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At least 109 records · Page 6Linked to original sources
PubMed1991

[Spectrum analysis of heart rate. A method of studying the role of the autonomic nervous system in the regulation of blood circulation].

Spectral analysis of heart rate variability has recently been shown to be a reliable noninvasive test for quantitative assessment of cardiovascular automatic regulatory responses. In 12 ambulant normotensive healthy young males (mean age 23 +/- 1 years) after a period of 10 min. for stabilisation, a continuous ecg recording (lead CM-5) for 8 min. was obtained in the supine and standing position, with a controlled respiration rate 15/min. Power spectrum of 512 point time series (R-R intervals) in both positions was calculated using a fast Fourier transform-based window periodogram method. Based upon results from the literature the power spectrum analysis was performed on two components: low frequency LF (0.05-0.15 Hz) and high frequency HF (0.15-0.50 Hz). Mean R-R interval decreased on standing position from 0.79 +/- 0.10 s to 0.59 +/- 0.11 s (p less than 0.001). The ratio HF/LF in supine was 0.63 +/- 0.70 and on standing position 2.54 +/- 0.73 (p less than 0.001). The relative LF component of the total HR power spectrum increased from 22.8% +/- 12.1% to 42.9 +/- 14.4% (p less than 0.001) after changing the position from supine to standing, and the relative HF component decreased from 56.3 +/- 22.4% to 25.5 +/- 16.2 (p less than 0.001). The total power was significantly lower when standing in comparison to supine position (681 +/- 519 s2, 1188 +/- 963 s2 respectively, p less than 0.05). Our results suggest that heart rate fluctuations in supine position in normal men are mainly vagally determined (HF power spectrum component).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Interaction between sleep and growth hormone. Evaluated by manual polysomnography and automatic power spectrum analysis.

The relation between nightly growth hormone (GH) secretion and sleep is poorly understood. To examine whether disturbances in GH secretion are reflected in abnormal sleep patterns 8 subjects with isolated GH deficiency and 9 subjects with excess of GH (acromegalics) underwent all night sleep studies, polysomnography. Moreover, the effect of correcting GH concentration on sleep patterns were examined in the same subjects. The results showed that all subjects with GH disturbances had abnormal REM and delta sleep and normalization of GH concentration was followed by correction of the sleep stages. By power spectrum analysis of the sleep EEG it was showed that during low GH concentration the sleep energy was low, and high GH concentration was associated with high sleep energy, and correction of abnormal plasma GH levels resulted in normalization of REM and delta sleep energy per time unit.

Adult↗
PubMed1998

Imaging and spectrum analysis of contrast agents in the in vivo rabbit eye using very-high-frequency ultrasound.

We have conducted initial studies that demonstrated the feasibility of employing ultrasonic contrast agents with very-high-frequency ultrasound (VHFU), using wideband transducers with center frequencies near 40 MHz. These studies were undertaken with an ultimate objective of quantifying perfusion in vessels in the eye and other organs. We expanded the model developed by Lizzi et al. (1983) to incorporate the scattering characteristics from encapsulated bubbles, such as contrast agents. Our analysis shows how the spectral slopes and intercepts measured from contrast agents are related to factors that include the radii and concentration of contrast-agent particles. We conducted in vitro experiments to validate the theoretical predictions and obtained excellent agreement. We obtained in vivo VHFU data from the eyes of anesthetized rabbits before and after injection of Albunex and Aerosomes. Digitally computed B-mode images demonstrated echo enhancement within the ciliary body and its processes. The magnitudes of these enhancements were quantified using calibrated spectrum-analysis techniques.

Albumins↗
PubMed2001

Power spectrum analysis of heart rate and blood flow velocity variability measured in the umbilical and uterine arteries in early pregnancy: a comparative study.

OBJECTIVE: To compare power spectral derived variability parameters from the fetal side of the placental circulation with those from the maternal side of the placental circulation, during early pregnancy. METHODS: Doppler velocity waveforms were obtained from both the umbilical and the uterine arteries in a study group of 40 pregnant women between 10 and 14 (n = 25) and 15 and 20 (n = 15) weeks of gestation. The coefficient of variation of both the beat-to-beat heart rate variability and the blood flow velocity variability was determined. The ratio of the integrated low-frequency components (< 0.2 Hz) and the integrated high-frequency components (> 0.2 Hz) from normalized power spectrum analysis (LH-ratio) was established, to reflect sympathovagal balance. RESULTS: The coefficient of variation and LH-ratio of fetal heart rate variability constitute only a fraction of the same maternal heart rate variability parameters. Nevertheless a highly significant increase (P < 0.001) in LH-ratio was demonstrated with advancing gestational age. The coefficient of variation and LH-ratio of blood flow velocity variability were significantly lower in the fetal umbilical artery only in the 10-14-weeks' gestation group. Due to a decrease of the maternal uterine blood flow velocity variability parameters with advancing gestational age, statistically equal fetal and maternal values for coefficient of variation and LH-ratio were found in the 15-20 weeks' gestation group. CONCLUSIONS: The increase in LH-ratio of fetal heart rate variability indicates functional development of the fetal autonomic nervous system at 15-20 weeks' gestation. The umbilical blood flow velocity variability may be secondary to maternal uterine arterial flow variability rather than due to primary changes in fetal cardiovascular function.

