Ultrasound speed and attenuation in homogenates of bovine skeletal muscle.

The attenuation and speed of ultrasound were measured in homogenates of post-rigor bovine skeletal muscle, and found to increase in proportion to the concentration of muscle. Extrapolation of the data to tissue concentrations yielded an attenuation of 7.5 dB cm-1 at pH 5.7, 20 degrees C and 7.3 MHz. This was close to that measured in the minced tissue, 8.3 dB cm-1, and between values previously recorded across and along the fibres of intact muscle. Corresponding measurements for the speed of ultrasound in homogenates, extrapolated to the native tissue concentration, were: 1555 +/- 9 m s-1 at 0 degree C, 1592 +/- 10 m s-1 at 20 degrees C and 1616 +/- 9 m s-1 at 37 degrees C. These were not significantly different from measurements of minced muscle at the same temperatures. Measurements of the attenuation of 7.3 MHz ultrasound in suspensions of myofibrils indicated that attenuation by the myofibrils caused at least 64% of the attenuation in muscle homogenates at pH 5.7. Re-analysis of the viscous loss arising from relative movement of the myofibrils in their surrounding fluid, indicated that this mechanism could account for no more than 15% of the attenuation in muscle homogenates. Attenuation due to scattering was calculated to be at least two orders of magnitude smaller than that observed in either homogenates or suspensions of myofibrils. It was concluded that the contribution of scattering to the attenuation was small, and that the attenuation was caused by processes involving an absorption of energy.(ABSTRACT TRUNCATED AT 250 WORDS)