1,721,084 research outputs found
Electromagnetic device for imaged guided microwave ablation
Full text linkThis dissertation demonstrates the design of a microwave imaging system for monitoring liver thermal ablation treatments.
Liver cancer is the third most deadly cancer worldwide and has an increasing yearly fatality rate. Liver thermal ablation is considered to be an effective alternative to conventional treatment methods such as surgery. However, over the years, real-time monitoring of liver thermal ablation has become a big challenge because the existing modalities like computed tomography (CT), magnetic resonance imaging (MRI), positron emission tomography (PET), and Ultrasound imaging (US) have limitations in the applications at hand, that make them incapable or not suitable of providing real-time temperature values. Therefore, the assessment of the ablation procedure heavily relies on the clinician’s experience. Microwave imaging (MWI) is a potential candidate for this clinical need, since it provides a map of the dielectric properties of an unknown target from the knowledge of the scattered electromagnetic field. In fact, during liver thermal ablation treatments, the water molecules in the ablation zone dramatically reduce due to the heating. This process yields a change in dielectric properties values in the ablation zone as compared to the un-treated liver. The principle of microwave imaging for thermal ablation monitoring is to take advantage of the dielectric properties contrast between the ablated zone and the un-treated liver tissue. In fact, by recording and processing the scattered field at different stages of the treatment, it should be possible to image the evolution of the dielectric properties in the domain of interest. According to existing knowledge of the correspondence between liver’s dielectric properties values and temperature, it would then be possible to derive the local temperature in the ablation zone and hence determine the ablation stage.
Among the advantages of MWI for thermal ablation monitoring, it could be cited the low-cost, portability, capability of real-time imaging, harmless nature, as exploitation of low-power, non-ionizing radiation. Thanks to these circumstances. MWI has been considered for a number of biomedical applications, such as breast imaging, brain imaging, bone imaging, etc.
A microwave imaging system for monitoring liver thermal ablation treatment would be made by an array of antennas embedded into a coupling medium and located in close proximity to the human abdomen, in front of the area to be treated.
In this research, firstly, a numerical analysis was performed to determine the optimal working conditions in terms of operating frequency and coupling medium dielectric properties. Additionally, the dielectric properties of healthy ex vivo liver, as well as thermally ablated one were measured. Secondly, the antennas in the microwave imaging system were designed within the proposed working condition. Studies were performed with different antenna substrate materials looking for the most compact design. Three different antipodal Vivaldi antennas were designed and compared. After the microwave antenna design was completed, an in-silico assessment of the experimental set-up was performed, to define the optimal number of antennas and their spacing. The optimized set-up consists of eight antennas arranged in a staggered two-rows antennas array configuration immersed inside the coupling medium. Then, a simple yet representative experimental set-up for the validation of the imaging system was studied. The set-up foresees the 8 antennas inserted inside a tank filled with the coupling material; in front of the antenna array, a 3-D printed ellipsoidal phantom filled with tissue-mimicking liquid represents the thermally ablated zone. The retrieved images inside the domain of interest show that the designed system can detect the position of the ablated zone and identify it at different ablation stages. Finally, the chosen antenna was realized and experimentally verified, and a recipe to realize the coupling material was proposed and experimentally tested. Ultimately, the system was experimentally assessed with one antenna mechanically moved in a linear motion measuring the signal in front of the 3-D printed phantom. The numerical and experimental assessment of the microwave imaging system verifies the feasibility of such a system for liver ablation monitoring.
This study paves the way for the real-time monitoring of liver thermal ablation through microwave imaging techniques
A review on ground penetrating radar technology for the detection of buried or trapped victims
No full textThe localization of people buried or trapped under snow or debris is an emerging field of application of ground penetrating radar (GPR). In the last years, technological solutions and processing approaches have been developed to improve detection accuracy, speed up localization, and reduce false alarms. As such, GPR can play an active role in cooperative approaches required to tackle such emergencies. In this work, we present and briefly analyze the evolution of research in this field of application of GPR technology. In doing so, we adopt a point of view that takes into account that avalanches and collapsed buildings are two scenarios that call for different GPR approaches, since the former can be tackled through image processing of radar data, while the latter rely on the detection of the Doppler frequency changes induced by physiological movements of survivors, such as breathing. © 2014 IEEE
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
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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