In vivo breast tissue backscatter measurements with 7.5- and 10-MHz transducers.

Measurements of the ultrasound (US) backscatter coefficient (BSC) of fibroglandular and fatty breast tissues in vivo from 5.25 through 13 MHz, using the reference phantom method, are presented. Radiofrequency echo data were collected at a series of locations in the left breasts of 16 adults, age 46 to 84, and in a custom-built phantom calibrated for backscatter and attenuation. Matched regions of interest (ROIs) were then selected in these images, from which the backscatter coefficient and the backscatter frequency dependence were ratiometrically estimated, after compensation for attenuation. The mean results in fibroglandular tissues were 78.9 x 10(-3)/cm, sr at 7.2 MHz (n(ROI) = 43, n = 13) and 146 x 10(-3)/cm, sr at 10.3 MHz (n(ROI) = 19, n = 10) with frequency dependencies of f(2.28) and f(3.25). The corresponding results in subcutaneous fat were 2.59 x 10(-3)/cm, sr at 7.2 MHz (n(ROI) = 56, n = 16) and 7.08 x 10(-3)/cm, sr at 10.3 MHz (n(ROI) = 57, n = 16) with frequency dependencies of f(3.49) and f(3.43). These findings are discussed and compared to similar measurements in the literature.