Application of autoregressive spectral analysis for ultrasound attenuation estimation: interest in highly attenuating medium

Abstract
The authors deal with the application of parametric spectral analysis for attenuation estimation on the reflected ultrasound signal of biological tissues. A second-order autoregressive (AR2) model, whose parameters are estimated with the Burg algorithm, is used to estimate the center frequency on echo signals and its evolution versus depth. Data simulation of independent A-lines backscattered by a homogeneous medium of scatterers are generated by a computer model with attenuation values ranging from 1 to 5 dB/cmMHz, an ultrasonic frequency of 5 MHz and different pulse durations. The performance of the estimator is evaluated for time windows ranging from 5 to 0.3 /spl mu/s. The comparison is made with the classical short time Fourier analysis using a fast Fourier transform (FFT). It is found that the AR2 model provides a better estimation of attenuation than the Fourier technique: the relative error of attenuation is below 5% for windows between 0.6 to 2.5 /spl mu/s, while the one obtained with the Fourier technique lies between 3 and 16% for the same window sizes. However, the variance of attenuation estimate is the same with the two techniques. These results offer promises for determining attenuation in highly attenuating medium (material or biological tissue) either because of their structure or because high frequencies are used.<>