Instituto de Biofísica e Engenharia Biomédica - IBEB
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- 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.
- 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.
- Development of an Anthropomorphic Phantom of the Axillary Region for Microwave Imaging AssessmentPublication . Savazzi, Matteo; Abedi, Soroush; Ištuk, Niko; Joachimowicz, Nadine; Roussel, Hélène; Porter, Emily; O’Halloran, Martin; Costa, Jorge R.; Fernandes, Carlos A.; Felício, João M.; Conceição, Raquel C.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.
- A Novel Hybrid Nanosystem Integrating Cytotoxic and Magnetic Properties as a Tool to Potentiate Melanoma TherapyPublication . Cruz, Nuno; Pinho, Jacinta Oliveira; Soveral, Graça; Ascensão, Lia; Matela, Nuno; Reis, Catarina; Gaspar, Maria ManuelaCancer is a major health concern and the prognosis is often poor. Significant advances in nanotechnology are now driving a revolution in cancer detection and treatment. The goal of this study was to develop a novel hybrid nanosystem for melanoma treatment, integrating therapeutic and magnetic targeting modalities. Hence, we designed long circulating and pH-sensitive liposomes loading both dichloro(1,10-phenanthroline) copper (II) (Cuphen), a cytotoxic metallodrug, and iron oxide nanoparticles (IONPs). The synthetized IONPs were characterized by transmission electron microscopy and dynamic light scattering. Lipid-based nanoformulations were prepared by the dehydration rehydration method, followed by an extrusion step for reducing and homogenizing the mean size. Liposomes were characterized in terms of incorporation parameters and mean size. High Cuphen loadings were obtained and the presence of IONPs slightly reduced Cuphen incorporation parameters. Cuphen antiproliferative properties were preserved after association to liposomes and IONPs (at 2 mg/mL) did not interfere on cellular proliferation of murine and human melanoma cell lines. Moreover, the developed nanoformulations displayed magnetic properties. The absence of hemolytic activity for formulations under study demonstrated their safety for parenteral administration. In conclusion, a lipid-based nanosystem loading the cytotoxic metallodrug, Cuphen, and displaying magnetic properties was successfully designed.
- Preliminary Assays towards Melanoma Cells Using Phototherapy with Gold-Based NanomaterialsPublication . Lopes, Joana; Coelho, João Miguel Pinto; Vieira, Pedro Manuel Cardoso; Viana, Ana Silveira; Gaspar, Maria Manuela; Reis, CatarinaCancer like melanoma is a complex disease, for which standard therapies have significant adverse side effects that in most cases are ineffective and highly unspecific. Thus, a new paradigm has come with the need of achieving alternative (less invasive) and effective therapies. In this work, biocompatible gold nanoparticles (GNPs) coated with hyaluronic acid and oleic acid were prepared and characterized in terms of size, morphology and cytotoxicity in the presence of Saccharomyces cerevisiae, and two cell lines, the keratinocytes (healthy skin cells, HaCat) and the melanoma cells (B16F10). Results showed that these GNPs absorb within the near-infrared region (750–1400 nm), in the optical therapeutic window (from 650 to 1300 nm), in contrast to other commercial gold nanoparticles, which enables light to penetrate into deep skin layers. A laser emitting in this region was applied and its effect also analyzed. The coated GNPs showed a spherical morphology with a mean size of 297 nm without cytotoxic effects towards yeast and tested cell lines. Nevertheless, after laser irradiation, a reduction of 20% in B16F10 cell line viability was observed. In summary, this work appears to be a promising strategy for the treatment of non-metastatic melanoma or other superficial tumors.
- Study of the Refraction Effects in Microwave Breast Imaging Using a Dry SetupPublication . Godinho, Daniela M.; Felicio, Joao M.; Fernandes, Carlos A.; Conceicao, Raquel C.Medical Microwave Imaging (MWI) has been studied as a technique to aid breast cancer diagnosis. Several different prototypes have been proposed but most of them require the use of a coupling medium between the antennas and the breast, in order to reduce skin backscattering and avoid refraction effects. The use of dry setups has been addressed and recent publications show promising results. In this paper, we assess the importance of considering refraction effects in the image reconstruction algorithms. To this end, we consider a simplified homogeneous spherical model of the breast and analytically compute the propagating rays through the air-body interface. The comparison of results considering only direct ray propagation or refracted rays shows negligible impact on the accuracy of the images for moderately high permittivity media. Thus, we may avoid the computational burden of calculating the refracted rays in complex shapes.
- Development of a 3D Anthropomorphic Phantom Generator for Microwave Imaging Applications of the Head and Neck RegionPublication . Pelicano, Ana Catarina; Conceição, Raquel C.The development of 3D anthropomorphic head and neck phantoms is of crucial and timely importance to explore novel imaging techniques, such as radar-based MicroWave Imaging (MWI), which have the potential to accurately diagnose Cervical Lymph Nodes (CLNs) in a neoadjuvant and non-invasive manner. We are motivated by a significant diagnostic blind-spot regarding mass screening of LNs in the case of head and neck cancer. The timely detection and selective removal of metastatic CLNs will prevent tumor cells from entering the lymphatic and blood systems and metastasizing to other body regions. The present paper describes the developed phantom generator which allows the anthropomorphic modelling of the main biological tissues of the cervical region, including CLNs, as well as their dielectric properties, for a frequency range from 1 to 10 GHz, based on Magnetic Resonance images. The resulting phantoms of varying complexity are well-suited to contribute to all stages of the development of a radar-based MWI device capable of detecting CLNs. Simpler models are essential since complexity could hinder the initial development stages of MWI devices. Besides, the diversity of anthropomorphic phantoms resulting from the developed phantom generator can be explored in other scientific contexts and may be useful to other medical imaging modalities.
- 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.
- 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.
- Evaluation of Refraction Effects in Dry Medical Microwave Imaging SetupsPublication . Godinho, Daniela M.; Felicio, Joao M.; Fernandes, Carlos A.; Conceicao, Raquel C.Dry microwave imaging (MWI) systems are more practical, hygienic, and fast to operate since they do not require immersion liquid. However, the dielectric contrast between air and the part of the body under examination is larger, causing larger refraction effects. Including refraction in the image reconstruction algorithm significantly increases the computational effort, especially when imaging nonuniform shapes. Hence, our systematic study aims to evaluate the impact of neglecting refraction effects on MWI by using quantitative metrics and define objective guidelines that are lacking in the literature. We perform comparative studies with a spherical numerical phantom (which is typically used to represent simplified breast or head phantoms) by varying the phantom relative permittivity values between 4 and 40, metallic targets diameter between 5 and 15 mm, and the number of probing antennas. Additionally, the refraction effects are evaluated with anthropomorphic body phantoms representing a breast and the axillary region. We numerically and experimentally show that refraction tends to have a greater impact on imaging results when phantom relative permittivity values exceed 8, while it has a minor effect in the remaining tested cases. This favors potential fast real-time image reconstruction. This letter provides useful criteria to decide whether refraction should be considered or not for imaging reconstruction when developing new dry medical MWI setups.