Advanced Temperature Dielectric Spectroscopy Of Muscle Phantom At Microwave Frequencies (original) (raw)
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Microwave Estimation of Dielectric Properties of Biological Tissue Under Thermal Modification
Archiv Euromedica
The aim of this study was to estimate changes of tissue dielectric parameters under the action of high temperature. We fixed the shifts of dielectric properties of biological tissue samples, associated with short-time influence of high temperature (600C, 5 min.) in vitro. The dielectric properties of tissues (permittivity - ε and conductivity - σ) were determined using original software and hardware complex for near-field resonant microwave sensing developed at the Institute of Applied Physics of the RAS. The study of these parameters was performed at a depth of 5 mm. It was found that short processing of a biological sample in moderate hyperthermia (600C) leads to significant change of dielectric characteristics of the tissue. This is manifested in a significant decrease in the dielectric permittivity (in 2.48 times for an intact specimen) and conductivity (on 25.3%) of the studied biological sample, due to its dehydration. It was shown that used regimen of heating decreases the pe...
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...
Physics in Medicine and Biology, 2006
The development of ultrawideband (UWB) microwave diagnostic and therapeutic technologies, such as UWB microwave breast cancer detection and hyperthermia treatment, is facilitated by accurate knowledge of the temperature-and frequency-dependent dielectric properties of biological tissues. To this end, we characterize the temperature-dependent dielectric properties of a representative tissue type-animal liver-from 0.5 to 20 GHz. Since discrete-frequency linear temperature coefficients are impractical and inappropriate for applications spanning wide frequency and temperature ranges, we propose a novel and compact data representation technique. A single-pole Cole-Cole model is used to fit the dielectric properties data as a function of frequency, and a second-order polynomial is used to fit the Cole-Cole parameters as a function of temperature. This approach permits rapid estimation of tissue dielectric properties at any temperature and frequency.
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.
Design and evaluation of medical microwave radiometer for measuring tissue temperature
2019 URSI Asia-Pacific Radio Science Conference (AP-RASC)
Medical microwave radiometry is a passive non-invasive technique for measuring tissue temperature gradient in the human body. Design and evaluation of a medical microwave radiometer centered at 1.3 GHz with 330 MHz bandwidth is presented here. An active noise source with noise equivalent temperature of 303 K is used for temperature calibration. Radiometer characterization results are presented for matched load maintained at thermal steady state and hot spot in a tissue phantom. Radiometer measurements recorded using a dielectric loaded waveguide and substrate integrated waveguide (SIW) antenna with a slot demonstrated the ability to measure the temperature gradient at depth.
The Microwave Properties of Tissue and Other Lossy Dielectrics
2004
This thesis describes work on the theoretical modelling and experimental measurement of the complex permittivity of dielectrics. The main focus of research has been into the characterisation of permittivity of planar and layered samples within the millimetre wave band. The measurement method is based on the free-space measurement of the transmission and reflection coefficients of samples. A novel analytical method of determining the transmission and reflection coefficients as functions of frequency arising from a generalised structure of planar dielectric layers is also described and validated. The analytical method is based on signal flow techniques. The measurement and analytical techniques have been applied in two main areas: firstly, the acquisition of new data on human skin in the band 57 to 100GHz and secondly, the detection and location of defects in composite materials for which a band of 90 to 100GHz was used. Measurements have been made on the complex permittivity of a single sample of excised human skin fixed in formaldehyde. The experimental results have been corrected to account for the fixing process in formaldehyde and are projected to body temperature. This data is, to the best of the author's knowledge, the first of its kind to be published. Predicted skin permittivity based on various relaxation models varies widely and only partially fits the measured data. The experimental results have been used to determine the parameters of a Cole-Cole function which gives the best fit to the measured data. The measured skin data has also been used to calculate power deposition in skin exposed to millimetre wave radiation. This work concludes that a skin surface temperature rise of only 0.2 0 C results from a thirty second exposure to signals of 100W/m 2. Experimental work with fibreglass composite samples has shown that defects such as delaminations, voids, matrix cracks and improper cure result in resolvable differences in the dielectric properties of the samples at 90-100GHz. The measurement technique is particularly sensitive to the detection of cracks and its spatial resolution is 20mm or better. Whilst confirming the general conclusions of previously published work, the specific findings of this study are novel.
