Optimal multisine excitation design for broadband electrical impedance spectroscopy
Optimal multisine excitation design for broadband electrical impedance spectroscopy
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DOI：
10.1088/0957-0233/22/11/115601
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发表时间：
2011-11-01
影响因子：
2.4
通讯作者：
Schoukens, J.
中科院分区：
文献类型：
--
作者：
Sanchez, B.;Vandersteen, G.;Schoukens, J.
电阻抗谱（EIS）可用于表征生物材料，应用范围从细胞培养到身体组成，包括组织和器官状态。细胞治疗和组织工程的出现开辟了一个新的和有前途的应用领域。虽然在大多数情况下，可以使用基于频率扫描的经典测量技术，但基于宽带激励的EIS使动态生物系统能够在测量时间和注入能量受到约束时进行表征。心肌再生、微流体系统中的细胞表征和动态电阻抗断层扫描都是此类应用的例子。这种类型的快速EIS测量技术的弱点在于其固有的精度损失。然而，由于大多数实际应用对所使用的激励没有限制，因此可以适当地设计输入功率谱以最大化从测量获得的精度。本文讨论了生物电阻抗测量中最佳多正弦激励的设计问题。最佳多正弦通过最小化Cramer-Rao下限获得，或者通过最大化从测量获得的精度获得。此外，由于没有解析解存在的全局优化涉及时域和频域联合，本文提出了多线优化方法的部分在两个域，然后结合的结果。至于频域方法，一个新的贡献是多正弦幅度功率谱。在时域中，通过降低其波峰因数来优化多正弦。此外，还讨论了不同的多正弦幅值功率谱以及频率个数和频率分布对阻抗谱信息量和精度的影响。该理论是支持一组验证测量时，激励与最佳和平坦的多正弦信号和相比，一个单一的频率交流阻抗分析仪时，表征RC电路。体内健康心肌组织电阻抗测量表明，基于多正弦激励的宽带阻抗谱能够表征动态生物系统。
Electrical impedance spectroscopy (EIS) can be used to characterize biological materials in applications ranging from cell culture to body composition, including tissue and organ state. The emergence of cell therapy and tissue engineering opens up a new and promising field of application. While in most cases classical measurement techniques based on a frequency sweep can be used, EIS based on broadband excitations enables dynamic biological systems to be characterized when the measuring time and injected energy are a constraint. Myocardial regeneration, cell characterization in micro-fluidic systems and dynamic electrical impedance tomography are all examples of such applications. The weakness of such types of fast EIS measuring techniques resides in their intrinsic loss of accuracy. However, since most of the practical applications have no restriction over the excitation used, the input power spectrum can be appropriately designed to maximize the accuracy obtained from the measurements. This paper deals with the problem of designing the optimal multisine excitation for electrical bioimpedance measurements. The optimal multisine is obtained by the minimization of the Cramer-Rao lower bound, or what is the same, by maximizing the accuracy obtained from the measurements. Furthermore, because no analytical solution exists for global optimization involving time and frequency domains jointly, this paper presents the multisine optimization approach partially in both domains and then combines the results. As regards the frequency domain approach, a novel contribution is made for the multisine amplitude power spectrum. In the time domain, multisine is optimized by reducing its crest factor. Moreover, the impact on the information and accuracy of the impedance spectrum obtained from using different multisine amplitude power spectra is discussed, as well as the number of frequencies and frequency distributions. The theory is supported by a set of validation measurements when exciting with the optimal and flat multisine signals and compared to a single frequency ac impedance analyzer when characterizing an RC circuit. In vivo healthy myocardium tissue electrical impedance measurements show that broadband EIS based on multisine excitations enable the characterization of dynamic biological systems.