Fig. 15

Block diagram describing processing steps required to compute the backscatter coefficient (BSC). a A biological tissue, containing ultrasound scatterers distributed in space, is interrogated by an ultrasound wave. b The interaction of the ultrasound wave with the tissue produces a backscattered RF image discretized into rectangular measurement windows. c Using the same ultrasound system, a reference RF image is taken on a reference phantom with a known BSC, and discretized rectangular measurement windows are distributed at the same depth and lateral positions as in the case of the tissue image. d, e At every location of a measurement window, power spectra are computed for both images. f To eliminate effects of the system point spread function (PSF) and beam diffraction (which are system dependent and not tissue dependent), a spectral ratio is computed at each location and calibrated by the known BSC of the reference phantom. g At this stage, the tissue BSC is still affected by total attenuation, which needs to be removed. h Depth-dependent attenuation is removed for each measurement window location, which yields a BSC parametric image in i that is system independent. Averaging over multiple acquisitions with different probe positions and/or orientations is practically required to improve robustness