Passive thermoacoustic tomography—A new kind of acoustic imaging for material testing and medicine

Passive thermoacoustic tomography is a method for reconstructing temperature distributions inside objects, using the intensity of ultrasonic thermal acoustic radiation emitted from within the object. Methods for the reconstruction of 2-D and 3-D temperature distributions were analyzed by computer simulation. The standard error of reconstruction did not exceed 0.25 K (for about 300 measurements and fluctuation error of every measurement 0.1 K). The physical experiments for temperature reconstruction were carried out using a glycerin phantom with a heated area at a depth of 16 mm. The radiation was measured in one plane with angles of 0 and 45 degrees to the phantom border. The 2-D internal temperature distribution in this plane was reconstructed with a standard error of 0.4 K. The 1-D temperature transversal distribution was studied in a human hand immersed in water, the radiation being measured from both sides of the hand. The reconstructed distribution was approximated by a cubic parabola with an error of less than 0.5 K. Application of correlation properties of thermal acoustical radiation is discussed as well. [Work supported by Russian Basic Research Foundation Grant No. 98-01-