ABC of medical computing. Adaptive computer technology.
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Results for “Computer Peripherals”
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Performance characteristics and image fidelity of gray-scale monitors.
Gray-scale monitors are an essential element of electronic radiology, and their ability to provide images that are perceived to be identical to those available on conventional or laser-printed film is crucial to success of electronic radiology. Image fidelity is measured in physical characteristics (luminance, dynamic range, distortion, resolution, and noise) and with psychophysical techniques, including receiver operator characteristics analysis with clinical images and testing with contrast-detail patterns to determine threshold contrast. Currently, laser-printed images facilitate greater information transfer than does a gray-scale monitor because of their higher absolute luminance (500 ft-L vs 60 ft-L), greater perceived dynamic range, and better spatial resolution. In the near future, the developments of gray-scale monitors with 150-200 ft-L luminance, a display standard based on just noticeable differences, and algorithms to improve similarities between gray-scale display images and laser-printed images will help increase the acceptability of monitors as a means to make primary diagnoses.
Computer Peripherals↗
Hemodynamics of hemorrhage in the conscious rat and chicken.
Hemodynamic responses to hemorrhage in conscious chicks (n = 10, 233 g) and rats (n = 10, 309 g) were compared. The animals were fitted with miniature pulsed Doppler aortic flow probes 2 days (chickens) or 5 days (rats) before catheterization, and the experiment began 1 (chickens) or 2 (rats) days later. Mean arterial pressure (MAP) and cardiac output (CO) were recorded continuously and simultaneously digitized to compute total peripheral resistance (TPR). MAP, CO, and TPR values were graphed on-line by a microcomputer and stored for later analysis. A 4-ml hemorrhage reduced MAP and CO by 25 and 43% in the rat, and 15 and 4% in the chickens, respectively. The fall in CO in the rat was due to reduction of stroke volume (SV) unlike the birds where SV was well maintained. TPR was elevated 65% in the rats and fell 13% in the chickens. The minimal fall in CO and SV in these conscious birds suggests that anesthetic agents used previously (i.e., urethane, paraldehyde, phenobarbital, and pentobarbital sodium) suppressed cardiac function. However, they do not account for the lack of a peripheral vascular response during hemorrhage. The chicken apparently maintains MAP by a volume regulating mechanism operating independently of peripheral vascular tone inasmuch as circulating fluid volume restitution is rapid and occurs without vasoconstriction. The rat maintains MAP through reflex cardiac and peripheral vascular responses which eventually may contribute to transvascular fluid loss and the ultimate collapse after prolonged hemorrhagic hypotension.
Animals↗
Spatial memory and path integration studied by self-driven passive linear displacement. I. Basic properties.
According to path integration, the brain is able to compute the distance of a traveled path. In this research we applied our previously reported method for studying memory of linear distance, a crucial mechanism in path integration; our method is based on the overt reconstruction of a passive transport. Passive transport is a special case of navigation in which no active control is performed. Blindfolded subjects were first asked to travel 2 m forward, in darkness, by driving with a joystick the robot on which they were seated. The results show that all subjects but two undershot this distance, i.e., overestimated their own displacement. Then, subjects were submitted to a passive linear forward displacement along 2, 4, 6, 8, or 10 m, and had to reproduce the same distance, still blindfolded. The results show that the distance of the stimulus was accurately reproduced, as well as stimulus duration, peak velocity, and velocity profile. In this first condition, the imposed velocity profile was triangular and therefore stimulus distance and duration were correlated. In a second condition, it was shown that distance was correctly reproduced also when the information about stimulus duration was kept constant. Here, different velocity profiles were used as stimuli, and most subjects also reproduced the velocity profile. Statistical analyses indicated that distance was not reproduced as a consequence of duration, peak velocity, or velocity profile reproduction, but was uniquely correlated to stimulus distance. The previous hypothesis of a double integration of the otolith signal to provide a distance estimate can explain our results. There was a large discrepancy between the accuracy with which the subjects matched the velocity profiles and that of distance reproduction. It follows that, whereas the dynamics of passive motion are stored and available to further use, distance is independently estimated. It is concluded that vestibular and somatosensory signals excited by passive transport can be used to build a dynamic as well as a static representation of the traveled path. We found a close quantitative similarity between the present findings on distance reproduction and those obtained from active locomotion experiments in which the same paradigm was used. This resemblance suggests that the two types of navigation tasks draw on common physiological processes and extends the relevance of our results to naturally occurring path integration.
