Analysis of human skin tissue by millimeter-wave reflectometry

Background/pupose: Millimeter-wave reflectometry is a potentially interesting technique to analyze the human skin in vivo in order to determine the water content locally in the skin. Purpose of this work is to investigate the possibility of skin-tissue differentiation. In addition, it addresses the influence of the pressure of the probe on the skin, the influence of an airgap between probe and skin as well as the influence of a bandage between probe and skin. Methodology: Reflection coefficients at various positions on the skin are measured in the 40 – 60 GHz range and the examined effects are quantified in terms of magnitude and phase of the reflection coefficient. Also the possibility to perform tissue differentiation is quantified. Results: It is indicated that differentiation of skin tissue can be performed on the basis of the magnitude of the reflection coefficient provided that no air-gap exists between probe and skin. The influence of probe pressure can be substantial in particular for phase measurements. The presence of an airgap between probe and skin reduces the differentiation capability of the considered measurement technique, whereas a bandage between probe and skin did not significantly affect the differentiation power. Conclusion: The results of this work confirm the potential of millimeter-wave reflectometry for determination of water content in skin tissue which may lead to interesting applications as early detection of skin cancer and through-bandage monitoring of wounds.