PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Fourier Analysis”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

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

At least 19 recordsLinked to original sources
PubMed1986

[Left ventricular wall motion abnormalities evaluated by factor analysis as compared with Fourier analysis].

Factor analysis was applied to multigated cardiac pool scintigraphy to evaluate its ability to detect left ventricular wall motion abnormalities in 35 patients with old myocardial infarction (MI), and in 12 control cases with normal left ventriculography. All cases were also evaluated by conventional Fourier analysis. In most cases with normal left ventriculography, the ventricular and atrial factors were extracted by factor analysis. In cases with MI, the third factor was obtained in the left ventricle corresponding to wall motion abnormality. Each case was scored according to the coincidence of findings of ventriculography and those of factor analysis or Fourier analysis. Scores were recorded for three items; the existence, location, and degree of asynergy. In cases of MI, the detection rate of asynergy was 94% by factor analysis, 83% by Fourier analysis, and the agreement in respect to location was 71% and 66%, respectively. Factor analysis had higher scores than Fourier analysis, but this was not significant. The interobserver error of factor analysis was less than that of Fourier analysis. Factor analysis can display locations and dynamic motion curves of asynergy, and it is regarded as a useful method for detecting and evaluating left ventricular wall motion abnormalities.

Adult↗
PubMed1990

Rapid detection of spatial pattern by Fourier analysis.

Fast Fourier transform analysis can be used to accurately and rapidly detect pattern in large two-dimensional arrangements of points, such as the locations of cells in culture or plants in a unit square. We present here a sample study of pattern in spatial random point processes. This is evidently the first time that Fourier transform-based cross-correlation techniques have been applied to the analysis of point processes of biological origin. Radial profiles of the power spectra and autocorrelation estimates revealed a nearly constant interpore distance of 0.49 +/- 0.04 mm in the locations of eccrine gland pores on the surface of human skin. Additionally, gland-free areas may exist near hair follicles.

Algorithms↗
PubMed1986

Evaluation of the response of a round hole scintillation camera collimator by the Fourier analysis method.

The Fourier analysis method was used to investigate the response of scintillation camera collimators with parallel holes. This method which takes into account the septal penetration was applied to the case of round hole collimators having a hexagonal distribution. Modulation transfer functions, MTF have been determined to verify the accuracy of the computed Fourier coefficients of the collimator function. Comparisons between the geometric and the penetrating plus geometric transfer function are shown for round and hexagonal holes.

Evaluation Studies as Topic↗
PubMed1992

[Analysis of circadian blood pressure profiles using Fourier analysis].

Blood pressure is subject to considerable circadian and situational fluctuation. In 24-h blood-pressure monitoring the severity of arterial hypertension is generally classified on the basis of the arithmetic mean of the diastolic blood pressure between 07.00 and 22.00 hours. In the present study Fourier analysis was used to generate continuous functions from the discrete blood-pressure values measured during 24-h blood-pressure monitoring in a sample of 50 normotensive persons aged from 25 to 80 years. A common reference profile was then constructed from these 50 profiles. This reference profile is characterized by the fact that the sum of the integrals over the squares of the distances between the individual profiles and the reference profile is the smallest possible. The reference profile is thus the best approximation of all normotensive profiles and practically ignores individual blood pressure fluctuations. The individual 24-h profiles of 80 patients with untreated arterial hypertension were classified on the basis of the daytime mean as mild, moderate or severe arterial hypertension and also each is described by a Fourier series. The pathological profiles were then compared with the normotensive reference profile. The comparison was made, not only with respect to the absolute pressure over 24 h, but also with respect to the circadian fluctuations in blood pressure. Comparison of the profiles shows that the Fourier analysis of 24-h blood-pressure profiles presented here permits reliable analysis and classification of arterial hypertension and can thus be used for more precise evaluation of the influence of antihypertensives on 24-h blood-pressure profiles.

