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At least 775 records · Page 43Linked to original sources

PubMed1982

Reconstruction and imaging of the beating heart.

Computer methods are discussed which have been developed by the Medical Image processing Group (formerly at SUNY/Buffalo, now at the University of Pennsylvania) for the reconstruction of the beating human heart from x-ray projections. Two data collection modes are emphasized: the dynamic spatial reconstructor and gated cardiac scanning with a rotate-only (third-generation) computed tomography scanner. How the reconstructed beating heart can be displayed by means of dynamic computer graphics is also illustrated.

Animals↗

PubMedDate not supplied

Radiation therapy treatment planning using concurrent programming.

Concurrent programming can be applied to the problem of computer graphic simulation of radiation treatment of tumors (radiation treatment planning). Running several tasks or programs simultaneously on behalf of a single user provides a big improvement over the traditional sequential approach, in which editing a treatment plan and computing and displaying dose distributions are separate operations which must be invoked by explicit commands. With our system, the user sees isodose contours being updated automatically and continuously as the plan is edited; this greatly facilitates plan optimization. The complexity of parallel processing has resulted in a 'conventional wisdom' which discourages this technique. The usual approach is to have parallel processes share a common global data structure, which makes interaction hard to control and discourages modularity and data abstraction. We have developed an alternative approach based on message streams which instead enhances modularity and data abstraction while still providing the advantages of parallel processing. The system is very reliable and is used routinely in a practical clinical environment.

Computer Simulation↗

PubMed2000

Using diagnostic radiology in human evolutionary studies.

This paper reviews the application of medical imaging and associated computer graphics techniques to the study of human evolutionary history, with an emphasis on basic concepts and on the advantages and limitations of each method. Following a short discussion of plain film radiography and pluridirectional tomography, the principles of computed tomography (CT) and magnetic resonance imaging (MRI) and their role in the investigation of extant and fossil morphology are considered in more detail. The second half of the paper deals with techniques of 3-dimensional visualisation based on CT and MRI and with quantitative analysis of digital images.

Animals↗

PubMed1977

Serial electrocardiograms in hypertensive cardiovascular disease.

A graphic method for depicting serial changes in electrocardiograms is described and demonstrated for patients being treated in an antihypertension clinic. For these patients, the diagnostic categories, normal, left ventricular hypertrophy, and biventricular hypertrophy, are of primary interest. For each electrocardiogram, 14 measurements are used to compute posterior probabilities for each of the three categories. A triangular grid is used to plot each set of probabilities for an electrocardiogram as one point, which by its position in the triangle can be related to the three categories simultaneously. Points representing successive electrocardiograms can be plotted in the same triangle, giving a pattern of change with time. This pattern of change has been corroborated with associated clinical information on a number of patients. This display, which can be produced quickly and efficiently on a computer graphics terminal, should be considered as a possible tool in evaluating the status of individual hypertensive patients in terms of increase or decrease of ventricular hypertrophy and the efficacy of therapeutic measures.

Aged↗

PubMed1998

The virtual reality arthroscopy training simulator.

Arthroscopy has already become an irreplaceable method in diagnostics. The arthroscope, with optics and light source, and the exploratory probe are inserted into the knee joint through two small incisions underneath the patella. Currently, the skills required for arthroscopy are taught through hands-on clinical experience. As arthroscopies became a more common procedure even in smaller hospitals, it became obvious that special training was necessary to guarantee qualification of the surgeons. On-the-job training proved to be insufficient. Therefore, research groups from the Berufsgenossenschaftliche Unfallklinik Frankfurt am Main approached the Fraunhofer Institute for Computer Graphics to develop a training system for arthroscopy based on virtual reality (VR) techniques. Two main issues are addressed: the three-dimensional (3-D) reconstruction process and the 3-D interaction. To provide the virtual environment a realistic representation of the region of interest with all relevant anatomical structures is required. Based on a magnetic resonance image sequence a realistic representation of the knee joint was obtained suitable for computer simulation. Two main components of the VR interface can be distinguished: the 3-D interaction to guide the surgical instruments and the 2-D graphical user interface for visual feedback and control of the session. Moreover, the 3-D interaction has to be realized by means of Virtual Reality techniques providing a simulation of an arthroscope and an intuitive handling of other surgical instruments. Currently, the main drawback of the developed simulator is the missing of haptic perception, especially of force feedback. In cooperation with the Department of Electro-Mechanical Construction at the Technical University Darmstadt a haptic display is designed and built for the VR arthroscopy training simulator. In parallel we developed a concept for the integration of the haptic display in a configurable way.

Arthroscopy↗

PubMed1982

Stereotactic neurosurgery using 3-D image data from computed tomography.

