Dielectric Characterization of <italic>In Vivo</italic> Abdominal and Thoracic Tissues in the 0.5–26.5 GHz Frequency Band for Wireless Body Area Networks

Abstract

The dielectric properties of biological tissues are of utmost importance in the development of wireless body area networks (WBANs), especially for implanted devices. The early design stages of medical devices like capsule endoscopy, pacemakers, or physiological sensors rely on precise knowledge of the dielectric properties of the tissues present in their surrounding medium. Many of these applications make use of electromagnetic phantoms, which are software or physical models that imitate the shape and the electromagnetic properties of the tissues. They are used for designing devices in software simulations and for testing them in laboratory trials, aiding in both the development of WBAN antennas or in communication link evaluations. The existing reports about dielectric in vivo properties are limited and have drawbacks like: low variety of characterized tissues, lacking some relevant ones, and limitations and inhomogeneity in the measured frequency range. This paper aims at filling that gap by providing a new database of dielectric properties of biological tissues measured in vivo. In particular, it is focused on the tissues of the thoracic and the abdominal regions, measured at the same wide frequency band, on the same animal specimen, and under the same conditions. The properties have been obtained by measuring porcine tissues in the 0.5-26.5 GHz band with the open-ended coaxial technique. In this paper, we focus on those tissues that have been scarcely characterized so far in the literature, like heart, esophagus, stomach, and pancreas. The Cole-Cole fitting parameters of the measured tissues and their uncertainties are provided.INDEX TERMS Biological materials, body sensor networks, dielectric measurement, in vivo, permittivity.

Multiclass Classification of Hepatic Anomalies with Dielectric Properties: From Phantom Materials to Rat Hepatic Tissues

“…The uncertainty calculation described in [15,16] was adopted in literature for dielectric property measurements of biological tissues to identify the possible error sources [17]. Factors contributing to the uncertainty were listed as measurement repeatability, systematic errors, system drift, cable movements [17,18].…”

Dielectric Properties of Ovine Heart at Microwave Frequencies

“…The slim form open-ended coaxial probes from 85070E Dielectric Probe Kit (Keysight, Santa Rosa, CA, USA) that were used in this study are suitable for both ex vivo and in vivo measurements over the frequency range of interest [ 1 , 39 , 40 ]. While this study considers ex vivo measurements, the method has been applied successfully to in vivo measurements [ 1 , 17 , 40 ]. While care needs to be taken to control for confounding factors such as the temperature of the tissue, time from excision and measurement uncertainties, the open-ended coaxial probe method has been demonstrated to be the most applicable for measuring the dielectric properties of biological tissues over the microwave frequency range [ 1 ].…”

“…While the manufacturer recommends the probe should be inserted 5 mm into the material under test, this was avoided in this study as it would cause damage to the tissue. Instead, a good contact between the tissue and the probe has been considered to be adequate in numerous studies on dielectric properties of biological tissues [ 1 , 17 , 18 , 21 , 45 , 46 ]. The pressure applied between the probe and the sample was moderate as excessive probe-sample pressure can cause inaccurate measurements [ 1 ].…”

“…In a more recent study by Fornes-Leal et al from 2019 [ 17 ], dielectric properties of the porcine heart, among other porcine thoracic tissues, were measured in vivo at the frequency range from 500 MHz to 26.5 GHz. In this study, the heart was treated as a homogeneous organ and while the measurements were made at five different locations on each organ that was measured, the anatomical part of the heart that was measured is not specified.…”

In Vivo Dielectric Properties of Healthy and Benign Rat Mammary Tissues from 500 MHz to 18 GHz

“…In [6,7], effect of tissue hydration to dielectric properties was explored by performing experiments on rat muscle, rat fat, and mouse kidney tissues. In another study [8], dielectric properties of abdominal and thoracic tissues of cattle were investigated to enable research on wireless body area networks. In [9,10], rat skin and swine skin dielectric properties were characterized for testing of implantable antennas.…”