International journal of bio-medical computing最新文献

This paper considers new computer methodologies for assessing the impact of different types of public health information. The example used public service announcements (PSAs) and mass media news to predict the volume of attempts to call the CDC National AIDS Hotline from December 1992 through to the end of 1993. The analysis relied solely on data from electronic databases. Newspaper stories and television news transcripts were obtained from the NEXIS electronic database and were scored by machine for AIDS coverage. The PSA database was generated by computer monitoring of advertising distributed by the Centers for Disease Control and Prevention (CDC) and by others. The volume of call attempts was collected automatically by the public branch exchange (PBX) of the Hotline telephone system. The call attempts, the PSAs and the news story data were related to each other using both a standard time series method and the statistical model of ideodynamics. The analysis indicated that the only significant explanatory variable for the call attempts was PSAs produced by the CDC. One possible explanation was that these commercials all included the Hotline telephone number while the other information sources did not.

In this paper a hypermedia system for parasite identification is described. The knowledge base is relative to the class of the Trematoda parasites and reports agent, vector, disease, related category of the International Classification of Diseases and geographic area. A graphic user-friendly human-machine interface has been realized for this system.

The assessment of blood flow in the gastrointestinal mucosa could be a useful indicator for the diagnosis and treatment of several diseases, such as ulcers, gastritis, colitis or early cancer. The quantity of blood flow is roughly estimated by computing the spatial hemoglobin distribution in the mucosa. The method presented here enables a practical realization by calculating approximately the hemoglobin concentration based on a spectrophotometric analysis of endoscopic true-color images, which are recorded during routine examinations. A system model based on the reflectance spectroscopic law of Kubelka-Munk is derived, which enables an estimation of the hemoglobin concentration by means of the color values of the images. Additionally, a transformation of the color values is developed, in order to improve the luminance independence. Applying this transformation and estimating the hemoglobin concentration for each pixel of interest, the hemoglobin distribution can be computed. The results obtained are mostly independent of luminance. An initial validation of the method is made by a quantitative estimation of the reproducibility.

Transferability of discriminant functions is potentially useful both from an economical point of view and because, in general, medical knowledge, in this case discriminant functions, should be transferable. In the present study we have evaluated the transferability of discriminant functions, estimated from routine laboratory analysis, age and sex in two consecutively recorded populations with hypercalcemia including 162 and 257 patients with hypercalcemia. Discriminant functions were developed for each sex to distinguish between hypercalcemia associated with malignancy and hypercalcemia associated with other medical diseases. The total diagnostic accuracy in Herlev was 82 and 78%, in women and men, and increased to 87 and 86% in both sexes considering cases classified with posterior probability levels of 60%. In Hvidovre the total diagnostic accuracy was 81 and 84% in women and men, and increased to 83 and 89% at posterior probability levels higher than 60%. Transfer of the discriminant functions between the hospitals was followed by a decrease in diagnostic accuracy of 6–16%. At a posterior probability of 60% the diagnostic accuracies were 79% or more in the receiving hospital, in both sexes, except for men in Hvidovre. In relation to these results the concept of genuine and non-genuine transfer factors is introduced and discussed.

This paper deals with accurate estimation of the degrees of freedom (DOF) of a body segment, starting from the trajectories of clusters of markers acquired with a suitable measurement system. The most commonly employed estimation procedures involve two sequential steps, a trajectory smoothing algorithm and a DOF reconstruction routine. Three optimized smoothing and reconstruction schemes are described, analyzed and tested and their performances are compared with each other and with those of a more traditional technique which contains no optimization criteria. All three schemes include an iterative, weighted-least-squares DOF reconstruction routine and a self-tuning, zero-phase-shift, 4th-order Butterworth filter. Both routines are extensively described and validated on the basis of numerically-simulated marker trajectories. Test results, analyzed on a statistical basis, show that the use of an optimization routine provides a visible improvement in DOF reconstruction. This performance has also been confirmed using stereophotogrammetric data collected on a subject wearing an external fracture fixation device which provides reference values for the bone DOF. Angular DOF estimated applying the optimized method to skin technical clusters are much closer to the reference values than the non-optimized values. Smoothing of data further improves the reconstruction accuracy while a far less crucial role is played by the order in which smoothing and reconstruction routines are applied.

A 2D marker-free method for tracking the human lower limb segments has been developed and tested. The method is based on model matching using distance transformations, and is intended for use in analysis of human gait. The model used consists of five line segments, which are matched to the contours of the lower limb segments. Experiments have been made on two different kinds of objects; a rigid model of a leg and a human leg. Only movement in the sagittal plane has been considered. An image sequence of the moving object was captured, and the method was used for tracking the segments of the object in each image. The results were then compared to data obtained using markers mounted at the ankle joint, the knee joint and the hip joint. The experiments on the rigid body were done to assess the accuracy of the method under perfect conditions. The average difference between the estimated joint positions and the reference positions was found to be less than 2 mm for all three joints, with a standard deviation of less than 1 mm. To test the method in a more realistic situation, it was applied to a human leg during the stance phase of walking. Measurements were made on three healthy male subjects. The average differences between the estimated joint positions and the reference marker positions were less than 6 mm. 10 mm and 22 mm, for the ankle joint, the knee joint, and the hip joint, respectively. The corresponding standard deviations were less than 4 mm, 7 mm and 9 mm, respectively. The satisfying results, though obtained controlled laboratory conditions, show that this method might be useful in gait analysis.

Automatic recognition of Morse-code is generally developed at a fixed typing rate. However, this is not suitable for the disabled due to their difficulty in maintaining a stable typing rate. In this paper, a system recognizing varying typing speeds is developed using an adaptive technique, the Least-Mean Square (LMS) algorithm. This system helps the disabled have a wide latitude and varying typing speeds in single-switch communication with the Morse-code.

Verapamil is supposed to suppress the initiation of circus movement supraventricular tachycardia by affecting the atrioventricular node. In electrophysiological tests, programmed stimulation is usually performed by using the same location for pacing and premature stimulus. Spontaneous ectopic activity starts from a different location than the sinus node and can therefore find altered re-entry conditions. In this study a 3D computer model based on Huygen's principle is used for simulation of the spread of excitation in the human heart in combination with a posterobasal, right or left lateral accessory pathway (AP). The effect of verapamil on properties of the atrioventricular node were modelled by prolonging the effective refractory period and basal conduction time. For each of the three APs, ectopic foci at the atrial base and between sinus node and AP were modelled at various coupling intervals for investigating re-entrant activation. In the control state (without verapamil) only orthodromic echoes were found. The maximum echo zone (EZ) range was found near the AP. If stimuli were selected further away from the AP on the atrial basis, the EZ range decreased until no EZ was found. The EZ range decreased from it's maximum value near the AP. towards the difference of the effective refractory periods between AP and AV-node near the sinus node. Verapamil abolished the EZ in case of a posteroscptal AP. For a lateral AP the administration of verapamil resulted in an orthodromic and antidromic EZ depending on the atrial premature activation site. A maximum orthodromic EZ was found for premature stimuli near the AP. As stimulus site moved away from the AP. the EZ range first decreased continuously to zero leading eventually to an antidromic EZ. These findings suggest the important influence of the site of premature stimuli with respect to the accessory pathway and AV-node on the inducibility of atrial re-entry.