Tuba Yilmaz - Academia.edu (original) (raw)

Papers by Tuba Yilmaz

Balkan Journal of Electrical and Computer Engineering

With the advancements in machine learning (ML) algorithms, microwave dielectric spectroscopy emer... more With the advancements in machine learning (ML) algorithms, microwave dielectric spectroscopy emerged as a potential new technology for biological tissue and material categorization. Recent studies reported the successful utilization of dielectric properties and Cole-Cole parameters. However, the role of the dataset was not investigated. Particularly, both dielectric properties and Cole-Cole parameters are derived from the S parameter response. This work investigates the possibility of using S parameters as a dataset to categorize the rat hepatic tissues into cirrhosis, malignant, and healthy categories. Using S parameters can potentially remove the need to derive the dielectric properties and enable the utilization of microwave structures such as narrow or wideband antennas or resonators. To this end, in vivo dielectric properties and S parameters collected from hepatic tissues were classified using logistic regression (LR) and adaptive boosting (AdaBoost) algorithms. Cole-Cole parameters and a reproduced dielectric property data set were also investigated. Data preprocessing is performed by using standardization and principal component analysis (PCA). Using the AdaBoost algorithm over 93% and 88% accuracy is obtained for dielectric properties and S parameters, respectively. These results indicate that the classification can be performed with a 5% accuracy decrease indicating that S parameters can be an alternative dataset for tissue classification.

2019 IEEE Conference on Antenna Measurements & Applications (CAMA)

Dielectric properties of rat nasal tissue and nasal carcinoma is given in this work between 500 M... more Dielectric properties of rat nasal tissue and nasal carcinoma is given in this work between 500 MHz to 6 GHz. Nasal carcinoma is induced by oral administration of single dose 20 7,12-Dimethylbenz[a]anthracene (DMBA) dissolved in 1 ml olive oil to 47 days old Sprague Dawley (SD) rats. A granular tissue anomaly in one rat along with bleeding is observed after 15 weeks from the administration of the carcinogenic agent. Invivo dielectric properties are collected both from the granular nasal carcinoma tissue and healthy counterpart with open-ended coaxial probe technique. A median dielectric property discrepancy is observed in the whole frequency range between the nasal carcinoma and healthy tissues.

Sensors

Dielectric properties of biological tissues are traditionally measured with open-ended coaxial pr... more Dielectric properties of biological tissues are traditionally measured with open-ended coaxial probes. Despite being commercially available for laboratory use, the technique suffers from high measurement error. This prevents the practical applications of the open-ended coaxial probes. One such application is the utilization of the technique for skin cancer detection. To enable a diagnostic tool, there is a need to address the error sources. Among others, tissue heterogeneity is a major contributor to measurement error. The effect of tissue heterogeneity on measurement accuracy can be decreased by quantifying the probe sensing depth. To this end, this work (1) investigates the sensing depth of the 2.2 mm-diameter open-ended coaxial probe for skin mimicking material and (2) offers a simple experimental setup and protocol for sensing depth characterization of open-ended coaxial probes. The sensing depth characterized through simulation and experiments using two double-layered configura...

2018 IEEE International Symposium on Antennas and Propagation & USNC/URSI National Radio Science Meeting, 2018

In this paper, a monopole antenna designed to operate in a matching medium is described. The dime... more In this paper, a monopole antenna designed to operate in a matching medium is described. The dimensions of the antenna is optimized with Multi-Objective Particle Swarm Optimization (MOPSO) to obtain the desired reflection coefficient and gain characteristics. All simulations are performed with HFSS in an automated manner by the PSO algorithm via Matlab. The reflection coefficient of the antenna is tested by embedding it to the characterized matching medium. The dielectric properties of the medium is verified with the well known open ended coaxial probe measurement technique. The antenna will be tested with a phantom material mimicking the brain tissues and the results of the microwave imagine algorithm will be presented.

