Papers by Raquel C Conceição
Validation of Dielectric Properties Estimation from Magnetic Resonance Images to Accelerate Medical Microwave Applications
2023 17th European Conference on Antennas and Propagation (EuCAP)
Experimental Assessment of Axillary Lymph Node Microwave Tomography Using Anthropomorphic Phantoms
IEEE Journal of Electromagnetics, RF and Microwaves in Medicine and Biology
Sensors
Dental caries is a major oral health issue which compromises oral health, as it is the main cause... more Dental caries is a major oral health issue which compromises oral health, as it is the main cause of oral pain and tooth loss. Early caries detection is essential for effective clinical intervention. However, methods commonly employed for its diagnosis often fail to detect early caries lesions, which motivates the research for more effective diagnostic solutions. In this work, the relative permittivity of healthy permanent teeth, in caries-prone areas, was studied between 0.5 and 18 GHz. The reliability of such measurements is an important first step to, ultimately, evaluate the feasibility of a microwave device for caries detection. The open-ended coaxial probe technique was employed. Its performance showed to be compromised by the poor probe-tooth contact. We proposed a method based on applying coupling media to reduce this limitation. A decrease in the measured relative permittivity variability was observed when the space between the probe tip and tooth surface was filled by coup...
Sensors
In the last decades, researchers have shown the potential of using Electrocardiogram (ECG) as a b... more In the last decades, researchers have shown the potential of using Electrocardiogram (ECG) as a biometric trait due to its uniqueness and hidden nature. However, despite the great number of approaches found in the literature, no agreement exists on the most appropriate methodology. This paper presents a systematic review of data acquisition methods, aiming to understand the impact of some variables from the data acquisition protocol of an ECG signal in the biometric identification process. We searched for papers on the subject using Scopus, defining several keywords and restrictions, and found a total of 121 papers. Data acquisition hardware and methods vary widely throughout the literature. We reviewed the intrusiveness of acquisitions, the number of leads used, and the duration of acquisitions. Moreover, by analyzing the literature, we can conclude that the preferable solutions include: (1) the use of off-the-person acquisitions as they bring ECG biometrics closer to viable, uncon...
Modelling level I Axillary Lymph Nodes depth for Microwave Imaging
Physica Medica
Sensors
Breast cancer is the most common and the fifth deadliest cancer worldwide. In more advanced stage... more Breast cancer is the most common and the fifth deadliest cancer worldwide. In more advanced stages of cancer, cancer cells metastasize through lymphatic and blood vessels. Currently there is no satisfactory neoadjuvant (i.e., preoperative) diagnosis to assess whether cancer has spread to neighboring Axillary Lymph Nodes (ALN). This paper addresses the use of radar Microwave Imaging (MWI) to detect and determine whether ALNs have been metastasized, presenting an analysis of the performance of different artifact removal and beamformer algorithms in distinct anatomical scenarios. We assess distinct axillary region models and the effect of varying the shape of the skin, muscle and subcutaneous adipose tissue layers on single ALN detection. We also study multiple ALN detection and contrast between healthy and metastasized ALNs. We propose a new beamformer algorithm denominated Channel-Ranked Delay-Multiply-And-Sum (CR-DMAS), which allows the successful detection of ALNs in order to achie...
Initial study for the investigation of breast tumour response with classification algorithms using a microwave radar prototype
2016 10th European Conference on Antennas and Propagation (EuCAP), 2016
In this paper classification algorithms will be used to investigate the presence of tumours in th... more In this paper classification algorithms will be used to investigate the presence of tumours in the breast, from signals collected with a radar microwave imaging prototype from the University of Bristol. A number of features will be extracted from the scattering of breast tumours and will then be used in classification algorithms such as Linear Discriminant Analysis or Quadratic Discriminant Analysis. The results from the classifier will allow creating an image of the considered synthetic breast phantom in which normal breast tissue is classified as a “miss” and tumour tissue is classified as a “hit”.
