[Acoustic method of determining the temperature of biological tissues during local heating]

The acoustical method of noninvasive control of temperature increment in deep localized heated regions based on a phase or time delay of a probe acoustical signal during its passing through a heated area was discussed. It was shown using a high-intensity focused ultrasonic radiator as a heating device that the sensitivity of the developed experimental apparatus to temperature change was 0.1 degrees C, the size of the heated area being 2 mm, and the spatial resolution in the direction perpendicular to the acoustical axis of the probe system was approximately 1.5 mm. The "non-invasiveness" and high sensitivity of the system was shown to hold promise for its effective clinical application, particularly for a prolonged heating of large tissue areas. In order to realize this potentiality information a priori should be available on such parameters of studied tissue as a sound velocity temperature coefficient, an absorption coefficient, tissue density and thermal heat capacity.