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At least 19 recordsLinked to original sources
PubMed1985

Classification of carotid bifurcation disease using quantitative Doppler spectrum analysis.

Spectrum analysis of continuous-wave Doppler recordings from the region of the carotid bifurcation was used to classify the degree of stenosis in the internal (ICA) and external (ECA) carotid arteries. Measurements of systolic peak frequency, end-diastolic frequency, and the degree of spectral broadening were used to define five ICA disease categories: 0% to 15% diameter reduction (DR), 16% to 49% DR, 50% to 80% DR, greater than 80% DR, and occlusion. The results were compared to contrast arteriography in 122 patients (243 arteries). The agreement with angiography in classifying ICA stenosis was 82%. Doppler spectrum analysis identified 96% of hemodynamically significant disease (greater than 50% DR) in the ICA and ECA and 97% of ICA occlusions. Attention to the common carotid artery waveform and the ICA diastolic frequency improved the accuracy of predicting greater than 80% DR and occlusion of the ICA. Noninvasive classification of carotid bifurcation disease is useful in clinical decision making to select the angiographic technique most likely to accurately define disease morphology and to follow up patients for disease progression.

Aged↗
PubMed1988

Shear-layer detection in poststenotic flow by spectrum analysis of Doppler signals.

Spectrum analysis of the Doppler signals was performed 0.5 tube diameters downstream from an axisymmetric constriction with an area reduction of 80 percent in steady flow at a jet Reynolds number of 2840. Both pulsed and continuous wave (CW) Doppler spectra showed significant reverse flow components in the separated flow. The pulsed Doppler spectra exhibited sudden changes when the sample volume crossed the shear layer between the center jet and the separated flow. A power spectrum equation was theoretically derived from continuity of flow to define the Doppler shift frequency for the shear layer velocity. The CW Doppler spectrum showed a minimum spectrum density at a frequency which equalled the shear layer Doppler shift frequency derived from the equation. The pulsed spectra exhibited the sudden changes at the same frequency as well.

Blood Flow Velocity↗
PubMed1991

Evoked otoacoustic emissions: correlates between spectrum analysis and audiogram.

Correlations between spectrum analysis of evoked otoacoustic emissions (EOAEs) and hearing losses have been calculated in 150 patients with pure sensorineural hearing loss. Significant correlations were found. The greater the high-frequency spectral components of the EOAE, the better the high-frequency hearing. However the relationship is complex, and it does not seem possible to establish an audiogram knowing only the spectrum analysis of EOAEs.

Adult↗
PubMed1986

Relative accuracy of the diagnostic components of noninvasive carotid arterial tests: a comparison of pulsed Doppler arteriography and spectrum analysis.

Pulsed Doppler ultrasonography (UA), sound spectrum analysis, and subjective interpretation of the audible signal are valuable methods for assessing carotid arterial disease; however, the relative contribution of each in making a diagnosis is disputed. To investigate this issue, 258 noninvasive carotid studies with measured x-ray comparisons were reviewed. Internal carotid spectra, UA images, and images combined with the technician's comments were each interpreted blindly by three independent readers. Percentage of stenosis was categorized into six groups: 0, 1% to 24%, 25% to 49%, 50% to 74%, 75% to 99%, and 100%. Each reader's assessment of the individual noninvasive components and his overall reading of the complete study were compared with x-ray findings and with those of the other two readers. The readings of the three observers were consistent within each diagnostic component (p less than 0.001). For each reader, the technician's comments significantly improved the accuracy of ultrasonic imaging alone (p less than 0.001). Spectrum analysis was as good as the image plus technician's comments and, for two of three readers, was better than the image alone (p less than 0.001).

Angiography↗
PubMed1990

[Spectrum analysis of Doppler signals].

Doppler signal spectrum analysis contains useful haemodynamic information. Several parameters of the spectrum can be documented in numerics. Random interaction of the reflectors, the size of the ultrasound sample volume and the procedure of signal analysis influence the results and hence may cause misinterpretation of the data selected. Essential mechanisms influencing the clinician's Doppler-spectrum-analysis are discussed on the basis of a series of 59 angiographically and sonographically examined carotid arteries as well as in the light of theoretical considerations and a review of the literature. Peak frequency linked with a battery of spectrum parameters accuracy are useful to differentiate various degrees of lumen narrowing. Identification or exclusion of minor plaques cannot be achieved with sufficient sensitivity and specificity.

Carotid Arteries↗
PubMedDate not supplied

Electroencephalographic power spectrum analysis as a monitor of anesthetic depth in horses.

