Derivation of extracellular fluid volume fraction and equivalent dielectric constant of the cell membrane from dielectric properties of the human body. Part 1: Incorporation of fat tissue into cell suspension model in the arm

Abstract

The non-invasive characterisation of cell pathophysiology is clinically important. A cell suspension model is applied to derive the extracellular fluid (ECF) volume fraction and the equivalent dielectric constant of the cell membrane epsilon m from the dielectric properties of human arms. Frequency-dependent dielectric constants and electrical conductivities of arms are obtained from 35 surgical patients over a frequency range of 5-1000 kHz. The cell suspension model is applied to fit the data using a complex non-linear least-squares method. The arms show typical dielectric dispersions, although the cell suspension model yields a poor fitting in dielectric constants at lower frequencies and electrical conductivities at higher frequencies. In contrast, a new cell suspension model, taking into account the fat tissue component, remarkably improves the overall fitting performance, allowing estimation of the volume fractions of ECF (0.34 +/- 0.05) and fat tissue (0.16 +/- 0.04) and the equivalent epsilon m (23 +/- 9). The resulting estimates of the volume fraction of fat tissue are in good correlation with arm skinfold thickness (fat volume fraction of arm = 2.42 x 10(-3) x arm skinfold thickness (mm) + 0.099, R = 0.756, p < 0.0001). Therefore it is concluded that the newly derived cell suspension model is well suited for the description of the dielectric properties of human tissues and thus the derivation of the ECF volume fraction and equivalent epsilon m.

Derivation of extracellular fluid volume fraction and equivalent dielectric constant of the cell membrane from dielectric properties of the human body. Part 2: A preliminary study for tracking the progression of surgical tissue injury

“…The cell suspension model incorporating fat tissue was applied to fit real and imaginary parts of e* of the body segments and, in each body segment, estimate the best-fit values of the volume fraction of cells in suspension qb, the equivalent dielectric constant of the cell membrane ~ .... a distribution parameter of the relaxation time of a dielectric dispersion/3, and the volume fraction of fat-free mass in the whole tissue q (TATARA and TSUZAKI, 2000).…”

“…The dielectric constant e, electrical conductivity ~-(in S m -I ) and complex dielectric constant e* of the body segments were obtained from the resistance and reactance of the body segments, assuming a cylinder of the body segment in length ([i, i = A for right arm, T for left side of trunk, and L for right leg) and crosssectional area (A i, i = A for right arm, T for left side of trunk, and L for right leg) (TATARA and TSUZAKI, 2000).…”

“…in the accompanying paper (TATARA and TSUZAKI, 2000), the cell suspension model incorporating fat tissue satisfactorily described the dielectric properties of the arm, and thus provided estimates of the extracellular fluid (ECF) volume fraction and the equivalent dielectric constant of the cell membrane e,,,. it is the purpose of this work to determine whether these cell parameters can track changes in cell pathophysiology in critically ill patients.…”

A microwave system based on a UWB microstrip antenna for non‐invasive in vitro measurement of glycemia in human blood: An experimental study

“…Therefore, when it comes to non‐invasive measurement, sensors based on electromagnetic fields or antennas are commonly used. In this regard, some research has been done, with microwave microstrip resonators being one of the prospective technologies for developing such a device 22–25 …”

“…In this regard, some research has been done, with microwave microstrip resonators being one of the prospective technologies for developing such a device. [22][23][24][25] Our work is part of the continuity of non-invasive methods that aim to improve the quality of blood glucose monitoring for patients who have diabetes. We suggested a microwave system for detecting glycemia in human blood using UWB antenna radiation in several blood samples.…”