Sensitivity and specificity analysis of fringing-field dielectric spectroscopy applied to a multi-layer system modelling the human skin
Sensitivity and specificity analysis of fringing-field dielectric spectroscopy applied to a multi-layer system modelling the human skin
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DOI：
10.1088/0031-9155/56/24/007
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发表时间：
2011-12-21
影响因子：
3.5
通讯作者：
Froehlich, Juerg
中科院分区：
文献类型：
--
作者：
Huclova, Sonja;Baumann, Dirk;Froehlich, Juerg
研究了介电光谱检测多层结构内部介电变化的灵敏度和特异性。我们专注于为感知人体皮肤的生理变化提供基础，即表皮和真皮层。利用数值模拟方法研究了人体皮肤有效介电常数的变化与介电参数和表皮、真皮层层厚的变化之间的关系。数值模型包括直接放置在多层皮肤模型上的条纹场探针。得到的介电光谱在100 kHz至100 MHz范围内对不同的层参数和传感器几何形状进行了灵敏度和特异性分析。首先，采用同轴探针，对表皮和真皮层参数的特定变化进行敏感性分析。其次，根据计算得到的介电谱及其一阶导数和二阶导数的根和对应的符号变化，分析了该系统的特殊性。通过对共面探针和缩放后的同轴探针的介电光谱的比较，证明了所得结果的可转移性。此外，同轴探针和交叉探针的灵敏度作为电极距离的函数进行了比较。研究发现，检测表皮和真皮层介电特性变化的灵敏度与频率密切相关。根据对介电光谱的分析，有效介电参数的变化理论上可以唯一地归因于介电常数和电导率的特定变化。然而，在实际应用中，测量不确定性可能会降低系统的性能。
The sensitivity and specificity of dielectric spectroscopy for the detection of dielectric changes inside a multi-layered structure is investigated. We focus on providing a base for sensing physiological changes in the human skin, i.e. in the epidermal and dermal layers. The correlation between changes of the human skin's effective permittivity and changes of dielectric parameters and layer thickness of the epidermal and dermal layers is assessed using numerical simulations. Numerical models include fringing-field probes placed directly on a multi-layer model of the skin. The resulting dielectric spectra in the range from 100 kHz up to 100 MHz for different layer parameters and sensor geometries are used for a sensitivity and specificity analysis of this multi-layer system. First, employing a coaxial probe, a sensitivity analysis is performed for specific variations of the parameters of the epidermal and dermal layers. Second, the specificity of this system is analysed based on the roots and corresponding sign changes of the computed dielectric spectra and their first and second derivatives. The transferability of the derived results is shown by a comparison of the dielectric spectra of a coplanar probe and a scaled coaxial probe. Additionally, a comparison of the sensitivity of a coaxial probe and an interdigitated probe as a function of electrode distance is performed. It is found that the sensitivity for detecting changes of dielectric properties in the epidermal and dermal layers strongly depends on frequency. Based on an analysis of the dielectric spectra, changes in the effective dielectric parameters can theoretically be uniquely assigned to specific changes in permittivity and conductivity. However, in practice, measurement uncertainties may degrade the performance of the system.