Time and Phase Shift Detection Methods to Estimate a Characteristic Speed of Sound/Temperature Rate of a Bilayer Phantom

This study proposes the application of two signal processing methods to obtain speed of sound changes related to internal temperatures of a generic bilayer soft tissue phantom in the range of 25°C to 29°C based on temporal changes measurement from ultrasonic signals. The methods were calibrated using signals obtained from sunflower oil. Cross-correlation and phase shift were used to estimate this parameter, the former requiring subtraction of the accumulated delays in the deeper layer given by the upper layer. Values of Δt and flight times were obtained for each medium, as well as their linear regression on velocity. The average velocity change per degree Celsius was -1.4671 ms −1 /°C for fat and 2.0562 ms −1 /°C for soft tissue.