ABSOLUTE BACKSCATTER COEFFICIENT OVER A WIDE-RANGE OF FREQUENCIES IN A TISSUE-MIMICKING PHANTOM CONTAINING 2 POPULATIONS OF SCATTERERS

The acquisition and interpretation of in vivo ultrasonic measurements in tissue encounter problems associated with limited access to the reg ion of interest, intermixed scattering structures with different chara cteristic dimensions, and system-dependent effects, This work addresse s these problems by adapting and testing a technique for measuring the absolute attenuation and the absolute backscatter coefficient (effect ive backscatter cross section per unit volume of material), as a funct ion of frequency, in a single-transducer backscatter configuration, Th e frequency-dependent attenuation and backscatter coefficients of a ti ssue-mimicking gelatin phantom containing a random distribution of two populations of scatterers were measured, Three transducers with diffe rent center frequencies and focusing characteristics were used in orde r to verify that system-dependent effects were removed by the techniqu e and to investigate the change in the measured parameters across a br oad range of frequencies (2 to 60 MHz), A spherical autocorrelation mo del was applied to measurements of the backscatter coefficient in orde r to estimate the size of scatterers. Measurements demonstrate that th e backscatter and attenuation properties of a mixture of two distinct intermixed scatterer-size populations change as a function of the freq uency range across which the model is applied, Comparison of both the magnitude and the frequency dependence of the experimental results wit h the theoretical prediction of the backscatter coefficient showed goo d agreement.