Experimental Evaluation of an Axillary Microwave Imaging System to Aid Breast Cancer Staging
IEEE Journal of Electromagnetics, RF and Microwaves in Medicine and Biology, 2021
The number of metastasised Axillary Lymph Nodes (ALNs) is a key indicator for breast cancer stagi... more The number of metastasised Axillary Lymph Nodes (ALNs) is a key indicator for breast cancer staging. Its correct assessment affects subsequent therapeutic decisions. Common ALN screening modalities lack high enough sensitivity and specificity. Level I ALNs produce detectable backscattering of microwaves, opening the way for Microwave Imaging (MWI) as a complementary screening modality. Radar-based MWI is a low-cost, non-invasive technique, widely studied for breast cancer and brain stroke detection. However, new specific challenges arise for ALN detection, which deter a simple extension of existing MWI methods. The geometry of the axillary region is more complex, limiting the antenna travel range required for maximum resolution. Additionally, unlike breast MWI setups, it is impractical to use liquid immersion to enhance energy coupling to the body; therefore, higher skin reflection masks ALNs response. We present a complete study that proposes dedicated imaging algorithms to detect ALNs dealing with the above constraints, and evaluate their effectiveness experimentally. We describe the developed setup based on a 3D-printed anthropomorphic phantom, and the antenna-positioning configuration. To the authors’ knowledge, this is the first ALN-MWI study involving a fully functional anatomically compliant setup. A Vivaldi antenna, operating in a monostatic radar mode at 2-5 GHz, scans the axillary region. Pre-clinical assessment in different representative scenarios shows Signal-to-Clutter Ratio higher than 2.8 dB and Location Error lower than 15 mm, which is smaller than considered ALN dimensions. Our study shows promising level I ALN detection results despite the new challenges, confirming MWI potential to aid breast cancer staging.
Sensors, 2022
Recently, several studies have demonstrated the potential of electrocardiogram (ECG) to be used a... more Recently, several studies have demonstrated the potential of electrocardiogram (ECG) to be used as a physiological signature for biometric systems (BS). We investigated the potential of ECG as a biometric trait for the identification and authentication of individuals. We used data from a public database, CYBHi, containing two off-the-person records from 63 subjects, separated by 3 months. For the BS, two templates were generated: (1) cardiac cycles (CC) and (2) scalograms. The identification with CC was performed with LDA, kNN, DT, and SVM, whereas a convolutional neural network (CNN) and a distance-based algorithm were used for scalograms. The authentication was performed with a distance-based algorithm, with a leave-one-out cross validation, for impostors evaluation. The identification system yielded accuracies of 79.37% and 69.84% for CC with LDA and scalograms with CNN, respectively. The authentication yielded an accuracy of 90.48% and an impostor score of 13.06% for CC, and it ...
Sensors, 2020
We produced an anatomically and dielectrically realistic phantom of the axillary region to enable... more We produced an anatomically and dielectrically realistic phantom of the axillary region to enable the experimental assessment of Axillary Lymph Node (ALN) imaging using microwave imaging technology. We segmented a thoracic Computed Tomography (CT) scan and created a computer-aided designed file containing the anatomical configuration of the axillary region. The phantom comprises five 3D-printed parts representing the main tissues of interest of the axillary region for the purpose of microwave imaging: fat, muscle, bone, ALNs, and lung. The phantom allows the experimental assessment of multiple anatomical configurations, by including ALNs of different size, shape, and number in several locations. Except for the bone mimicking organ, which is made of solid conductive polymer, we 3D-printed cavities to represent the fat, muscle, ALN, and lung and filled them with appropriate tissue-mimicking liquids. Existing studies about complex permittivity of ALNs have reported limitations. To addr...
Bladder-state monitoring using ultra wideband radar
ABSTRACT This paper describes the development of a bladder-state monitoring device based on Ultra... more ABSTRACT This paper describes the development of a bladder-state monitoring device based on Ultra Wideband Radar. Three-layer dielectrically representative bladder phantoms were created, mimicking a range of muscle and bladder wall-to-wall distances. The bladder monitoring process involves the illumination of the bladder with a Ultra Wideband pulse. Due to the dielectric contrast between urine and bladder wall tissue at microwave frequencies, an electromagnetic reflection is generated at both the anterior and posterior bladder wall. These reflections are recorded, the salient features are extracted and processed by a classification algorithm to estimate the volume of urine present in the bladder.
