Doppler evaluation of fetal hemodynamics

Maulik, Debabrata; Saini, Vasant D.; Nanda, Navin C.; Rosenzweig, Mark S.

doi:10.1016/0301-5629(82)90129-6

Cited by 49 publications

(17 citation statements)

References 8 publications

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“…But, such an increase is not observed in a fetus with abnormal growth. 10 In addition to conventional Doppler indices to extract new features, the DWT method was applied to the umbilical artery Doppler signals in order to investigate the increase in the amount of blood flow. Figure 1 shows the decomposed umbilical artery Doppler signals for a 32-week normal pregnant subject to the fifth level.…”

Section: Resultsmentioning

confidence: 99%

“…Recently, the most widely used indices for the evaluation of Doppler sonograms in the obstetrics field are defined as the resistivity index, the pulsatility index, and the systolic/diastolic ratio. [9][10][11][12] Previously, the method of the fast Fourier transform (FFT) spectral analysis was used in Doppler systems. Afterward, the short-time Fourier transform (STFT) has been the commonly used method for generating time-frequency representations of the Doppler blood flow signals.…”

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confidence: 99%

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Spectral Analysis of Umbilical Artery Doppler Signals During Gestation Utilizing Discrete Wavelet Transform

Kara¹,

Latifoğlu²,

Imal³

et al. 2009

Experimental Techniques

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V arious noninvasive techniques are used to evaluate the fetal surveillance. Doppler ultrasound allows for the examination of direction, velocity, and volume of blood flow. Umbilical artery blood flow velocity waveform measurement is one of these methods that is widely used in clinical practice for the evaluation of fetal condition. 1 Doppler systems are based on the principle that the ultrasound waves, emitted by an ultrasonic transducer, are returned partially back to the transducer by the moving red blood cells (erythrocytes), thereby inducing a shift in the frequency, which is proportional to the emitted frequency and the velocity along the direction of the ultrasound beam. The Doppler equation is defined as follows:where v is the velocity of the blood flow; f t , the frequency of the emitted ultrasonic signal; c, the velocity of sound in tissue; Df D , the measured Doppler frequency shift; and u, the angle of incidence that is between the direction of blood flow and the direction of the emitted ultrasonic beam. 2,3 Since the scatters within the ultrasound beam usually do not move at the same speed, a spectrum of Doppler frequencies will be observed. 4The spectral analysis of ultrasound Doppler signals is an efficient tool for blood flow analysis. 5,6 Since the velocity components are proportional to the frequency shifts, it is possible to track the velocity distribution by obtaining the power spectral density (PSD) estimates. The Doppler signal PSD, commonly referred to as the ''Doppler spectrum,'' provides a useful image of the velocity histogram of the erythrocytes, which statistically describes the flow as a distribution of the number of erythrocytes traveling through the sample volume at a given velocity. 7 The most usual way of displaying the information resulting from the spectral analysis is the Doppler sonogram. In a sonogram, the horizontal axis represents time (t), the vertical axis frequency (f), and the gray level intensity represents the power level of the corresponding frequency at each point of time. As the color tone of the sonogram turns into black, it implies that the power level is increased, and as it becomes lighter, the power level decreases. The variation of the spectral properties of the Doppler signal and a number of extents related to the blood flow can easily be tracked by monitoring the sonogram.The Doppler sonography waveform analysis of umbilical and uterine artery is the gold standard for the evaluation of normal and abnormal blood flow in the second and third trimesters. 1,2 The umbilical artery waveform in normal pregnancy is characterized by forward velocity levels, which remain high in diastole and increase with gestational age. 8 Decreased diastolic velocities, and occasionally reverse flow, are seen in certain cases of fetal complications. These changing waveforms have been associated with raised placental resistance. 9When the sonogram of the Doppler signals is obtained, the mean and/or the maximum frequency waveform can be estimated. The maximum frequency waveform extra...

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Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

Spectral Analysis of Umbilical Artery Doppler Signals During Gestation Utilizing Discrete Wavelet Transform

Kara¹,

Latifoğlu²,

Imal³

et al. 2009

Experimental Techniques

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“…5 Maulik found that the first moment of FVW was more representative of the total flow than either peak or mean velocity, and suggested that the PI of the first moment may be a more sensitive measure of blood flow. 8 More recently, however, Thompson et al found that the mean of the maximum FVW could be measured with much more accuracy and reproducibility than either the mean of the median or the mean of the first moment. 9 In addition, maximum FVW was better at predicting growth-retarded infants than either of the other two methods.…”

Section: Discussionmentioning

confidence: 99%

Comparison of umbilical artery flow velocity waveform indices as measured by continuous wave Doppler ultrasound.

