Frequency dependence of backscatter coefficient versus scatterervolume fraction

摘要

Various groups are using the frequency dependence ofnbackscattering to characterize tissue. In most cases, sparse scatterernconcentrations are assumed in relating scattering parameters to tissuenproperties. This study addresses the relationship between backscatternfrequency dependence and scatterer volume fraction. Backscatterncoefficients (BSC) in the 2.5 to 9.0 MHz frequency range were measurednfor agar-gel phantoms containing Sephadex scatterers (mean diameter 42nΜm) at volume fractions ranging from 5 to 50%. The BSC increased withnscatterer volume fraction at low scatterer concentrations; at highernconcentrations, the BSC reached a maximum with concentration and thenndecreased with yet increasing scatterer concentrations, as has beennnoted by previous authors. In addition, the volume fraction for thenmaximum backscatter coefficient varied with frequency, generally beingngreater at higher frequencies than lower frequencies, and the frequencyndependence of the backscatter coefficient was greater for the highernscatterer concentrations than for the lower concentrations. Thesenresults are predicted by continuum models, where the spatialnautocorrelation function depends on scatterer volume fraction