2019 International Conference on Electromagnetics in Advanced Applications (ICEAA), 2019

Broadband dielectric property measurements of biological tissues is mostly performed with open en... more Broadband dielectric property measurements of biological tissues is mostly performed with open ended coaxial probe technique due to a number of advantages such as flexible sample shape and size. However, the technique is known to suffer from high error rates; thus, envisioned applications of the technique remains hampered by this problem. One way to mitigate such error for medical applications is to perform tissue classification with machine learning algorithms. In this work, Cole-Cole parameters of rat liver dielectric properties are used for training and testing of an in house Support Vector Machine (SVM) algorithm to enable malignant tissue classification. Cole-Cole parameters are fitted with Particle Swarm Optimization (PSO) to a total of 700 dielectric property measurements collected from 22 rats. The Cole-Cole parameters are fed to the SVM algorithm and k-fold cross validation is used to prevent the algorithm from memorizing the data. Hepatic malignancies are classified with 9...

Diagnostics

Dielectric properties of biological materials are commonly characterized with open-ended coaxial ... more Dielectric properties of biological materials are commonly characterized with open-ended coaxial probes due to the broadband and non-destructive measurement capabilities. Recently, potential diagnostics applications of the technique have been investigated. Although the technique can successfully classify the tissues with different dielectric properties, the classification accuracy can be improved for tissues with similar dielectric properties. Increase in classification accuracy can be achieved by addressing the error sources. One well-known error source contributing to low measurement accuracy is tissue heterogeneity. To mitigate this error source, there is a need define the probe sensing depth. Such knowledge can enable application-specific probe selection or design. The sensing depth can also be used as an input to the classification algorithms which can potentially improve the tissue classification accuracy. Towards this goal, this work investigates the sensing depth of a commer...

2019 International Applied Computational Electromagnetics Society Symposium (ACES), 2019

Dermal tissue characterization based on dielectric properties can be utilized as a non-invasive m... more Dermal tissue characterization based on dielectric properties can be utilized as a non-invasive method for diagnosis of skin cancers. To enable such technology, there is a need to develop techniques that can rapidly and accurately collect the dielectric properties of the skin tissues. Therefore, the current measurement techniques and tools has to be optimized for skin cancer detection. To this end, this study presents dielectric property measurements with open-ended coaxial probes having small apertures customized for detection of skin cancer. Relative permittivity and conductivity of rat skin tissue is characterized with open-ended coaxial probes with outer diameters of 0.9mm and 0.5mm between 0.5GHz-6GHz and the measurement results are compared with the traditional probes having diameter of 2.2mm. The results agree well with the reported literature data.

Microwave hyperthermia (MH) requires the selective focusing of microwave energy on the targeted r... more Microwave hyperthermia (MH) requires the selective focusing of microwave energy on the targeted region while minimally affecting the healthy tissue. Emerging from the simple nature of the linear antenna arrays, this work demonstrates focusing maps as an application guide for MH focusing by adjusting the antenna phase values. The focusing of the heating potential (HP) on different density breast models is performed via the proposed method using Vivaldi antennas. The effect of the tumor conductivity on the focusing is discussed. As a straightforward approach and utilizing the Vivaldi antennas, the system can be further combined with MH monitoring application.

This paper presents a comparative study in an attempt to identify the best frequency of operation... more This paper presents a comparative study in an attempt to identify the best frequency of operation for a potential microwave glucose sensor. Two patch antennas operating at 2.45 GHz and 5.8 GHz are designed to radiate towards high permittivity and high loss de-ionized water medium. Antennas are covered with superstrates to limit the contact with the liquid and mounted at the bottom of containers. From the measured S11 response of the antennas with changing glucose levels, it was concluded that the antenna operating at the higher frequency is more sensitive to the changes in the glucose levels.

