Broadband dielectric spectroscopy on human blood

Abstract

BackgroundDielectric spectra of human blood reveal a rich variety of dynamic processes. Achieving a better characterization and understanding of these processes not only is of academic interest but also of high relevance for medical applications as, e.g., the determination of absorption rates of electromagnetic radiation by the human body. MethodsThe dielectric properties of human blood are studied using broadband dielectric spectroscopy, systematically investigating the dependence on temperature and hematocrit value. By covering a frequency range from 1 Hz to 40 GHz, information on all the typical dispersion regions of biological matter is obtained. Results and conclusionsWe find no evidence for a low-frequency relaxation ("α-relaxation") caused, e.g., by counterion diffusion effects as reported for some types of biological matter. The analysis of a strong Maxwell-Wagner relaxation arising from the polarization of the cell membranes in the 1-100 MHz region ("β-relaxation") allows for the test of model predictions and the determination of various intrinsic cell properties. In the microwave region beyond 1 GHz, the reorientational motion of water molecules in the blood plasma leads to another relaxation feature ("γ-relaxation"). Between β-and γ-relaxation, significant dispersion is observed, which, however, can be explained by a superposition of these relaxation processes and is not due to an additional "δ-relaxation" often found in biological matter. General significanceOur measurements provide dielectric data on human blood of so far unsurpassed precision for a broad parameter range. All data are provided in electronic form to serve as basis for the calculation of the absorption rate of electromagnetic radiation and other medical purposes. Moreover, by investigating an exceptionally broad frequency range, valuable new information on the dynamic processes in blood is obtained.

Development of a multi frequency impedance measurement system for use in MEMS flow cytometers

“…The transition to a γ type response is typically considered to occur in the region of 1 GHz and is linked to water molecule relaxation effects. An additional δ response in the region between the β and γ response is also present (Wolf 2011). At frequencies in the MHz region (β response) it is possible to investigate the structure of the cytoplasm within the cell.…”

“…The low frequency α response is linked to the cell membrane impedance. This response typically dominates from DC to approximately 200 kHz (Wolf 2011;Britt and Hoffman 1979). There are indications the α response is absent in, for example, undamaged red blood cells and only present in haemolysed material (Wolf 2011).…”

“…This response typically dominates from DC to approximately 200 kHz (Wolf 2011;Britt and Hoffman 1979). There are indications the α response is absent in, for example, undamaged red blood cells and only present in haemolysed material (Wolf 2011). The more complex β response is linked to Maxwell-Wagner (Fricke 1953) dispersion.…”

“…This has been sub divided into two regions β1 and β2, based on the different mechanisms dominant at the separate peaks. The first occurs in the 1 MHz region (Wolf 2011;Beving 1994). The transition to a γ type response is typically considered to occur in the region of 1 GHz and is linked to water molecule relaxation effects.…”

Equivalent Permittivity Based on Debye Model of Blood and Its SAR

“…The precise knowledge of the dielectric properties of blood is prerequisite for fixing limiting values for electromagnetic pollution [1]. But according to the Assessment conclusions and suggestions of WHO's international EMF project, research on the association between extremely-low frequency (ELF) fields and the risk of blood disease is not clear.…”