Electrical discontinuity of tissue substitute models at 27.12 MHz

Tissue-substitute models consisting of layers of synthetic, electrically equivalent subcutaneous fat, muscle, and bone shaped in conformation with the normal anatomy are used for rapid determination of distribution of temperature and specific absorption rate throughout the tissues when exposed to electromagnetic radiation. The surfaces of the bisected models are approximated during a short exposure period, then separated and scanned with a thermograph. A method was developed to eliminate the electrical discontinuity at the bisected surfaces while allowing separation and subsequent thermographic scanning. A thin layer of silk screen wetted with propylene glycol saturated with sodium chloride was used at the fat interface and a 0.9% sodium chloride solution was used to wet the screen at the muscle interface to eliminate electrical discontinuity during exposure to 27.12-MHz diathermy. Tests showed that in the presence of an electrical discontinuity the heating pattern was grossly distorted. With the method used, the electrical discontinuity is minimized and the subsequent thermographic scanning reveals that the heating pattern is equivalent to that of an intact model.