Osypka M, Gersing E
Zentrum Physiologie und Pathophysiologie der Universität, Göttingen, Germany.
Physiol Meas. 1995 Aug;16(3 Suppl A):A49-55. doi: 10.1088/0967-3334/16/3a/005.
The complex impedance of each kind of tissue depends on the frequency in a characteristic manner. Using appropriate measuring frequencies, EIT can provide a differentiating insight into the interior of a body. Therefore, a knowledge of the tissue impedance spectra of various organs is essential for choosing the appropriate frequencies. The impedance data of various tissues in different states (normal, altered by ischaemia or cancerous) show that the characterizing differences occur at frequencies below 500 kHz and down to a few kilohertz. Moreover, the spectra show that the imaginary component of impedance essentially contributes to the characterization of the kind and state of a tissue, even though the dissipative and reactive components are connected by the Kramers-Kronig relations. The course of a dispersion and the position in the frequency range, determined by the distribution of the time constants in the tissue, are clearly presented by the imaginary component. Tomographic imaging combined with spectroscopy for tissue characterization requires a frequency range of at least 10-800 kHz. The upper frequency limit depends on the fluid content of the tissue under investigation.
每种组织的复阻抗都以一种独特的方式依赖于频率。通过使用合适的测量频率，电阻抗断层成像（EIT）能够提供对人体内部的差异化洞察。因此，了解各种器官的组织阻抗谱对于选择合适的频率至关重要。不同状态（正常、因缺血改变或癌变）下各种组织的阻抗数据表明，特征性差异出现在低于500 kHz直至几kHz的频率范围内。此外，这些谱图表明，尽管耗散分量和电抗分量通过克拉默斯 - 克朗尼格关系相联系，但阻抗的虚部对组织的类型和状态表征起着重要作用。由组织中的时间常数分布所决定的色散过程和在频率范围内的位置，通过虚部清晰地呈现出来。用于组织表征的断层成像与光谱学相结合需要至少10 - 800 kHz的频率范围。频率上限取决于所研究组织的液体含量。