Dielectric properties of biological materials are commonly characterized with open-ended coaxial ... more Dielectric properties of biological materials are commonly characterized with open-ended coaxial probes due to the broadband and non-destructive measurement capabilities. Recently, potential diagnostics applications of the technique have been investigated. Although the technique can successfully classify the tissues with different dielectric properties, the classification accuracy can be improved for tissues with similar dielectric properties. Increase in classification accuracy can be achieved by addressing the error sources. One well-known error source contributing to low measurement accuracy is tissue heterogeneity. To mitigate this error source, there is a need define the probe sensing depth. Such knowledge can enable application-specific probe selection or design. The sensing depth can also be used as an input to the classification algorithms which can potentially improve the tissue classification accuracy. Towards this goal, this work investigates the sensing depth of a commer...

Simple Summary This work investigates the effect of skin tissue heterogeneity on the sensing dept... more Simple Summary This work investigates the effect of skin tissue heterogeneity on the sensing depth of the open-ended coaxial probe to exploit the potential use of the probe for skin cancer detection and to establish a simple measurement protocol for skin depth characterization. Skin depth was calculated through simulations and measurements. Heterogeneity was obtained using double-layered materials composed of gel-like skin mimicking material and liquid olive oil, triton X-100. It was concluded that the sensing depth was not dependent on the frequency between 0.5 to 6 GHz, was affected by the material located at the aperture of the probe, and lastly the dielectric property contrast between layers. Namely the degree of heterogeneity affects the probe sensing depth. Abstract Dielectric properties of biological tissues are traditionally measured with open-ended coaxial probes. Despite being commercially available for laboratory use, the technique suffers from high measurement error. Thi...

In the manuscript, we propose a new technique for determination of Debye parameters, representing... more In the manuscript, we propose a new technique for determination of Debye parameters, representing the dielectric properties of materials, from the reflection coefficient response of open-ended coaxial probes. The method retrieves the Debye parameters using a deep learning model designed through utilization of numerically generated data. Unlike real data, using synthetically generated input and output data for training purposes provides representation of a wide variety of materials with rapid data generation. Furthermore, the proposed method provides design flexibility and can be applied to any desired probe with intended dimensions and material. Next, we experimentally verified the designed deep learning model using measured reflection coefficients when the probe was terminated with five different standard liquids, four mixtures,and a gel-like material.and compared the results with the literature. Obtained mean percent relative error was ranging from 1.21±0.06 to 10.89±0.08. Our wor...

2018 Progress in Electromagnetics Research Symposium (PIERS-Toyama), Aug 1, 2018

Development of new modalities for breast cancer detection have been a research interest due to th... more Development of new modalities for breast cancer detection have been a research interest due to the drawbacks of existing diagnostic technologies such as imaging with ionizing waves. In particular, microwave imaging has been investigated in the literature as a new modality for breast cancer detection. Microwave imaging is a promising technique due to the high dielectric contrast between benign and malignant lesions. With this motivation, the dielectric properties of the benign and malignant breast tissues were measured and such measurements have been performed with the open ended contact probes. The open ended contact probe technique widely used in laboratory environment to characterize the dielectric properties of materials with high permittivity and conductivity due to the advantages such as broad band measurement capabilities and limited sample size requirements. The utilization of the open ended contact probe technique as a breast cancer diagnostic technology have been previously envisioned in the literature. One such application is integration of these probes to biopsy guides to diagnose whether the breast lesions are benign or malignant. However, due to the poor measurement accuracy and repeatability the utilization of the technique as a diagnostic technology was not realized. The drawbacks of the technology mostly stem from the mathematical approaches and the deviations from the initial calibration conditions. In this work, to increase the accuracy of the open ended contact probe measurement technique, the probe structure is redesigned by removing the microwave connections and integrating the probe with the RF cable. Probe simulations are performed with Computer Simulation Technology (CST). The probe is tested with both known materials such as methanol and phantom experiments. Oil in gelatine dispersion phantom materials are composed and measured with the designed probe. Probes with small aperture diameters were also evaluated to investigate the potential practical utilization of such probes. Dielectric properties are calculated with an in-house dielectric property retrieval algorithm. A good agreement is obtained with the reference dielectric property measurements.

