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At least 1,063 records · Page 59Linked to original sources
PubMed1993

[A new multichannel system for detection of sleep apnea syndrome].

A new multichannel system is presented which records and analyzes polysomnographic data. The reasonably priced hardware and software makes the diagnosis and therapy of sleep apnea syndrome possible even in smaller internal departments. By using this system, adjustments to the nCPAP therapy can be undertaken. A newly developed analog-digital converter and software functions record simultaneously up to 24 channels. It performs the functions of commercially available instruments for induction plethysmography. The system has a modular setup. It is also possible to record special parameters, such as transcranial Doppler signals. Without any difficulty, instruments already used in the sleep laboratory can be included into this multichannel system. For instance, the screening device for the sleep apnea syndrome MESAM IV can be easily integrated. With this combination, it is possible to adjust sleep apnea patients to the nCPAP therapy by using the MESAM IV device. The software also enables analysis of breathing parameters and algorithmic revision of channels. In this way, filters can be integrated and amplitude calculations can be conducted.

Analog-Digital Conversion↗
PubMedDate not supplied

A dual-processor computer for arrhythmia analysis.

In order to facilitate the analysis of 24-hour tape recordings of ECG for rhythm by the AZTEC technique, we have configured a dual-processor system. It samples the ECG signal from a tape playback unit at a rate of 7501.88 Hz, allowing analysis at 30 x real time. An approach to error recognition and containment for the program, which utilizes the sampling of events, is discussed. Steps are taken to reduce errors caused by human sampling of "high risk" regions of the record.

Analog-Digital Conversion↗
PubMed1995

Low frequency analysis of opening sound for detection of single leg separation of Björk-Shiley Convexo-Concave heart valves.

The aim of the study was to evaluate the potential of low frequency analysis of valve opening sounds in order to detect the presence of single leg separation of the outlet strut of Björk-Shiley convexo-concave (BSCC) valves. Single leg separation is believed to precede outlet strut fracture. Phonocardiograms (PCG) of 28 patients with BSCC mitral valves were recorded and filtered to limit the frequency bandwidth between 90 and 1400 Hz (-20 dB). Twenty-four patients had BSCC valves that were presumably unimpaired and four patients had BSCC valves with single leg separation. Spectral analysis consisted of computing the power spectrum for 30 opening sounds for each patient using a fast Fourier transform (FFT) algorithm on an IBM-PC compatible computer. For each patient, the power spectra of the selected opening sounds were averaged and normalized in amplitude on a 0-100% linear scale. A ratio of the high to the low frequency area of the averaged power spectra was computed and evaluated as a diagnostic feature to identify the valves with single leg separation. Six cut-off frequencies serving to distinguish between high and low frequency areas of the spectra were tested: 400, 450, 500, 550, 600, and 650 Hz. The results showed that the high-to-low frequency area ratios tested were all able to identify valves with single leg separation. The correct classification performance was 96.4%. The sensitivity to detect valves with single leg separation was 75% and the specificity was 100%. The positive predictive value was 100% and the negative predictive value 96%. The study confirmed the potential of low frequency analysis of valve opening sounds to detect single leg separation of the outlet strut of BSCC valves implanted in humans.

Algorithms↗
PubMed1995

Asynchronous closure and leaflet impact velocity of bileaflet mechanical heart valves.

The effect of gravitational field on the asynchronous closure of four different types of bileaflet heart valves (BHV) were investigated in an in vitro mock circulation system. The experimental study involved the 29 mm St. Jude Medical Standard, 29 mm CarboMedics, 29mm Edwards-Duromedics and 29 mm Edwards-Tekna BHVs. The valves were tested in the mitral position on an inclined 45 degrees plane of the pulsatile mock flow loop. The test valves were orientated with their pivotal axis horizontal so that the gravitational vectors on the two leaflets were clearly disparate. Using a specially designed laser optical system, the time difference at which the closing leaflets made their first contacts with the valve housing was measured. The closing velocity of each leaflet was measured separately by the laser sweeping technique (LST). The experiments were conducted under physiologic ventricular and aortic pressures at the heart rates of 70, 90, and 120 beats/minute with the corresponding flow rates of 5.0, 6.0, and 7.5 liters/minute. Asynchronous closing motions were registered in all four tested BHVs. The leaflet closing motions were random in nature, but indicated clear dependency on the orientations with respect to the gravitational field. The lower leaflet which makes a generally level swing to close, was assisted initially by the gravity and was always found to close earlier than the upper leaflet, which swing upward to close. The initial closure of the upper leaflet was against the gravity which delayed the leaflet motion. Depending on the BHV designs, the time delays between the two leaflets were found to vary from beat to beat but to follow certain probability distributions. In general, the leaflet/housing contact time between the two valve leaflets exhibited the clear trend of decreasing delay time at closure with the increase of the heart rate. For each of the valves tested, the average impact velocity of the first closing leaflet was found always smaller than that of the second closing leaflet at all three heart rates tested. The impact velocities of both the BHV leaflets were found to increase with the heart rate. The difference in the closing velocities between the two leaflets decreases with the increase of the heart rate and is generally proportional to the impact time delay between the two leaflets.

