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At least 343 records · Page 19Linked to original sources
PubMed1987

Conformational analysis of the cholecystokinin C-terminal octapeptide: a nuclear magnetic resonance and computer-simulation approach.

The C-terminal octapeptide portion of cholecystokinin (CCK8) has well-defined biological properties which include action as a neurotransmitter and induction of gall-bladder contraction and pancreatic enzyme secretion. Many analogues of CCK8 have been prepared and tested for potency, making this an ideal model system in which to initiate evaluation of structure-function relationships. The present study uses high-resolution proton nuclear magnetic resonance (NMR) spectroscopy and energy minimization techniques to evaluate the solution (DMSO) and in vacuo conformation(s) of CCK8. The NMR results provide amide and C alpha H alpha chemical shift temperature dependencies and all phi dihedral angles and chi 1 rotamer populations. The energy minimization data located deep potential energy wells, for which all torsion angles are reported. Collectively, the data support models for CCK8 where the structures are characterized by a high degree of folding. These conformations are characterized by sharp turns, possibly stabilized by hydrogen-bonds. Taken together with pharmacologic data and somewhat similar folded structures implied from fragments of CCK8, it is suggested that both electrostatic and steric effects are needed for full biological potency.

Computer Simulation↗
PubMed1983

Energy and nutrient calculations using an Optical Character Reader system.

A new application of the Optical Character Reader (OCR) system for dietary data tabulation has been presented. Comparison of the reproducibility of energy and nutrient values, when hand calculation, on-line computer, and OCR methods of calculation are used, revealed no significant differences. The OCR system increased turn-around time for obtaining results, but use of a clinician's time was greatly reduced in comparison to either the hand calculation or the on-line computer method. Once the initial investment for an OCR system had been made, a significant reduction was realized in the cost of a clinician's time used for energy and nutrient calculations. When the factors of reproducibility, time, and cost were considered, this study found the OCR method for dietary calculations as acceptable as either hand calculation or on-line computer methods. Clinicans using the OCR or hand calculation method did not need computer facilities, but computer keyboard terminals were required for the on-line method.

Computers↗
PubMed1996

Simple and rapid production of radiographic slides or prints using a personal computer and a laser imager.

A simplified and rapid method for making radiographic slides or prints using a personal computer, a computer monitor adapter and a laser imager is described. When the divided monitor output of a personal computer is connected to a laser imager in the Radiology Department, radiographs and text on the personal computer can be printed out from the laser imager. By selecting slide size print format, 12 slide-sized images can be printed on a film. In addition, by selecting other print formats various sized images can be printed on film, which then can be used as teaching files or as backlight display panels for scientific exhibits. This method can only produce gray-scale printouts, which are sufficient for radiological presentations. Any radiology department can utilize this system by simply installing a computer monitor adapter.

Audiovisual Aids↗
PubMed1996

Perception of detail and greyscale range in X-ray fluoroscopy images captured with a personal computer and frame-grabber.

OBJECTIVE: To assess the dynamic range of radiological images captured with a personal computer frame-grabbing system coupled to an X-ray fluoroscopy machine. METHODS: A 386DX-40 MHz, IBM compatible, computer with an SVGA monochrome graphics subsystem and a 387 co-processor, installed with a Screen Machine frame-grabber and controlled by a program specially written was used. Various systems were examined and the observer's perceptions of the results assessed. RESULTS: The dynamic range available to an ordinary X-ray fluoroscopy system was found to be restricted to about 750 mV. Similar measurements showed that the dynamic range was always restricted to 3/4-1/2 of the full available signal because of a high value of the dark voltage of the TV camera's target on all seven systems measured. The dynamic range of the computer-frame grabber system was found to be significantly wider than the Image Intensifier-TV camera chain but, surprisingly, it was affected by the type of file format used for image storing on disk. Clinical images from a barium meal examination as well as CT images captured after optimisation of the frame-grabber were found to contain large quantities of noise in the first two least significant bit planes making them redundant and limiting the grey levels needed for image display to less than 64. This number was also less than the 80 grey levels that could be discriminated by the human eye on the computer monitor. CONCLUSIONS: It was concluded that 6 bit digitisation would have been sufficient for image capture. The advantages of the wider dynamic range of the frame-grabber and the processing capabilities of the computer were tested for the possibility of improving the perception of detail. However, the results were negative. The limiting spatial resolution measured with a variable density bar pattern at all magnifications was about 0.4 lp/mm lower from that measured directly on the fluoroscopic screen. A detail perception test had the same result. The perception success was significantly lower with the digital images at all but the highest of the exposure rates and despite the use of image processing filters.