Diagnostics

This paper reviews non-invasive blood glucose measurements via dielectric spectroscopy at microwa... more This paper reviews non-invasive blood glucose measurements via dielectric spectroscopy at microwave frequencies presented in the literature. The intent is to clarify the key challenges that must be overcome if this approach is to work, to suggest some possible ways towards addressing these challenges and to contribute towards prevention of unnecessary ‘reinvention of the wheel’.

Sensors, Apr 14, 2020

This work investigates the in vivo dielectric properties of healthy and benign rat mammary tissue... more This work investigates the in vivo dielectric properties of healthy and benign rat mammary tissues in an attempt to expand the dielectric property knowledge of animal models. The outcomes of this study can enable testing of microwave medical technologies on animal models and interpretation of tissue alteration-dependent in vivo dielectric properties of mammary tissues. Towards this end, in vivo dielectric properties of healthy rat mammary tissues and chemically induced benign rat mammary tumors including low-grade adenosis, sclerosing adenosis, and adenosis were collected with open-ended coaxial probes from 500 MHz to 18 GHz. The in vivo measurements revealed that the dielectric properties of benign rat mammary tumors are higher than the healthy rat mammary tissues by 9.3% to 35.5% and 19.6% to 48.7% for relative permittivity and conductivity, respectively. Furthermore, to our surprise, we found that the grade of the benign tissue affects the dielectric properties for this study. Finally, a comparison with ex vivo healthy human mammary tissue dielectric properties revealed that the healthy rat mammary tissues best replicate the dielectric properties of healthy medium density human samples.

Diagnostics

SAFE (Scan and Find Early) is a novel microwave imaging device intended for breast cancer screeni... more SAFE (Scan and Find Early) is a novel microwave imaging device intended for breast cancer screening and early detection. SAFE is based on the use of harmless electromagnetic waves and can provide relevant initial diagnostic information without resorting to X-rays. Because of SAFE’s harmless effect on organic tissue, imaging can be performed repeatedly. In addition, the scanning process itself is not painful since breast compression is not required. Because of the absence of physical compression, SAFE can also detect tumors that are close to the thoracic wall. A total number of 115 patients underwent the SAFE scanning procedure, and the resultant images were compared with available magnetic resonance (MR), ultrasound, and mammography images in order to determine the correct detection rate. A sensitivity of 63% was achieved. Breast size influenced overall sensitivity, as sensitivity was lower in smaller breasts (51%) compared to larger ones (74%). Even though this is only a preliminar...

2021 XXXIVth General Assembly and Scientific Symposium of the International Union of Radio Science (URSI GASS)

2021 XXXIVth General Assembly and Scientific Symposium of the International Union of Radio Science (URSI GASS)

2019 23rd International Conference on Applied Electromagnetics and Communications (ICECOM)

Sensors

Open-ended coaxial probes can be used as tissue characterization devices. However, the technique ... more Open-ended coaxial probes can be used as tissue characterization devices. However, the technique suffers from a high error rate. To improve this technology, there is a need to decrease the measurement error which is reported to be more than 30% for an in vivo measurement setting. This work investigates the machine learning (ML) algorithms’ ability to decrease the measurement error of open-ended coaxial probe techniques to enable tissue characterization devices. To explore the potential of this technique as a tissue characterization device, performances of multiclass ML algorithms on collected in vivo rat hepatic tissue and phantom dielectric property data were evaluated. Phantoms were used for investigating the potential of proliferating the data set due to difficulty of in vivo data collection from tissues. The dielectric property measurements were collected from 16 rats with hepatic anomalies, 8 rats with healthy hepatic tissues, and in house phantoms. Three ML algorithms, k-neare...

