Extracting Dielectric Properties for MRI-based Phantoms for Axillary Microwave Imaging Device

Godinho, Daniela M.; Felício, João M.; Castela, Tiago; Silva, Nuno; Orvalho, M. Lurdes; Fernandes, Carlos A.; Conceição, Raquel C.

doi:10.23919/eucap48036.2020.9135980

Cited by 6 publications

(8 citation statements)

References 18 publications

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“…MWI presents several advantages compared to other imaging systems used for breast cancer screening, namely it is low-cost, non-invasive, portable, and it employs non-ionizing radiation. A MWI system dedicated to ALN diagnosis is under study in our research group [ 8 , 9 , 10 , 11 ], and, in recent years, other authors addressed the possibility of imaging ALNs with this technique [ 12 ]. A critical step to assess the viability of this technology is to test it by means of numerical simulations and experiments on anthropomorphic phantoms.…”

Section: Introductionmentioning

confidence: 99%

Development of an Anthropomorphic Phantom of the Axillary Region for Microwave Imaging Assessment

Savazzi

Abedi

Ištuk

et al. 2020

Sensors

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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 address these, we measured the complex permittivity of both human and animal lymph nodes using the standard open-ended coaxial-probe technique, over the 0.5 GHz–8.5 GHz frequency band, thus extending current knowledge on dielectric properties of ALNs. Lastly, we numerically evaluated the effect of the polymer which constitutes the cavities of the phantom and compared it to the realistic axillary region. The results showed a maximum difference of 7 dB at 4 GHz in the electric field magnitude coupled to the tissues and a maximum of 10 dB difference in the ALN response. Our results showed that the phantom is a good representation of the axillary region and a viable tool for pre-clinical assessment of microwave imaging technology.

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Section: Introductionmentioning

confidence: 99%

Development of an Anthropomorphic Phantom of the Axillary Region for Microwave Imaging Assessment

Savazzi

Abedi

Ištuk

et al. 2020

Sensors

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“…Both the cavities of the axillary region and ALN models were filled with liquid mixtures [11] mimicking fat and metastasised ALN tissues, respectively. The information about the dielectric properties of metastasised ALNs is still limited [4], [5], [12], [13], so we assumed they have similar dielectric properties to breast tumours.…”

Section: Experimental Prototype Systemmentioning

confidence: 99%

“…Our group has been working on a Microwave Imaging (MWI) system to detect and diagnose ALNs [3], [4], [5]. MWI is a lowcost and low-power technique and has had promising results for early breast cancer diagnosis [6] and brain stroke detection [7].…”

Section: Introductionmentioning

confidence: 99%

Optimisation of Artefact Removal Algorithm for Microwave Imaging of the Axillary Region Using Experimental Prototype Signals

Godinho

Felício

Fernandes

et al. 2021

2021 15th European Conference on Antennas and Propagation (EuCAP)

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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 application.

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“…In this paper, we use MRI scans for two purposes: (i) the creation of numerical anatomically realistic models of the axillary region with both healthy and metastasized ALNs; (ii) and estimation of dielectric properties of heterogeneous structures (e.g., ALNs) from MR images, which are difficult to measure with traditional techniques. We recently presented a brief description of our preliminary methodology and results of the estimation of ALN dielectric properties with only one patient 24 . In this paper, we present our improved methodology, which uses state‐of‐the‐art dielectric property information of other structures to infer ALN properties and validate it in a larger database of patients’ MRIs with both healthy and metastasized ALNs.…”

Section: Introductionmentioning

confidence: 99%

“…We recently presented a brief description of our preliminary methodology and results of the estimation of ALN dielectric properties with only one patient. 24 In this paper, we present our improved methodology, which uses stateof-the-art dielectric property information of other structures to infer ALN properties and validate it in a larger database of patients' MRIs with both healthy and metastasized ALNs. We also present an open-access repository of axillary region numerical models, which can be used for electromagnetic simulations, and, we believe, is an important contribution to the community.…”

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confidence: 99%

Development of MRI‐based axillary numerical models and estimation of axillary lymph node dielectric properties for microwave imaging

et al. 2021

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Purpose: Microwave imaging (MWI) has been studied as a complementary imaging modality to improve sensitivity and specificity of diagnosis of axillary lymph nodes (ALNs), which can be metastasized by breast cancer. The feasibility of such a system is based on the dielectric contrast between healthy and metastasized ALNs. However, reliable information such as anatomically realistic numerical models and matching dielectric properties of the axillary region and ALNs, which are crucial to develop MWI systems, are still limited in the literature. The purpose of this work is to develop a methodology to infer dielectric properties of structures from magnetic resonance imaging (MRI), in particular, ALNs. We further use this methodology, which is tailored for structures farther away from MR coils, to create MRI-based numerical models of the axillary region and share them with the scientific community, through an open-access repository. Methods:We use a dataset of breast MRI scans of 40 patients, 15 of them with metastasized ALNs. We apply image processing techniques to minimize the artifacts in MR images and segment the tissues of interest. The background, lung cavity, and skin are segmented using thresholding techniques and the remaining tissues are segmented using a K-means clustering algorithm. The ALNs are segmented combining the clustering results of two MRI sequences. The performance of this methodology was evaluated using qualitative criteria. We then apply a piecewise linear interpolation between voxel signal intensities and known dielectric properties, which allow us to create dielectric property maps within an MRI and consequently infer ALN properties. Finally, we compare healthy and metastasized ALN dielectric properties within and between patients, and we create an open-access repository of numerical axillary region numerical models which can be used for electromagnetic simulations. Results:The proposed methodology allowed creating anatomically realistic models of the axillary region, segmenting 80 ALNs and analyzing the corresponding dielectric properties. The estimated relative permittivity of those ALNs ranged from 16.6 to 49.3 at 5 GHz. We observe there is a high variability of

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Extracting Dielectric Properties for MRI-based Phantoms for Axillary Microwave Imaging Device

Cited by 6 publications

References 18 publications

Development of an Anthropomorphic Phantom of the Axillary Region for Microwave Imaging Assessment

Development of an Anthropomorphic Phantom of the Axillary Region for Microwave Imaging Assessment

Optimisation of Artefact Removal Algorithm for Microwave Imaging of the Axillary Region Using Experimental Prototype Signals

Development of MRI‐based axillary numerical models and estimation of axillary lymph node dielectric properties for microwave imaging

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