A method of SAR measurement using a high‐molecular‐weight gel phantom: On the correspondence of the surface of the clouded region to the surface of equipower absorption

Abstract

AbstractAs a method for evaluating the electromagnetic exposure of biological bodies, a visualization technique of the absorbed power inside the phantom using high‐molecular‐weight gel is proposed. Such gel containing a small amount of nonionic surfactants has the property of quickly becoming clouded at a temperature above a certain value. Therefore, it is possible to observe the portion with a temperature increase due to absorption of electromagnetic energy as a clouded region. The surface of the clouded region represents an equitemperature surface indicating the temperature at which the phantom is clouded. Hence, this is basically the equal power absorption surface. However, depending on the influence of the thermal conduction, the shape of the clouded region and the absorption power distribution may not coincide. In this paper, the equality of the clouded region shape and the equal power absorption surface is verified. The measured shape of the clouded region formed inside the phantom and the absorbed power distribution within the phantom derived by the three‐dimensional FD‐TD (Finite‐Difference Time‐Domain) method are compared. In addition, the influence of thermal conduction on the temperature distribution in the phantom is discussed. It is confirmed that the clouded shape caused by electromagnetic wave exposure and the computed equal power absorption surface agree well if the electromagnetic wave illumination time is less than about 1 minute. The validity of this method measuring the amount of electromagnetic wave exposure from the clouded shape is confirmed. © 2001 Scripta Technica, Electron Comm Jpn Pt 1, 85(3): 51–60, 2002