1,720,963 research outputs found
Real-time 3D microwave tomography of brain stroke status using low-computing demand
No full textThis paper approaches the medical problem of the after-onset monitoring of a brain stroke via a real-time linear imaging algorithm and a low-complexity microwave scanner. This procedure allows using low computing requirements for tracking physical pathology changes, such as stroke shape evolution and he partial typology variation of the infarcted zones, both significant medical issues. The system consists of a 22-antenna device,
and the imaging algorithm uses a differential single-frequency approach. It exploits a pair of measured scattering matrices taken at two different instants, the Born approximation, and the truncated singular value decomposition, to form in-time 3D tomographic dielectric contrast variation maps in real-time using a stand-alone low-capacity device without needing a graphics processing unit. The results confirm the continuous stroke followup
capabilities of the system, with the possibility to track both the shape and type transformations (hemorrhage and ischemia), even in mimicked complex clinical scenarios
Microwave Imaging Evaluation of Prior Structural Information on the Inversion-Kernel Building Apply to a Brain Stroke Monitoring Scenario
Full text linkThis work investigates the impact of prior structural information on the inversion kernel used to follow up on a brain stroke condition. To that end, we perform a numerical study that mimics an intracranial hemorrhage and aims to retrieve the morphological evolution of the stroke-affected area between different time instants via direct inversion based on the Born Approximation and the truncated singular value decomposition. Then, we consider different operators, imaging kernels, adding tissue shape information, and evaluating the imaging retrieval performance via the structural similarity index, the dice similarity coefficient, the normalized Hausdorff distance, and a sizebased metric, similarity metrics. The results confirm that more apriori information improves overall performance; however, more importantly, they show that even with approximated kernels, less information, and a more realistic clinical scenario, the imaging might perform well enough as a medical indication
Enabling high-quality compost for a smart domestic production
Full text linkCompost home production is an open challenge due to the need for continuous human intervention to monitor and regulate the critical parameters that play a fundamental role in the production of high-quality compost. The temperature and humidity require fine and uniform control over the entire mass to ensure a proper composting process development. This article presents a new prototype of a domestic smart composter that guarantees optimal control of the compost maturation process. This result is made possible by combining the ad-hoc design of a multi-sensor electronic board and microwave imaging techniques which provide a dual function: they allow both to control and monitor temperatures uniformly over the entire biomass
Hybrid imaging kernel calibration applied on microwave scanner for brain stroke monitoring
Full text linkThis paper validates a calibration procedure applied on a microwave imaging (MWI) kernel based on the combination of pre-computed simulated data and available S-parameters measurements. The assessed technique compensates for the image degradation caused by mild and non-modeled features of the imaging device, such as the unavoidable manufacturing discrepancies in the antenna array. The testing considers a synthetically mimicked experimental scenario of a hemorrhagic stroke condition and a realistic scanner prototype. This approach allows a thorough comparative assessment of the calibration effect on the electric field estimation used by the MWI algorithm, hardly achievable with measurements. The results show the capability of the calibration procedure to reduce the retrieved images’ distortions and artifacts compared to the non-calibrated approach, being an essential milestone toward its application in real-life scenarios
Microwave Imaging for Parkinson’s Disease Detection: A Phantom-Based Feasibility Study Using Temperature-Controlled Dielectric Variations
Full text linkParkinson’s disease (PD) is characterized by pathological changes in the substantia nigra, which in its early stages may manifest as structural and functional asymmetries between the two hemispheres. Microwave imaging has recently emerged as a promising non-invasive tool to detect subtle dielectric variations. In the context of Parkinson’s disease, such contrasts are expected to arise from the underlying physiological alterations in brain tissue, although their magnitude has not yet been fully characterized. In this work, we investigate the feasibility of differential microwave imaging, where detection is based on permittivity contrasts, through a controlled phantom study. A simple two-dimensional head phantom was constructed using a 3D-printed cylindrical container filled with water, incorporating a Teflon tube to represent the substantia nigra. The tube was filled with hot water, whose gradual cooling emulated small dielectric changes. Since the dielectric properties of water vary linearly with temperature over 0.5–3 GHz, we first validated this dependence through both numerical analysis and experimental measurements. Four antennas were then employed in a differential imaging configuration, with image reconstruction performed via the multi-frequency bi-focusing algorithm. The results show that the system can successfully detect a dielectric contrast corresponding to a temperature variation as small as 0.4 °C, equivalent to approximately 0.17% in relative permittivity. While the exact dielectric changes associated with PD remain to be determined, these results demonstrate that the proposed approach is sensitive to very small contrasts, supporting the potential of differential microwave imaging as a candidate tool for future investigations into Parkinson’s disease detection
Review of microwave near-field sensing and imaging devices in medical applications
Full text linkMicrowaves can safely and non-destructively illuminate and penetrate dielectric materials, making them an attractive solution for various medical tasks, including detection, diagnosis, classification, and monitoring. Their inherent electromagnetic properties, portability, cost-effectiveness, and the growth in computing capabilities have encouraged the development of numerous microwave sensing and imaging systems in the medical field, with the potential to complement or even replace
current gold-standard methods. This review aims to provide a comprehensive update on the latest advances in medical applications of microwaves, particularly focusing on the near-field ones working within the 1-15 GHz frequency range. It specifically examines significant strides in the development of clinical devices for brain stroke diagnosis and classification, breast cancer screening, and continuous blood glucose monitoring. The technical implementation and algorithmic aspects of prototypes
and devices are discussed in detail, including the transceiver systems, radiating elements (such as antennas and sensors), and the imaging algorithms. Additionally, it provides an overview of other promising cutting-edge microwave medical applications, such as knee injuries and colon polyps detection, torso scanning and image-based monitoring of thermal therapy intervention. Finally, the review discusses the challenges of achieving clinical engagement with microwave-based technologies
and explores future perspectives
Early Detection of Alzheimer’s Disease via Machine Learning-Based Microwave Sensing: An Experimental Validation
Full text linkThe early diagnosis of Alzheimer’s disease remains an unmet medical need due to the cost and invasiveness of current methods. Early detection would ensure a higher quality of life for patients, enabling timely and suitable treatment. We investigate microwave sensing for low-cost, non-intrusive early detection and assessment of Alzheimer’s disease. This study is based on the emerging evidence that the electromagnetic properties of cerebrospinal fluid are affected by abnormal concentrations of proteins recognized as early-stage biomarkers. We design a conformal six-element antenna array placed on the upper portion of the head, operating in the 500 MHz to 6.5 GHz band. It measures scattering response due to changes in the dielectric properties of intracranial cerebrospinal fluid. A multi-layer perceptron network extracts the diagnostic information. Data classification consists of two steps: binary classification to identify the disease presence and multi-class classification to evaluate its stage. The algorithm is trained and validated through controlled experiments mimicking various pathological severities with an anthropomorphic multi-tissue head phantom. Results support the feasibility of the proposed method using only amplitude data and lay the foundation for more extensive studies on microwave sensing for early Alzheimer’s detection
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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