Artifacts↗
PubMed2000

New approach for making accurate cross sections of casts.

This article describes a new procedure for producing cross sections of a cast, a denture, or an impression and a method of presenting the results in graphic form to show variance. To test the method, identically colored, duplicate dentures were embedded in plaster blocks formed from a precisely engineered and calibrated brass box. A modified jig and saw allowed the plaster blocks to be positioned, held, and sectioned at any required location with a high degree of accuracy. The sectioned surfaces of the duplicate dentures were scanned. The resultant profiles were registered in location frames on the computer screen, traced by computer to produce outlines, and printed onto transparent film for the purpose of comparison. In vitro results showed the relationship between congruent outer forms and provided clear visual evidence of the accuracy of the procedure used and a way to further in vivo use.

Calcium Sulfate↗
PubMed1998

New visualization techniques for in utero surgery: amnioscopy with a three-dimensional head-mounted display and a computer-controlled endoscope.

Endoscopic fetal surgery may reduce preterm labor associated with open hysterotomy but is partially limited by current visualization technology. We investigated a three-dimensional (3D) imaging system coupled to a head-mounted display (3D-HMD) and also employed a computer-controlled zoom endoscope for noninsufflated amnioscopy. Pregnant sheep were prepared in aseptic fashion for general anesthesia. Uterine access was obtained following maternal laparoscopy. A 10-mm zoom endoscope (Vista Medical Technologies, Carlsbad, CA) was used to examine the fetus and uterine contents. Fetal limbs were exteriorized for microsurgery. A new system (Vista Medical Technologies) was attached to an operative microscope, permitting projection of a 3D image via an HMD. The fetus and umbilical cord were inspected using the zoom endoscope, which changes the depth of focus under computer control. Basic manipulations of the fetus and cord were easily completed. Real-time 3D fetal imaging was accomplished. The added depth perception enabled detailed fetal and placental examination, fostering manipulation of the fetus and cord. The HMD was adjusted to fit several surgeons, permitting a natural operative posture. This unit has the capacity to display any video, CT, MR, or ultrasound image as a picture-in-picture. The success of minimally invasive fetal surgery is in part dependent on the development of video technologies capable of providing both magnification and optimal resolution. The zoom endoscope affords excellent visibility of multiple surgical targets without instrument repositioning. A 3D HMD system such as this provides greater anatomic detail and an appreciation of fetal movements that may make intrauterine procedures more feasible.

Animals↗
PubMed1999

Wrist and forearm postures of users of conventional computer keyboards.

The aim of this study was to perform a comprehensive investigation to document wrist and forearm postures of users of conventional computer keyboards. We instrumented 90 healthy, experienced clerical workers with electromechanical goniometers to measure wrist and forearm position and range of motion for both upper extremities while typing. For an alphabetic typing task, the left wrist showed significantly greater (p < .01) mean ulnar deviation (15.0 degrees +/- 7.7 degrees) and extension (21.2 degrees +/- 8.8 degrees) than the right wrist (10.1 degrees +/- 7.2 degrees and 17.0 degrees +/- 7.4 degrees for ulnar deviation and extension, respectively). Conversely, the right forearm had greater mean pronation (65.6 degrees +/- 8.3 degrees) than the left forearm (62.2 degrees +/- 10.6 degrees). We noted minimal functional differences in the postures of the wrists and forearms between alphabetic and alphanumeric typing tasks. Ergonomists should consider the statistically significant and probable practical difference in wrist and forearm posture between the left and right hand in ergonomic interventions in the office and in the design of computer keyboards. Actual or potential applications of this research include guiding the design of new computer keyboards.

Adult↗
PubMed1997

The Psychophysics Toolbox.

The Psychophysics Toolbox is a software package that supports visual psychophysics. Its routines provide an interface between a high-level interpreted language (MATLAB on the Macintosh) and the video display hardware. A set of example programs is included with the Toolbox distribution.

Computer Terminals↗
PubMed1994

Computer-assisted 3D reconstruction of the terminal branches of the cerebral arteries. III. Posterior cerebral artery and circle of Willis.

We present a three-dimensional anatomical computer model of the terminal branches of the posterior cerebral artery and circle of Willis, acquired from equidistant serial anatomical slices of three brains. The reconstructions provide a clear picture from all angles of the complicated course of the terminal branches of the cerebral arteries. This can help to identify the arteries in conventional and magnetic resonance angiography. Our rendition of the cerebral arteries can be matched with CT, MR und PET images to indicate the areas of extension of the individual branches, allowing neuromorphological and functional correlations.

Basilar Artery↗
PubMed1996

Accommodative and binocular vision disorders associated with video display terminals: diagnosis and management issues.

