This study researches the behaviour of spectral broadening index (SBI) obtained from spectra achived using short-time Fourier transform (STFT) analysis compared to that of SBI based on autoregressive (AR) modeling of clinical Doppler lower extremity vein signal. Doppler signals from 12 healthy subject with eight different physiologic situations were analysed. Sonograms obtained from Doppler signals were used to compare the applied methods in terms of their frequency resolution and their effectiveness for the determination of SBI. The AR based sonograms produced narrower spectra compared to STFT sonograms. Besides, the magnitude of the STFT based SBI was larger than that of the AR based SBI. Furthermore, standard deviations and coefficient of variations of STFT and AR based SBIs changed depending on each physiologic situation. The results of this research have also shown that despite the qualitative improvement in the individual frequency spectra, there was no quantitative advantage in using the AR approach over the STFT for the determination of SBI. Moreover there was also an additional computational complexity income connections with AR modeling. (C) 2007 Elsevier Inc. All rights reserved.