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At least 289 records · Page 16Linked to original sources
PubMed1994

A method of measuring fingertip loading during keyboard use.

A single keycap on a standard alphanumeric computer keyboard was instrumented with a piezoelectric load cell and the fingertip motion was recorded with a high-speed video motion analysis system. Contact force histories between the fingertip and the keycap were recorded while four subjects typed a standard text for five minutes. Each keystroke force history is characterized by three distinct phases: (I) keyswitch compression, (II) finger impact and (III) fingertip pulp compression and release. Each keystroke force history contained two relative maxima, one in phase II and one in phase III. The subject mean peak forces ranged from 1.6 to 5.3 N and the subject mean peak fingertip velocities ranged from 0.3 to 0.7 m/s. Motion analyses and force measurements suggest a ballistic model of finger motion during typing.

Computer Terminals↗
PubMedDate not supplied

Assessment of commercial compression algorithms, of the lossy DCT and lossless types, applied to diagnostic digital image files.

The need for diagnostic image compression of the lossy or irreversible type has been declining due to the rapid increase in commercially available formatted hard disk capacity. It is estimated that the latter has increased about three orders of magnitude in the past 14 years while the size of diagnostic image files has, of course, remained constant. During the same period, despite claims for significantly improved performance by vendors, it seems that only small progress has been made in commercial lossless and lossy compression algorithms. There is still no consensus for lossy compression to a level acceptable for diagnosis. This is mostly considered to be around a ratio of 10:1. However, acceptable compression ratios depend heavily on the type of images processed and may be compared with the 3:1 ratio produced by lossless algorithms. This last value was shown to increase to more than 5.5:1 for gamma-camera images when corrected for the noise content of individual bit planes and for the display capabilities of computer monitors. Therefore, any possible benefits of lossy over lossless compression become questionable when the currently available hard disk capacity and network transmission speed are considered against the inevitable loss of information in the lossy type of compression.

Algorithms↗
PubMed1997

An optical system for measuring inclination and area of occlusal facets.

Occlusal facets are regarded as an individual record of occlusal contacts that result from various mandibular movements. Analysing characteristics of the facets is important for the functional assessment of the stomatognathic system. A new system which quantifies such characteristics optically has been developed. This system is composed of optical devices, a graphic image-processor, a set of stages for mounting and positioning the model and laser indicators of the measuring point. The system enables the inclination and area of each facet and its location to be measured and its processed image displayed on the graphic monitor.

Computer Graphics↗
PubMed1992

Obstacles encountered in the development of the low vision enhancement system.

The Johns Hopkins Wilmer Eye Institute and the NASA Stennis Space Center are collaborating on the development of a new high technology low vision aid called the Low Vision Enhancement System (LVES). The LVES consists of a binocular head-mounted video display system, video cameras mounted on the head-mounted display, and real-time video image processing in a system package that is battery powered and portable. Through a phased development approach, several generations of the LVES can be made available to the patient in a timely fashion. This paper describes the LVES project with major emphasis on technical problems encountered or anticipated during the development process.

Audiovisual Aids↗
PubMed1998

Evaluation of a personal-computer-based teleradiology system serving an isolated Canadian community.

OBJECTIVE: To evaluate a personal-computer-based teleradiology system for the interpretation of radiologic studies from an isolated community. METHODS: During a 5-month study period, 240 radiologic studies from the Grand Manan Hospital, Grand Manan, NB, were digitized and transmitted via telephone lines to the Saint John Regional Hospital, NB, for interpretation. The first 110 cases were interpreted with the use of a 1 K x 1 K monitor, and the remaining cases were interpreted with a 2 K x 2 K monitor. The teleradiology image reports were compared with the plain film reports for each case and discrepancies were identified. A panel reviewed all clinically significant discrepant cases to determine the source of the discrepancy. RESULTS: There was 90.9% concordance between the teleradiology and plain film reports in the studies interpreted with the 1 K x 1 K monitor and a 88.4% concordance in the studies interpreted with the 2 K x 2 K monitor. Only 1.7% (4/240) of the discrepancies were attributed to an inadequate teleradiology digital image. CONCLUSION: A personal-computer-based teleradiology system can be used to provide diagnostic imaging service of high quality to an isolated community.

Computer Communication Networks↗
PubMed1976

On-line computer processing of pressure data from cardiac catheterizations.

A flexible program system for on-line analysis of pressure data from cardiac catheterizations is described. The programs are implemented on an IBM 1800 computer, equipped with remote oscilloscope/keyboard terminals. The current computer system can handle any combination of up to 4 pressure signals. During catheterization, measurement specifications (i.e. calibration levels or sites of pressure recordings) are entered via the keyboard immediately before each recording. As an option the whole expected measurement sequence may be stored on disk before the catheterization starts. This method will minimize the necessary interaction with the computer when the same catheterization procedure is used on several occasions. Changes from the predetermined scheme may, however, be undertaken before each recording to meet with unexpected events that may arise during the catheterization. After computer detection of calibration levels, the recorded signals are digitized during 20 seconds and analysed beat-by-beat. Calculated values are averaged and presented on the terminal oscilloscope in tabular and/or graphic form. The waveform analysis performed by the program system is validated in a statistical comparison between manually and automatically computed values.

Cardiac Catheterization↗
PubMed1977

Catalog card production with a programmable terminal.

Application of a programmable terminal and printer to the cataloging task of a small medical library is described. The application is independent of a computer; the terminal is used in "local" mode only. Full sets of catalog cards are produced, following a single typing of descriptive cataloging data and tracings. Books can be cataloged the same day they are received. Actual cost per book is just over a dollar, for equipment rental, card stock, and the cataloger's time at the console, after call number, tracings, and main entry for the book have been determined.

Catalogs, Library↗
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↗
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↗