Establishment of the method for quantitative measurement of SAR value using a high molecular gel phantom

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A new technique for visualization or three dimensional measurement of power absorbed by the human body has been developed by using a high molecular gel phantom whose cloudiness varies with the change in temperature. The gel phantom contains non ionic surface active agent in addition to salt, sugar and alcohol. The electric-, optical-, and mechanical-property of the phantom are adjusted to the desired values by varying those concentration. The region which exceeds a specific temperature called clouding point by absorbing electromagnetic power becomes white and opaque due to segregation of non ionic surface active agent. Therefore, the absorbed power can be visualized by using the gel phantom.A series of standard phantoms have been given at some typical frequencies which are commonly used for various purposes. That is, relationships between the phantom composition and physical property such as electric-, mechanical- and thermal properties have been given, Based on this knowledge, various kinds of phantoms can be developed.The SAR value represents average power density absorbed by a small region on the boundary between the clouded- and nonclouded-region of the phantom as long as thermal conduction of the phantom is negligible. Furthermore, the coordinates of the small region on the boundary can be measured with a laser range finder. Thus, it is concluded that local SAR is made visible or measurable in three dimensional ways. The validity of the method of SAR measurement has been shown by FD-TD based numerical analysis.