Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Spectrum Analysis”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 271 records · Page 15Linked to original sources
PubMed1990

[Correlation function and power spectrum analysis of auditory brainstem responses (ABR)].

Correlation function and power spectrum analyses were made for ABR of 20 normal ears and 14 ears with retrocochlear lesions. Power spectrum of normal ABR had three peaks, F0, F1 and F2; their frequencies being 125, 552.5, 967.5Hz respectively; the spectrographic shapes were of good similitude. The curve of cross correlation function in normal ABR was V-shaped, with the valley at 6-8 ms delay. In ABR of the retrocochlear lesions, the peaks of power spectrogram appeared lower and smoother with F1, F2 shifting to left and varying obviously. Their curves of cross correlation function were even and had no regular pattern. We have found that, F1 and F2 shift may be a characteristic of hearing disorder and the analysis of cross correlation function could help for the detection of useful signal from distorted signals.

Auditory Diseases, Central↗
PubMed1986

Effect of quantitated stenoses on arterial sound spectrum analysis.

Spectral analysis of carotid Doppler signals has been shown to be accurate in determining the degree of carotid artery stenosis when compared with arteriography. Since the Doppler angle and the amount of gain used during measurement may affect results, an in vitro study was performed measuring peak frequency, mode frequency, and percent window at various Doppler angles and gains to determine if these latter factors could affect results of the test. A spectrum analyzer with an 8 MHz continuous-wave Doppler probe was utilized. Seven cross-sectional area stenoses (0 to 100 percent) were applied to an undiseased bifurcated cadaver artery which was suspended in a saline bath and placed in a pulsatile circulatory system. At each stenosis, peak frequency, mode frequency, and percent window were measured at three Doppler angles (45 degrees, 60 degrees, and 75 degrees) at a constant gain and at three different gains (low, medium, and high) at a constant Doppler angle of 60 degrees. Arterial pressure was measured distal to the stenoses. Critical stenoses were present at greater than 82 percent area reduction. At a Doppler angle of 60 degrees and medium gain, correlation coefficients between percentage of stenosis and peak frequency, mode frequency, and percent window were 0.9520, 0.8369, and -0.9861, respectively. However, peak frequency and mode frequency actually decreased at stenotic areas of more than 82 percent and were similar to frequencies seen at stenotic areas of 61 percent. Peak frequency significantly decreased as Doppler angle increased, so there was an even greater overlap of peak frequency values at larger angles. Percent window did not appear to be affected by Doppler angle. At an angle of 60 degrees and different gains, there appeared to be very little overlap of percent window values between any stenoses. Peak frequency and mode frequency did not appear to be affected by gain. This study demonstrates an excellent correlation between percentage of stenosis and peak frequency and percent window. However, peak frequency was significantly affected by changes in Doppler angle and did not differentiate subcritical (61 percent) from critical (96 percent) stenoses. Percent window, however, was not significantly affected by Doppler angle or gain and was able to differentiate between all degrees of stenosis.

Arterial Occlusive Diseases↗
PubMed1990

[Computer-assisted spectrum analysis of Doppler ultrasonograms in occlusive lesions of the carotid arteries].

Efficacy of surgical treatment is related to the early diagnosis of extracranial injuries to the carotid arteries. Thirty-five patients with initial manifestations of brain circulatory failure were examined with the aid of spectral computer analysis of ultrasonograms (SCA USG). According to SCA and radiocontrast angiography, 3 grades of stenosis were distinguished: grade I--unevenness of contours, grade II--stenosis exceeding 50%, and grade III--occlusion. Based on the grades of stenosis, 7 quantitative parameters of SCA USG and significance of each parameter were analyzed with the aid of dispersion analysis. The postoperative period was characterized by positive dynamics of the quantitative parameters of SCA USG: spectral enlargement, systolic acceleration; the time of the systolic peak rise.

Adult↗
PubMedDate not supplied

Doppler power frequency spectrum analysis in the diagnosis of carotid artery disease.

