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At least 55 records · Page 3Linked to original sources
PubMed1997

Doppler spectrum analysis versus direct femoral artery pressure measurement for rapid assessment of aortoiliac obstruction.

Adequate patient selection is required to limit the clinical workload and improve the cost-effectiveness of noninvasive hemodynamic evaluation of the aortoiliac system. In a prospective blinded fashion the traditional invasive technique of direct femoral artery pressure measurements and the computerized Doppler spectrum analysis of blood flow velocities in the common femoral artery were studied. Both tests for rapid assessment of aortoiliac obstruction were compared with duplex ultrasonographic imaging, using a peak systolic velocity ratio of 2.5 to demonstrate stenoses of 50% or more. In a series of 17 consecutive patients (34 aortoiliac segments) with suspected aortoiliac obstructive disease, a good level of agreement (kappa = 0.6) was found for both methods when compared with duplex scanning. Analysis of deviations from the duplex registrations indicated an overestimation of the pathologic cases using femoral artery pressure measurements and an underestimation using Doppler spectrum analysis of blood flow velocities in the common femoral artery. Both methods were well tolerated, but femoral artery pressure measurements had a higher technical failure rate. Because of its noninvasive character and its feasibility the Doppler technique is preferred for the selection of patients for more extensive duplex sonographic investigation.

Aortic Diseases↗
PubMedDate not supplied

[Compression spectrum analysis of the EEG in severe cranio-cerebral trauma].

Analysis of the quantitative values of compression spectrum analysis (CSA) of the EEG obtained in 53 examinations of 21 patients with severe craniocerebral trauma on the basis of multidimensional statistical and factor analysis made it possible to reveal signs which correlated best with the clinical data. Spatial and time characteristics of CSA, the variability of standardized capacities according to the ranges of physiological rhythms in particular, proved to be most informative as regards the prognosis.

Adult↗
PubMed1998

In vitro diagnosis of axillary lymph node metastases in breast cancer by spectrum analysis of radio frequency echo signals.

Axillary lymph node status is of particular importance for staging and managing breast cancer. Currently, axillary lymph node dissection is performed routinely in cases of invasive breast cancer because of the lack of accurate noninvasive methods for diagnosing lymph node metastasis. We investigated the diagnostic ability of ultrasonic tissue characterization based on spectrum analysis of backscattered echo signals to detect axillary lymph node metastasis in breast cancer in vitro compared with in vitro B-mode imaging. Immediately after surgery, individual lymph nodes were isolated from axillary tissue. Each lymph node was scanned in a water bath using a 10-MHz instrument, and radio frequency data and B-mode images were acquired. Spectral parameter values were calculated, and discriminant analysis was performed to classify metastatic and nonmetastatic lymph nodes. Forty histologically characterized axillary lymph nodes were enrolled in this study, including 25 nonmetastatic and 15 metastatic lymph nodes. A significant difference existed in the spectral parameter values (slope and intercept) for metastatic and nonmetastatic lymph nodes. Spectral parameter-based discriminant function classification of metastatic vs. nonmetastatic lymph nodes provided a sensitivity of 93.3%, specificity of 92.0%, and overall accuracy of 92.5%. In comparison, B-mode ultrasound images of in vitro lymph nodes provided a sensitivity of 73.3%, specificity of 84.0%, and overall accuracy of 80.0%. Receiver operating characteristic (ROC) analysis comparing the efficacy of both methods gave an ROC curve area of 0.9888 for spectral methods, which was greater than the area of 0.8980 for B-mode ultrasound. Hence, this in vitro study suggests that the diagnostic ability of spectrum analysis may prove to be markedly superior to that of B-mode ultrasound in detecting axillary lymph node metastasis in breast cancer. Because of these encouraging results, we intend to conduct an investigation of the ability of spectral methods to classify metastatic axillary lymph nodes in vivo.

Adult↗
PubMed1992

[Autonomic function and severity of hypertrophic cardiomyopathy by power spectrum analysis on heart rate variability].