Gilbert

Nicolaides²,

Sel³

et al. 1988

Journal of Ultrasound in Medicine

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This study examines four methods, automated and man· ual, of calculating the pulsatility index (PI) of fetal umbilical artery flow velocity waveforms (FVW) and compares these values to the resistance index (RI), the A/8 ratio, and the degree of absence of end diastolic frequencies. The FVWs were obtained by the Doptek continuous wave Doppler ultrasound. All of the maximum envelope indices had significant correlations; a highly C ontinuous wave Doppler ultrasound systems are becoming more widely used for the mea· surement of fetal and maternal flow velocity waveforms (FVW) in the prediction of pregnancy complications and in the assessment of fetal well being. t.z There are presently three main angle independent indices used to evaluate the FVW: 1) the A/8 ratio, or the peak systolic to end diastolic ratio; 3 2) the resistance index (RI), or peak systolic minus end diastolic frequencies divided by the peak systolic frequency;• and 3) the pulsatility index (PI), or peak systolic minus the nadir (or negative peak) diastolic frequencies divided by the mean maximum frequency over one cardiac cycle. 5 In the analysis of the umbilical artery FVW from normal preg· nancies, there is a highly significant correlation between these indices. 6 In some pathological pregnancies in significant difference was found between the automated and the manual methods of determining Pl. When PI was measured manually, there was a better correlation between the A/8 ratio, Rl, and degree of absence of end diastolic frequencies than when the automated methods methods were used. KEY woRos: Doppler, ultrasound, flow velocity waveform, pulsability index, blood flow (J Ultrasound Med 7:549, 1988). which the end diastolic frequencies are greatly reduced or even absent, however the A/B ratio and the Rl cannot be used, because the former approaches infinity and the latter approaches unity. 67 For this reason, the PI has become the most commonly used index in the assessment of peripheral impedance to downstream flow in complicated pregnancies.Most continuous wave Doppler machines use an onboard spectrum analyzer to estimate the maximum envelope of the FVW in calculating Pl. The analyzer can determine an intensity-weighted mean for FVW and calculate PI as well. A manual method with a light pen is also available to evaluate FVW envelope. This study examines these methods of determining PI in both normal and in pathologic pregnancies, and compares these values to the A/B , RI, and degree of absence of end diastolic frequencies. METHODSThe Doptek (continuous wave Doppler ultrasound and spectrum analyzer 9000, Doptek Ud, Chichester, UK) offers three methods for calculating maximum FVW en-

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“…There are different requirements measuring the baby blood flow before birth and at the time of birth for this reason, we are looking at the measurement before the time of birth, derived from Doppler maximum frequency waveforms, in the umbilical artery are the RI, PI and S/D indexes [5][6][7].…”

Section: Introductionmentioning

confidence: 99%

Fractal Analysis of Umbilical Artery Doppler Signals from Normal Pregnant Subject Using Hurst Exponent

Kara

Latifoğlu

Güney

2007

2007 Frontiers in the Convergence of Bioscience and Information Technologies

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Doppler signals from the umbilical artery of 20 women with normal pregnancy between 18-20 weeks of gestation were recorded. As a new alternative technique to take the place of traditional short-time Fourier transform (STFT) method, the application of fractal analysis method to the umbilical artery Doppler signals is presented. Traditional Doppler indexes which are resistance index (RI), pulsality index (PI), systolic: diastolic ratio (S/D) indexes have been calculated from the maximum frequency envelope of Doppler sonograms and from the fractal dimension curve. Area under the curve from ROC curve for RI, PI and S/D indexes derived from maximum frequency waveform were calculated as 0.937, 0.959, 0.930 respectively and area under the curve for RI, PI and S/D indexes derived from fractal dimension curve were calculated as 0.939, 0.960, and 0.941 respectively. These results shown that, Furthermore, this result showed the Doppler indexes derived from fractal dimension curve are more sensitive than the Doppler indexes derived from maximum velocity curve.

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Doppler evaluation of fetal hemodynamics

Cited by 49 publications

References 8 publications

Spectral Analysis of Umbilical Artery Doppler Signals During Gestation Utilizing Discrete Wavelet Transform

Spectral Analysis of Umbilical Artery Doppler Signals During Gestation Utilizing Discrete Wavelet Transform

Comparison of umbilical artery flow velocity waveform indices as measured by continuous wave Doppler ultrasound.

Fractal Analysis of Umbilical Artery Doppler Signals from Normal Pregnant Subject Using Hurst Exponent

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