IBEB - Artigos em Conferências
Permanent URI for this collection
Artigos em Conferências
Browse
Browsing IBEB - Artigos em Conferências by Title
Now showing 1 - 10 of 24
Results Per Page
Sort Options
- Best Practices for Accurate Results Using Numerical Solvers for Microwave Body ScreeningPublication . Martins, Raquel A.; Godinho, Daniela M.; Felício, João M.; Savazzi, Matteo; Costa, Jorge R.; Conceição, Raquel C.; Fernandes, Carlos A.In this paper, we indicate best practices that should be observed when using numerical solvers for microwave body sensing. We show the impact of not minding these aspects in the case of microwave breast scanning, using the Computer Simulation Technology software tool. To this end we simulate a homogeneous breast with a 5-mm radius spherical tumor placed inside. The breast is illuminated by a broadband antenna that operates in the 2-6 GHz band. The scattering parameters are then processed to reconstruct the reflectivity map of the breast. The results highlight that the conclusions drawn from simulations may be misleading or meaningless when the solver type or positioning of model elements (body and antennas) are not carefully applied. This is particularly critical when considering more complex scenarios, such as inhomogeneous or multilayer body models.
- Detection of Microcalcifications in Digital Breast Tomosynthesis using Faster R-CNN and 3D Volume RenderingPublication . Matela, Nuno; Almeida, Pedro; Clarkson, Matthew; Mota, AnaMicrocalcification clusters (MCs) are one of the most important biomarkers for breast cancer and Digital Breast Tomosynthesis (DBT) has consolidated its role in breast cancer imaging. As there are mixed observations about MCs detection using DBT, it is important to develop tools that improve this task. Furthermore, the visualization mode of MCs is also crucial, as their diagnosis is associated with their 3D morphology. In this work, DBT data from a public database were used to train a faster region-based convolutional neural network (R-CNN) to locate MCs in entire DBT. Additionally, the detected MCs were further analyzed through standard 2D visualization and 3D volume rendering (VR) specifically developed for DBT data. For MCs detection, the sensitivity of our Faster R-CNN was 60% with 4 false positives. These preliminary results are very promising and can be further improved. On the other hand, the 3D VR visualization provided important information, with higher quality and discernment of the detected MCs. The developed pipeline may help radiologists since (1) it indicates specific breast regions with possible lesions that deserve additional attention and (2) as the rendering of the MCs is similar to a segmentation, a detailed complementary analysis of their 3D morphology is possible.
- Detection of Microcalcifications in Digital Breast Tomosynthesis using Faster R-CNN and 3D Volume RenderingPublication . Mota, Ana M.; Clarkson, Matthew J.; Almeida, Pedro; Matela, NunoMicrocalcification clusters (MCs) are one of the most important biomarkers for breast cancer and Digital Breast Tomosynthesis (DBT) has consolidated its role in breast cancer imaging. As there are mixed observations about MCs detection using DBT, it is important to develop tools that improve this task. Furthermore, the visualization mode of MCs is also crucial, as their diagnosis is associated with their 3D morphology. In this work, DBT data from a public database were used to train a faster region-based convolutional neural network (R-CNN) to locate MCs in entire DBT. Additionally, the detected MCs were further analyzed through standard 2D visualization and 3D volume rendering (VR) specifically developed for DBT data. For MCs detection, the sensitivity of our Faster R-CNN was 60% with 4 false positives. These preliminary results are very promising and can be further improved. On the other hand, the 3D VR visualization provided important information, with higher quality and discernme nt of the detected MCs. The developed pipeline may help radiologists since (1) it indicates specific breast regions with possible lesions that deserve additional attention and (2) as the rendering of the MCs is similar to a segmentation, a detailed complementary analysis of their 3D morphology is possible.
- Development of a Transmission-Based Open-Ended Coaxial-Probe Suitable for Axillary Lymph Node Dielectric MeasurementsPublication . Savazzi, Matteo; Porter, Emily; OHalloran, Martin; Costa, Jorge R.; FERNANDES, CARLOS; M. Felício, João; Conceicao, Raquel C.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 the contrast between materials with different dielectric properties. The promising initial results motivate the further application of the method to the case of axillary lymph nodes.
