Investigation of Anemia and the Dielectric Properties of Human Blood at Microwave Frequencies (original) (raw)
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Application of Machine Learning to Predict Dielectric Properties of In Vivo Biological Tissue
Sensors
In this paper we revisited a database with measurements of the dielectric properties of rat muscles. Measurements were performed both in vivo and ex vivo; the latter were performed in tissues with varying levels of hydration. Dielectric property measurements were performed with an open-ended coaxial probe between the frequencies of 500 MHz and 50 GHz at a room temperature of 25 °C. In vivo dielectric properties are more valuable for creating realistic electromagnetic models of biological tissue, but these are more difficult to measure and scarcer in the literature. In this paper, we used machine learning models to predict the in vivo dielectric properties of rat muscle from ex vivo dielectric property measurements for varying levels of hydration. We observed promising results that suggest that our model can make a fair estimation of in vivo properties from ex vivo properties.
Physics in Medicine and Biology, 1996
Three experimental techniques based on automatic swept-frequency network and impedance analysers were used to measure the dielectric properties of tissue in the frequency range 10 Hz to 20 GHz. The technique used in conjunction with the impedance analyser is described. Results are given for a number of human and animal tissues, at body temperature, across the frequency range, demonstrating that good agreement was achieved between measurements using the three pieces of equipment. Moreover, the measured values fall well within the body of corresponding literature data.
Physics in Medicine and Biology, 1996
A parametric model was developed to describe the variation of dielectric properties of tissues as a function of frequency. The experimental spectrum from 10 Hz to 100 GHz was modelled with four dispersion regions. The development of the model was based on recently acquired data, complemented by data surveyed from the literature. The purpose is to enable the prediction of dielectric data that are in line with those contained in the vast body of literature on the subject. The analysis was carried out on a Microsoft Excel spreadsheet. Parameters are given for 17 tissue types.
The Dielectric Properties of Biological Tissues: I
1996
The dielectric properties of tissues have been extracted from the literature of the past five decades and presented in a graphical format. The purpose is to assess the current state of knowledge, expose the gaps there are and provide a basis for the evaluation and analysis of corresponding data from an on-going measurement programme. † Present address:
The dielectric properties of biological tissues: I. Literature survey
Physics in Medicine and Biology, 1996
The dielectric properties of tissues have been extracted from the literature of the past five decades and presented in a graphical format. The purpose is to assess the current state of knowledge, expose the gaps there are and provide a basis for the evaluation and analysis of corresponding data from an on-going measurement programme.
Sensors, 2020
Medical devices making use of radio frequency (RF) and microwave (MW) fields have been studied as alternatives to existing diagnostic and therapeutic modalities since they offer several advantages. However, the lack of accurate knowledge of the complex permittivity of different biological tissues continues to hinder progress in of these technologies. The most convenient and popular measurement method used to determine the complex permittivity of biological tissues is the open-ended coaxial line, in combination with a vector network analyser (VNA) to measure the reflection coefficient (S11) which is then converted to the corresponding tissue permittivity using either full-wave analysis or through the use of equivalent circuit models. This paper proposes an innovative method of using artificial neural networks (ANN) to convert measured S11 to tissue permittivity, circumventing the requirement of extending the VNA measurement plane to the coaxial line open end. The conventional three-step calibration technique used with coaxial open-ended probes lacks repeatability, unless applied with extreme care by experienced persons, and is not adaptable to alternative sensor antenna configurations necessitated by many potential diagnostic and monitoring applications. The method being proposed does not require calibration at the tip of the probe, thus simplifying the measurement procedure while allowing arbitrary sensor design, and was experimentally validated using S11 measurements and the corresponding complex permittivity of 60 standard liquid and 42 porcine tissue samples. Following ANN training, validation and testing, we obtained a prediction accuracy of 5% for the complex permittivity.
Dielectric properties of the tissues with different histological structure: Ex vivo study
Journal of Experimental Biology and Agricultural Sciences
This study aimed to estimate the dielectric properties of tissues with different histological structures. For this, specimens of fibrous (n=9), muscular (n=7), and fatty (n=11) human tissues were studied. The estimation of dielectric permittivity and conductivity of these specimens was tested with a program and apparatus device for near-field resonance microwave sensing, including 5 applicators with different depths of study. Results of the study demonstrated that this technology can visualize the shape, localization, and linear decisions of biological objects. The currently used method allows distinguishing the tissue histological type. It was stated that fibrous tissue has a maximal level of median and highest dielectric permittivity, and the minimal value of this parameter was fixed for fatty specimens (in 4.26 and 4.53 times lower than in fibrous one, respectively). Muscular tissue has an intermediate value of dielectric permittivity, approaching a level close to fibrous tissue.
Study of Dielectric Properties of Biological Tissues in the Microwave Frequency Range
2009
The complex dielectric constants at room temperature of various goat tissues (liver, muscle, kidney, heart and brain) and corn syrup were measured in the frequency range 1 to 10 GHz with the help of a HP Network Analyzer N5230A. Open ended coaxial cable method was employed for the measurement. The system imperfections are completely avoided by calibrating the system with four known materials and their reflection coefficients were used in the calculation along with the reflection coefficient of the sample. The relaxation frequency in the δ region, spread of relaxation, volume fraction of protein present in tissues are calculated from the measured dielectric data. The dielectric constant of corn syrup samples suggests the feasibility of using corn syrup as a tissue equivalent for microwave imaging applications. Introduction and Scope Electrical properties of biological materials and their interaction with electromagnetic waves have attracted the attention of researchers working in the...
Dielectric response of some biological tissues
Bioelectromagnetics, 2001
The dielectric properties of two freshly excised mice tissue samples (kidney, skeletal muscle) and also freshly excised Ehrlich solid tumor were measured in the frequency range from 20 Hz to 100 kHz using RLC bridges. The data were ®tted to a summation of multiple Cole±Cole dispersion and also to the constant power law which is related formally to the fractal geometries of tissues using a genetic algorithm for optimization developed by the author. The data were in good agreement with the Cole±Cole equation for the three samples. Bioelectromagnetics 22:272±279, 2001.