A diffraction beam used for ultrasonic local heating expressed as the superposition of Gaussian beams

Abstract

Spatially uniform temperature elevation at a target inside a body is desirable for ultrasonic hypothermia and other medical applications. It has been shown for the two-dimensional case [Hynynen et al., Ultrasound Med. Biol. 7, 397 (1981)] that a “volcano”-shaped acoustic intensity profile is ideal for achieving such a temperature distribution. To generate this intensity distribution, the velocity at the surface of the transducer is found to be described by a Bessel-type function by an inverse Hankel transformation. The diffraction beam generated by the transducer can also be expressed as the superposition of Gaussian beams [M. A. Breazeale and J. J. Wen, J. Acoust. Soc. Am. 83, 1752–1756 (1988)], which are better suited for calculation of temperature elevation. The results of acoustic intensity distribution of the superpositon of Gaussian beams will be compared with those of the Bessel-type function. [Work supported by the American Cancer Society (IN-156) and by NSF and Vermont Epscor.]