Frequency dependence of acoustic parameters of freshly excised tissues of Sprague Dawley rats

A modified version of the pulse echo technique was used to measure the velocity of propagation and attenuation of ultrasound in excised tissue of young-adult Sprague-Dawley rats. The measurements were made at ultrasonic frequencies of 1.0, 2.25, 5.0, 7.5 and 10.0 MHz. The temperature of the tissues was monitored continuously to within +/- 0.1 degrees C of the ambient temperature. The acoustic parameters were measured in the liver, kidney, cardiac muscle and gastrocnemius muscle. All measurements were carried out in the near field region of the ultrasonic beam. It was observed that the velocity of propagation in tissues showed a slight dispersion with frequency. The attenuation in tissues increased with increasing frequency.