To examine the relation of autonomic function and severity of hypertrophic cardiomyopathy (HCM) with and without ventricular tachycardia (VT) and poor blood pressure response on Treadmill exercise, 30 patients with HCM and 10 healthy controls were selected. Autonomic function was assessed by heart rate variability (HRV) on 24hr-Holter monitoring. The power spectrum analysis was classified into LF component, HF component and ratio of LF/HF. (1) Night time HF and LF decreased, and LF/HF increased in HCM compared with healthy controls. (2) HF decreased more in HCM with VT. (3) LF/HF also decreased in HCM with poor blood pressure response on exercise. These results suggest that autonomic function may be altered in HCM, and severity of HCM proved to be able to be assessed by power spectrum analysis of HRV.

Autonomic Nervous System↗
PubMed1992

Relationship of age to power spectrum analysis of EEG during sleep.

We describe a method of power spectrum analysis of all-night sleep EEGs in 20 normal subjects aged 18-43 years. The analysis calculates the energy of the whole sleep period, the various frequency bands, and selected sleep stages automatically. The numerical value of the energies was directly comparable between subjects, presented in numbers (microV2s) and displayed as a color density spectral array with fixed power values for each color. A significant relationship between age and power spectra was found, in that total energy/minute was higher in younger subjects than in older. The energy in delta sleep/minute also showed an inverse relationship with age.

Adolescent↗
PubMed1997

Chaos theory and power spectrum analysis in computerized cardiotocography.

Power spectrum and chaos theory analysis, methods recently applied to fetal surveillance, may offer an effective tool for recognising fetal hypoxia and consequential collapse of fetal homeostasis earlier than at present. However, strict continuity and high precision of input data is an indispensable prerequisite. If one overlooks this requirement the results may be misleading. The aim of the present work was to find a method that provides strictly continuous and highly precise beat-to-beat FHR data values. It was found that only the determination of heart beat intervals between successive R peaks, using the digital FECG recording technique developed here, meets the necessary requirements for power spectrum and chaos theory analysis.

Cardiotocography↗
PubMed1990

Power spectrum analysis of fetal heart rate variability using the abdominal maternal electrocardiogram.

A signal analysis procedure is described for obtaining the power spectrum of the fetal and maternal heart rates as recorded from the abdomen. This technique, which includes the subtraction of an averaged maternal ECG waveform using a cross-correlation function and the fast Fourier transform algorithm, enables the detection of all the fetal QRS complexes in spite of their coincidence with the maternal ECGs. The power spectrum of the fetal heart rates (FHR) obtained from 15 women at 32-41 weeks gestation were studied and two indices were measured which are related to the long term and short term variabilities in the FHR signal. It was found that quantitative evaluation of the FHR variability can be obtained using power spectrum analysis.

Adult↗
PubMed1989

Evaluation of renal allograft function by Doppler spectrum analysis. A preliminary study.

A decreased renal function is rather common after renal transplantation. The causes of this decreased function are diverse and difficult to differentiate. Yet, duplex examination, and especially quantitative Doppler spectrum analysis of the blood velocities in the renal artery, may be an effective method for differentiating between some of these causes. Forty-five renal transplant recipients were included in this preliminary study. Doppler spectra were recorded from the renal artery to the allograft. Parameters were derived from every Doppler spectrum in order to characterize each spectrum. Renal allograft function was evaluated on the basis of a number of clinical parameters. A significant correlation was found between the clinical parameters and the Doppler spectrum parameters indicative for changes in the peripheral resistance. Patients with a normal renal allograft function showed Doppler spectra with a high diastolic flow, typical of a vascular bed with a low peripheral resistance. Patients with a decreased renal allograft function caused by a stenosis in the renal artery could be distinguished by a low peak velocity and a low pulsatility index. A decreased allograft function caused by allograft rejection or cyclosporin nephrotoxicity also led to characteristic arterial flow disturbances. In these cases, the peripheral resistance was increased, and this was primarily reflected in a decrease in the diastolic blood velocity. We conclude that quantitative analysis of the blood velocities in the renal artery by Doppler spectrum analysis seems to be a useful, noninvasive diagnostic tool that discriminates between some of the causes of a decreased renal allograft function.

