On the estimation of acoustic attenuation coefficient from peaks of echo envelope

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Abstract
A noticeable problem in estimating the acoustic attenuation coefficient (the slope of the attenuation versus frequency, a parameter denoted by .beta.) of soft tissue using current frequency-domain methods is the large variance of the estimate. As a consequence, the reliability of the measurement of the value of .beta. as a method of tissue characterization is reduced. This variance of the .beta. estimate can be much decreased by using a newly developed time-domain method.sbd.the envelope peak (EP) method. When the value of .beta. is estimated from the same rf samples of one A line based on the maximum-likelihood principle, theoretical analysis indicates that in comparison with the frequency methods, the EP method produces more independent data points for least-squares fitting, each data point having a smaller variance. The results of these two effects is a reduction of nearly 50 times in the variance of the .beta. estimate under typical scan conditions. Preliminary results from phantom experiments and in vivo liver scan supported the above analysis.

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