Absolute backscatter coefficient over a wide range of frequenciesin a tissue-mimicking phantom containing two populations of scatterers

摘要

The acquisition and interpretation of in vivo ultrasonicnmeasurements in tissue encounter problems associated with limited accessnto the region of interest, intermixed scattering structures withndifferent characteristic dimensions, and system-dependent effects. Thisnwork addresses these problems by adapting and testing a technique fornmeasuring the absolute attenuation and the absolute backscatterncoefficient (effective backscatter cross section per unit volume ofnmaterial), as a function of frequency, in a single-transducernbackscatter configuration. The frequency-dependent attenuation andnbackscatter coefficients of a tissue-mimicking gelatin phantomncontaining a random distribution of two populations of scatterers werenmeasured, Three transducers with different center frequencies andnfocusing characteristics were used in order to verify thatnsystem-dependent effects were removed by the technique and toninvestigate the change in the measured parameters across a broad rangenof frequencies (2 to 60 MHz). A spherical autocorrelation model wasnapplied to measurements of the backscatter coefficient in order tonestimate the size of scatterers. Measurements demonstrate that thenbackscatter and attenuation properties of a mixture of two distinctnintermixed scatterer-size populations change as a function of thenfrequency range across which the model is applied. Comparison of bothnthe magnitude and the frequency dependence of the experimental resultsnwith the theoretical prediction of the backscatter coefficient showedngood agreement