Huclova Sonja, Fröhlich Jürg, Falco Lisa, Dewarrat François, Talary Mark S, Vahldieck Rüdiger
Laboratory for Electromagnetic Fields and Microwave Electronics, ETH Zurich, Gloriastrasse 35, 8092 Zurich, Switzerland.
Annu Int Conf IEEE Eng Med Biol Soc. 2009;2009:4461-4. doi: 10.1109/IEMBS.2009.5333820.
The human skin consists of several layers with distinct dielectric properties. Resolving the impact of changes in dielectric parameters of skin layers and predicting them allows for non-invasive sensing in medical diagnosis. So far no complete skin and underlying tissue model is available for this purpose in the MHz range. Focusing on this dispersiondominated frequency region multilayer skin models are investigated: First, containing homogeneous non-dispersive sublayers and second, with sublayers obtained from a three-phase Maxwell-Garnett mixture of shelled cell-like ellipsoids. Both models are numerically simulated using the Finite Element Method, a fringing field sensor on the top of the multilayer system serving as a probe. Furthermore, measurements with the sensor probing skin in vivo are performed. In order to validate the models the uppermost skin layer, the stratum corneum was i) included and ii) removed in models and measurements. It is found that only the Maxwell-Garnett mixture model can qualitatively reproduce the measured dispersion which still occurs without the stratum corneum and consequently, structural features of tissue have to be part of the model.
人体皮肤由具有不同介电特性的多层结构组成。解析皮肤各层介电参数变化的影响并对其进行预测，有助于在医学诊断中实现非侵入式传感。到目前为止，在兆赫兹范围内还没有用于此目的的完整皮肤及皮下组织模型。针对这个以色散为主的频率区域，研究了多层皮肤模型：第一种包含均匀的非色散子层，第二种子层由带壳细胞状椭球体的三相麦克斯韦-加尼特混合物构成。使用有限元方法对这两种模型进行数值模拟，多层系统顶部的边缘场传感器用作探头。此外，还使用该传感器对活体皮肤进行了测量。为了验证模型，在模型和测量中分别对最上层皮肤层——角质层进行了两种处理：一是将其包含在内，二是将其去除。结果发现，只有麦克斯韦-加尼特混合物模型能够定性地再现测量得到的色散，即使在没有角质层的情况下色散仍然存在，因此，组织的结构特征必须是模型的一部分。
