In vitro estimation and imaging of attenuation coefficients and instantaneous frequency for breast tissue characterization.

For breast tissue characterization, three acoustic parameters, integrated attenuation coefficient(IAC), frequency-dependent attenuation coefficient(FDAC) and instantaneous frequency(IF), were estimated in vitro and processed to make images of these parameters for resected human breast specimens. Experimental system with a 5 MHz center frequency was used and the same estimating and imaging system was connected with a clinical diagnostic device with a 7.5 MHz annular array probe (Aloca SSD 270) for in vivo type studies. To estimate these parameters, fast Fourier transform and spectral difference method were adopted for IAC and FDAC and the Hilbert transform for IF. Large statistical variances were found in the estimated values of these parameters. These dispersions of data may be due to insufficient size and tissue heterogeneity of the breast specimens. Additional miscellaneous problems may be involved. However, all of these can be, in part, overcome by averaging procedures. The significance of estimating and imaging these parameters for breast tissue characterization was discussed.