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PubMed1993

[The microcomputer study and processing of the values of the blood pressure and intersystolic interval in laboratory animals].

A system is created for study of the agents, affecting the arterial pressure and baroreflectory sensitivity, which comprises:transducer for arterial pressure Statham P23 ID, connected to a polygraph Biomedica O.T.E.; eight-bite analogous-numerical transformer; microcomputer, compatible to Apple 2+; two diskette devices and printer. The arterial pressure of the lab animals (rats, rabbits, cats) is directly measured in a. carotis communis by means of the transducer and is recorded on the polygraph. For the system a computer program is designed which allows archivation of the primary experimental data; automatic and precise determination of the momentary values of the systolic and diastolic arterial pressure and intersystolic interval; determination of the baroreflectory sensitivity by means of linear regressive analyses; printing of the results under the form of diagrams and tables. By means of this system much time is spared, related to the accounting and handling of the experimental data.

Analog-Digital Conversion↗
PubMed1993

Visualization of intracellular calcium during necrotaxis.

Granulocytes are known to exhibit positive chemotaxis towards erythrocytes destroyed by laser irradiation (necrotaxis). A computerized method for visualizing intracellular calcium concentration in granulocytes during necrotaxis has been developed. Successive bursts of fluorescence were observed: 1 degree) about 10 s after the creation of the necrotactic source; 2 degrees) when the granulocyte touched the target.

Analog-Digital Conversion↗
PubMedDate not supplied

Fundamentals of image processing for personal computers.

Photographic images make an important contribution to medical education. Conventional means of display have included 35-mm projection, film, videotape, and more recently, analog videodiscs that accompany computer-based text. The availability of compact discs, with their enormous storage capacity, and of powerful central processing units now permits consideration of digital storage of visual images for display by the personal computer. The data processing required for the representation and transfer of high-quality images is forbidding, however, even with today's technology. The problem is compounded if one anticipates display of full-motion video. In this tutorial we first review the nature of analog signals and the process of capturing them in digital format. We then consider mass storage and the concept of compressing data into smaller amounts of information that can be processed and transferred by personal computers with the use of optical disc drives. A look into the future provides a vision of high-definition television-quality video in digital format.

Analog-Digital Conversion↗
PubMed1993

[A simple method of digitizing analog scintigrams for quantification and digital archiving].

This study was undertaken to evaluate a quick, reliable and cheap method of digitizing analog scintigrams. 40 whole-body bone scintigrams were obtained simultaneously in analog and genuine digital format. The analog scans on x-ray film were then digitized secondarily by three different methods: 300 dpi flat-bed scanning, high-resolution camera scanning and camcorder recording. A simple exposure approach using a light box, a cheap camcorder, a PC and image grabber hard- and software proved to be optimal. Visual interpretation showed no differences in clinical findings when comparing the analog images with their secondarily digitized counterparts. To test the possibility of quantification, 126 equivalent ROIs were drawn both in the genuine digital and the secondarily digitized images. Comparing the ROI count to whole-body count percentage of the corresponding ROIs showed the correlation to be linear. The evaluation of phantom studies showed the linear correlation to be true within a wide activity range. Thus, secondary digitalization of analog scintigrams is an easy, cheap and reliable method of archiving images and allows secondary digital quantification.

Analog-Digital Conversion↗
PubMed1993

[Evaluation of underexposed conventional x-ray films following digitization].

Inadequate exposure of analogue radiographs is reported in the literature to occur in 5-25% of cases. Therefore, the present study was performed to test whether selective image processing after digitization could reveal diagnostic details on underexposed radiographs. In addition, the minimal exposure values required for diagnostic purposes after adequate image processing were studied. Phantom studies, organ preparations and measurements of physical parameters with decreasing exposure values were performed. The detection of anatomic and pathologic (nondisplaced fracture lines, microcalcification and renal stones) structures were evaluated by 12 readers. Radiographs with exposure values 20-40% lower than "ideal" values can provide adequate diagnostic images after digital processing. The diagnostic information is significantly impaired with values under 50% of the correct exposure values. In conclusion, this method is adequate to save underexposed radiographs for diagnostic purposes and to avoid repeated examinations.

Analog-Digital Conversion↗
PubMed1993

[The high-resolution analysis of the P wave recorded via the esophagus: a new diagnostic approach in patients with paroxysmal atrial fibrillation].

BACKGROUND: P-wave signal averaged ECG has recently been proposed in the evaluation of patients with Paroxysmal Atrial Fibrillation (PAF). The aim of this study was to verify the utility of this method in the characterisation of these patients utilizing a transoesophageal signal. METHODS: The study population consisted of two groups of subjects: Group A, 34 consecutive patients (16 males; 57 +/- 9 yrs) with a documented PAF and without any underlying heart disease, and Group B, normal controls (9 males; 44 +/- 6 yrs). A signal-averaged ECG, triggered with the oesophageal P-wave, obtained from an X, Y, Z lead system was recorded in each patient, utilizing the AEROTEL HIPEC 200 system. The three orthogonal averaged ECGs were band-pass filtered (non-recursive filter, 40-250 Hz) and combined into a spatial vector magnitudo. We evaluated the filtered P-wave duration (Ad, msec) and the Root Mean Square (RMS) voltages of the last 10, 20, and 30 msec of the P vector magnitudo (RMS 10, 20, 30; mcV). RESULTS: The patients with PAF presented with a significantly longer Ad duration (A 126.6 +/- 12.4 vs B 96.8 +/- 12.5 msec, < 0.001), and lower amplitudes of RMS 10, 20, 30 (RMS 10 A 4.8 +/- vs B 9 +/- 2.7 p < 0.005; RMS 20 A 6.9 +/- 2.3 vs B 15.7 +/- 7.3 p < 0.005; RMS30 A 12.1 +/- 5.1 vs B 25.3 +/- 11.5 p < 0.005). An Ad > or = 100 msec, a value of RMS 10 < or = 6.5, RMS 20 < or = 9 and RMS 30 < or = 12.5 mcV showed high values of sensitivity, specificity and positive predictive value (Ad 85%, 100%, 100%, RMS10 93%, 80%, 90%, RMS20 84%, 90%, 96%, RMS30 72%, 90%, 72%). The combined duration/voltage criteria (Ad +/- 110 msec and RMS10 < or = 6.5 mcV or RMS20 < or = 9 mcV) showed a sensitivity of 80% and 76% with a specificity and positive predictive value of 100%. CONCLUSIONS: The P-wave triggered transoesophageal atrial signal averaged ECG appears able to identify patients with PAF; however, prospective studies must investigate the possible clinical use of these findings.

Adult↗
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↗