An Acoustic Phase Shift Technique for the Non-Invasive Measurement of Temperature Changes in Tissues

An acoustic phase shift technique for non-invasive measurement of temperature changes in tissues is described, The technique uses a tone burst to monitor acoustic phase shifts which are correlated with temperature changes from the temperature dependence of the acoustic propagation velocity. The stability and accuracy of the system are discussed. Results o f i n-vitro experiments in beef and in-vivo experiments o n a renal adenocarcinoma I mplanted subcutaneously in a rat during local hyperthermia by scanned focused ultrasound are described. A high correlation between the change in acoustic propagation velocity and the peak measured temperature is reported. Ektension of the technique to clinical use is discussed.