ULTRASOUND HEATING IN A TISSUE-BONE PHANTOM

Temperature rise generated by focused ultrasound beams was tested on s emipermanent tissue-bone phantoms. The phantoms were capped (sealed) p lastic hollow cylindrical containers filled with tissue-mimicking mate rial (TMM), in which were imbedded 25 mu m diameter copper-constantan thermocouples (TC) and a piece of compact human or cow bone. The acous tic frequency specific attenuation coefficient of TMM was adjusted to be 0.3 dB cm(-1) MHz(-1) as specified by the FDA for a frequency range of 1-5 MHz. A high density 0.318 cm thick polyethylene sheet was chos en as the material to make caps of the phantoms. A formula developed t o estimate the upper limit of temperature rises at tissue-bone interfa ces generated by focused ultrasound has been proved to be appropriate experimentally using the semipermanent phantoms.