Dielectric Properties of Healthy Ex-Vivo Ovine Lung Tissue at Microwave Frequencies
IEEE Transactions on Dielectrics and Electrical Insulation
Knowledge of dielectric properties of lung tissue is fundamental for the improvement of lung disease diagnostics and therapeutic solutions (e.g. microwave imaging and microwave thermal ablation treatment). Although lung disease rates are increasing, lung tissue remains one of the least characterized tissues due to its heterogeneity, variability in air content, and handling difficulties. In this work, dielectric properties of ex-vivo ovine lung tissue samples were measured in the frequency range 500 MHz-8 GHz, together with measurements of sample density (air content). Different Cole-Cole models were applied to the measured dielectric properties values. The best fitting model was chosen, and results were compared with available literature. Furthermore, the dielectric property measurements were correlated with the air content of the samples. Updated Cole-Cole models for lung tissue of different density is provided in the 500 MHz-8 GHz range. The existence of air content threshold in lung is shown. Below this limit, the properties begin to change drastically with the change in density. Index Terms-Cole-Cole model fitting, dielectric spectroscopy, lung tissue air content, lung tissue dielectric properties, open-ended coaxial probe I. INTRODUCTION NOWLEDGE of tissue dielectric properties is paramount in various electromagnetic-based medical applications such as diagnostics, therapy, dosimetry, and monitoring. A diagnostic and monitoring technique relying on dielectric properties knowledge is Microwave Imaging (MWI) [1]. MWI determines the position of healthy and malignant tissue based on contrast in dielectric properties. Examples of its use from the literature are in the liver [2], and lately, in lung tissue [3]. A therapeutic technique that benefits from an accurate knowledge of the dielectric properties is microwave thermal ablation (MWA) [2], [4], [5]. While tissues such as liver [5]-[7], heart [6], muscle [5], [6], [8], and breast tissue [9] are well characterized, lung tissue remains insufficiently studied in the microwave range due to handling difficulties and tissue heterogeneity [6]. Nevertheless, the number of lung diseases diagnosed yearly is continuously rising, the incidence of lung cancer is second This research was funded by Government of Ireland, Disruptive Technology Innovation Fund (DTIF), grant number DT2020189. K. Vidjak and M. Cavagnaro are with the
Dielectric properties of animal tissues in vivo at frequencies 10 MHz – 1 GHz
Bioelectromagnetics, 1981
An open-ended coaxial line sensor in conjunction with an automatic network analyzer was used to measure in vivo the permittivity of several feline tissues (skeletal and smooth muscle, liver, kidney, spleen, and braingray and white matter) at frequencies between 10 MHz and 1 GHz. The estimated uncertainties of measurement were between 1.5% and 5%. The data are in general agreement with previously obtained data in vitro and in vivo. Significant differences in the properties of different types of the same tissue (eg, skeletal and smooth muscle) were observed. Many tissues were found to be non-homogeneous in its permittivity.
Research of a microwave radiometer for monitoring of internal temperature of biological tissues
Eastern-European Journal of Enterprise Technologies, 2019
ABSTRACT Currently, there is growing interest among specialists in the use of non-invasive dose-free technologies for diagnosis and monitoring treatment of various diseases. Microwave radiometry enables non-invasive detection of thermal abnormalities in internal tissues of the human body. The current level of development of the method of microwave radiometry makes it possible to non-invasively detect malignant neoplasms at early stages according to characteristics of the person's own radiothermal fields. For a wider implementation of the method, it is necessary to overcome a series of scientific and technical barriers that impede its development. First of all, it is necessary to ensure miniaturization of the equipment used. An analytical review of the current state of development in the field of medical radiometers has been performed. Miniaturization of equipment is an important area for studies. It was shown that application of the proposed scheme for designing a null balance radiometer with a sliding scheme of reflection compensation with two matched RF loads will enable creation of a miniature highly stable radiometer. The measurement error of this device does not depend on the ambient temperature, intrinsic temperature of the device and impedance of the studied area of the body. The device calibration procedure was considered and noise signal calculations were performed. Results of experimental verification of correctness of choice of the way of designing the miniature radiometer circuit were presented. Introduction of thermal compensation has made it possible to reduce measurement error associated with the device heating to 0.2 °C when intrinsic temperature of the radiometer changed by 20 °C. It was shown that a radiometer operating in the frequency band 3.4–4.2 GHz can be used to detect various diseases and monitor internal temperature of tissues during treatment. With introduction of autonomous power supply and wireless communication with a smartphone, the miniature radiometer can be used as a wearable device to monitor temperature of internal tissues in everyday human life.