BACKGROUND: With the rapid computerization of the workplace, school and home office, it is likely that a vast majority of Americans will be using computers for significant amounts of time in the near future. Research has demonstrated a high prevalence of accommodative and binocular vision disorders in symptomatic VDT users, which underscores the importance of the assessment and management of accommodation and binocular vision for patients working with computers. METHODS/RESULTS: This paper presents a simplified approach for the diagnosis and management of accommodative and binocular vision disorders in VDT users. The emphasis is on modifications of the traditional examination routine to make the assessment as sensitive as possible to the vision problems associated with VDT use. CONCLUSIONS: To meet the needs of symptomatic VDT users, optometrists must perform a comprehensive assessment of accommodation and binocular vision. The use of appropriate testing, when combined with attention to the environmental factors associated with VDT use, will enable optometrists to understand the reasons for symptoms and design an effective treatment program.

Accommodation, Ocular↗
PubMed2002

The use of video refraction to measure the dynamic properties of the near triad in observers of a 3-D display.

OBJECTIVE: Recording of the dynamic behaviour of the near triad during viewing of a three-dimensional (3-D) display is attempted. This may then be used to identify the possible origin of asthenopia and other ocular problems which occur whilst viewing such displays. METHODS: Subjects viewed a 3-D display through an image splitter. Video recordings of ocular responses (pupil diameter, vergence and accommodation) were made with a commercially available video refraction unit at a distance of 1.2 m from the subject. Continuous recordings were made whilst a step-wise disparity of up to 2.6 degrees was introduced between the targets presented to the two eyes, but the accommodative stimulus remained unchanged. Image analysis from the recordings was carried out on a personal computer. RESULTS: Results showed various complex patterns of response, with the accommodation and vergence recorded reflecting the effect of stimulus conflict. Difficulty in fusional convergence was recorded when disparity was large, and the recordings reflected the subjects' comments. CONCLUSION: The video refraction method is a useful tool for studying the dynamic behaviour of the near triad.

Accommodation, Ocular↗
PubMed2001

Generation of TACT image slices using different reconstruction algorithms: effects on natural caries detection.

OBJECTIVE: The purpose of this study was to determine whether the method of reconstruction of tuned-aperture computed tomography (TACT) slices has an influence on observer performance in caries detection. STUDY DESIGN: Eight images of each of 40 extracted posterior teeth were acquired by using a solid state intraoral detector. Stacks of tuned-aperture computed tomography slices were generated by using the minimum and average reconstruction methods. Slices of the 2 experimental conditions were presented to 8 observers in a balanced order. Images were viewed on a high-resolution 21-in color monitor. Observers scored the presence/absence of caries by using a 5-point confidence scale. Observers' assessments were compared with histologic examinations of tooth sections. Receiver operating characteristic curves measured observers' diagnostic performance. Analysis of variance was used to test for possible significant differences between observers and between experimental conditions. Sensitivity, specificity, accuracy, and interobserver reliability were also calculated. RESULTS: No statistically significant differences between the 2 methods of reconstruction were found for the detection of either occlusal (P =.07) or proximal (P =.52) caries. Interobserver reliability was similar for both experimental conditions. CONCLUSIONS: The minimum and average methods of TACT reconstruction provide comparable performances for caries detection tasks.

Algorithms↗
PubMed2003

An application framework for computer-aided patient positioning in radiation therapy.

The importance of exact patient positioning in radiation therapy increases with the ongoing improvements in irradiation planning and treatment. Therefore, new ways to overcome precision limitations of current positioning methods in fractionated treatment have to be found. The Department of Medical Physics at the German Cancer Research Centre (DKFZ) follows different video-based approaches to increase repositioning precision. In this context, the modular software framework FIVE (Fast Integrated Video-based Environment) has been designed and implemented. It is both hardware- and platform-independent and supports merging position data by integrating various computer-aided patient positioning methods. A highly precise optical tracking system and several subtraction imaging techniques have been realized as modules to supply basic video-based repositioning techniques. This paper describes the common framework architecture, the main software modules and their interfaces. An object-oriented software engineering process has been applied using the UML, C + + and the Qt library. The significance of the current framework prototype for the application in patient positioning as well as the extension to further application areas will be discussed. Particularly in experimental research, where special system adjustments are often necessary, the open design of the software allows problem-oriented extensions and adaptations.

Computer Terminals↗
PubMed2002

A modified Perkins Brailler for text entry into windows applications.

In this paper, we describe how a Perkins Brailler can be adapted so that it can function as a keyboard to a personal computer. The paper describes the earlier work of others and the hardware and software of our system and concludes with indications of how the system may be improved.

Blindness↗