Electroencephalographic (EEG) power spectrum analysis was performed in 18 conscious, adult horses for evaluation as control values for EEG data obtained during anesthesia. Computer-processed total amplitudes for the frequency range 0 to 32 Hz were mainly between 400 and 600 microV, with 80% spectral edge frequency between 16.6 and 32.5 Hz. The highest electrical activity was in the delta band (41.3 +/- 4.4% of total amplitude); there was a less pronounced activity in the beta (34.2 +/- 5.2%), theta (13.6 +/- 1.5%), and alpha (10.0 +/- 1.0%) bands. The applicability of EEG power spectrum analysis as a guide to depth of anesthesia was evaluated in four horses by comparing simultaneously recorded EEG data and clinical signs of anesthesia. Global changes in cerebrocortical electrical activity were detected with a single, monopolar (left frontoatlanto-occipital) EEG lead. Increasing depth of halothane anesthesia was accompanied by a pronounced shift in EEG activity from beta to theta and delta frequency bands, a decrease in 80% spectral edge frequency from 21.5 +/- 2.4 Hz to 12.6 +/- 2.2 Hz, a reduction in the beta/delta ratio of fractional amplitudes from 2.37 +/- 0.84 to 0.49 +/- 0.04, and a slight inconsistent increase in total amplitude from 96.1 +/- 37.3 microV to 185.5 +/- 53 microV. These results show that changes in the clinical signs of anesthetic depth in horses can be described numerically by use of EEG power spectrum analysis.

Anesthesia, General↗
PubMed1990

A spatial power spectrum analysis of the electroencephalogram.

The method of spatial power-spectrum analysis has been applied to measurements of the distribution of rms alpha-band potential on the scalp. Data was recorded using the 31-Electrode System and spatial power-spectrum estimates (PSEs) were obtained from Mercator projections of the potential interpolated using the triangular method. PSEs were calculated using the Lim and Malik algorithm for maximum-entropy power-spectrum estimation. In order to investigate the utility of spatial power-spectrum analysis, PSEs were obtained from subjects in two conditions; resting with eyes closed (EC) and resting with eyes open and fixed on a single point (EO). A stepwise discriminant analysis was performed with features from the PSEs and the resultant discriminant function was applied to data not considered in the formulation of the function. Over 92% of test data was correctly classified. The features used in the discriminant function identify spatial waves which are most useful in separating data. The results demonstrate that waves oriented along front-back and right-left lines are most important in separating data into EC and EO groups.

Brain↗
PubMed1985

Doppler frequency spectrum analysis and digital subtraction angiography in carotid artery disease.

The aim of the study was to evaluate the diagnostic accuracy of frequency spectrum analysis complementary to direct Doppler sonography in comparison to conventional biplane arteriography and transvenous digital subtraction angiography in internal carotid artery stenosis. In a group consisting of 229 carotid arteries visualized by conventional biplane arteriography, Doppler frequency spectrum analysis had a specificity of 97% and concerning all stenoses and occlusions, a sensitivity of 89%. In a second group consisting of 198 carotid arteries imaged by transvenous digital subtraction angiography, Doppler sonographic examination had a specificity of 65% only, and concerning all categories of stenoses and occlusions a sensitivity of 85%. These differences concerning specificity are not interpreted as false positive diagnoses in Doppler spectrum analysis but are considered to be due to false negative findings of digital subtraction angiography in stenoses of less than 50% vessel diameter reduction.

Carotid Artery Diseases↗
PubMed1987

Power spectrum analysis in the study of ocular mechanisms.

The use of power-spectrum analysis in the study of ocular dynamics is becoming increasingly widespread. This paper summarizes the key points of signal acquisition and power-spectrum analysis, emphasizing aspects which we have found to be of relevance when the technique is applied to experiments in binocular accommodation. The considerations and conclusions are relevant to other areas of investigation into ocular dynamics and similar biological systems.

Accommodation, Ocular↗
PubMed1985

Toward quantification of athetotic movements by frequency spectrum analysis.

The frequency spectrum of the elbow movements of one normal subject and six handicapped subjects were obtained in order to investigate the possibility of using this technique in quantifying athetosis. The frequency spectrum technique appears to be useful but data from more subjects must be obtained and specific details regarding scaling need to be investigated.

Adolescent↗
PubMedDate not supplied

Direct and indirect evaluation of lesions obstructing the carotid bifurcation. A comparison of Doppler spectrum analysis with angiography.

The diagnostic accuracy of real-time continuous wave (c.w.) Doppler spectrum analysis and of indirect periorbital Doppler examination for detecting carotid bifurcation disease was evaluated. The results of non-invasive studies were compared with contrast arteriograms of patients studied for symptomatic cerebrovascular disease (91%) or for asymptomatic bruits (9%). Periorbital examination was insensitive to less than 75% carotid stenoses and sensitivity to severe stenoses or occlusions was respectively 56% and 85% (mean 73%). Mean sensitivity of real-time C.W. Doppler spectrum was 93% and sensitivity to stenoses of less than 45% diameter reduction was equal to 76%, while specificity in identifying normal carotid arteries was 89% for an accuracy of the method of 91%. Positive and negative predicting values were respectively 89% and 93%. Direct Doppler interrogation of the carotid arteries with real-time C.W. Doppler spectrum analysis was able to distinguish operable stenoses from inoperable occlusions in 87% of the cases.

Angiography↗
PubMedDate not supplied

Chloral hydrate anesthesia: EEG power spectrum analysis and effects on VEPs in the rat.

