Temperature dependence of speed of propagation in soft tissues and the effect of fixation at ultrasonic frequencies

Temperature dependence (2S-40°C) of speed of propagation in the frequency range 4.0–10.0 MHZ for various soft tissues (liver, spleen, heart and kidney) has been measured. The effect of fixation and the storage condition is also examined. It is found that in these tissues the speed of propagation in­creases with increasing temperature and the average temperature coefficient being 0.76 m/sec/°C. Examination of data reveal that protein content, water content, and ether soluble solids are primarily responsible for affecting the propagation speed. It in­creases with the increasing protein concentration and the ether soluble solids. We have found that the effect of fixation is to reduce the propagation speed in the range 18–23 m/sec. However, in the case of freezer fixed tissues it does not show any significant change.