Balkan Journal of Electrical and Computer Engineering

With the advancements in machine learning (ML) algorithms, microwave dielectric spectroscopy emer... more With the advancements in machine learning (ML) algorithms, microwave dielectric spectroscopy emerged as a potential new technology for biological tissue and material categorization. Recent studies reported the successful utilization of dielectric properties and Cole-Cole parameters. However, the role of the dataset was not investigated. Particularly, both dielectric properties and Cole-Cole parameters are derived from the S parameter response. This work investigates the possibility of using S parameters as a dataset to categorize the rat hepatic tissues into cirrhosis, malignant, and healthy categories. Using S parameters can potentially remove the need to derive the dielectric properties and enable the utilization of microwave structures such as narrow or wideband antennas or resonators. To this end, in vivo dielectric properties and S parameters collected from hepatic tissues were classified using logistic regression (LR) and adaptive boosting (AdaBoost) algorithms. Cole-Cole parameters and a reproduced dielectric property data set were also investigated. Data preprocessing is performed by using standardization and principal component analysis (PCA). Using the AdaBoost algorithm over 93% and 88% accuracy is obtained for dielectric properties and S parameters, respectively. These results indicate that the classification can be performed with a 5% accuracy decrease indicating that S parameters can be an alternative dataset for tissue classification.

2019 IEEE Conference on Antenna Measurements & Applications (CAMA)

Dielectric properties of rat nasal tissue and nasal carcinoma is given in this work between 500 M... more Dielectric properties of rat nasal tissue and nasal carcinoma is given in this work between 500 MHz to 6 GHz. Nasal carcinoma is induced by oral administration of single dose 20 7,12-Dimethylbenz[a]anthracene (DMBA) dissolved in 1 ml olive oil to 47 days old Sprague Dawley (SD) rats. A granular tissue anomaly in one rat along with bleeding is observed after 15 weeks from the administration of the carcinogenic agent. Invivo dielectric properties are collected both from the granular nasal carcinoma tissue and healthy counterpart with open-ended coaxial probe technique. A median dielectric property discrepancy is observed in the whole frequency range between the nasal carcinoma and healthy tissues.

Sensors

Dielectric properties of biological tissues are traditionally measured with open-ended coaxial pr... more Dielectric properties of biological tissues are traditionally measured with open-ended coaxial probes. Despite being commercially available for laboratory use, the technique suffers from high measurement error. This prevents the practical applications of the open-ended coaxial probes. One such application is the utilization of the technique for skin cancer detection. To enable a diagnostic tool, there is a need to address the error sources. Among others, tissue heterogeneity is a major contributor to measurement error. The effect of tissue heterogeneity on measurement accuracy can be decreased by quantifying the probe sensing depth. To this end, this work (1) investigates the sensing depth of the 2.2 mm-diameter open-ended coaxial probe for skin mimicking material and (2) offers a simple experimental setup and protocol for sensing depth characterization of open-ended coaxial probes. The sensing depth characterized through simulation and experiments using two double-layered configura...

2018 IEEE International Symposium on Antennas and Propagation & USNC/URSI National Radio Science Meeting, 2018

In this paper, a monopole antenna designed to operate in a matching medium is described. The dime... more In this paper, a monopole antenna designed to operate in a matching medium is described. The dimensions of the antenna is optimized with Multi-Objective Particle Swarm Optimization (MOPSO) to obtain the desired reflection coefficient and gain characteristics. All simulations are performed with HFSS in an automated manner by the PSO algorithm via Matlab. The reflection coefficient of the antenna is tested by embedding it to the characterized matching medium. The dielectric properties of the medium is verified with the well known open ended coaxial probe measurement technique. The antenna will be tested with a phantom material mimicking the brain tissues and the results of the microwave imagine algorithm will be presented.