Acceleration↗
The development of the skeletal system in children and the influence of muscular strength.
In a study on 14 healthy children aged from 6 to 13 years, the volumetric spongiosa bone density (SBD), cortical bone density (CBD), bone cross-sectional area (BCSA), cortical area (CA), and bone strength index (BSI) at the distal radius were analyzed using peripheral quantitative computer tomography (pQCT Bone Scanner XCT-900, Stratec, Pforzheim, Germany). BSI values were calculated on the basis of the moment of resistance and cortical density using system integrated software. These parameters were correlated with grip strength measurements obtained using a grip dynamometer. There were age-dependent increases in BCSA (r = 0.68), CA (r = 0.78), BSI (r = 0.79). SBD and CBD, however, did not show an increase with age. Grip strength correlates strongly with the parameters of bone geometry BCSA (r = 0.8), CA (r = 0.86), and BSI (r = 0.9) at p < 0.01. SBD and CBD showed no significant correlation to grip strength. The results of this study suggest that an increase in cortical thickness and cross-sectional area represent the most important adaptation mechanisms of the growing bones in response to biomechanical usage. These parameters represent the most important factors of bone strength. Volumetric bone density (material characteristic) of spongiosa and cortical bone is an age-independent parameter which does not change significantly with increasing muscular strength in healthy subjects. These relationships must be considered when selecting parameters to be used as success criteria in studies on the influence of physical exercise on bone status.
Adolescent↗
Using the Pathfinder system to reduce missed abnormal cervical cytologic smear cases in a rescreening program.
OBJECTIVE: To evaluate the effect of Pathfinder (CompuCyte Corp., Cambridge, Massachusetts, U.S.A.), a process control instrument for microscopes used by cytotechnologists to monitor the mechanical aspects of their screening process, on the false negative cervical cytologic smear rate as detected in daily quality assurance rescreening. STUDY DESIGN: Pathfinder was put into routine use in a large cytology laboratory. After cytotechnologists were trained in its use, they monitored their time spent screening each slide, the area (percent) of the slide screened and the average percentage of overlap of fields of view. The number of abnormal cases missed in screening before and after the introduction of Pathfinder was determined by rescreening a random 10% of the "negative" cases. The evaluation took place over a nine-month period. RESULTS: A decrease in the number of missed abnormal cases was identified. The false negative rate for atypical cells of undetermined significance (ASCUS) fell from 37/2,336 (1.6%) to 12/1,772 (0.7%), for a 56% decrease. The change in the number of squamous intraepithelial lesion cases, even over a nine-month period, was too small for comment. CONCLUSION: The effect of the continuous feedback and process standardization provided by the Pathfinder system was a decrease in the number of abnormal cases missed. This was due primarily to a marked decrease in the number of ASCUS cases missed. The Pathfinder provides a number of innovative management tools to ensure consistent high quality screening.
Cervix Uteri↗
A method for evaluating head-controlled computer input devices using Fitts' law.
The discrete movement task employed in this study consisted of moving a cursor from the center of a computer display screen to circular targets located 24.4 and 110.9 mm in eight radial directions. The target diameters were 2.7, 8.1, and 24.2 mm. Performance measures included movement time, cursor path distance, and root-mean-square cursor deviation. Ten subjects with no movement disabilities were studied using a conventional mouse and a lightweight ultrasonic head-controlled computer input pointing device. Average movement time was 306 ms greater (63%) for the head-controlled pointer than for the mouse. The effect of direction on movement time for the mouse was relatively small compared with the head-controlled pointer, which was lowest at 90 and 270 deg, corresponding to head extension and head flexion, respectively. Average path distance and root mean square displacement was lowest at off-diagonal directions (0, 90, 180, and 270 deg). This methodology was also shown to be useful for evaluating performance using an alternative head-controlled input device for two subjects having cerebral palsy, and measured subtle performance improvements after providing a disabled subject with lateral torso support.
Adult↗
Appendicular measurements in screening women for low axial bone mineral density.
