Anisotropy in bovine skeletal muscle in vitro: frequency dependent attenuation and backscatter coefficient over a wide range of frequencies

Our goal was to correlate muscle fibers orientation with anisotropy of ultrasonic parameters. The ultrasonic attenuation and the backscatter coefficient were measured with a reflection technique in bovine skeletal muscle samples. Frequencg dependent attenuation and backscattering measurements were made at two angles of incidence. Ultrasonic waves were propagated both across and along the muscle fibers. Two different transducers (5 and 20 MHz center frequency) were used to explore a wide range of frequencies (2 to 30 MHz). A linear frequency dependence of the attenuation was found over the range 2 to 30 MHz and the slope of attenuation was observed to be highly anisotropic (mean values were 3.1 dB/cm.MHz for propagation along the fibers with the 5 and the 20 MHz transducers and 0.9 dB/cm.MHz and 1.3 dB/cm.MHz for propagation across the fibers respectively with the 5 and the 20 MHz transducers). The backscatter coefficient was found to be anisotropic too. The integrated backscatter coefficient for propagation across the fibers was higher than for propagation along the fibers (the difference was approximately 10 dB) with the 5 and the 20 MHz transducers. The frequency dependence of the backscatter coefficient was found to be af ^2,5 for propagation along the fibers and bf^1,4 for propagation across the fibers with the 5 MHz transducer (1 is the frequency)