2019 International Conference on Electromagnetics in Advanced Applications (ICEAA), 2019

Broadband dielectric property measurements of biological tissues is mostly performed with open en... more Broadband dielectric property measurements of biological tissues is mostly performed with open ended coaxial probe technique due to a number of advantages such as flexible sample shape and size. However, the technique is known to suffer from high error rates; thus, envisioned applications of the technique remains hampered by this problem. One way to mitigate such error for medical applications is to perform tissue classification with machine learning algorithms. In this work, Cole-Cole parameters of rat liver dielectric properties are used for training and testing of an in house Support Vector Machine (SVM) algorithm to enable malignant tissue classification. Cole-Cole parameters are fitted with Particle Swarm Optimization (PSO) to a total of 700 dielectric property measurements collected from 22 rats. The Cole-Cole parameters are fed to the SVM algorithm and k-fold cross validation is used to prevent the algorithm from memorizing the data. Hepatic malignancies are classified with 9...

Diagnostics

Dielectric properties of biological materials are commonly characterized with open-ended coaxial ... more Dielectric properties of biological materials are commonly characterized with open-ended coaxial probes due to the broadband and non-destructive measurement capabilities. Recently, potential diagnostics applications of the technique have been investigated. Although the technique can successfully classify the tissues with different dielectric properties, the classification accuracy can be improved for tissues with similar dielectric properties. Increase in classification accuracy can be achieved by addressing the error sources. One well-known error source contributing to low measurement accuracy is tissue heterogeneity. To mitigate this error source, there is a need define the probe sensing depth. Such knowledge can enable application-specific probe selection or design. The sensing depth can also be used as an input to the classification algorithms which can potentially improve the tissue classification accuracy. Towards this goal, this work investigates the sensing depth of a commer...

2019 International Applied Computational Electromagnetics Society Symposium (ACES), 2019

Dermal tissue characterization based on dielectric properties can be utilized as a non-invasive m... more Dermal tissue characterization based on dielectric properties can be utilized as a non-invasive method for diagnosis of skin cancers. To enable such technology, there is a need to develop techniques that can rapidly and accurately collect the dielectric properties of the skin tissues. Therefore, the current measurement techniques and tools has to be optimized for skin cancer detection. To this end, this study presents dielectric property measurements with open-ended coaxial probes having small apertures customized for detection of skin cancer. Relative permittivity and conductivity of rat skin tissue is characterized with open-ended coaxial probes with outer diameters of 0.9mm and 0.5mm between 0.5GHz-6GHz and the measurement results are compared with the traditional probes having diameter of 2.2mm. The results agree well with the reported literature data.

Microwave hyperthermia (MH) requires the selective focusing of microwave energy on the targeted r... more Microwave hyperthermia (MH) requires the selective focusing of microwave energy on the targeted region while minimally affecting the healthy tissue. Emerging from the simple nature of the linear antenna arrays, this work demonstrates focusing maps as an application guide for MH focusing by adjusting the antenna phase values. The focusing of the heating potential (HP) on different density breast models is performed via the proposed method using Vivaldi antennas. The effect of the tumor conductivity on the focusing is discussed. As a straightforward approach and utilizing the Vivaldi antennas, the system can be further combined with MH monitoring application.

This paper presents a comparative study in an attempt to identify the best frequency of operation... more This paper presents a comparative study in an attempt to identify the best frequency of operation for a potential microwave glucose sensor. Two patch antennas operating at 2.45 GHz and 5.8 GHz are designed to radiate towards high permittivity and high loss de-ionized water medium. Antennas are covered with superstrates to limit the contact with the liquid and mounted at the bottom of containers. From the measured S11 response of the antennas with changing glucose levels, it was concluded that the antenna operating at the higher frequency is more sensitive to the changes in the glucose levels.