Abstract—Businesses have come to rely on their data ware-house as a key component in their Inform... more Abstract—Businesses have come to rely on their data ware-house as a key component in their Information Technol-ogy infrastructure. The costs of the architecture to support these environments are significant. Therefore, choosing the wrong architecture can be a very costly decision. However, considerable confusion exists in relation to MapReduce and Parallel Database Management Systems (DBMS). In the past, MapReduce has been presented as a replacement for the Parallel Database Management Systems, as an additional tool that works alongside the Parallel DBMS, but also as an inferior tool by others. This paper will consider the broader themes of the paradigms rather than the specific implementations of MapReduce and Parallel DBMS. It will discuss MapReduce and Parallel Database Management Systems as competing and complimentary paradigms. The aim of this paper is to provide a high-level comparison between MapReduce and Parallel DBMS, providing a selection of criteria which can be used to ...
Thermal Properties of Ex Vivo Biological Tissue at Room and Body Temperature
2020 14th European Conference on Antennas and Propagation (EuCAP), 2020
In electromagnetic hyperthermic applications, the thermal properties of the biological tissue und... more In electromagnetic hyperthermic applications, the thermal properties of the biological tissue under treatment, as well as its dielectric properties, influence the deposition of the electromagnetic energy and the heat distribution into the tissue. Thus, their knowledge can allow to accurately model the therapeutic results. The induced heat distribution and the consequent temperature increase rate are ruled by the thermal properties of the biological tissues. The aim of this work is to experimentally investigate the thermal properties of ex vivo liver, lung, kidney, muscle and bone marrow at room (N=66) and body (N=45) temperatures; and to correlate these properties with the density and water content of the tissue.
2020 14th European Conference on Antennas and Propagation (EuCAP), 2020
We assess the feasibility of a transmission-based open-ended coaxial-probe for tissue dielectric ... more We assess the feasibility of a transmission-based open-ended coaxial-probe for tissue dielectric properties estimation. The ultimate goal is to use it for axillary lymph node dielectric measurement, which is not trivial when applying the state-of-the-art reflection-based open-ended coaxial-probe. The proposed technique consists in placing the material under test between two opposite open-ended coaxial-probes and record the transmission coefficient. We numerically assess three coaxial probe configurations, in order to ensure adequate transmission and sensing volume. The final setup allows for enough propagation through a 5mm sample (which will be sufficient for the measurements of axillary lymph nodes), while confining the sensing volume to the region of interest. Experimental tests on two materials of different permittivity ranges showed good agreement between the measured and numerical transmission coefficient. Moreover, we observed that the transmission coefficient can highlight t...
2017 XXXIInd General Assembly and Scientific Symposium of the International Union of Radio Science (URSI GASS), 2017
In this paper we use Support Vector Machines (SVM) to aid breast cancer diagnosis using the micro... more In this paper we use Support Vector Machines (SVM) to aid breast cancer diagnosis using the microwave imaging radar prototype from the University of Bristol. We extract features from the electromagnetic signals collected with a microwave imaging system and classify them with a SVM classifier. The classifier will give an indication on whether the electromagnetic signals are more likely to belong to a focal point in the breast corresponding to healthy tissue — a “miss” — or to tumour tissue — a “hit”. The proposed work has the potential to ultimately aid microwave imaging and help avoid false positives and detect tumours that were imaged as false negatives.