Adult↗
PubMed1990

Improved detection of anterior left ventricular aneurysm with multiharmonic fourier analysis.

Single and multiharmonic Fourier analysis of LAO 30-45 degrees gated blood-pool studies were performed in a selected group of 30 patients with a left ventricular anterior aneurysm proven by contrast angiography. The sensitivity of the first harmonic phase image for the diagnosis of ventricular aneurysm was 80%. The clear phase shift (greater than 110 degrees) between the normal and the aneurysmal areas was missing in six patients. Peak acceleration images (negative maximum of the second derivative of the Fourier series) were calculated for each pixel with the analytical Fourier formula using two or three harmonics. A clear phase shift (greater than 126 degrees) than appeared in all the patients. This improvement was related to the increased weight of the second and third harmonics in the aneurysmal area when compared to control patients or to patients with dilative cardiomyopathy. Multiharmonic Fourier analysis clearly improved the sensitivity of the diagnosis of anterior left ventricular aneurysm on LAO 30 degrees-45 degrees gated blood-pool images.

Cardiomyopathy, Dilated↗
PubMed1977

Size and shape of the hominoid distal femur: fourier analysis.

A quantitative description of the shape of the distal femur is provided by Fourier analysis. Fourier analysis also facilitates the separation of the size and shape components which allows the removal of the distorting effect of size. Hence, comparisons between the hominoid groups can be based solely on shape. A sample of 91 hominoid distal femora from the Cleveland Museum of Natural History was used to make comparisons based on size and shape as well as shape only. It is suggested that unless the effect of size is minimized or removed, generally not possible with the traditional metrical approach, measures of biological distance will be distorted.

Animals↗
PubMed1992

Elliptic Fourier analysis of megakaryocyte nuclei in chronic myeloproliferative disorders.

Elliptic Fourier analysis was applied to megakaryocyte nuclei in bone marrow biopsies from 15 patients with chronic myelocytic leukemia with megakaryocyte predominance and from 15 patients with chronic megakaryocytic granulocytic myelosis. To assess the reliability of this procedure, the biopsies were evaluated also by the semiautomatic measurement of nuclear area and form factor, and both methods were compared with respect to the degree of morphologic differences obtained between these two types of chronic myeloproliferative disorders (CMPDs). Discriminant analysis revealed correct reclassification of all cases both for elliptic Fourier analysis and for semiautomatic planimetry, whereas discriminant scores were much higher for Fourier analysis. Thus, simple planimetric features such as nuclear area and form factor, in contrast to Fourier analysis, are not able to detect the full degree of morphologic differences between megakaryocyte nuclei in different CMPDs. Elliptic Fourier analysis therefore seems to be a useful procedure for the accurate description of such complicated structures as megakaryocyte nuclei in CMPD.

Analysis of Variance↗
PubMed1978

Fourier analysis of the echocardiogram.

Fourier analysis has been applied to the analysis of echocardiograms, with the result that anterior mitral leaflet waveforms have been classified in a manner which is unambiguous and which lends itself easily to present-day automated technology.

Echocardiography↗
PubMed1991

Simulated bipolar cells in fovea of human retina. V. Use of Fourier analysis to determine resolution.

Fourier analysis is used to study resolution of images processed by the matrix of simulated red-center (BCR) and green-center (BCG) bipolar cells (BC) of the human central fovea. Simulated achromatic and chromatic sine and square waves, and a two-bar stimulus are used to activate the BCs. Due to the "honeycomb" packing of the cones and BC matrices Fourier transforms are computed row by row using a one-dimensional FFT. Resolution computed by the Fourier transform is compared with the resolution index (RI), which is a method for determining resolution based on two-point discrimination in the space domain. In general the harmonic with the maximum amplitude gives the best correlation with RI for the three stimuli. Amplitudes at all spatial frequencies are enhanced by increasing the number of cycles in the sine and square wave gratings. Results with simulated BCs compare favorably with human and macaque psychophysics measuring contrast sensitivity. Square wave gratings are better than sine wave greetings for studying resolution.