Dielectric properties of biological materials are commonly characterized with open-ended coaxial ... more Dielectric properties of biological materials are commonly characterized with open-ended coaxial probes due to the broadband and non-destructive measurement capabilities. Recently, potential diagnostics applications of the technique have been investigated. Although the technique can successfully classify the tissues with different dielectric properties, the classification accuracy can be improved for tissues with similar dielectric properties. Increase in classification accuracy can be achieved by addressing the error sources. One well-known error source contributing to low measurement accuracy is tissue heterogeneity. To mitigate this error source, there is a need define the probe sensing depth. Such knowledge can enable application-specific probe selection or design. The sensing depth can also be used as an input to the classification algorithms which can potentially improve the tissue classification accuracy. Towards this goal, this work investigates the sensing depth of a commer...

Simple Summary This work investigates the effect of skin tissue heterogeneity on the sensing dept... more Simple Summary This work investigates the effect of skin tissue heterogeneity on the sensing depth of the open-ended coaxial probe to exploit the potential use of the probe for skin cancer detection and to establish a simple measurement protocol for skin depth characterization. Skin depth was calculated through simulations and measurements. Heterogeneity was obtained using double-layered materials composed of gel-like skin mimicking material and liquid olive oil, triton X-100. It was concluded that the sensing depth was not dependent on the frequency between 0.5 to 6 GHz, was affected by the material located at the aperture of the probe, and lastly the dielectric property contrast between layers. Namely the degree of heterogeneity affects the probe sensing depth. Abstract Dielectric properties of biological tissues are traditionally measured with open-ended coaxial probes. Despite being commercially available for laboratory use, the technique suffers from high measurement error. Thi...

In the manuscript, we propose a new technique for determination of Debye parameters, representing... more In the manuscript, we propose a new technique for determination of Debye parameters, representing the dielectric properties of materials, from the reflection coefficient response of open-ended coaxial probes. The method retrieves the Debye parameters using a deep learning model designed through utilization of numerically generated data. Unlike real data, using synthetically generated input and output data for training purposes provides representation of a wide variety of materials with rapid data generation. Furthermore, the proposed method provides design flexibility and can be applied to any desired probe with intended dimensions and material. Next, we experimentally verified the designed deep learning model using measured reflection coefficients when the probe was terminated with five different standard liquids, four mixtures,and a gel-like material.and compared the results with the literature. Obtained mean percent relative error was ranging from 1.21±0.06 to 10.89±0.08. Our wor...

2018 Progress in Electromagnetics Research Symposium (PIERS-Toyama), Aug 1, 2018

Development of new modalities for breast cancer detection have been a research interest due to th... more Development of new modalities for breast cancer detection have been a research interest due to the drawbacks of existing diagnostic technologies such as imaging with ionizing waves. In particular, microwave imaging has been investigated in the literature as a new modality for breast cancer detection. Microwave imaging is a promising technique due to the high dielectric contrast between benign and malignant lesions. With this motivation, the dielectric properties of the benign and malignant breast tissues were measured and such measurements have been performed with the open ended contact probes. The open ended contact probe technique widely used in laboratory environment to characterize the dielectric properties of materials with high permittivity and conductivity due to the advantages such as broad band measurement capabilities and limited sample size requirements. The utilization of the open ended contact probe technique as a breast cancer diagnostic technology have been previously envisioned in the literature. One such application is integration of these probes to biopsy guides to diagnose whether the breast lesions are benign or malignant. However, due to the poor measurement accuracy and repeatability the utilization of the technique as a diagnostic technology was not realized. The drawbacks of the technology mostly stem from the mathematical approaches and the deviations from the initial calibration conditions. In this work, to increase the accuracy of the open ended contact probe measurement technique, the probe structure is redesigned by removing the microwave connections and integrating the probe with the RF cable. Probe simulations are performed with Computer Simulation Technology (CST). The probe is tested with both known materials such as methanol and phantom experiments. Oil in gelatine dispersion phantom materials are composed and measured with the designed probe. Probes with small aperture diameters were also evaluated to investigate the potential practical utilization of such probes. Dielectric properties are calculated with an in-house dielectric property retrieval algorithm. A good agreement is obtained with the reference dielectric property measurements.

