EXPERIMENTAL DEMONSTRATION OF THE FREQUENCY-DEPENDENCE OF THE EFFECTIVE SCATTERER NUMBER DENSITY

In previous papers, a data reduction method for determining a frequenc y-dependent ''effective scatterer number density'' in ultrasound was r eported [Chen et al., J. Acoust. Sec. Am. 95, 77-95 (1994); 96, 2556-2 563 (1994)]. The effective scatterer number density is the actual numb er density of scatterers multiplied by a frequency-dependent factor th at depends on the differential scattering cross sections of the scatte rers. Evaluation of this technique based on measurements applied to a phantom with a distribution of scatterer diameters is reported here. T his condition yields an effective scatterer number density that depend s on the dominant scatterer concentration at the analysis frequency. M easured scatterer number densities at 3.5, 5, and 8 MKz were in agreem ent with theoretical computations of this parameter for the phantom. ( C) 1996 Acoustical Society of America.