This paper describes the use of EEG power spectrum analysis as a tool in identifying and controlling the state of an animal, a major source of variability in evoked potential (EP) data. Also described is a procedure of anesthetic administration combined with on-line EEG power spectrum analysis that permits an animal to be maintained in a stable, moderately anesthetized state during which VEP's are qualitatively comparable to those seen in the unanesthetized animal. Anesthesia level in acute preparations was varied by IV injections of chloral hydrate, and the EEG and light-flash VEP's were recorded from visual cortex. Under deep anesthesia, EEG activity was concentrated in the 0.1 Hz to 3 Hz band with very little contribution from frequencies higher than 10 Hz. After this period of deep anesthesia, EEG frequency distribution became bimodal with peaks in the 0.1-3 Hz and 5-7 Hz ranges, and a minor frequency band between 10 and 30 Hz. This moderate anesthetic state persisted for about 30 min. Two distinct forms of VEP's were highly correlated with these EEG frequency distributions. VEP's associated with the moderate anesthetic state were comparable to those reported from awake, chronic preparations. In VEP's associated with deep anesthesia, negative components were greatly attenuated or entirely absent; amplitudes of the positive components were increased as were the latencies of all components.

Animals↗
PubMed1987

Effect of epoch length on power spectrum analysis of the EEG.

To study the effect of epoch length on the variability of power spectrum analysis of the EEG, 22 64-s segments of EEG were analyzed using epoch lengths of 2, 4, 8, 16, and 32 s. Nine of these segments exemplified EEG changes during transient anesthetic states or surgical conditions. Epoch-to-epoch variability was computed within frequency bins for all segments, and ANOVA with hierarchal classification was used to determine the length of the EEG segment necessary to identify a statistically significant change in those EEG segments recorded during changing conditions. In 16 segments, the epoch-to-epoch variability with power spectra were computed using 2-s epochs was significantly less than the variability when power spectra were computed using longer epoch lengths. In five segments, no significant difference existed between the variance at 2-s epochs and longer (4-s) epochs. In one case, an EEG containing a burst-suppression pattern, the variability was significantly increased when 2-s epochs were used. Analysis using 2-s epochs also identified changes more rapidly than analysis using any longer epoch length in eight of nine segments, and the differences were clinically significant as well (over 30 s faster when 2-s epochs were used instead of 16-s epochs). These findings suggest the preferability of short epoch lengths when power spectrum analysis is used for intraoperative EEG monitoring.

Analysis of Variance↗
PubMed1979

Detection of carotid occlusive disease by ultrasonic imaging and pulsed Doppler spectrum analysis.

Ultrasonic imaging of the cervical carotid arteries by ultrasonic arteriography and duplex scanning combined with pulsed Doppler spectrum analysis were investigated in a series of patients undergoing arteriography. By using the ultrasonic image as a guide for precise placement of the pulsed Doppler sample volume, the characteristics of blood flow at points of interest in the carotid arteries could be determined. Audible analysis of the Doppler signal permitted correct diagnosis of 23 of 26 (88%) high-grade stenoses or occlusions with ultrasonic arteriography and 24 of 26 (92%) with duplex scanning. Spectrum analysis of Doppler signals obtained with the duplex scanner detected all of the 22 high-grade stenoses. Spectral abnormalities of a lesser degree also were detected in 18 of 23 vessels (78%) with atherosclerotic plaques which should not have reduced cerebral blood flow. These techniques permit the accurate detection of and the distinction between high-grade stenoses and occlusion, as well as the identification of many plaques which are not large enough to affect intracranial hemodynamics.

Arterial Occlusive Diseases↗
PubMed1989

Electrophysiological characterization of human subcortical structures by frequency spectrum analysis of neural noise (field potential) obtained during stereotactic surgery. Preliminary presentation of frequency power spectrum of various subcortical structures.

Neural noise, or field potential, was recorded during stereotactic thalamotomy in 46 cases of various involuntary movement disorders. Frequency power spectrum analysis of neural noise from various anatomical substrates was performed, and the relationship between resultant frequency power spectrum and anatomical substrates, as defined by Schaltenbrand-Bailey's atlas, was examined. Frequency power spectrum was fairly characteristic for each subcortical structure.

Brain↗
PubMed1991

Intraoperative Doppler spectrum analysis of blood flow in the internal mammary artery used for myocardial revascularization.

Intraoperative Doppler-derived measurements of blood flow velocity were used to characterize the hemodynamics in 6 internal mammary artery grafts before and after anastomosis to the left anterior descending artery. Pulsed Doppler spectrum analysis demonstrated a change from a systolic to a predominantly diastolic flow pattern. The presented technique is a valuable aid to differentiate intraoperatively between normal and low flow states in the internal mammary artery. In addition, this study serve as a pilot study to investigate the clinical applicability of Doppler spectrum analysis in the functional assessment of the internal mammary artery in the pre- and postoperative stages of myocardial revascularization.

Aged↗