Analog-Digital Conversion↗
PubMed1995

"Informed consent" interactive videodisc for patients having a colonoscopy, a polypectomy, and an endoscopy.

These "informed consent" interactive videodisc programs use both graphic and live action sequences to describe in detail the diagnostic procedures of Endoscopy, Colonoscopy, and Polypectomy. Both benefits and possible risks are listed and described. After each sequence, the patient is asked whether the explanation is understood and/or whether the patient would like to discuss the procedure in more detail with a physician. The programs were designed for use with marginally literate patients and require no reading ability. Both programs are also ideal for general patient education.

Analog-Digital Conversion↗
PubMed1995

The design and application of microcomputer human body information balance diagnosis and treatment instrument.

In Chinese medical theory, it is thought that if the "Yin and Yang balance, person will be healthy." Chinese medicine studies the human body as a whole which has specific functions. Chinese medical main and collateral channels are confirmed by experts at home and abroad as Ra kind of internal structure system that really exists.S It has been confirmed that imbalances caused by almost all diseases can be reflected in main and collateral channels system; the channels can adjust and control the physiological function and pathological expression of human body's viscera and bowels. The adjustment for the human body can be accomplished through reaction points of body surface and main and collateral channels. Since 1989, the studies of other countries have confirmed that the human body is a combined control system that owns various adjustment mechanism. The adjustment and control for human body state can be accomplished through biological information. Based on the above theory, the authors of this paper designed the instrument that can make diagnosis and treatment automatic. Biological information sensors are attached to the points of main and collateral channels, and they sense the signals of disease of the human body. Through an A/D converter, the signal is input into a microcomputer. The CPU makes a comprehensive analysis and diagnosis according to the program and the signs and amplitude of signal deviation values detected from the left and right main and collateral channels points; it gives relevant information treatment prescription. After D/A converting, the information treatment wave generator is activated. The composed information wave treats the human body through the main and collateral channels points, and the changes after treatment are fed back to the computer through biological information sensors to amend the treatment prescription and generate the new information treatment combination wave, which is again fed back. At last, the body system will reach stability and balance through many circulations. Through 300 cases of clinical practice, the total effective rate for 22 kinds of disease such as stomach ache, coronary heart disease, and Meniere's disease reaches 90.0%. Among these, the marked effect accounts for 7.3%; the improvement accounts for 82.7%. After processing by statistics, it shows that the instrument has a marked curative effect. In theory, the instrument has the functions of diagnosis, treatment, health care, adjustment of body immunity, prevention of cancer, the curing of nerve functional diseases and some nerve and spirit diseases, etc. It is estimated that the instrument will be used in more fields; it has good application prospects, and will become a new therapy in home medical care.

Analog-Digital Conversion↗
PubMed1996

Image acquisition. Sites, technologies, and approaches.

This article examines the current and future methodologies for image capture. Data conversion devices and systems, radiographic techniques of ionizing and nonionizing radiation, passive imaging, and digital image data requirements are explored. The author also discusses the problem of how to connect acquisition devices to PACS.

Analog-Digital Conversion↗
PubMed1995

[The objective and perspective of recording electrical activity from the central nervous system].

In 1929 Hans Bergr successfully recorded electrical activity from the human brain using surface scalp electrodes. Since, the EEG has brought significant contributions to the fields of clinical neurology and neurophysiology. As a clinical diagnostic tool, the EEG has provided information for functional as well anatomical (structural) brain disturbances. As a functional diagnosis, the EEG is far superior to other functional tests such as PET, SPECT or functional MRI because of its excellent temporal resolution representing moment to moment changes in the level of consciousness. However, the progress has been hampered due to difficulty in quantifying EEG data because of its extreme dynamics and variability, which perhaps reflects yet unknown brain functions. This difficulty will be overcome by improved quantification methods and statistical measures using various computer applications including topographic mapping, power spectrum analysis, covariance, correlation or coherence function. Because of its poor spacial resolution, the EEG has relinquished its place to CT and MRI scans as an anatomical diagnostic tool. The surface recorded electrical activity is greatly attenuated and distorted by the time it reaches to the scalp. This is due to the inhomogeneous tissues (CSF, dura, skull, scalp) that intervene between the recording electrodes and cortical surface. Because the human body or head consists of electroconductive media of various geometries, current distortion, far-field potentials or paradoxical lateralizations further complicate the interpretation of EEG in postulating the location of anatomical generator sources from surface recorded EEG. Advanced computer technology is in progress to quantify the EEG data by taking into account the factors of conductivity, geometry shape and individual head size. This will improve the accuracy of localizing current generator sources in relationship to brain anatomy. By solving these problems in a methodical fashion, EEG will become the revelation for understanding the functional anatomy of brain and will step closer to Berger's dream, "EEG is a window of human mental activity".