Adolescent↗
PubMed1993

Transadventitial localisation of atheromatous plaques by fluorescence emission spectrum analysis of mono-L-aspartyl chlorin e6.

OBJECTIVE: The aim was to demonstrate specific detection of the fluorescence spectra of mono-L-aspartyl chlorin e6 (NPe6) emitted from atherosclerotic arterial lesions using an extravascular approach. METHODS: Cholesterol fed atherosclerotic rabbits were injected intravenously with 0.5 mg.kg-1 of NPe6. A fluorescence spectrum analysis system with a dual real time imaging system and a flexible endoscopic catheter was used. The pulsed excimer dye laser excited the photosensitiser. The fluorescence spectra were measured by a fluorescence spectrophotometer. RESULTS: Analysis of fluorescence spectra detected from outside the adventitia showed that a fluorescence spectrum peak at 675 nm was obtained only in parts of the artery with an atheromatous plaque; however, no fluorescence could be shown in aortic segments free of atheroma. It was also noted that the intensity of the specific peak of the spectrum detected from outside a vessel was closely related to the depth of atheromatous lesions, as determined by histological analysis. An in vivo study revealed good correlation between the peak intensity (which could vary with the amount of NPe6 accumulated in the tissue) measured laparoscopically from outside the abdominal aorta and the peak intensity measured angioscopically from inside the abdominal aorta. CONCLUSIONS: It is possible to detect atheroma from outside a vessel by fluorescence spectrum analysis employing NPe6 as the probe.

Animals↗
PubMed1996

Method for single-trial readiness potential identification, based on singular spectrum analysis.

This paper presents a brief description and the advantages of the singular spectrum analysis (SSA). SSA has recently been recommended for analysis of short, noisy time series. The method was applied to single trials of EEG activity at Cz, Fz, C4, Pz and C3, recorded 3.6 s prior to and 1.2 s after the onset of a voluntary motor act. This specific activity is known in its averaged form as readiness potential (RP) and is considered to reflect the preparation of the voluntary movement. However, some physiological investigations require identification of the parameters of single-trial RPs-their onset and successive phases. SSA is based on analysis of the principal components in vector space of delay coordinates of time series. As a result, SSA algorithm decomposes real data records to components reflecting the trend, alpha and beta frequency bands, respectively, whose oscillations appear or disappear in different time instants. The latter were interpreted to distinguish different dynamical stages of the movement preparatory process.

Adult↗
PubMed1985

Vasculogenic impotence evaluated by high-resolution ultrasonography and pulsed Doppler spectrum analysis.

Vasculogenic impotence was evaluated by high-resolution sonography and quantitative Doppler spectrum analysis in 21 patients and two normal volunteers. Erection was induced by intracorporeal injection of papaverine, and B-scan imaging and Doppler analysis were performed with the penis flaccid and erect. The corpora cavernosa and its deep arteries, median septum, and corpus spongiosum were clearly displayed in every subject, with the dorsal vein and dorsal artery seen ventral to the corpora cavernosa. In the flaccid state, in all subjects, Doppler analysis demonstrated flow in the dorsal arteries but not in the deep arteries. During erection, the B-mode image showed varying degrees of enlargement of the corpora cavernosa, with increased tissue echogenicity, as well as a hypoechoic area in the peri-arterial region. The diameter of the penile arteries and flow within them also increased by varying degrees. Quantification of blood flow through all deep and dorsal arteries is feasible with this technique.

Adult↗
PubMed1979

A comparison of EEG activity in the left and right cerebral hemispheres by power-spectrum analysis during language and non-language tasks.

In 10 female subjects, power-spectrum analysis was performed on the alpha activity elicted during the resting state, 4 right hemispheric tasks, and 3 left hemispheric tasks. The data were treated in 3 ways: approach 1, comparing the right and left hemispheric alpha activity; approach 2, comparing the right and left hemispheric alpha activity adjusted for the resting state; and approach 3, comparing the right and left hemispheric alpha activity adjusted for the previous task. Approaches 1 and 2 revealed few significant differences in the alpha activity of the hemispheres, but approach 3 provided data that better fit the theory of decreased power spectrum of attenuation of activity in the activated hemisphere. Thus, approach 3 may be useful in developing an electroencephalographic test for determining cerebral dominance for language.

