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Results for “Analog-Digital Conversion”

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PubMed1979

Apperceptive signals demonstrating the dynamic disturbance of myocardial ischemia.

Analog pressure signals (catheter-tip manometers) from the left atrium, left ventricle, and aorta and a flow signal from the arota were obtained in 25, open-chest, anesthetized dogs in which 115 episodes of ischemia were produced in an area of the left ventricle subtended by the distal left anterior descending coronary artery and its last major diagonal branch. The left ventricular pressure and its first derivative (dP/dt) were displayed as an X-Y loop. The character of this loop went through a unique series of dynamic changes in 110 of the 115 ischemic episodes, indicating that this is a useful tool for monitoring myocardial ischemia. Spectrum pairs of the above signals were analyzed with digital computational transfer functions in 14 ischemic episodes of three experiments and preliminary assessment reveals unique pole and zero changes in many pairs during each episode which also may prove to be a useful indicator of the hemodynamic disturbance incurred during myocardial ischemia.

Analog-Digital Conversion↗
PubMed1994

[The noninvasive demonstration of functional reinnervation after heart transplantation].

Although RR interval variability appears to be an ideal method for assessing reinnervation after heart transplantation, it has been shown that respiratory sinus arrhythmia is caused by the mechanical effect of respiration on the right atrium. The neck-suction induces heart rate changes only by means of nervous reflex and its hemodynamic effect is local and hence appears as a useful method for assessing reinnervation. We tested the presence of autonomic reinnervation in 18 heart transplant recipients, compared to 12 donor-age-matched controls. We measured the power of RR interval low- (LF, around 0.1 Hz) and respiratory fluctuations (HF) before and during rhythmic neck-suction stimulation at 0.1 Hz and at a frequency (0.20 Hz) similar to, but distinct from, that of respiration (controlled at 0.25 Hz), before and during 0.04 mg/kg atropine infusion, using autoregressive spectral analysis of RR interval, respiration and neck pressure signals. The relationship between pairs of signals at each frequency was quantitatively assessed by bivariate coherence function. All transplanted subjects showed low-amplitude HF, related to respiration. Detectable LF (whose power was lower than in controls: 1.15 +/- 0.39 versus 6.08 +/- 0.27 1n-ms2, p < 0.001), non coherent with respiration, were present in 11/18 transplanted subjects, and correlated with months since transplantation (r = +0.59, p < 0.05). HF neck suction induced the presence of a 0.20 Hz fluctuation in 12/12 controls, distinct from and greater than the 0.25 Hz respiratory component (7.28 +/- 0.26 versus 6.69 +/- 0.74 1n-ms2, p < 0.01); this was not seen in any of the transplanted subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMedDate not supplied

Assessment of the response of right ventricular performance to decreasing levels of mechanical assistance by on-line pressure area relationships.

The rapid assessment of the response of right ventricular (RV) performance to decreasing levels of mechanical assistance may be an important adjunct in determining if a patient can tolerate the removal of such a device. This report describes the use of on-line pressure area relationships to assess RV function in a patient supported with an RV assist device (RVAD). Mid RV short axis cross-sectional area was measured on-line by transesophageal echocardiography with an automated endocardial border detection feature. RV pressure was measured with a high fidelity catheter. Pressure and area were plotted simultaneously on a computer workstation interfaced with the pressure and echo systems to yield on-line pressure area loops. The following indices of RV performance were calculated while RVAD flow was decreased in 1 L/min increments: stroke work' (SW' = integral of PdA)[mmHg*cm2], stroke area (SA = Maximum Area-Minimum Area)[cm2], and fractional area change (FAC = SA/Maximum Area*100)[%]. SW', SA, and FAC significantly increased with decreasing RVAD flow: SW'(from 32 to 61 mmHg*cm2), SA (from 2.58 to 4.37 cm2), and FAC (from 20 to 32%). In conclusion, the increase in these parameters of RV performance with decreasing mechanical assistance suggested that this patient would tolerate removal of the RVAD, which was subsequently successful. This method of on-line pressure area relationships may be useful to predict the need for further mechanical assistance.

Analog-Digital Conversion↗
PubMed1976

International standard (C.C.I.T.T.) for transmitting biomedical analogue and digital data on the public telephone network.

Analogue transmission of biomedical signals over the public telephone network has advantages from the economic point of view over digitalized transmission. This paper deals with the special problems encountered with the transmission of biomedical signals. Furthermore, the new international transmission standard C.C.I.T.T. recommendation V. 16 is introduced. This standard has recently been adopted by the relevant study group and has been presented to the Plenary Assembly of the C.C.I.T.T. for final approval. This standard is compatible with the existing public telephone networks. The technical specifications of this standard allow the transmission of the three-channel ECG for diagnostic purposes, e.g., remote processing and computer-assisted evaluation, as well as the transmission of the one-channel ECG with acoustic coupling, e.g., in emergency cases and for pace maker monitoring.

Analog-Digital Conversion↗
PubMed1994

A force plate and display system for studying ground reaction forces in dogs.

We have developed and implemented a low cost system for measuring ground reaction forces in dogs with normal and abnormal ambulation as they walk or trot over a floor mounted plate that measures vertical and horizontal forces. Orthogonally mounted strain gages measure the forces imposed. A bridge amplifier conditions the signals which are sampled and converted to digital form for display on an operator initiated graphical user interface (GUI) which displays the forces as a function of time on the screen of a Macintosh computer. The system also allows the input of timing of the velocity of approach to the plate and the foot strike can be monitored (via tap reply) on the computer screen to verify the fidelity of the foot strike on the active surface of the plate. The data gathered on a particular strike is stored as a "raw" signal, analyzed and recorded in a spread sheet text format for later analysis.

Analog-Digital Conversion↗
PubMed1994

Preliminary impacts of PACS technology on radiology department operations.

The potential benefits of digital imaging to clinical operations focuses on both quantitative and qualitative improvements. In the future it is postulated that it will totally replace analog imaging, creating the 'filmless' Radiology department. Although this could result in dramatic savings in film costs, realization of this scenario will require continued improvements in the performance and cost of component technologies, acceptance by the medical and legal communities of the reliability of the medium, and changes in the practice and process of radiology. Baltimore VAMC has recently become one of the truly 'filmless' radiology departments through use of a leading commercial Picture Archiving and Communications System (PACS) and DHCP's Digital Imaging System. This document outlines the results of a preliminary assessment of PACS technology as it is installed at Baltimore, and its impact on operations.

Analog-Digital Conversion↗
PubMed1994

Dr. Browse, a digital image file format Browser.

The emerging widespread adoption of the Digital Imaging Communications in Medicine (DICOM) standard will increase the demand for radiologic image transfer between radiologic image acquisition, archive, display and printing devices. Unfortunately, there are and will continue to be many devices that do not and will not support this standard, especially older radiologic equipment and devices from nonradiologic vendors. Determining the image file format characteristics of images from such equipment is often difficult, and done on an ad hoc basis. We have developed a software tool that assists users in determining the image file format parameters of unknown radiologic images.

Analog-Digital Conversion↗
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↗