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Results for “Analog-Digital Conversion”

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At least 505 records · Page 28Linked to original sources
PubMed1986

Pacemaker malfunction: fact or artifact?

In summary, the present examples illustrate how pacemaker malfunction can be simulated by the sources of artifact produced or detected by the monitoring equipment. This form of pseudopacemaker malfunction remains a common cause of mistaken diagnosis of pacemaker malfunction. A thorough understanding of the examples outlined above should help distinguish true pacemaker malfunction from pseudopacemaker malfunction produced by artifact.

Amplifiers, Electronic↗
PubMed1987

Power spectrum analysis in the study of ocular mechanisms.

The use of power-spectrum analysis in the study of ocular dynamics is becoming increasingly widespread. This paper summarizes the key points of signal acquisition and power-spectrum analysis, emphasizing aspects which we have found to be of relevance when the technique is applied to experiments in binocular accommodation. The considerations and conclusions are relevant to other areas of investigation into ocular dynamics and similar biological systems.

Accommodation, Ocular↗
PubMed1986

The effect of varying high pass filter parameters on the detectability of isolated pulmonary nodules in digitized chest images.

The effect of image processing of digital radiographic data on lesion detectability in clinical images has not been systematically studied. In this experiment, we evaluated a low frequency suppression filter program applied to CT digital radiographic localization images (General Electric Scoutview). Three different filter parameters affecting edge enhancement and local image contrast were applied to a set of digital chest images. A standard observer detection experiment comparing the variously filtered digital images and standard chest radiographs in the detection of lung nodules (11 peripheral lung fields, one superimposed on aortic arch) was performed. Standard chest radiography was more sensitive than the digital chest images, although some improvement was noted with increase in local image contrast and edge enhancement. Both image formats were equally specific. Image processing would be better evaluated using a digital imaging system with better performance parameters.

Analog-Digital Conversion↗
PubMed1986

[Analysis of the chromosome number in cells by flow cytometry].

A new flow-cytometric method is described that permits analysis of the number of chromosomes of individual cells. Preliminary stained mitotic cells are passed through a specially designed flow chamber in which they are destroyed just before passing through the focused laser beam of the flow cytometer. Signals from chromosomes of the destroyed cells are counted, and the results are represented as a distribution of the number of chromosomes in the cells. The method may be applied for the detection of relatively rare cells with abnormal numbers of chromosomes in biological and clinical research.

Analog-Digital Conversion↗
PubMed1985

[ECG-directed DSA of the pulmonary arteries--technic and initial clinical experiences].

ECG-triggered DSA of the pulmonary arteries enables far-reaching avoidance of image artifacts which are due to pulsation. However, trigger delay and image duration must be adapted subtly to the individual heart rate. Whereas adaptation of trigger delay can be effected via programming of the new generation of equipment, further improvements will be necessary to achieve an adequate image life or duration of the pulsed irradiation. Experience collected so far has shown that ECG-DSA of the pulmonary arteries yields results that are as valid as those obtained via perfusion scintigraphy, so that this method can be used in initial examination to establish the diagnosis of pulmonary embolism. The use of ECG-DSA is not indicated in absolute cardiac arrhythmia.

Adult↗
PubMed1985

Digital radiography.

This paper is a review of digital radiography, the application of digital electronic technology to medical X-ray imaging. At some stage in the formation of an image the detected X-ray fluence is converted into a digital format for processing and display. In many X-ray procedures digital methods offer considerable advantages over previously used techniques in speed, precision, flexibility, sophistication of processing, or other characteristics. These in turn can lead to reductions in degree of invasiveness, X-ray exposure, or contrast material dose or certain other advantages such as reduced time per X-ray procedure. The major digital X-ray imaging techniques are discussed, ranging from contrast enhancement to image subtraction schemes to more recently developed methods such as temporal filtering of image sequences at realtime video rates. Digital imaging systems are categorized according to detector geometry, and the relative merits of each are discussed. Examples of clinical applications are given.

Analog-Digital Conversion↗
PubMed1985

[Digital radiography--methods and clinical application].

The term "Digital Radiography" covers all x-ray techniques which produce a projected image with the help of digital imaging techniques, which are very similar to a conventional x-ray film image. The advantage of "Digital Radiography" is the possibility of digital image processing, like the subtraction technique, the selective material filtering technique and the quantitative image plotting technique. With the equipments now in use, the digital projected image is produced by the line or on an even level. One example of the in-line projected image is the so-called "topogram", produced via computed tomography equipment. With the help of an x-ray video chain, it is possible to produce digital images on an even level. This technique is used, for example, for "digital video subtraction angiography" (DVSA). Today, digital radiography is clinically used only in the "DVSA" and the "topogram" systems. A survey of the clinical use and the improved future possibilities of digital radiography is given, and the special features of the method are discussed.

Analog-Digital Conversion↗
PubMed1985

Cardiac applications of digital radiography.

Digital radiography is a rapidly developing new approach to cardiovascular imaging that converts radiographic and fluoroscopic video images into digital format for subsequent image enhancement, analysis, and storage. Cardiac applications proven clinically useful to date include intravenous and reduced-contrast load direct left ventriculography, aortic root bypass graft visualization, and selective coronary arteriography, which allows quantification of arterial stenoses and flow reserve. Myocardial functional reserve can be assessed using exercise or atrial pacing. Advantages over standard radiography include reduced radiation and contrast medium burden, visualization of very low contrast medium concentrations, and an image format that can be directly analyzed by quantitative techniques. As these cardiac applications are developed and improved archiving is implemented, it is likely that the digital approach will replace standard cardiac angiography.

Analog-Digital Conversion↗
PubMed1985

[Method of enhancing the diagnostic information value of the atrial vectorcardiogram].

An automated differentiation of the P loop from other VCG loops, its 20-fold magnification, visualization, and computation of its major spatial and projection parameters have been made possible, giving precise information on its configuration, duration, the direction of recording, as well as relative positions and directions of its instantaneous vectors. Digital computerization of the traces has produced different vector and scale characteristics of the spatial Pxyz loop.

Adult↗