N = 4, X = 0.20 mm3; mandibular first premolar: N = 4, X = 0.08 mm3). The volume differences between tooth groups were not significant as measured by analysis of variance (ANOVA). These volumes represented a 13.99% loss of applied sealant for all premolars (maxillary second premolar: 19.72%; maxillary first premolar: 15.37%; mandibular second premolar: 8.46%; mandibular first premolar: 6.37%). The area of wear and the depth of wear also were measured.

Humans↗
PubMed1995

Visualization of dynamic simulations of muscle thin filaments.

Following a novel computational formalism, the thin filament of muscle can be modeled by a computational machine containing a large number of finite automata that have one-to-one correspondence with the constituent protein molecules. Computer graphics can be used to visualize the correspondence between the states of finite automata and the configurations of protein molecules according to the structural data. The dynamic simulation of the muscle filament that corresponds to the concurrent state transitions of finite automata can be represented as a sequence of video images. The kinetic and structural knowledge of individual protein molecules is, therefore, integrated into a coherent and functional system. This type of computation and visualization can also be useful for the investigation of molecular structure, function, and interaction in various complex biological systems.

Actin Cytoskeleton↗