フランジ付きセミリジッド開放終端同軸型プローブを用いた人体皮膚組織の電気定数In-Vivo測定

摘要

電波の人体安全性評価には人体組織の電気定数が不可欠であるが，周波数領域測定法では，人体の特定組織を対象としたin-vivo測定は容易でない．人体皮膚組織を対象としたin-Vivo測定法の確立を目的として，セミリジッド同軸ケーブルを用いてフランジ付きの開放終端ブロープを試作し，額部と腹部の負荷アドミタンスの測定値とMisraの式から皮膚組織の複素比誘電率を推定した．その結果，複素比誘電率は額部と腹部ともに数百MHz～数GHzの周波数範囲においてAgilentブロープによる測定結果と概ね一致すること，in-vitro測定に基づくGabrielデータとは額部ではよく一致するが，腹部では30～40%小さく測定されること，などがわかった．%In-vivo measurement of dielectric properties for specified human-body tissues is not easy to conduct in the frequency domain. In this study, we used a newly developed open-ended semi-rigid coaxial probe (flange probe) with a flange to measure the frequency characteristics of load admittance for forehead and abdomen in the frequency range from 100MHz to 25GHz with a network analyzer, and estimated their relative complex permittivities based on the Mistra's formula. For validation, we compared the results with the in-vitro measurement data by Gabriel and those measured by using a specially designed open-ended coaxial probe (Agilent probe), which enables us to obtain complex relative permittivities directly. As a result, we found that the flange probe and Agilent probe provide good agreement on the measured results both for the forehead and abdomen, though their results agree well with the Gabriel data for the forehead but are smaller than the data by 30-40 % for the abdomen.