Optimisation of Artefact Removal Algorithm for Microwave Imaging of the Axillary Region Using Experimental Prototype Signals
2021 15th European Conference on Antennas and Propagation (EuCAP), 2021
Microwave Imaging (MWI) has the potential to aid breast cancer staging through the detection of A... more Microwave Imaging (MWI) has the potential to aid breast cancer staging through the detection of Axillary Lymph Nodes (ALNs). This type of system can present some challenges, mainly due to the irregular axillary surface. The optimisation of the artefact removal algorithm to successfully remove the surface reflections is of great importance. In this paper, we propose using Singular Value Decomposition (SVD) as an artefact removal algorithm and study the effect of choosing different subsets of antenna positions for artefact removal on imaging results using experimental signals. We show that different subsets of antenna positions affect the results and in some cases prevent the targets detection. Our analysis allowed us to find an optimal combination of parameters which results in Signal-to-Clutter Ratio higher than 2.77 dB and Location Error lower than 14.9 mm for three different experimental tests. These results are relevant for the development of dedicated algorithms for ALN-MWI appl...
Numerical Assessment of Microwave Imaging for Axillary Lymph Nodes Screening Using Anthropomorphic Phantom
2021 15th European Conference on Antennas and Propagation (EuCAP), 2021
We numerically assess the potential of microwave imaging (MWI) for the detection of axillary lymp... more We numerically assess the potential of microwave imaging (MWI) for the detection of axillary lymph nodes (ALNs). The proposed MWI system is radar-based, in which a broad-band signal (2-6 GHz) is transmitted by a single probing antenna to scan the axillary region. The full-wave simulations include a realistic phantom of the underarm region which was previously developed by the authors. The phantom includes the main tissues of the axillary region and the corresponding dielectric properties. We show that the proposed system can successfully detect an ALN embedded in a homogeneous fatty medium. Additionally, we show that despite the strong reflection of the muscle - caused by the high dielectric contrast between fat and muscle - we are able to distinguish an ALN from the background. To the best of our knowledge, this is the first study in literature which employs an anatomically realistic phantom to study ALN MWI.
Overview of microwave medical applications in Europe since the beginning of the COST action TD1301 — MiMed
In the last twenty years, Microwave Imaging (MWI) has emerged as one of the most promising novel ... more In the last twenty years, Microwave Imaging (MWI) has emerged as one of the most promising novel medical imaging modalities. With European researchers being at the forefront of MWI development of medical applications, the creation in 2013 of the Action network “MiMed” (Microwave MEDical) in the framework of the European cooperation in Science and Technology (COST) was welcomed with vivid enthusiasm. MiMed has polarised mostly independent research efforts into the design of several MWI devices. Such a reserve of knowledge and numerous initiatives carried by MiMed have constituted a unique opportunity for researchers to leverage existing experience and expertise to streamline the transition from simulation/phantom testing to full clinical trials and clinical adoption of MWI devices. Moreover, collaboration among participants has provided the support to overcome common challenges and bring MWI from “research bench to patient bedside”, boosting the European Research Area and its excelle...
Head and Neck Numerical Phantom Development for Cervical Lymph Node Microwave Imaging
In this paper, we present a methodology to build a numerical phantom for the head and neck region... more In this paper, we present a methodology to build a numerical phantom for the head and neck regions, which can be used to develop a cervical lymph node microwave imaging device. We have shown a pipeline of data processing steps which can be applied to Magnetic Resonance Images (MRI) of the head and neck. Such models will be the starting point to start developing a microwave imaging device suitable to detect metastasized cervical lymph nodes and as a result contribute to the correct staging of head and neck cancer.
Feasibility study of focal lens for multistatic microwave breast imaging
2019 23rd International Conference on Applied Electromagnetics and Communications (ICECOM), 2019
Microwave Imaging is an emerging technique to aid breast cancer diagnosis. Current multistatic se... more Microwave Imaging is an emerging technique to aid breast cancer diagnosis. Current multistatic setups involve complex and heavy signal processing techniques, such as to remove the energy coupling between adjacent sensors, which masks the response from inner tissues. We investigate a novel approach using a dielectric lens in order to reduce the coupling effects between antennas, thus reducing the signal processing burden, while preserving all the advantages of multistatic setups. In this paper, we show that we can successfully detect simulated breast targets on reconstructed images using a setup with a dielectric lens.
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Papers by Raquel C Conceição