Power Frequency Spectral Analysis (PFSA) which evaluates the power of the frequency components at a selected interval, was applied in this preliminary study using a 5MHz Doppler continuous wave flow velocity meter and a modified Edwards Spectraview 500 analyzer. PFSA was used to study the common, internal and external carotid arteries of ten young adult control subjects and 31 patients with angiographically documented carotid bifurcation lesions. Two useful indices are described: (1) the frequency band width at 50% of maximum power (f50%) and (2) the highest frequency recorded (fmax). An f50% wider than 1900 Hz (corresponding to spectrum broadening) identified stenoses as low as a 15% diameter reduction. An fmax higher than 6500 Hz practically always indicated a 50% or greater diameter reduction. Eighty two percent of stenoses with 11-25% diameter reduction were detected, as were 95% of stenoses from 36-50%. All stenoses from 51-99% were identified.

Angiography↗
PubMed1995

[Effects of bisoprolol and ramipril on short-term variability of systolic blood pressure during mental stress test: spectrum analysis].

UNLABELLED: The mid frequency component (MFC = 66-128 mHz) of blood pressure is an index of sympathetic vascular control. To investigate the effect of bisoprolol (B) and ramipril (R) treatment (TT) on the short-term variability of systolic blood pressure (SBP) diastolic blood pressure (DPB) and heart rate (HR) reactivity during mental stress, we studied 54 mild essential untreated hypertensive patients (24 men, 45 +/- 9.6 years, BP > 160/90 mmHg after a 15-days placebo run-in period) who were randomly assigned to double blind treatment (B: 10 mg/day: n = 28 and R: 5 mg/day: n = 26). A Stroop Word Color Conflict Test (SWCCT) was performed before and after 2 months of treatment. Hemodynamic parameters (BP and HR) were measured by a non invasive device (Finapres 2300E, Ohmeda-Maurepas) and underwent spectral analysis (SBP: mmHg.Hz-1/2, HR: beats/min.Hz-1/2, Anapres 1.2, Notocord-Orgametrie Systems, Igny-Lille) at rest and during SWCCT. The sympathetic vascular activity was assessed by calculating the area of the mid-frequency component (MFC = 66-128 Hz). RESULTS: [table: see text] CONCLUSION: The absolute variations in sympathetic activity during SWCCT as demonstrated by analysis of MFC of SBP and HR is not affected by chronic ramipril treatment, whereas bisoprolol attenuates sympathetic reactivity during SWCCT.

Adult↗
PubMed2003

Autonomic nervous dysfunction in patients with liver cirrhosis using 123I-metaiodobenzylguanidine myocardial scintigraphy and spectrum analysis of heart-rate variability.

BACKGROUND: It has been reported that nitric oxide (NO) synthase is induced in patients with liver cirrhosis (LC), and that an excessive production of NO enhances sympathetic nervous function. The present report describes a study of the feasibility of evaluation of abnormalities of autonomic nervous function by 123I-metaiodobenzylguanidine (MIBG) myocardial scintigraphy and heart-rate variability in patients with LC. METHODS: Low-frequency (LF) power, high-frequency (HF) power, LF/HF, and 1/f fluctuations of heart rate variability were examined in 50 patients with LC (LC group), and 50 normal subjects (N group). Echocardiogram, urinary nitrite and nitrate, and cathecholamines were examined. RESULTS: Fractional shortening was observed for the hyperdynamic state of patients in the LC group according to Child's A-C classification. Washout rate of MIBG, LF/HF, and blood levels of norepinephrine increased and HF power decreased with the progression of LC. However, the urinary secretion of nitrite and nitrate were significantly increased only in cirrhotic patients with Child C. CONCLUSIONS: The present results indicate that autonomic abnormalities appear early in LC, and that these abnormalities can be detected by MIBG myocardial scintigraphy and analysis of heart-rate variability. We consider these methods to be clinically useful for the quantitative detection of hyperdynamic circulation of liver cirrhosis.

3-Iodobenzylguanidine↗
PubMedDate not supplied

[Possibilities of laser-endoscopic spectrum analysis in laryngology].

This paper discusses the potential application of a laser-endoscopic spectral analyzer in fibrolaryngoscopy for early detection of neoplasms (luminescence combined with spectrophotometry) as well as for examination of the laryngeal mucosa by measuring oxygenation and blood flow in microcirculation with the aid of spectrophotometry. The results of examinations of 35 patients have shown that the laser-endoscopic spectral analyzer can be used to perform premorphological rapid tests in cancer diagnosis and to assess the efficacy of therapeutic methods.