Color Perception↗
PubMed1991

Fourier analysis as a planimetric procedure--application to malignant and normal urothelial cells with reactive changes.

The shape of urothelial cell nuclei in 27 urinary cytological preparations has been quantified by means of Fourier analysis. Fourier amplitudes were calculated as parameters of the nuclear shape. The T-test and a discriminance analysis showed significant differences in nuclear shape between preparations with malignant urothelial cells and nonmalignant cells with reactive changes. Only one preparation was reclassified false-negatively. No preparation was reclassified false-positively. No significant differences were found between normal cells with and without reactive changes. Thus it can be concluded that nuclear shape is an important criterion for the diagnosis of urothelial carcinomas in urinary cytological preparations. Fourier analysis allows the complete reproduction of the convex shape of a nucleus and it seems to be useful as an additional quantitative procedure in the diagnosis of malignant tumours.

Carcinoma, Transitional Cell↗
PubMedDate not supplied

Study of the peripheral blood leucocyte population by Fourier analysis of the cell volume histogram.

The Fourier transformation is proposed as a technique for the description of cell volume histogram data. In order to test the applicability of this transformation, peripheral blood leucocytes were studied as model populations and the technique assessed by determining the extent to which the Fourier coefficients could be applied as descriptors of various pathologic abnormalities of the differential leucocyte count. Histograms of leucocyte volume distribution were plotted for 87 cases with a variety of abnormalities of the peripheral blood leucocyte population. These histograms were submitted to Fourier analysis and the coefficients thus obtained were used as the basis of a multivariate classification system designed to distinguish certain predefined abnormalities of the differential count. The results obtained suggest that Fourier analysis may prove a valuable technique for the interpretation of cell volume histogram data, and its potential applications are discussed.

Cell Count↗
PubMed1991

Fourier analysis of the cerebrovascular system.

We performed Fourier analysis of the middle cerebral artery blood flow velocity waveform envelope in 14 normal subjects (group A) and 15 patients, of whom five had arteriovenous malformations (group B), five had cerebral vasospasm (group C), and five had arterial hypertension (group D). Measurements were obtained under conditions of normocapnia, hypercapnia, and hypocapnia. The Fourier coefficients measured in the first five harmonics of the Doppler waveforms of group A were used as the reference baseline and were compared with the coefficients found in the other three groups. Group B showed significantly lower Fourier coefficients, while groups C and D showed higher coefficients (p less than 0.05). The elevation of the Fourier coefficients occurred in an alternating pattern in group C and a decremental pattern in group D. This distinction was attributed to possible differences in the underlying pathophysiological processes. The degree of vascular distensibility of the cerebral arterioles, inferred from the shape of the Fourier analysis curves, was compared in all four groups. Vascular distensibility was characterized as abnormal in arteriovenous malformations, vasospasm, and arterial hypertension. Fourier coefficients may be better indicators of cerebrovascular abnormalities than mean blood flow velocity in hypertension and pulsatility index in arteriovenous malformations, vasospasm, and hypertension.

Adult↗
PubMed1990

Recognition of cell surface modulation by elliptic Fourier analysis.

A development of elliptic Fourier analysis, consisting in an alignment of harmonics according to their clockwise or counter-clockwise rotation, resolves the discrepancy between calculated harmonic frequencies and observed morphological periodicities. The new technique is supported by consistent data of empiric and fractal contours, comparatively analyzed and visualized with and without harmonic alignment. The method is particularly suitable for the recognition of periodic modulations of the cell surface. A preliminary analysis of two different cell populations (echinocytes and chondrocytes) shows distinct patterns of surface modulation that allow an effective discrimination of the cell type, while providing relevant information about the respective cytological configurations.

Algorithms↗
PubMed1986

The propagation of stochastic pixel noise into magnitude and phase values in the Fourier analysis of digital images.