Adult↗
PubMed1992

[Modification of the sympatho-vagal interaction in mitral valve prolapse syndrome. Evaluation of heart rate variability by spectrum analysis].

To determine whether clinical manifestations in patients with mitral valve prolapse (MVP) are associated with altered sympatho-vagal tone, 46 patients (mean age 27 +/- 6, range 20-45 years; 18 males and 28 females) were studied by power spectrum analysis of RR variability. Patients were divided in 2 groups, according to echocardiographic criteria: Group A: 11 patients with classical MVP; Group B: 35 patients with non classical MVP. These patients were compared with 30 healthy subjects (Group C) well matched for age, body surface area and heart rate. Our findings indicate that at rest there is a significant difference in the high-frequency component between Group A and Group C. Similarly, during the increase in sympathetic activity induced by 70 degrees head-up tilt all groups showed an increase in the low-frequency component, that was more evident in Group A. The data generated from our laboratory suggest that mitral regurgitation (Group A) is a probable cause of vagal tone increase and that there is an adaptive long-term mechanism towards sympathetic conditions. In addition, probably the normalization, demonstrable by the effect of sympathetic activity in tilt, can mask a dysfunction that may be differently evoked.

Adult↗
PubMed1997

Power spectrum analysis of heart rate variability in Guillain-Barré syndrome. A longitudinal study.

Power spectrum analysis of heart rate variability was repeatedly carried out on 13 patients with Guillain-Barré syndrome for up to 1 year by Fourier analysis of regular beat-to-beat (R-R) intervals which were recorded for 5 min, converted into a continuous function by linear interpolation and resampled at 5 Hz. Low-frequency (LF) power (reflecting a mixture of parasympathetic and sympathetic activity) and high-frequency (HF) power (reflecting parasympathetic tone) were calculated by integrating the spectra from 0.04 to 0.15 Hz and from 0.15 to 0.4 Hz, respectively. At the height of the disease, the HF component was significantly decreased. The LF:HF ratio, which has been suggested to be an indicator for sympathetic activity, was increased compared with the follow-up value after 1 year. Both measures returned to normal gradually over time. Pooled-data analysis suggested that both HF and LF power were significantly related to the responses of standardized parasympathetic function tests, while the LF:HF ratio was inversely correlated with sympathetic vasomotor activity. In patients presenting with tachycardia, LF and HF power were strikingly decreased compared with patients with normal heart rates, while in patients showing vagal over-reactivity, the power of both spectral bands was significantly increased. The results suggest that spectral analysis of heart rate variability is useful for investigating the cardiovascular neural regulation in patients with Guillain-Barré syndrome. In this disorder, the sympathovagal balance is clearly shifted to sympathetic predominance at the height of the disease.

Adult↗
PubMed1978

Spectrum analysis of transient phenomena of the left ventricular pressure.

The application of "real time" spectrum analysis to left ventricular pressure during transient phenomena is described. Transient phenomena generated by the injection of drugs (norepinephrine-isoproterenol), anoxia and occlusion of aorta and carotids show sudden changes in the frequency of heart contraction. Propranolol stabilizes the heart rate in similar circumstances.

Animals↗
PubMed1984

[Doppler frequency spectrum analysis of extracranial carotid artery lesions].

Signals registered from the extracranial carotid artery by direct Doppler-ultrasound with a MHz transducer were subjected to real-time frequency spectrum analysis. A systolic maximal frequency over 3500 Hz was considered abnormal, together with a broadened spectrum. The study was made on 157 subsequently operated carotid arteries, not all of which had previous angiographic studies. Of 47 with a normal angiogram 45 were correctly classified non-invasively (specificity 96%). The non-invasive diagnosis was correct in 16 of 17 occlusions of the internal carotid artery demonstrated angiographically. An abnormal Doppler frequency analysis was present in only 7 of 14 stenoses with a decreased vessel lumen below 25%. An abnormal Doppler frequency analysis was present in 78 of 79 stenoses with more than 25% reduction in lumen diameter, diagnostic sensitivity for all stenoses being 91%.

Adult↗