Showing papers on "Artifact (error) published in 1977"

Minimizing Electrode Motion Artifact by Skin Abrasion

Abstract: Motion artifacts frequently cause erroneous results in biopotential measurement. When surface electrodes and conducting paste are used, a major cause of motion artifact is change in skin potential. The most effective means of minimizing this artifact is light abrasion of the sidn with fine sandpaper. A very mild paste is then required to avoid skin irritation.

Correction for spectral artifacts in cross-sectional reconstruction from x rays.

Abstract: A monoenergetic response correction is described which, along with adequate filtration, may be used to remove the spectral shift artifact encountered in three‐dimensional reconstruction from x rays. Reconstructions were carried out by means of a convolution algorithm for simulated data using this method. These are compared with reconstructions obtained using fixed‐length water‐bath scans as a remedy for the special artifact. These studies suggest that the spectral artifact can be successfully eliminated from computerized cross‐sectional scans without resorting to the use of the water bath while, at the same time, improving quantum statistics and/or permitting operation at a lower tube current.

Pacemaker artifact suppression in coronary monitoring

Abstract: In heart monitoring systems for use with patients whose hearts may be stimulated by an artificial pacer and which system includes heart rate indicating means, there is provided circuitry for suppressing the recharge waveform portion of a pacer signal artifact in addition to suppression of the discharge pulse portion of the signal artifact, thereby to prevent inaccuracies in the heart rate indication arising from the pacer signal artifact. In addition to suppressing the discharge pulse portion of a pacer signal artifact with conventional means, the invention recognizes that the recharge waveform of the pacer signal may cause a false impression of a QRS complex which actuates heart rate indicating means and provides novel circuitry for suppressing such recharge waveform. Circuitry is provided for recognizing the occurrence of a pacer discharge pulse and for generating a suppression signal in timed relation thereto which, when arithmetically added to the recharge waveform portion, acts to cancel or suppress such recharge portion. The suppression signal is of inverse polarity to the recharge waveform portion and is generated by sampling the pacer signal artifact substantially at the beginning of the recharge waveform to determine the magnitude thereof. In a preferred embodiment, a pacer signal artifact and the termination of the discharge pulse portion thereof is identified by novel rate and duration measuring circuitry.

A simple technique for correlating film and EMG in locomotion studies

Abstract: Two recurring problems hampering investigations of muscular activity patterns during locomotion are electrical “noise” and movement artifact in the electromyographic (EMG) signal and proper synchronization of behavioral events to the EMG. A relatively simple technique for achieving these ends is presented. Vigorous locomotor movements of unrestrained animals are recorded on 16-mm film and synchronized with one or more EMGs from selected muscles with little electrical noise or movement artifact interference. The system employs telemetry which is compared to hardwire techniques.

Biopotential movement artifact inhibiting system

Abstract: The broadband auditory thresholds of marine mammals are determined by an apparatus which compensates for the animals' movement artifact. A number of evoked responses to audio stimuli are average during discrete time intervals. This approach reduces the effects of potentials attributed to movements of the animal, for example, the opening and closing of the blow hole. A threshold detector circuit, a tape delay and related circuitry electronically cooperate to block potentials attributed to the movement artifact when the potentials exceed the likely magnitude of the evoked response. Optionally, an oscilloscope is used to provide a visual representation of the evoked response and the potentials are manually inhibited when the movement artifact masks or otherwise overrides the evoked response.

Pseudotibiotalar slant: a positioning artifact.

Abstract: Pseudotibiotalar slant is a positioning artifact which duplicates a finding recently reported as a new observation in the ankles of patients with sickel cell anemia and the configuration of tibiotalar slant described in juvenile rheumatoid arthritis, hemophilia, and multiple epiphyseal dysplasia. The configuration was produced on radiographs of the author's ankle by flexion of the knee and external rotation. It is a nonspecific finding which should prompt inquiry into the possibility of ipsilateral knee and∕or hip abnormality.

Source Guide to History of Measurement Technology Material: Part 1: Introduction and Artifact Collections

Abstract: Measurement hardware before the 19th century is reasonably well reported in historical works. More modern electrical devices have not been studied as extensively, presumably because of the high degree of understanding needed of the historian and because the artifacts and written information are not easy to locate. This article provides a brief summary of the history of sensing, a working guide to dominant world collections of sensing apparatus, and an introductory guide to the literature available on sensing methods. It is intended as an aid to historical sensing technique research.