- Effect of Varying Prior Information in Axillary 2D Microwave TomographyPublication . Savazzi, Matteo; Karadima, Olympia; Felicio, Joao M.; Fernandes, Carlos A.; Kosmas, Panagiotis; Conceicao, Raquel C.We numerically assess the potential of microwave tomography (MWT) for the detection and dielectric properties estimation of axillary lymph nodes (ALNs), and we study the robustness of our system using prior information with varying levels of accuracy. We adopt a 2-dimensional MWT system with 8 antennas (0.5-2.5 GHz) placed around the axillary region. The reconstruction algorithm implements the distorted Born iterative method. We show that: (i) when accurate prior knowledge of the axillary tissues (fat and muscle) is available, our system successfully detects an ALN; (ii) ±30% error in the prior estimation of fat and muscle dielectric properties does not affect image quality; (iii) ±7mm error in muscle position causes slight artifacts, while ± 14mm error in muscle position affects ALN detection. To the best of our knowledge, this is the first paper in the literature to study the impact of prior information accuracy on detecting an ALN using MWT.
- Extracting Dielectric Properties for MRI-based Phantoms for Axillary Microwave Imaging DevicePublication . Godinho, Daniela M.; Felicio, Joao M.; Castela, Tiago; Silva, Nuno A.; Orvalho, M. Lurdes; Fernandes, Carlos A.; Conceicao, Raquel C.Microwave Imaging (MWI) is an emerging medical imaging technique, which has been studied to aid breast cancer diagnosis in the frequency range from 0.5 to 30 GHz. The information about the dielectric properties of each tissue is essential to assess the viability of this type of systems. However, accurate measurements of heterogeneous tissues can be very challenging, and the current available information is still very limited. In this paper, we present a methodology for extracting dielectric properties to create anatomical models of the axillary region. These models will be used in a MWI device to aid breast cancer diagnosis through the detection of metastasised axillary lymph nodes. We apply segmentation tools to Magnetic Resonance Images (MRI) of the breast and assign dielectric properties to each tissue, extracting preliminary information about the properties of axillary lymph nodes. This study may open a way to more quickly extract dielectric properties of tissues and/or validate measurements, accelerating the development of microwave-based medical devices.
- Feasibility study of focal lens for multistatic microwave breast imagingPublication . Godinho, Daniela M.; Felicio, Joao M.; Fernandes, Carlos A.; Conceicao, Raquel C.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.
- How the Number and Distance of Electrodes Change the Induced Electric Field in the Cortex during Multichannel tDCSPublication . Videira, Andreia S.; Canadas, Diogo; De O. Pires, Leonor; Andrade, Alexandre; Ferreira, Hugo A.; Miranda, Pedro C.; Fernandes, Sofia R.Multichannel transcranial direct current stimulation (tDCS) is a promising approach to target neuromodulation of neural networks by making use of variable number of electrodes and distances to facilitate/inhibit specific connectivity patterns. Optimization of the electric field (EF) spatial distribution through computational models can provide a more accurate definition of the stimulation settings that are more effective. In this study, we investigate the effect of increasing the number of cathodes around a central anode placed over the target. We demonstrate that anode-cathode distance has the largest influence in the EF and using more than 3 cathodes did not result in considerable changes in the EF magnitude and direction. This could be relevant for simultaneous tDCS-electroencephalography (EEG) applications, by saving electrode positions for EEG acquisition. Clinical Relevance- This study demonstrates that distance between electrodes is more relevant than electrode number in determining the electric field distribution, and that a highly-focused stimulation can be equally effective with fewer electrodes.
- Impact of Antenna Configuration and Artefact Removal Algorithms for Axillary Microwave ImagingPublication . M. Godinho, Daniela; L. Cidadão, Pedro; C. Conceição, RaquelMicrowave Imaging (MWI) has been studied to aid breast cancer staging through the detection of Axillary Lymph Nodes (ALNs) metastasised by breast cancer. The anatomy of the axillary region imposes a limited angular view on MWI prototypes which may hinder artefact removal performance and, consequently, a correct detection of ALNs. In this initial study, we compare different antenna configurations for axillary MWI, while evaluating the performance of different artefact removal algorithms. The imaging results highlight the importance of choosing an optimal combination of antenna configuration and artefact removal algorithm for accurate target detection.
- Initial study for detection of multiple lymph nodes in the axillary region using Microwave ImagingPublication . Eleutério, Ricardo; Conceicao, Raquel C.Breast cancer staging largely depends on the evaluation of whether there are cancer cells in the axillary lymph nodes. This work proposes a non-invasive method of detecting metastases in the lymph nodes using an Ultra-Wideband Microwave Imaging radar system. Energy profiles of the axilla are created with this system in which high energy regions may indicate the presence of metastasised lymph nodes.
- «
- 1 (current)
- 2
- 3
- »