A METHOD FOR DETERMINATION OF FREQUENCY-DEPENDENT EFFECTIVE SCATTERERNUMBER DENSITY

Previous researchers have shown that for low scatterer concentrations, the scatterer number density in an ultrasound pulse-echo experiment c an be obtained from ratios of the fourth to the second moment of the b ackscattered signal. In this paper a new method is presented for deter mining an effective scatterer number density, which is the actual numb er density multiplied by a frequency-dependent factor that depends on the differential scattering cross sections of all scatterers. The meth od of data reduction goes beyond the work of previous authors in that, in addition to accounting for the possibility that different sets of scatterers may dominate the echo signal at different frequencies, it a lso explicitly retains both the temporal nature of the data acquisitio n and the properties of the ultrasound field in the data reduction. Te sts of the method in phantoms yielded good agreement between measured values of the effective scatterer number density and number densities calculated using first principles.