The use of Fourier analysis in nuclear medicine gated blood pool ventriculography provides a useful example of the application of Fourier methods to digital medical imaging. In particular, the nuclear medicine experience demonstrates that there is diagnostic significance not only in the pixel averages of temporal Fourier magnitude and phase computed in various image regions, but also in the distributions of the individual pixel values about those averages. However, a region containing pixels that are perfectly synchronous on average would still yield a finite distribution of calculated Fourier coefficients due to the propagation of stochastic pixel noise into the calculated values. We have studied this noise component of both the magnitude and phase distributions using phantom studies and computer simulation. In both approaches, several thousand one-pixel 'ventriculograms' were generated, all identical to each other except for stochastic noise. Fourier magnitudes and phases at several frequencies were calculated and histograms generated. A theoretical prediction of the distributions was developed and shown to fit the experimental results well. Our formalism can be used to estimate study count requirements or, for fixed study counts, to assess the stochastic noise contribution in the interpretation of measured phase and magnitude distributions.

Angiocardiography↗
PubMedDate not supplied

Monitoring of cerebral perfusion during anesthesia by time-compressed Fourier analysis of the electroencephalogram.

Time-compressed Fourier analysis of the electroencephalogram has proven to be a useful analytical procedure during anesthesia and surgery which simplifies data interpretation by presenting the EEG in a time-compressed frequency domain rather than the conventional time domain. This method of data analysis graphically accentuates the electroencephalographic correlates of ischemia-induced cerebral dysfunction and other cerebral oxygen consumption abnormalities. The ability to accentuate trends in frequency and power is derived from sequential plotting of spectra to produce a graph with three dimensional axes of frequency, time, and power. In carotid endarterectomies the system has proven more useful than the conventional EEG in assessing the need for a vascular shunt to maintain internal carotid flow during endarterectomy. In open-heart surgery time-compressed EEG spectral analysis has allowed early recognition of cerebral ischemia resulting from arterial hypotension and venous hypertension. Five cases are presented which demonstrate the ability of our system to reflect developing cerebral ischemia.

Aged↗
PubMed1989

Fourier analysis of cell motility: correlation of motility with metastatic potential.

We report the development of a computerized, mathematical system for quantitating the various types of cell motility. This Fourier analysis method simultaneously quantifies for individual cells (i) temporal changes in cell shape represented by cell ruffling, undulation, and pseudopodal extension, (ii) cell translation, and (iii) average cell size and shape. This spatial-temporal Fourier analysis was tested on a series of well-characterized animal tumor cell lines of rat prostatic cancer to study in a quantitative manner the correlation of cell motility with increasing in vivo metastatic potential. Fourier motility coefficients measuring pseudopodal extension correlated best with metastatic potential in the cell lines studied. This study demonstrated that Fourier analysis provides quantitative measurement of cell motility that may be applied to the study of biological processes. This analysis should aid in the study of the motility of individual cells in various areas of cellular and tumor biology.

Adenocarcinoma↗
PubMed1985

Assessment of the site of ventricular activation by Fourier analysis of gated blood-pool studies.

We studied the use of first-harmonic Fourier analysis of gated blood-pool images to assess the site of ventricular activation in a group of 12 patients undergoing electrophysiologic pacing studies. We acquired gated blood-pool studies during pacing at up to four sites at each of two different rates. A total of 50 studies were made. At a pacing rate of 100 beats/min, when the pacing electrode was at the right-ventricular apex, 9/13 times the Fourier activation site agreed; at the right-ventricular outflow tract, 7/8; at the anterolateral left-ventricular wall, 4/4. When the Fourier activation site was at the right-ventricular apex, 9/9 times the pacing electrode was there; at the right-ventricular outflow tract, 7/10; in the left ventricle, 4/4. Fourier analysis of gated blood-pool studies can help identify the site of ventricular activation but is not sufficiently accurate to fully replace endocardial mapping.

Cardiac Pacing, Artificial↗