Action Potentials↗
PubMedDate not supplied

[The use of a Russian software-hardware package for the quantitative analysis of coronary angiograms].

The software and hardware complex developed by the Cardiology Research Center, Russian Academy of Medical Sciences, jointly with the Technomash Research Production Association on the basis of a IBM 386DX personal computer equipped with a VS-100 video controller and a DS P31 VS signal processor board. Testing has indicated that it provides a qualitative image and a quantitative analysis both of phantoms and real images of coronarograms, but more accurately in the analysis of the image obtained from a film projector. Valid results are yielded when lenses more than 1 mm in diameter are used. Clinical tests have shown that the software and hardware complex may yield a rather qualitative image and calculate the required diameter of a vessel, virtually without prolonging the time of intervention, which is particularly important while making intervention procedures and implementing research programmes.

Analog-Digital Conversion↗
PubMed1986

Computers in biology: the future is today.

Which are the applications of microcomputers in biology today? Some areas where the work with microcomputers is becoming increasingly important are considered: laboratory applications, event simulation and word processing. Almost all laboratory computer applications can be described as one of the following functions: 1. control of experiments, including timing and synchronizing external voltages; 2. data acquisition, usually through digital conversion of analog electrical signals; 3. data storage and, 4. data analysis. Event simulation is considered both as a research tool and as an important element in the educational area. Word processing and the automatic creation of literature references lists is considered as an ignored role of the microcomputers in the laboratory field. What about the influence of biology in computer technology? As specialized magazines say, many laboratories of biotechnologist are working hard to build a molecular computer. That is, an artificially designed ultramicroscopic machine built of proteins, nucleic acids, metals and non-metals in a planned arrangement. And this is not the end. The latest application able to expand our horizon in the biological field may be starting to be used at this moment.

Analog-Digital Conversion↗
PubMed1976

Analog vs. digital photogrammetry for optic cup analysis.

This report compares the reproducibility of analog and digital photogrammetry for topographical analysis of the optic cup. Ten simultaneous stereophotographs of each of three optic discs were taken with the Zeiss fundus camera plus a twin-prism stereoseparator. Digital processing produced photogrammetric contours of the optic cup and estimates of its geometry. Optic cup contours from the same stereopairs were also drawn with an analog stereoplotter and were analyzed by manual planimetry. The reproducibility of digital photogrammetry and analysis for estimation of cup depth, cup width, cup cross sectional area, and cup volume was concluded to be generally superior to the reproducibility of analog photogrammetry and manual analysis.

Analog-Digital Conversion↗
PubMed1976

Automated rodent respiratory monitor and histogram computer--a preliminary report.

The system described in this paper was designed to monitor total inhaled volume (V), tidal volume (VT), and respiratory frequency (f) of Fisher rats before, during, and after exposure to cigarette smoke. The systems consists of three major subsystems: plethysmograph, analog signal conditioner, and histogram computer. The volume type whole body plethysmograph incorporates a rubber nose seal. Tidal flow rate (V) from the tube, measured by a pneumotachometer, is integrated by the signal conditioning system to obtain VT and V. Both V and V are displayed on a strip chart recorder. A rat will often exhibit considerable sniffing, especially in the presence of cigarette smoke. Consequently, average tidal volume (VT) and average respiratory frequency (f) are not accurate measurements of typical VT and f. Sensitivity of the system to changes in typical VT and f is important snce the system will be used to evaluate the effects of subtle differences in types of experimental cigarettes. A microprocessor was used in conjunction with a cathode ray tube to compute and display both the VT and respiratory period (T = 1/f) as histograms. From the histograms the most common (typical) VT (mode of the histogram) and the most common T can be easily observed and recorded. The histogram computer also calculates and digitally displays VT and f.

Analog-Digital Conversion↗
PubMed1976

A charge coupled transversal filter for biomedical signal conditioning.

The analysis and processing of biological signals is often hampered by the contamination of these low frequency, often low amplitude waveforms by motion artifact in fluid-filled catheter systems and skin electrodes, power line hum, and so on. Although noise suppression techniques have relied upon low pass filtration of the analog signals with active or passive RLC filters, even the most recent active RLC filter implementations display operational characteristics not entirely satisfactory for low frequency applications.

Analog-Digital Conversion↗