Doppler ultrasound is widely used in medical applications to extract the blood Doppler flow velocity in the arteries via spectral analysis. The spectral analysis of non-stationary signals and particularly Doppler signals requires adequate tools that should present both good time and frequency resolutions. It is well-known that the most commonly used time-windowed Fourier transform, which provid...

BACKGROUND/AIMS Clinical validation is required to determine whether Doppler measurements are comparable before and after administering ultrasound contrast agent (USCA). The purpose of this study is to explore whether the use of USCA affects spectral Doppler analysis in recipients of liver transplantation (LT). METHODS For this study, 36 patients were examined using Doppler ultrasonography (U...

Thomas JH: Incidence of recurrent stenosis after carotid endarter-ectomy determined by digital subtraction angiography. Digital transvenous angiography in follow-up examinations after carotid reconstruction. SUMMARY Doppler analysis of flow in intracranlal arteries is now possible using a 2 MHz probe allowing sufficient penetration of bone to obtain signals noninvasivety. Thirty-two normal subj...

We present a modified stratified jet model to interpret the observed spectral energy distributions of knots in 3C 273 jet. Based on the hypothesis of the single index of the particle energy spectrum at injection and identical emission processes among all the knots, the observed difference of spectral shape among different 3C273 knots can be understood as a manifestation of deviation of the equi...

OBJECTIVE To evaluate the use of the spectral Doppler (SDoppler) to quantify inflammatory activity and to detect nail echotextural differences in patients with psoriatic arthritis and onychomycosis. METHODS Two patients, one with psoriatic arthritis but with no joint pain nor nail clinical change and the other with onychomycosis and rheumatoid arthritis were included. The gray scale ultrasoun...

Periodogram is an important tool to reveal hidden periodicities in a given time series but does not tell whether the resulting spectral lines are associated with constant or random amplitude harmonics. Applications dealing with random amplitude models include Doppler spread targets and detection in the presence of fading. We propose to estimate the variance of the harmonic amplitude and then ma...

This paper proposes a new nonparametric method for estimation of spectral moments of a zero-mean Gaussian process immersed in additive white Gaussian noise. Although the technique is valid for any order moment, particular attention is given to the mean Doppler (first moment) and to the spectral width (square root of the centered second-spectral moment). By assuming that the power spectral densi...