Contrast In Dielectric Properties Research Articles

Radiation-Free Microwave Technology for Breast Lesion Detection Using Supervised Machine Learning Model.

Mammography is the gold standard technology for breast screening, which has been demonstrated through different randomized controlled trials to reduce breast cancer mortality. However, mammography has limitations and potential harms, such as the use of ionizing radiation. To overcome the ionizing radiation exposure issues, a novel device (i.e. MammoWave) based on low-power radio-frequency signals has been developed for breast lesion detection. The MammoWave is a microwave device and is under clinical validation phase in several hospitals across Europe. The device transmits non-invasive microwave signals through the breast and accumulates the backscattered (returned) signatures, commonly denoted as the S21 signals in engineering terminology. Backscattered (complex) S21 signals exploit the contrast in dielectric properties of breasts with and without lesions. The proposed research is aimed to automatically segregate these two types of signal responses by applying appropriate supervised machine learning (ML) algorithm for the data emerging from this research. The support vector machine with radial basis function has been employed here. The proposed algorithm has been trained and tested using microwave breast response data collected at one of the clinical validation centres. Statistical evaluation indicates that the proposed ML model can recognise the MammoWave breasts signal with no radiological finding (NF) and with radiological findings (WF), i.e., may be the presence of benign or malignant lesions. A sensitivity of 84.40% and a specificity of 95.50% have been achieved in NF/WF recognition using the proposed ML model.

Intelligent Tomographic Microwave Imaging for Breast Tumor Localization

Researchers are continuously exploring the potential use of microwave imaging in the early detection of breast cancer. The technique offers a promising alternative to mammography, a standard clinical imaging procedure today. The contrast in dielectric properties between normal and cancerous tissues makes microwave imaging a viable technique for detecting breast cancer. Experimental results are presented in this paper that demonstrate the detection of breast cancer using microwaves operating at 2.4 GHz. The procedure involves antenna fabrication, phantom tissue development, and image reconstruction. Design and fabrication of patch antenna are used in the study, described in detail. The patch antenna pair is used for transmitting and receiving source waves. Tissue mimicking models were developed from paraffin wax and glycerin for the dielectric constants of 9 and 47, respectively, representing the tissue and tumor. Further, AI-based tomographic images were obtained by implementing a filtered back-projection algorithm in the computer. In the results, the presence of the tumor is quantitatively analyzed.

Microwave-Based Colonoscopy: Preclinical Evaluation in an Ex Vivo Human Colon Model.

Introduction Microwave imaging can obtain 360° anatomical and functional images of the colon representing the existing contrast in dielectric properties between different tissues. Microwaves are safe (nonionizing) and have the potential of reducing the visualization problems of conventional colonoscopy. This study assessed the efficacy of a microwave-based colonoscopy device to detect neoplastic lesions in an ex vivo human colon model. Methods Fresh surgically excised colorectal specimens containing cancer or polyps were fixed to a 3D positioning system, and the accessory device was introduced horizontally inside the ex vivo colon lumen and moved along it simulating a real colonoscopy exploration. Measurements of the colon were taken every 4 mm with the microwave-based colonoscopy device and processed with a microwave imaging algorithm. Results 14 ex vivo human colorectal specimens with carcinomas (n = 11) or adenomas with high grade dysplasia (n = 3) were examined with a microwave-based device. Using a detection threshold of 2.79 for the dielectric property contrast, all lesions were detected without false positives or false negatives. Conclusions This study demonstrates the use of a microwave-based device to be used as an accessory of a standard colonoscope to detect neoplastic lesions in surgically excised colorectal specimens.

Non-invasive detection and discrimination of breast tumors at early stage using spiral antenna

Abstract In this paper, an Archimedean spiral antenna-based biosensor has been proposed for the early detection of breast tumor. By monitoring the variation of S11 over 1–3.5 GHz frequency range, the proposed scheme can identify the tumor location, as well as distinguish the types of tumor (benign or malignant) based on shapes and dielectric properties contrast. To validate the concept, full wave simulation using CST microwave suite are performed along with VNA based experimental measurements on breast phantoms and tumors, prepared by easily available materials like glass, petroleum jelly, mixture of water and wheat flour. The demonstrated device is able to detect the tumor of less than 1 mm in radius and positioned anywhere in 5 × 5 × 5 cm of breast fat. The proposed method is easy to use, low cost, safe, comfortable, non-invasive and non- ionizing in nature.

