Frequency dependence of ultrasound attenuation and backscatter in breast tissue

Attenuation and backscatter of ultrasound in human breast tissues were measured over the frequency range relevant to breast imaging (3-7 MHz). The first step in the measurement process consisted of generating an ultrasound attenuation image of a macroscopic slice of excised breast tissue. This image depicted the various tissue constituents in the samples so that a region of homogeneous tissue could be selected for further investigation. Ultrasound signals used in the computation of the frequency dependent attenuation and backscatter coefficients were then collected from several points within this region of interest. The measured attenuation and backscatter were averaged over all the points in the region of interest and plotted as functions of frequency which ranged from 3 to 7 MHz. The results showed that the attenuation coefficient of homogeneous regions of infiltrating duct carcinoma was higher than that of fat but somewhat less than that of fibrous and parenchymal tissues. On the other hand the backscattering coefficient of ductal carcinoma samples was similar to that of fat but much lower than the backscatter coefficient of parenchymal tissue. The discriminability of the different breast tissue types under these measures, as well as the relevance of the results to clinical imaging are discussed.