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Results for “Analog-Digital Conversion”

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PubMedDate not supplied

Effect of sampling frequency on EMG power spectral characteristics.

During digitization of surface EMG, the signal is converted by an Analog-to-Digital (A/D) convertor at a specific sampling rate. This sampling rate should be selected cautiously because a high rate may include noise signals and a low rate may lead to errors. The present study was undertaken to show the effect of sampling rate on EMG power spectrum. The study was carried out on nine subjects and EMG record was done from deltoid muscle at sampling rates of 4, 6, 8 and 10 KHz during maximal voluntary contraction. Biopotential coupler with a response range of 5 Hz to 2 KHz was used during recording of the EMG signal which was processed later by Fast Fourier Transform software. The study showed a linear relationship between the sampling rate and the mean power frequency (MPF). But there was no distinct effect of sampling rate on mean and root mean square (RMS) of the digitized signal.

Adolescent↗
PubMed1975

[A hybrid system for documentation of pathological findings (author's transl)].

Considerations on the theory of communication point to the importance of "redundant" data in medicine. These usually arise from texts such as catamneses, descriptions of findings etc., and escape digital data pooling and storage on organizational and financial grounds. Here, microfilm is available as an economical storage medium taking little room. Developments in recent years enable integration of automatic analog storage into digital information systems. The use of such a hybrid system in the field of pathology is described.

Analog-Digital Conversion↗
PubMed1993

[The mapping of the local content of water and dry matter by using ultrathin frozen sections].

The possibility and applications of quantitative dry mass and water content mapping using an image analysis of darkfield intensity digitalization were shown on ultrathin freeze-dried cryosections. The distribution map obtained may be further used both for direct measurements of local dry mass and water content under physiological state and pathological disorders and for calculation of the concentration values obtained by quantitative X-ray mapping on freeze-dried cryosections in terms of millimoles per litre of cellular water.

Analog-Digital Conversion↗
PubMedDate not supplied

[The spectral-correlational analysis of the electrical activity of the rabbit brain in the organization of a goal-directed blinking reaction ].

At organization of the blinking reaction directed to a cessation of the motivational hunger dominant the spectral power of biopotentials of the frontal, sensorimotor cortical areas and the blinking cortical centres of both eyes, VMH and LH increases in the range of the delta- and theta-frequencies. Coherence (Coh) of electrical activity of the frontal and sensorimotor cortical areas increases, Coh between potentials of the swallowing cortical area and the blinking cortical zones corresponding to the trained and non-trained eyes is being asymmetrically reconstructed. Coh function of the electrical activity of the LH, VMH and potentials of different cortical areas changes uniformly. Coh of electrical activity of the VMH and LH, NIII and MPO increases in the whole analysed frequency range, Coh between potentials of the MPO and LPO, LPO and VMH increases in the delta- and decreases in the theta- and alpha-frequency ranges. It is suggested that in the process of preparation of the goal-directed reaction all the cerebral cortex areas and subcortical structures under study related to alimentary motivation and the blinking function are involved into the dominant constellation.

Analog-Digital Conversion↗
PubMed1993

[The value of digital-analog Holter monitoring systems in the noninvasive diagnosis of heart rhythm disorders].

By using the Custo Mega ECG monitoring system as an example, the value and efficiency of digital analog Holter monitoring systems in the non-invasive diagnosis of cardiac arrhythmias have been analyzed. The findings suggest that the Holter monitoring system produces high reliability, sensitivity (80.8-100%), and specificity (70.9-100%) in analyzing arrhythmic phenomena on ECG as compared to other Holter monitoring systems and electronic pacemakers.

Analog-Digital Conversion↗
PubMedDate not supplied

[Quantification of motor activity in biomedicine].

A computer-assisted analysis of motor activity was carried out using ultrasound waves, that are not invasive and free from any kind of interference, because of their specific characteristics. We worked out the Doppler's effect which determines a frequency variation on the reflected wave from any body in motion. That variation is linked to the velocity of the moving body and the superimposition of the emitted wave with those reflected, results in beats, which have a frequency proportional to the motor activity velocity. Our research group planned and carried out an electronic quantification apparatus that can be interfaced with a personal computer system by means of an Analog to Digital acquisition card. The performed test on the apparatus confirmed that the theory that the number of antinodes detected was proportional to the space covered by the moving body. The equipment was also tested on several types of animals.

Analog-Digital Conversion↗
PubMedDate not supplied

[A spectral-correlational analysis of the electrical activity of the rabbit brain during the extinction of an endogenous food conditioned reflex].

Spectral analysis of electrical activity showed that at the end of extinction of the alimentary conditioned responses, elaborated on the basis of the hunger dominant, the spectral density of electrical activity of the cortical centre of the goal-directed reaction (blinking) of the trained eye and that of the lateral preoptic area, lateral hypothalamus, and ventromedial hypothalamus raised in the delta-band. To the end of the extinction the coherence (Cog) of biopotentials of the cortical centres of blinking of both eyes and electrical activity of the ventro-medial hypothalamus and medial preoptic area was changed in different directions. After the extinction of the goal-directed reaction Cog between biopotentials of the lateral hypothalamus and the electrical activity of the frontal cortex raised in the delta-band and Cog between the activity of the lateral hypothalamus and that of the cortical centres of blinking of both eyes lowered. The level of excitation of the structures included in the dominant constellation was suggested to raise to the end of the extinction of the endogenous conditioned response.

Analog-Digital Conversion↗
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↗