Ultrasound heating in a tissue-bone phantom

Temperature rise generated by focused ultrasound beams was tested on semipermanent tissue-bone phantoms. The phantoms were capped (sealed) plastic hollow cylindrical containers filled with tissue-mimicking material (TMM), in which were imbedded 25 mu m diameter copper-constantan thermocouples (TC) and a piece of compact human or cow bone. The acoustic 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 chosen as the material to make caps of the phantoms. A formula developed to estimate the upper limit of temperature rises at tissue-bone interfaces generated by focused ultrasound has been proved to be appropriate experimentally using the semipermanent phantoms.