scholarly journals Effect of Open-Ended Coaxial Probe-to-Tissue Contact Pressure on Dielectric Measurements

Sensors ◽  
2020 ◽  
Vol 20 (7) ◽  
pp. 2060 ◽  
Author(s):  
Gertjan Maenhout ◽  
Tomislav Markovic ◽  
Ilja Ocket ◽  
Bart Nauwelaers
Keyword(s):  
Contact Pressure ◽  
Tissue Sample ◽  
Extracellular Fluid ◽  
Biological Tissues ◽  
Dielectric Measurement ◽  
Uncertainty Interval ◽  
Dielectric Data ◽  
Coaxial Probes ◽  
Coaxial Probe ◽  
Cellular Organelles

Open-ended coaxial probes are widely used to gather dielectric properties of biological tissues. Due to the lack of an agreed data acquisition protocol, several environmental conditions can cause inaccuracies when comparing dielectric data. In this work, the effect of a different measurement probe-to-tissue contact pressure was monitored in the frequency range from 0.5 to 20 GHz. Therefore, we constructed a controlled lifting platform with an integrated pressure sensor to exert a constant pressure on the tissue sample during the dielectric measurement. In the pressure range from 7.74 kPa to 77.4 kPa, we observed a linear correlation of − 0.31 ± 0.09 % and − 0.32 ± 0.14 % per kPa for, respectively, the relative real and imaginary complex permittivity. These values are statistically significant compared with the reported measurement uncertainty. Following the literature in different biology-related disciplines regarding pressure-induced variability in measurements, we hypothesize that these changes originate from squeezing out the interstitial and extracellular fluid. This process locally increases the concentration of membranes, cellular organelles, and proteins in the sensed volume. Finally, we suggest moving towards a standardized probe-to-tissue contact pressure, since the literature has already demonstrated that reprobing at the same pressure can produce repeatable data within a 1% uncertainty interval.

scholarly journals Evaluation of a Reflection Method on an Open-Ended Coaxial Line and its Use in Dielectric Measurements

10.14311/882 ◽  
2006 ◽  
Vol 46 (5) ◽  
Author(s):  
R. Zajíček ◽  
J. Vrba ◽  
K. Novotný
Keyword(s):  
Biological Tissue ◽  
Tissue Sample ◽  
Coaxial Line ◽  
Dielectric Measurement ◽  
Network Analyzer ◽  
Reflection Method ◽  
Frequency Range ◽  
Discrete Elements ◽  
Biological Substance ◽  
Coaxial Probe

This paper describes a method for determining the dielectric constant of a biological tissue. A suitable way to make a dielectric measurement that is nondestructive and noninvasive for the biological substance and broadband at the frequency range of the network analyzer is to use a reflection method on an open ended coaxial line. A coaxial probe in the frequency range of the network analyzer from 17 MHz to 2 GHz is under investigation and also a calibration technique and the behavior of discrete elements in an equivalent circuit of an open ended coaxial line. Information about the magnitude and phase of the reflection coefficient on the interface between a biological tissue sample and a measurement probe is modeled with the aid of an electromagnetic field simulator. The numerical modeling is compared with real measurements, and a comparison is presented. 

scholarly journals Open-Ended Coaxial Probe Technique for Dielectric Measurement of Biological Tissues: Challenges and Common Practices

Diagnostics ◽  
2018 ◽  
Vol 8 (2) ◽  
pp. 40 ◽  
Author(s):  
Alessandra La Gioia ◽  
Emily Porter ◽  
Ilja Merunka ◽  
Atif Shahzad ◽  
Saqib Salahuddin ◽  
...  
Keyword(s):  
Biological Tissues ◽  
Dielectric Measurement ◽  
Probe Technique ◽  
Common Practices ◽  
Coaxial Probe

scholarly journals Challenges of Post-measurement Histology for the Dielectric Characterisation of Heterogeneous Biological Tissues

Sensors ◽  
2020 ◽  
Vol 20 (11) ◽  
pp. 3290
Author(s):  
Alessandra La Gioia ◽  
Martin O’Halloran ◽  
Emily Porter
Keyword(s):  
Dielectric Properties ◽  
Histological Analysis ◽  
Tissue Sample ◽  
Biological Tissues ◽  
Tissue Samples ◽  
Heterogeneous Samples ◽  
Heterogeneous Tissue ◽  
Reported Data ◽  
Heterogeneous Tissues ◽  
Coaxial Probe

The dielectric properties of biological tissues are typically measured using the open-ended coaxial probe technique, which is based on the assumption that the tissue sample is homogeneous. Therefore, for heterogeneous tissue samples, additional post-measurement sample processing is conducted. Specifically, post-measurement histological analysis may be performed in order to associate the measured dielectric properties with the tissue types present in a heterogeneous sample. Accurate post-measurement histological analysis enables identification of the constituent tissue types that contributed to the measured dielectric properties, and their relative distributions. There is no standard protocol for conducting post-measurement histological analysis, which leads to high numbers of excluded tissue samples and inconsistencies in the resulting reported data for heterogeneous tissues. To this extent, this study examines the post-measurement histological process and the challenges in associating the acquired dielectric properties with the different tissue types present in heterogeneous samples. The results demonstrate that the histological process inevitably alters the morphology of samples, thus introducing errors in the interpretation of the dielectric properties acquired from heterogeneous biological samples. Notably, sample size was seen to shrink by up to 90% through the histological process, meaning that sensing volume determined from fresh tissues is not directly applicable to histology images.

scholarly journals Design and Demonstration of a Microbiaxial Optomechanical Device for Multiscale Characterization of Soft Biological Tissues with Two-Photon Microscopy

2011 ◽  
Vol 17 (2) ◽  
pp. 167-175 ◽  
Author(s):  
Joseph T. Keyes ◽  
Stacy M. Borowicz ◽  
Jacob H. Rader ◽  
Urs Utzinger ◽  
Mohamad Azhar ◽  
...  
Keyword(s):  
Mechanical Response ◽  
Tissue Sample ◽  
Imaging Techniques ◽  
High Stress ◽  
Viscoelastic Behavior ◽  
Biological Tissues ◽  
The Body ◽  
Two Photon ◽  
Biomechanical Response ◽  
Tissue Specimens

AbstractThe biomechanical response of tissues serves as a valuable marker in the prediction of disease and in understanding the related behavior of the body under various disease and age states. Alterations in the macroscopic biomechanical response of diseased tissues are well documented; however, a thorough understanding of the microstructural events that lead to these changes is poorly understood. In this article we introduce a novel microbiaxial optomechanical device that allows two-photon imaging techniques to be coupled with macromechanical stimulation in hydrated planar tissue specimens. This allows that the mechanical response of the microstructure can be quantified and related to the macroscopic response of the same tissue sample. This occurs without the need to fix tissue in strain states that could introduce a change in the microstructural configuration. We demonstrate the passive realignment of fibrous proteins under various types of loading, which demonstrates the ability of tissue microstructure to reinforce itself in periods of high stress. In addition, the collagen and elastin response of tissue during viscoelastic behavior is reported showing interstitial fluid movement and fiber realignment potentially responsible for the temporal behavior. We also demonstrate that nonhomogeneities in fiber strain exist over biaxial regions of assumed homogeneity.

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