Assessment of bone density at hip, spine, radius and calcaneus can predict fracture risk. This paper examines whether women with low bone mineral density (BMD) at the hip and spine can be identified by radial or calcaneal BMD assessment, thus enabling pre-selection of such women for further investigation. BMD in the lumbar spine (LS), femoral neck (FN), trochanter (FT) and Ward's area (FW) was measured by dual energy X-ray absorptiometry (DEXA). These measurements were compared with total (Qtot), trabecular (Qtrab), subcortical (Qscort) and cortical (Qcort) BMD of the ultradistal radius measured by peripheral quantitative computed tomography (pQCT), and ultrasound attenuation (BUA) and velocity (VOS) at the os calcis. Measurements were performed on 216 perimenopausal women aged between 45 and 55 years who attended a randomized osteoporosis screening programme. Correlations for pQCT and ultrasound with DEXA measurements were, at best, moderate (r = 0.05-0.53), being poorest for Qcort and VOS. Similar correlations were found between ultrasound and pQCT measurements (r = 0.05-0.31). None of the pQCT or ultrasound measurements predicted low DEXA measurements. 50-56% of women in the lowest quartile (QU4) of Qtot, Qtrab, Qscort and BUA were also in QU4 of LS; 45-57% were in QU4 of FT and FW, but only 22-33% were in QU4 of FN. To detect all women with osteopenia at FN or LS using pQCT or ultrasound, almost the entire population would have to be screened. In conclusion, pQCT and os calcis ultrasound measurements cannot successfully predict hip and spine osteopenia and could not be used to pre-select women for DEXA hip and spine assessment.
Absorptiometry, Photon↗
Correlation of trabecular bone structure with age, bone mineral density, and osteoporotic status: in vivo studies in the distal radius using high resolution magnetic resonance imaging.
High resolution magnetic resonance (MR) images of the distal radius were obtained at 1.5 Tesla in premenopausal normal, postmenopausal normal, and postmenopausal osteoporotic women. The image resolution was 156 microm in plane and 700 microm in the slice direction; the total imaging time was approximately 16 minutes. An intensity-based thresholding technique was used to segment the images into trabecular bone and marrow, respectively. Extensions of standard stereological techniques were used to derive measures of trabecular bone structure from these segmented images. The parameters calculated included apparent measures of trabecular bone volume fraction, trabecular thickness, trabecular spacing, and trabecular number. Fractal-based texture parameters, such as the box-counting dimension, were also derived. Trabecular bone mineral density (BMD) and cortical bone mineral content (BMC) were measured in the distal radius using peripheral quantitative computed tomography (pQCT). In a subset of patients, spinal trabecular BMD was measured using quantitative computed tomography (QCT). Correlations between the indices of trabecular bone structure measured from these high-resolution MR images, age, BMD, and osteoporotic fracture status were examined. Cortical BMC and trabecular BMD at the distal radius, spinal BMD, trabecular bone volume fraction, trabecular thickness, trabecular number, and fractal dimension all decreased with age. Trabecular spacing showed the greatest percentage change and increased with age. In addition, significant differences were evident in spinal BMD, radial trabecular BMD, trabecular bone volume fraction, trabecular spacing, and trabecular number between the postmenopausal nonfracture and the postmenopausal osteoporotic subjects. Trabecular spacing and trabecular number showed moderate correlation with radial trabecular BMD but correlated poorly with radial cortical BMC. High resolution MR imaging, a potentially useful tool for quantifying trabecular structure in vivo, may have applications for understanding and evaluating skeletal changes related to age and osteoporosis.
Adult↗
Selecting computer hardware to get the right system, ask the right questions.
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Computer Peripherals↗
CyberNews.
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American Dental Association↗
Effects of a split keyboard design and wrist rest on performance, posture, and comfort.
The purpose of this study was to examine differences in experienced typists' performance, posture, and musculoskeletal pain when using a split, adjustable (SA) computer keyboard and when using a standard flat keyboard. In addition, the use of a wrist rest was examined for performance, posture, and musculoskeletal pain effects. Eighteen participants were exposed to the SA keyboard and a flat keyboard in a laboratory study of text typing for four consecutive hours on five days. The results indicated that after just 2 h of orientation and practice, the participants could perform as well on the SA keyboard as on the flat keyboard. The SA keyboard provided advantages for reduced wrist/hand pronation. There was no difference between the keyboards in the level of musculoskeletal pain reported by participants after typing. However, they reported increased pain in the back, neck, shoulders, and wrists from the beginning to the end of each of the experimental periods for both keyboards.