Humans↗
PubMed1975

[The spectrum analysis of the electromyogram: the adaptation of autoregressive models to the interference electromyogram].

Power-density spectra of interference electromyograms of M. biceps brach. and triceps brach. from two subjects were estimated by the Tukey spectral window and by autoregressive series. By fitting autoregressive models parametric represeentations of spectra are obtained. The models for the electromyograms obtained from biceps (agonist) and triceps (antagonist) differed in the length of the autoregressive series. The intra-individual variation of the spectra from three time intervals of the same contraction was relatively small.

Adaptation, Physiological↗
PubMed1990

Determination of volume of vortices in poststenotic pulsatile flow by ultrasonic Doppler power ratio and spectrum analysis.

Based on the principle of ultrasonic Doppler flowmetry, a power ratio was derived from independent forward and reverse flow Doppler shift signals to measure a ratio of the volume of vortices to the total vessel volume in poststenotic separated flow. The ratio was also proportional to the ratio of the cross-sectional areas of vortices to the vessel lumen. In vitro pulsatile flow experiments were performed to test the methodology and to study flow separation and vortex shedding downstream from model stenoses. The averaged flow cross-sectional area ratio linearly correlated (r = 0.91) with the actual area reduction of the stenosis.

Carotid Artery Diseases↗
PubMed2004

[Studies on organic protective coatings for anti-atomic oxygen effects by spectrum analysis].

This paper describes organic protective coatings on space material for anti-AO effects and the experiments to assess properties of the coatings. Organic protection was analyzed after exposures to ground state fast atomic (AO) radiation in the atomic oxygen beam facility for ground simulation experiments. The tests results have been analyzed with advanced FTIR, XPS and SEM. The test indicated that epoxy, alkyd and urethane organic coatings were highly reactive to AO with a strong degradation and changed in morphology of the surface layer. It is evident that siloxane coatings have excellent properties for anti-AO effects. The erosion product has SiO2 left on the surface, thus providing protection from further attack by the energetic oxygen atoms.

Materials Testing↗
PubMedDate not supplied

[Detection of metals in human tissues by spectrum analysis].

Potentialities of spectrography experts were demonstrated to be helpful to the employees of patient-care facilities (expertise and research institutions) in solving a variety of burning issues by joint effort. Tissue samplings, hairs and daily urine were comparatively analyzed, by the example of using the low-friction hip arthroplasty by comochrome friction Protasu-21WF, for the content of microelements (ME) belonging to the hip endoprosthesis. We found that MEs (Co, Cr, Mo) are mostly discharged during the first year of endoprosthesis utilization, after which, a regular reduction of concentrations was noted. No exceeding norms were registered in any cases, which denotes a minimal wear of the friction pair.

Alloys↗
PubMed1989

Frequency spectrum analysis of wrist motion for activities of daily living.

A frequency spectral analysis was performed on wrist motion data for 24 activities of daily living (ADLs). Wrist motion was measured using a triaxial electrogoniometer attached to the wrist using tape (for 12 subjects) and pins (for one subject). Results show that the average predominant frequency component of these ADLs was approximately 1 Hz with 75% of the spectral energy less than 5 Hz. The taped-on electrogoniometer, when compared with the pinned electrogoniometer, was adequate for calculating the predominant frequency component and spread of spectral data, but overestimated the magnitudes of the maximum spectral density and total area of the spectral curves. This discrepancy was largest for axial rotation.

Activities of Daily Living↗
PubMed1991

[Value of spectrum analysis of the ultrasonic Doppler signal in the diagnosis of occlusive diseases of the carotid arteries].

Spectral analysis of the ultrasound Doppler's signal (SA UDS) was used to examine 216 patients with occlusive lesions of the carotid arteries followed by correlation of the data obtained to the carotid angiography data. Based on the doppler-angiographic correlations, diagnostic criteria for SA UDS were elaborated. It has been demonstrated that Amax is the most significant criterion, the increase of which by over 3.2 kHz points to the development of ICA stenosis. The magnitude of that characteristic exceeding 6.0 kHz indicates that ICA stenosis reaches more than 50%. The significance of SA UDS in ICA stenoses up to 50% amounted to 81.8%, in stenoses over 50%, it was 98.6%. In ICA occlusion the significance of the method was 99%.

Adult↗