Determining Fractal Dimension of Umbilical Artery Doppler Signals Using Hurst Exponent |
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Authors: | Fatma Latifoğlu Sadık Kara Mehmet Güney |
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Institution: | Department of Electrical-Electronics Engineering, Erciyes University, 38039 Kayseri, Turkey. |
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Abstract: | Doppler signals from the umbilical artery of 20 women with normal pregnancy between 18 and 20 weeks of gestation were recorded.
The AR spectral analysis method has been used to obtain the Doppler sonograms of umbilical artery belonging to normal pregnant
subjects and fractal dimension curves were calculated using Hurst exponent. RI; PI and 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 0.931, 0.959, 0.938, respectively and
area under the curve for RI, PI and S/D indexes derived from fractal dimension curve were calculated as 0.933, 0.961, and
0.941, respectively. These results show that, the Doppler indexes derived from fractal dimension curve are as sensitive as
Doppler indexes derived from maximum velocity curve. Power Spectral Density graphics were derived from Doppler signals and
Hurst exponent values calculated to evaluate the blood flow changing during pregnancy. ROC curve for PSDHURST index was calculated as 0.97. According to this result, PSDHURST index is more sensitive to detect the blood flow changing than traditional Doppler indexes. |
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