During the last decade computer tomography (CT) scanners have provided images that show internal anatomy of unsurpassed resolution and that, since they are inherently digital, a format computer graphics software can easily process. By combining CT images, a specially designed head-mounted instrument, and the software to coordinate them, improved surgical accuracy can result for stereotactic surgery. Using the head-mounted frame and the interactive computer software described here, the entire stereotactic approach is transportable to computer systems of three major CT manufacturers. Neurosurgeons now have a tool that allows trajectory selection and probe placement entirely within the CT suite. Compared with conventional stereotaxis, the CT-aided approach offers increased accuracy, with a significant fluid contrast injection for finding reference points and the avoidance of important brain structures due to the direct visualization afforded with CT. Key interactive features are shown here that allow unrestricted views of anatomy in the area of surgical interest. For example, oblique views that are normal to the trajectory of neurosurgical instruments are extracted in real time during the surgical procedure. Standard sagittal (lateral) and coronal (frontal) image planes are also shown integrated with the interactive technique. The surgical procedure is outlined and details of the pattern recognition technique for image-to-frame registration are presented. Test, phantom, and patient results are given.

Brain↗

PubMed2003

Computational flow visualization in vibrating flow pump type artificial heart by unstructured grid.

Computational flow visualization in the casing of vibrating flow pump (VFP) was made for various conditions based on the novel techniques of fluid dynamics. VFP type artificial heart can generate the oscillated flow and can be applied to the left ventricular assist device. Flow pattern of blood in an artificial heart is closely connected to mechanical performance and serious biomechanical problems such as hemolysis and blood coagulation. To effectively design the VFP for a left ventricular assist device, the numerical codes for solving Navier-Stokes equations were developed for three-dimensional blood flow based on the finite volume method. Furthermore, the simulation techniques based on the artificial compressibility method and the unstructured grid were also developed here. The numerical calculations were based on the precise configurations and the flow conditions of the prototype device. From the viewpoint of computational fluid dynamics (CFD), the detailed discussion of flow patterns in the casing of VFP, which were closely connected with hemolysis and blood coagulation, was made and the computational results were visualized by the use of the recent technique of computational graphics. Some useful design data of VFP were presented.

Blood Flow Velocity↗

PubMed1985

Computer-assisted analysis in organic synthesis.

The planning of alternative routes for the synthesis of complex organic molecules has been facilitated by the formulation of guiding strategies that can be applied to a broad range of problems. Analysis of organic synthesis can be carried out in the retrosynthetic direction, opposite to the actual process of chemical synthesis, or bidirectionally, that is, as a combined retrosynthetic and synthetic search. An interactive computer program is described which utilizes the general strategies of retrosynthetic analysis and an appropriate database to generate pathways of chemical intermediates for chemical synthesis of a particular target structure. Computer graphics and standard chemical structures are used for man-machine communication.

Chemical Phenomena↗

PubMed1981

Theoretical studies on tricyclic antidepressants. IV. Probable submolecular topographic structures of the "amine pump" receptor.

A probable structure for the best tricyclic antidepressant with respect to inhibition of reuptake of norepinephrine into peripheral adrenergic nerve terminals has been reported. Using tha result as indicating the particular conformation in which the tricyclic antidepressant is likely to mimic the biogenic amine at the membrane "pump" receptor site, the topography of the receptor surface has been worked out by simulating space-filling models of the best inhibitors of the two types in the superposed state. With appropriate computer graphic facilities such surfaces can be used to screen other untested molecules and to predict their activity.

Animals↗

PubMed1994

Visualizing collagen fibril growth.

Collagen fibrils are among the most abundant protein polymers in living organisms. While the longitudinal packing of molecules in the fibrils has been agreed on for many years, there is continuous disagreement over the lateral packing. In this work, we describe a set of computer graphics programs that can be used to visualize fibril packing and simulate fibril growth. An example of a model and simulation are presented.

Collagen↗

PubMed2003

A new method for assessing arteriolar diameter and hemodynamic resistance using image analysis of vessel lumen.

To characterize the nonuniform diameter response in a blood vessel after a given stimulus (e.g., arteriolar conducted response), frequent serial diameter measurements along the vessel length are required. We used an advanced image analysis algorithm (the "discrete dynamic contour") to develop a quick, reliable method for serial luminal diameter measurements along the arteriole visualized by intravital video microscopy. With the use of digitized images of the arteriole and computer graphics, the method required an operator to mark the image of the two inner edges of the arteriole at several places along the arteriolar length. The algorithm then "filled in" these marks to generate two continuous contours that "hugged" these edges. A computer routine used these contours to determine luminal diameters every 20 microm. Based on these diameters and on Poiseuille's law, the routine also estimated the hemodynamic resistance of the blood vessel. To demonstrate the usefulness of the method, we examined the character of spatial decay of KCl-induced conducted constriction along approximately 500-microm-long arteriolar segments and the KCl-induced increase in hemodynamic resistance computed for these segments. The decay was only modestly fitted by a simple exponential, and the computed increase in resistance (i.e., 5- to 70-fold) was only modestly predicted by resistance increase based on our mathematical model involving measurements at two arteriolar sites (Tyml K, Wang X, Lidington D, and Oullette Y. Am J Physiol Heart Circ Physiol 281: H1397-H1406, 2001). We conclude that our method provides quick, reliable serial diameter measurements. Because the change in hemodynamic resistance could serve as a sensitive index of conducted response, use of this index in studies of conducted response may lead to new mechanistic insights on the response.

