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Results for “Analog-Digital Conversion”

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PubMedDate not supplied

Model-driven visualization of coronary arteries.

In a joint project between the Department of Computer and Information Sciences and the Department of Radiology, we are applying techniques of artificial intelligence to improve clinical performance in coronary arteries. Specifically, we are investigating how images from intravenous digital subtraction angiography (DSA) can be enhanced so that their efficacy for lesion detection and quantitation becomes comparable with that of the more dangerous procedure of selective coronary arteriography. The enhancement techniques (which include algorithms for 3-dimensional vessel detection, reconstruction and display, as well as for accurate lumen-size estimation) are based on models of (i) the 3-dimensional topological structure of the coronary arterial tree, (ii) myocardial dynamics, and (iii) the X-ray imaging process involved in producing digital subtraction angiograms. The evaluation of these model-driven visualization techniques is done by the standard psychophysical method of Receiver Operating Characteristic (ROC) analysis applied to observer performance tests on images from an animal coronary atherosclerosis model.

Analog-Digital Conversion↗
PubMedDate not supplied

Clinical indication of digital subtraction angiography.

Intravenous subtraction angiography with Technicare DR 960 has been performed in the Department of Diagnostic Radiology and Nuclear Medicine, National Medical Center Hospital. All procedures are based on the non-invasive technique, i.e. with 5 cm length and 19 G. of cannula to the ante-cubital vein, and small amount of contrast material of half ml per kg of body weight kg as maximum dosage for pediatric patients. Image quality was evaluated by visual classification such as excellent, good, fair and poor. Among 335 procedures, 303 cases have brought useful diagnostic informations. 156 cases were excellent and good (47%). There were several specialized informations which might be worthwhile for DSA evaluation, i.e. 1. overlapping images, 2. static dynamic images, 3. density controlled image analysis, 4. three vessel visualized images and 5. well demarcated tumor images of extremities. Since the halo image around the true lumen of aneurysma suggested the outline of the false lumen, this phenomena might indicate the aneurysmal wall thickness. Poor risk patients and outpatients have been selected as our DSA candidates. The patient who is indicated for catheter technique angiogram were not examined by DSA.

Aged↗
PubMedDate not supplied

[Cardiorhythmograph].

A device containing a digital meter of cardiointervals (with a measuring accuracy of +/- 2 msec) and a digital-to-analog converter (for 10 bits) is proposed. The device ensures the high-quality registration of cardiointervalograms. The parallel binary codes carrying information on the duration of cardiointervals are supplied to the perforator control unit or directly to the computer. To ensure the rational use of the whole width of the recorder tape, the possibility of changing the amplification scale of the output analog signal and the compensation of its noninformative steady component are provided. The circuit of the device includes the counter of the number of analyzed cardiocycles with the output where the logical unit is changed for zero (and vice versa) after every 50 measured intervals. The device is activated either by the built-in integrated-circuit amplifier of biopotentials or by the demodulator of frequency-modulated signals transmitting ECG over the telephone.

Analog-Digital Conversion↗
PubMed1981

Intravenous digital subtraction angiography.

The authors report the preliminary results obtained with a prototype of a digital subtraction unit in intravenous aortography. This new method in its actual state of development is not able to replace conventional arteriography. The new technique can be applied in selected clinical conditions where conventional arteriography is contraindicated or impossible. Further improvement of the spatial resolution of the digital image and reduction of the amount of contrast medium may extend clinical applications of this method which may be able to reduce substantially the cost and morbidity of angiography.

Abdomen↗
PubMed1981

Digital scintigraphy: principles, design, and performance.

In a digital camera the position of a scintillation event is computed following analog-to-digital conversion of photomultiplier pulse charges. Digital position analysis is essentially a mathematical inversion procedure based upon calibrated responses of the photomultipliers to scintillations from a narrow-beamed source that maps a detector's field of view. Operationally, a camera's image characteristics are optimized by means of computer-generated inversion reference tables, individually tailored to the specific response characteristics of each detector. Design considerations indicate that cameras of varied configurations, e.g., linear, disc-shaped, rectangular, or cylindrical, can be analyzed by this method. Also, for any given electro-optical system, energy resolution, spatial characteristics, and event-rate performance can be made superior to analog systems. The measured performances of a one-dimensional test camera, although limited in its optical and electronic design, support this conclusion.

Analog-Digital Conversion↗