Orientation and frequency dependence of backscatter coefficient in normal and pathological breast tissues

The backscatter coefficient was measured on five groups of normal and pathological breast specimens: (1) as a function of frequency (in the range 4-14 MHz) and (2) at a single fixed frequency (10 MHz), as a function of the angle of incidence between the beam and the specimen (approximately 60 degrees). The results of the study are discussed in relation to the content of cells and collagen fibers in breast tissues. The absolute value of backscatter coefficient is larger in tissues with a prevalence of collagenous fibers in comparison to tissues with only cells. In fibrofatty tissue, the inhomogeneity of the specimens is probably responsible for the highest backscatter value. The power law frequency dependence of the backscatter coefficient is of a diffractive nature in tissues characterized by only cells; in tissues with a strong prevalence of collagenous fibers, the power law frequency dependence increases. Periodicities in the angular patterns have been quantified by the autocorrelation functions for each group of specimens. The results of the study suggest a means for assessing tissue structure in normal and pathological breast tissue.