Animals↗

PubMed1993

The peak performance system for dynamic gait analysis.

The PEAK Rearfoot Clinical Assessment System provides automated computer tracking of tibial-calcaneal motion via video equipment. Multiple trials from a single subject or across subjects can be acquired from which angular displacements and velocities can be computed. Graphic and tabular reports can be customized to generate rapid and specific documentation.

Gait↗

PubMed2001

[Virtual bronchoscopy: a new non-invasive diagnostic method in pulmonology].

Virtual reality (3 dimensional modelling of the human body) has developed as a convergence of advancing digital imaging modalities and computer graphics technologies. With this method endoscopic simulations of cavitary organs are feasible. Virtual bronchoscopy was initially described in 1993. The authors selected patient with previously detected stenosis of the trachea or the main bronchi with bronchofiberscope. They performed targeted, thin-slice helical computer tomography of the lesions. These data were transferred to a workstation and the virtual endoscopic models of the airways were generated using dedicated software. Based on cases the authors describe their preliminary experience with the method. The findings were compared with those of bronchofiberscopy. Analyzing these results and the literature the potential clinical applications of virtual bronchoscopy are discussed.

Adult↗

PubMed1992

[Anchored cell analysis and sorting (ACAS) system].

Advanced biology and recent technology have provided sophisticated and objective method for analyzing biological characteristics on cells. Following that, many new instruments have developed. Diagnostic immunocytochemistry has become an accepted diagnostic tool in cell biology. In recent years, remarkable advances in technology provide a method for quantitative and objective analyses of cell characteristics. The newly developed computer assisted laser cytometer (ACAS 570) can be applied in clinical basis as well as in research laboratory. Fluorescent intensities of ancharage-dependent cells can be automatically analyzed and make it possible to separate a subpopulation of cells. This computer controlled system principally consists of argon ion laser, phase contrast microscope. Quantitative fluorescence measurements and computer graphic images can be obtained. The present paper demonstrates multiple applications of laser cytometer for evaluation of cell biology.

Antigens, Neoplasm↗

PubMedDate not supplied

[A computer system for analysis and presentation of the results of studies of the immune status of patients with a profile of resuscitation].

Logical principles for the use of computer technology in the assessment of medical information in intensive care units are outlined. A computer system for the assessment of the results of immune status studies has been presented. The potentials are demonstrated to form the data bank with realization of precedent search function, presentation of information with the help of computer graphics and calculation of highly informative secondary indexes on the basis of primary ones.

Computer Systems↗

PubMed1995

Intraoperative navigation in oral and maxillofacial surgery.

Surgical procedures in the oral and maxillofacial region may be difficult in areas of complex anatomy. Up to now, surgical planning has been based almost exclusively on the surgeon's experience and on the interpretation of 2-dimensional (2D) radiologic information. Our experiences with a commercially available 3D navigation system (Viewing Wand, ISG, Mississauga, Ontario, Canada) is reported upon. The system consists of a mechanical operating arm with 6 joints and 6 degrees of freedom working as a 3D digitizer and is interfaced to a computer graphics workstation. After registration of the position of the patient's head in relation to the tip of the instrument on the navigation arm, the surgeon can observe the 3D position and direction of the instrument in use on the monitor, i.e. on the computed tomography and/or magnetic resonance tomography images of the patient taken before. In 40 interventions performed so far, the accuracy was 2 mm and better. 3 cases are presented in this paper. The system facilitates surgery especially in anatomically complicated situations without the risk of damaging neighbouring structures. Planning of surgical interventions is much easier. By using computer assisted simulation and navigation systems, we expect an improvement in quality and a reduction in surgical risks. Thus, "looking ahead" surgery has become possible. More extensive and more radical interventions are likely to be performed in the near future. Responsibility for the surgical intervention, however, remains exclusively with the surgeon.

Carcinoma, Adenoid Cystic↗

PubMed1986

Interactive instruction in the radiographic anatomy of the chest.

An instructional program has been developed which is designed to instruct medical students in a systematic approach to the reading of the chest radiograph. A videodisc player is used to display a radiograph on a video monitor and computer graphics are superimposed over this image. Another feature is the use of a mouse pointer as an input device to identify structures on the radiograph. The instructional approach is based upon the drill and practice method. All questions and responses are created by the computer through the program's database manipulation.

Computer-Assisted Instruction↗

PubMed1984

Computerized simulation of bone remodeling: graphic demonstration of dynamic processes.

A computerized simulation model has been developed to study the histologic patterns of dynamic remodeling processes in trabecular bone. The osteoid seam thickness and the distance between the tetracycline labels are calculated based on (partly hypothesized) parameter values, such as matrix appositional rate, mineralization rate, number and life span of the osteoclasts, resorption rate, and mineralization lag time. The results of a simulation run are demonstrated using computer graphics. Such simulation results cast doubts on the validity of some approaches that attempt to infer details of remodeling processes from histologic measurements. For example, the distance between the tetracycline labels obtained by simulation illustrates the difficulty of over-or underestimating the matrix appositional rate by measuring it from a histologic section.

Bone Resorption↗