Basic study on the ultrasound attenuation of fibrous biological tissue in the frequency range of 10-40 MHz

To investigate the effects of a myofibrous structure of biological tissue on ultrasound attenuation, the frequency-dependence of attenuation in bovine muscle tissue was measured in the frequency range of 10-40 MHz. The frequency-dependence of attenuation was approximated by a power-law, af^b, in the measured frequency range. The exponent value `b´ of the sliced samples was 1.2 for parallel insonification with respect to the direction of myofibers and 1.9 for normal insonification, while it was 1.5 for the supernatant liquid extracted from the homogenized tissue suspension. These results suggest that the exponent value `b´ of fibrous structure is changed by the angle of insonification. It is well known that ultrasound attenuation of fibrous tissue at frequencies below 10 MHz depends on the direction of the fibrous structure. Our results suggest that this angular dependence of attenuation is caused by a change in the exponent value of frequency-dependent attenuation