Adolescent↗
An analysis of users' preference on keyboards through ergonomic comparison among four keyboards.
The usability of four kinds of keyboards as regards touch and feel was evaluated by measuring the performance and eliciting the preferences of a total of 24 Japanese participants in a test that consisted of typing English text. It was found that quiet keyboards with an indistinct tactile feedback tend to give higher uncorrected error rates than keyboards with a distinct tactile feedback and clicking sound, while no significant difference in throughput was found among the four keyboards. As regards preference, the test participants were divided into two groups: those who preferred keyboards with a distinct tactile feedback and clicking sound, and those who preferred keyboards with an indistinct tactile feedback and no sound. Analysis revealed that these two groups also showed different sensations and preferences with respect to several aspects of the touch and feel of keyboards. This result suggests that suppliers of computer keyboards should provide two kinds of keyboards, with distinct and indistinct tactile key switches, in order to satisfy as many users as possible.
Computer Peripherals↗
The gray-scale ink-jet printer: value in making hard copies of digital images.
Referring physicians often are supplied with copies of images to illustrate a report of the findings of a radiologic study or so that the radiologist can retain the original images. The increasing costs of production, film, and recovery of chemicals have enhanced the requirement for a clean, low-cost dry printing process. An ink-jet gray-scale paper printer (Unitone, Scitex Medical Systems, Bedford, MA) can print high-quality (300 dots per inch [dpi]) images with an effective 10-bit gray scale range by using the Hertz continuous ink-jet method [1-3], which does not require the use of a darkroom or hazardous chemicals. Several types of media (matte paper, glossy paper, transparency film) with a printing area of 26.9 x 43.7 cm (10.6 x 17.4 inches) may be used. The consumables are approximately 50-70% less expensive than the cost of silver halide film, providing a cost advantage over film for referral and archival copies. The results of an initial evaluation of the ink-jet printer at our institution are reported here.
Computer Peripherals↗
User's review of the Canon Colour Copier.
The ability to link the new Canon Colour Laser Copier to a computer opens up new boundaries of data manipulation. A report from the user's point of view, describes a system comprising the copier with computer input, slide scanner and flat copy capacity. Information is given on the types of materials produced, the types of users, the cost of purchase and maintenance, and the potential for generating profit.
Computer Peripherals↗
Optical character recognition. Let a scanner spare you those inputting ordeals.
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Computer Peripherals↗
Single-switch computer access for infants and toddlers.
Computer access was studied with children between the ages of 6 months and 18 months with no known handicapping conditions. The research focused on determining at what age young children can access a computer using a single-switch system to run a simple cause-and-effect program. The sample consisted of 80 children divided into four groups (6 to 8 months, 9 to 11 months, 12 to 14 months, and 15 to 17 months). Results demonstrated that some children as young as 6 months of age could control a computer-based, cause-and-effect program using a single-switch access system. Therefore, professionals who work with children with disabilities may consider introducing computers to children at this age or to children who are functioning near this cognitive developmental level.
Association Learning↗
[Teleradiography for diagnosis in emergency care. A clinical experience].
This work was aimed at evaluating the role of teleradiology in a diagnostic emergency room. Over a 6-month period (September 1991-February 1992), 2,000 films made in the emergency room were transmitted to a resident radiologist 1 kilometer away: each examination included patient's data (sex, age, site of trauma, etc.) which were sent by the admitting physician. A teleradiology system (Lumiscan 100 AT&T and Philips) was used. Films were digitized on a 1024 x 1024 x 8-bit image matrix and then transmitted over a dedicated standard phone line to the Department of Radiology. The autograph report was sent by fax to the emergency room. Four radiologists, of varying experience, independently reviewed a sample of 179 digitized radiographs and, 30 days later, the original films on a conventional light-box. The results appear to be encouraging because no significant differences were observed in the performance of any of the radiologists. Good video/films agreement was obtained, together with high sensitivity and specificity. A good result was the relatively small number (0.4% of all examined cases) of false negatives diagnosed on faxed films relative to the actual clinical diagnosis.
Computer Peripherals↗