Automated reconstruction of subsurface interfaces in Promethei Lingula near the Martian south pole by using SHARAD data

Subsurface layers are preserved in polar regions on Mars, which are considered to be a record of past climate changes on Mars. Orbital radar instruments like the SHAllow RADar (SHARAD) on board Mars Reconnaissance Orbiter (MRO) transmit radar signals to Mars and receive a set of signals returned from interfaces having a contrast in dielectric properties in the probed subsurface regions. These subsurface layers which are preserved in the upper ≈ 1 km of the Martian Polar Layered Deposits (PLDs) can be observed in SHARAD radargrams. Extraction of these layering features is the preliminary work before interpreting and understanding their origins. In this study, we use a new method based on log-Gabor filtering and Continuous Wavelet Transform (CWT)-based peak detection to extract subsurface radar reflections and a workflow to remove clutter reflections in order to reconstruct 3-D subsurface layers. These methods and workflow are then tested on the SHARAD data in the Promethei Lingula region near the Martian south pole. The results show that following this workflow, the ground surface and six subsurface interfaces can be reconstructed, which aids in the interpretation of the depositional and erosional history of this region.

Microwave Breast Imaging: Clinical Advances and Remaining Challenges.

Microwave breast imaging has seen significant academic and commercial development in recent years, with four new operational microwave imaging systems used with patients since 2016. In this paper, a comprehensive review of these recent clinical advances is presented, comparing patient populations and study outcomes. For the first time, the designs of operational microwave imaging systems are compared in detail. First, the current understanding of dielectric properties of human breast tissues is reviewed, considering evidence from operational microwave imaging systems and from dielectric properties measurement studies. Second, design features of operational microwave imaging systems are discussed in terms of advantages and disadvantages during clinical operation. Reported results from patient imaging trials are compared, contrasting the principal results from each trial. Additionally, clinical experience from each trial is highlighted, identifying desirable system design features for clinical use. Increasingly, evidence from patient imaging studies indicate that a contrast in dielectric properties between healthy and cancerous breast tissues exists. However, despite the significant and encouraging results from patient trials, variation still exists in the microwave imaging system design. This study seeks to define the current state of the art in microwave breast imaging, and identify suitable design characteristics for ease of clinical use.

Application of Markov Random Field on Microwave Near-Field Imaging of Breast Tumor

This paper solved an inverse scattering problem of near field under some conditions and presented a novel microwave near-field imaging method of breast tissues with tumors, which is based on the contrast of dielectric properties between normal breast tissues and tumors. We used microwave scatter- sounding method to detect the breast and obtained the reconstruction projection data. Then modeled the dielectric properties distribution of breast tissues with Markov Random Field (MRF) method. With the characteristics of radial distribution of the data, we established the relationship between dielectric properties distribution and detected data. Using Maximum a Posteriori (MAP) estimation, we obtained an optimization problem and solved it. The simulation result shows that the method is effective for imaging.

Analysis of Ground Penetrating Radar’s Capability for Detecting Underground Cavities: A Case Study in Japan Cave of Taman Hutan Raya, Bandung

Underground cavities or voids detection is essential especially when it comes to building construction. By knowing the presence of void lying underground, one could consider whether the subsidence is likely to be prevented or not. Ground penetrating radar is a high-frequency electromagnetic sounding technique that has been developed to investigate the shallow subsurface using the contrast of dielectric properties. This geophysical method is suitable to be used to detect and locate voids beneath the surface especially those that lie in shallow depth. This research focused on how GPR could be implemented as void detector using model simulation or forward modelling. The models applied in the forward modelling process are to be made as similar as the real condition in the case study location which took place in Tahura Japan Cave, Bandung, Indonesia. Forward modelling needs to be done so in the future, we might use the modelling results as the references in measuring real GPR data in the location. We used three models that we considered fairly representative to prove that GPR is capable of detecting and locating voids underneath the ground. This research resulted in the different amplitude region around the considerably homogeneous region. The different amplitude region is characterized having an arc shape and is considered to be air which is known as the key component of voids.

Three dimensions localization of tumors in confocal microwave imaging for breast cancer detection

ABSTRACTBasis of the microwave imaging is the contrast in dielectric properties of breast normal tissue and tumor. Confocal microwave imaging involves transmitting an ultrawideband signal through number of antennas and records the scattered signals. Then by synthetically focusing reflections from the breast, we can make image from breast. In this article, we demonstrate the feasibility of detecting 10‐ and 5‐mm tumors in three dimensions with different antenna arrangements with different number of antennas. Two models of hemispherical array are presented. An image formation algorithm is presented for 3D image making. Successful detection of 10‐ and 5‐mm tumors are achieved with the hemispherical arrangement. The influences of the different breast sizes for tumor detection are also explored. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2917–2929, 2015

