Correcting for focusing when estimating tissue attenuation from mean frequency shift

Determination of attenuating properties of the tissue from the echoes of waves emitted by the focused transducer requires to compensate the echo signal for the effects of focusing. We propose the diffraction/focusing effects correcting (FC) technique that compensates focusing-induced mean frequency shift (MFS) of the propagating pulse. The method corrects mean frequency estimates derived from echo pulses propagating in attenuating tissue with locally varying attenuation coefficient. The FC algorithm applies the diffraction correcting coefficients obtained experimentally from the probing pulses focused in water for assessing the expected values of MFS of pulses focused in attenuating tissue. The calculations involves the pulse ‘history’ that due to overall attenuation along the traveled path down-shifts the pulse spectrum resulting in variation of the focusing-induced MFS obtained in water.