Diagnostics

This paper reviews non-invasive blood glucose measurements via dielectric spectroscopy at microwa... more This paper reviews non-invasive blood glucose measurements via dielectric spectroscopy at microwave frequencies presented in the literature. The intent is to clarify the key challenges that must be overcome if this approach is to work, to suggest some possible ways towards addressing these challenges and to contribute towards prevention of unnecessary ‘reinvention of the wheel’.

Sensors, Apr 14, 2020

This work investigates the in vivo dielectric properties of healthy and benign rat mammary tissue... more This work investigates the in vivo dielectric properties of healthy and benign rat mammary tissues in an attempt to expand the dielectric property knowledge of animal models. The outcomes of this study can enable testing of microwave medical technologies on animal models and interpretation of tissue alteration-dependent in vivo dielectric properties of mammary tissues. Towards this end, in vivo dielectric properties of healthy rat mammary tissues and chemically induced benign rat mammary tumors including low-grade adenosis, sclerosing adenosis, and adenosis were collected with open-ended coaxial probes from 500 MHz to 18 GHz. The in vivo measurements revealed that the dielectric properties of benign rat mammary tumors are higher than the healthy rat mammary tissues by 9.3% to 35.5% and 19.6% to 48.7% for relative permittivity and conductivity, respectively. Furthermore, to our surprise, we found that the grade of the benign tissue affects the dielectric properties for this study. Finally, a comparison with ex vivo healthy human mammary tissue dielectric properties revealed that the healthy rat mammary tissues best replicate the dielectric properties of healthy medium density human samples.

Diagnostics

SAFE (Scan and Find Early) is a novel microwave imaging device intended for breast cancer screeni... more SAFE (Scan and Find Early) is a novel microwave imaging device intended for breast cancer screening and early detection. SAFE is based on the use of harmless electromagnetic waves and can provide relevant initial diagnostic information without resorting to X-rays. Because of SAFE’s harmless effect on organic tissue, imaging can be performed repeatedly. In addition, the scanning process itself is not painful since breast compression is not required. Because of the absence of physical compression, SAFE can also detect tumors that are close to the thoracic wall. A total number of 115 patients underwent the SAFE scanning procedure, and the resultant images were compared with available magnetic resonance (MR), ultrasound, and mammography images in order to determine the correct detection rate. A sensitivity of 63% was achieved. Breast size influenced overall sensitivity, as sensitivity was lower in smaller breasts (51%) compared to larger ones (74%). Even though this is only a preliminar...

2021 XXXIVth General Assembly and Scientific Symposium of the International Union of Radio Science (URSI GASS)

2021 XXXIVth General Assembly and Scientific Symposium of the International Union of Radio Science (URSI GASS)

2019 23rd International Conference on Applied Electromagnetics and Communications (ICECOM)

Sensors

Open-ended coaxial probes can be used as tissue characterization devices. However, the technique ... more Open-ended coaxial probes can be used as tissue characterization devices. However, the technique suffers from a high error rate. To improve this technology, there is a need to decrease the measurement error which is reported to be more than 30% for an in vivo measurement setting. This work investigates the machine learning (ML) algorithms’ ability to decrease the measurement error of open-ended coaxial probe techniques to enable tissue characterization devices. To explore the potential of this technique as a tissue characterization device, performances of multiclass ML algorithms on collected in vivo rat hepatic tissue and phantom dielectric property data were evaluated. Phantoms were used for investigating the potential of proliferating the data set due to difficulty of in vivo data collection from tissues. The dielectric property measurements were collected from 16 rats with hepatic anomalies, 8 rats with healthy hepatic tissues, and in house phantoms. Three ML algorithms, k-neare...