Design and preliminary experiments of a precision microwave tomography system

ABSTRACTThis article presents the image reconstruction results of measurement data from a preliminary test using the first‐developed precision microwave tomography (MT) system operating at 3–6 GHz for medical diagnosis. A simple phantom is used in the MT system to verify the data validation. The measurement dataset has very different patterns owing to the significant contrast of dielectric properties according to the existence of a phantom in the sensing area of the illumination tank at microwave frequencies. Thus, it is possible to obtain the image reconstruction from this measurement data. The detailed results are presented and discussed. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2445–2448, 2015

Electromagnetic-acoustic imaging of stiffness and dielectric properties in gels

Here we present a novel multi-modal imaging method, electromagnetic-acoustics (EMA) that combines acoustic radiation force and electromagnetic scattering. Experiments were carried out in gels using a focused megahertz ultrasound source, amplitude modulated at 160 Hz, to create an oscillating radiation force resulting in vibration of the gel in the focal region. At the same time an EM signal was transmitted into the gel and the backscattered EM signal recorded. The tissue that was in motion resulted in a Doppler shift of the EM signal which manifested itself as frequency modulation of the EM wave. The modulated component was detected by means of a demodulator and lock-in amplifier and the amplitude of the modulated signal we call the EMA signal. By steering the ultrasound beam through the sample, an EMA image can be created which has spatial resolution of the ultrasound but is sensitive to shear and dielectric properties. We show that the EMA signal is sensitive to changes in elasticity and conductivity in a gel. EMA may have utility in biomedical imaging by detecting diseases, which have contrast in dielectric properties without the cost and complexity of an magnetic resonance imaging system.

Mapping of evaporite deformation in a potash mine using ground penetrating radar: Upper Kama deposit, Russia

Abstract Understanding the deformation processes in potash mines is very important for safe mining, planning the methods of extracting the orebody, and the prevention of catastrophic water inflow. A variety of deformational structures are present in the Upper Kama potash deposit. Folding is a dominant and most common form of deformation of ductile evaporites (herein also referred to as salts). Brittle deformation occurs rarely but is of more significance from the perspective of mine safety because fractures affect the supporting capability of mine pillars and can provide passageway for water inflow. Continuous common offset ground penetrating radar (GPR) data were acquired in the potash mine operated by the Joint Stock Company (JSC) “Silvinit” to investigate a set of pre-existing fractures and related deformational structures. Open fractures, faults and folds were mapped using 2-D and 3-D GPR techniques. Detection of millimetric scale fractures was available due to high salt/air dielectric properties contrast and low background noise within uniform salt rock. FK filtering significantly improved fracture detection and imaging. A spatial model of one set of fractures was created using 3-D GPR imaging. Migration was applied to GPR data to obtain the true geometry of the strongly folded salt beds. The results of studies showed that GPR is capable of providing valuable information about deformation within the evaporite formations of the Upper Kama potash deposit.

Challenges in the Design of Microwave Imaging Systems for Breast Cancer Detection

Among the various breast imaging modalities for breast cancer detection, microwave imaging is attractive due to the high contrast in dielectric properties between the cancerous and nor ...

Experimental Investigation on Flanged Parallel-Plate Dielectric Waveguide Probe for Detection of Conductive Inclusions in Lossy Dielectric Medium

A flanged parallel-plate dielectric waveguide probe (PPDW) for microwave detection and localization of small inclusions in a lossy dielectric medium, based on detecting the contrast in dielectric properties between the inclusion and embedding medium has been proposed. In this paper, experimental evaluation of this probe for the detection and localization of small conductive inclusion is presented. Investigations were performed on solid lossy dielectric phantoms with conductive spherical inclusions representing tumors embedded. Preliminary experimental results demonstrate the potential of the PPDW to detect and locate a small inclusion exhibiting significant difference in dielectric properties from the host medium, embedded at reasonable depth.

Fundamental of ground penetrating radar in environmental and engineering applications

Ground Penetrating Radar (GPR) is a high frequency electromagnetic sounding technique that has been developed to investigate the shallow subsurface using the contrast of dielectric properties. The method operates on the simple principle that electromagnetic waves, emitted from a transmitter antenna, are reflected from buried objects and detected at another antenna, acting as receiver. GPR data is presented in the form of time-distance plots that are analogous to conventional reflection seismic records, and in fact the method has many similarities to seismic reflection method with a pulse of electromagnetic energy substituting for the elastic (seismic) energy. Nevertheless, the principles and theory of the method are based on the wave equation derived from Maxwell's equations for electromagnetic wave propagation. This paper has been written for tutorial purposes, and it is hoped that it will provide the reader with a good outline of GPR presenting an overview of its theoretical basis, guidelines for interpretation and some practical field examples.