Blood Flow Velocity↗
PubMed1997

[Studies on all-spectrum analysis for X-ray diffraction of Chinese herbal medicine calculus bovis].

Investigation on famouse Chinese herbal medicine-Niu huang (calculus bovis) was carried out by all-spectrum X-ray diffraction analysis. Diffraction spectrums, as well as the specific symboling peaks of calculus bovis, artificial bezoar, bile ductstone, human gallstone and hog gallstone, were recognized. The error distribution curves of d-delta d for specific symboling peaks was also obtained by calculation under diffrent testing conditions, by which we identified successfully three samples provided by a pharmaceutical factory. This article shows that all-spectrum X-ray diffraction analysis can be used to identify Chinese traditional crude drug, and provides for morphological and microscopical study.

Animals↗
PubMedDate not supplied

[Determination of the value of spectrum analysis of the Doppler signal in the assessment of the carotid artery bifurcation].

A prospective trial was set up in 100 patients, who underwent arteriography of the cerebropetal and cerebral arteries, to determine the value of the direct examination of the Carotid arteries using a continuous wave bidirectionnal Doppler with spectrum frequency analysis. The results of this non-invasive direct technique are compared with the biplane arteriography and with the indirect noninvasive oculoplethysmography (OPG-Gee). The conclusions of this study are that the direct Doppler examination with spectrum frequency-analysis is a very good tool in detecting lesions in the Carotid arteries, and is superior to the indirect OPG-Gee examination, especially in stenoses of 30-69%.

Angiography↗
PubMed1991

Validity of catheter-tip Doppler technique in assessment of coronary flow velocity and application of spectrum analysis method.

Measurement of coronary flow velocity in clinical cases contributes to understanding the pathophysiology of coronary circulation. To determine absolute coronary flow velocity, coronary blood flow was assessed with an end-mounted Doppler catheter (3Fr, 20 MHz), which was combined with a custom-designed fast-Fourier transformation analysis system. In vitro study using model circuit, actual flow velocity (8 to 96 cm/s) was well correlated with that determined by this catheter system (y = 1.01 X +1.5, r = 0.988). In a clinical study of 12 patients with normal coronary arteriograms, the Doppler catheter was positioned at the proximal left anterior descending artery. Clear flow velocity patterns, which consisted of predominant diastolic components and preceding small systolic components, were obtained in all cases. The peak flow velocity was 17 +/- 8 cm/s (mean +/- standard deviation) during systole and 44 +/- 12 cm/s during diastole in this portion. In 5 patients, the great cardiac vein flow, which reflects the left anterior descending artery flow, was simultaneously measured during rapid atrial pacing. During pacing, percent increases in flow velocity were well correlated with those in great cardiac vein flow (y = 0.90 x +6.4, r = 0.935). These results indicate that catheter-tip Doppler technique with fast-Fourier transformation analysis may be useful in quantitatively determining coronary flow velocity in clinical cases.

Aged↗
PubMedDate not supplied

[Detection and quantification of carotid atheroma. Respective value of vascular ultrasonography, spectrum analysis and digital intravenous angiography].

This retrospective study involved 37 subjects who were examined by means of intravenous digitalised angiography, vascular ultrasonography and spectral analysis of the Doppler signal. The last two examinations were found to give the most precise images and functional information. The concordances between angiography and ultrasonography on the one hand and spectral analysis on the other were 82 and 90 per cent. The authors have established a protocol in order to limit and systematize these examinations during screening for carotid atheroma: the risk factors are weighted; a score is obtained by summation; depending on the value of this score and the patient's age, the investigation procedure is pursued or not. The sequence always consists of ultrasonography followed by spectral analysis when plaque is detected and by angiography when the plaque is stenotic or ulcerated. In symptomatic patients, ultrasonography and digitalised angiography are performed routinely.

Arteriosclerosis↗
PubMedDate not supplied

Regression of uveal malignant melanomas following cobalt-60 plaque. Correlates between acoustic spectrum analysis and tumor regression.

Parameters derived from computer analysis of digital radio-frequency (rf) ultrasound scan data of untreated uveal malignant melanomas were examined for correlations with tumor regression following cobalt-60 plaque. Parameters included tumor height, normalized power spectrum and acoustic tissue type (ATT). Acoustic tissue type was based upon discriminant analysis of tumor power spectra, with spectra of tumors of known pathology serving as a model. Results showed ATT to be correlated with tumor regression during the first 18 months following treatment. Tumors with ATT associated with spindle cell malignant melanoma showed over twice the percentage reduction in height as those with ATT associated with mixed/epithelioid melanomas. Pre-treatment height was only weakly correlated with regression. Additionally, significant spectral changes were observed following treatment. Ultrasonic spectrum analysis thus provides a noninvasive tool for classification, prediction and monitoring of tumor response to cobalt-60 plaque.

Cobalt Radioisotopes↗