자전연소반응법에 의해 제조된 PZT의 전기적 특성에 미치는 Sr의 영향

PSZT are selected and SHS are applied to each system. The sintering properties of PSZT powders showed 7.754 g/㎤ of sintered density and 4 μm of grain size at sintering temperature of 1250℃. Curie temperature lowered gradually from 363.6℃ to 319.2℃ and relative dielectric constants increased rapidly by a quantity of Sr. This remarkable contrast in dielectric properties with powder preparation methods, in this study, was not due to grain size and sintered density but rather a crystallinity and sinterability of synthesized powders, extra-supplied Pb during reaction, mol fraction of rhombohedral phase and purity of starting materials.

Potential of near-field microwave imaging in breast cancer detection utilizing tapered rectangular waveguide probes

Microwave imaging for medical applications has been of interest for many years. A novel near-field microwave non-invasive testing and evaluation (NIT&E) technique utilizing tapered rectangular waveguide probes is presented for breast cancer detection. Near-field microwave NIT&E techniques can be a successful candidate for the detection of breast cancer because of their potential in dealing with materials of low conductivity (i.e. lossy dielectrics like the breast tissue). The physical basis for breast tumor detection with microwave imaging is the contrast in dielectric properties of normal and malignant breast tissues. A method adopting Fourier transform matching (FTM) technique and utilizing the reflection coefficient at the aperture of a tapered rectangular waveguide sensor radiating into a breast is described resulting in microwave images that indicate the presence of a tumor. These images demonstrate the feasibility of detecting breast tumors using this approach.

A large-scale study of the ultrawideband microwave dielectric properties of normal, benign and malignant breast tissues obtained from cancer surgeries

The development of microwave breast cancer detection and treatment techniques has been driven by reports of substantial contrast in the dielectric properties of malignant and normal breast tissues. However, definitive knowledge of the dielectric properties of normal and diseased breast tissues at microwave frequencies has been limited by gaps and discrepancies across previously published studies. To address these issues, we conducted a large-scale study to experimentally determine the ultrawideband microwave dielectric properties of a variety of normal, malignant and benign breast tissues, measured from 0.5 to 20 GHz using a precision open-ended coaxial probe. Previously, we reported the dielectric properties of normal breast tissue samples obtained from reduction surgeries. Here, we report the dielectric properties of normal (adipose, glandular and fibroconnective), malignant (invasive and non-invasive ductal and lobular carcinomas) and benign (fibroadenomas and cysts) breast tissue samples obtained from cancer surgeries. We fit a one-pole Cole–Cole model to the complex permittivity data set of each characterized sample. Our analyses show that the contrast in the microwave-frequency dielectric properties between malignant and normal adipose-dominated tissues in the breast is considerable, as large as 10:1, while the contrast in the microwave-frequency dielectric properties between malignant and normal glandular/fibroconnective tissues in the breast is no more than about 10%.For more information on this article, see medicalphysicsweb.org

Millimeter wave analysis of the dielectric properties of oil shales

Natural sedimentation processes give rise to fine layers in shales. If these layers alternate between organic-rich and organic-poor sediments, then the contrast in dielectric properties gives rise to an effective birefringence as the presence of hydrocarbons suppresses the dielectric constant of the host rock. We have measured these effects with a quasioptical millimeter wave setup that is rapid and noncontacting. We find that the strength of this birefringence and the overall dielectric permittivity provide two useful diagnostics of the organic content of oil shales.

Ultrawideband radar imaging system for biomedical applications

Ultrawideband (UWB) (3–10GHz) radar imaging systems offer much promise for biomedical applications such as cancer detection because of their good penetration and resolution characteristics. The underlying principle of UWB cancer detection is a significant contrast in dielectric properties, which is estimated to be greater than 2:1 between normal and cancerous tissue, compared to a few-percent contrast in radiographic density exploited by x rays. This article presents a feasibility study of the UWB imaging of liver cancer tumors, based on the frequency-dependent finite difference time domain method. The reflection, radiation, and scattering properties of UWB pulses as they propagate through the human body are studied. The reflected and back-scattered electromagnetic energies from cancer tumors inside the liver are also investigated. An optimized, ultrawideband antenna was designed for near field operation, allowing for the reduction of the air-skin interface. It will be placed on the fat-liver tissue phantom with a malignant tumor stimulant. By performing an incremental scan over the phantom and removing early time artifacts, including reflection from the antenna ends, images based on the back-scattered signal from the tumor can be constructed. This research is part of our effort to develop a UWB cancer detection system with good detection and localization properties.