1,720,962 research outputs found
A simplified edge illumination set-up for quantitative phase contrast mammography with synchrotron radiation at clinical doses
Full text linkThis work presents the first study of x-ray phase contrast imaging based on a simple implementation of the edge illumination method (EIXPCi) in the field of mammography with synchrotron radiation. A simplified EIXPCi set-up was utilized to study a possible application in mammography at clinical doses. Moreover, through a novel algorithm capable of separating and quantifying absorption and phase perturbations of images acquired in EIXPCi modality, it is possible to extract quantitative information on breast images, allowing an accurate tissue identification. The study was carried out at the SYRMEP beamline of Elettra synchrotron radiation facility (Trieste, Italy), where a mastectomy specimen was investigated with the EIXPCi technique. The sample was exposed at three different energies suitable for mammography with synchrotron radiation in order to test the validity of the novel algorithm in extracting values of linear attenuation coefficients integrated over the sample thickness. It is demonstrated that the quantitative data are in good agreement with the theoretical values of linear attenuation coefficients calculated on the hypothesis of the breast with a given composition. The results are promising and encourage the current efforts to apply the method in mammography with synchrotron radiation
Variable tilt-angle, parallel-hole collimation system for high-resolution molecular imaging gamma tomosynthesis
No full textPurpose: This study investigates a novel gamma tomosynthesis (GT) method based on a variable tilt-angle, parallel-hole collimator (VAPHC) which, mounting to a conventional gamma, is able to perform high-resolution three-dimensional imaging. Methods: The VAPHC has the remarkable feature to be modular, consisting of independent collimation elements able to tilt according to variable angles [−45° to +45°]. Spatial resolutions were measured in reconstructed GT images using a point source at different source-to-collimator distances, while sensitivity was evaluated over the range of slant angles using a disk-source. Image contrast (IC) and contrast-to-noise-ratio (CNR) of sub-centimeters tumors were evaluated using a breast phantom containing a background activity and spheres filled with 99mTc to simulate lesions at two depths. Breast phantom GT images were compared with planar and circularorbit SPECT acquisitions of equal scan-time. Results: Planar spatial resolutions range from 9 to 14mm over a depth range of 6–10 cm; spatial resolution in depth dimension becomes two times greater than those in the other dimensions. The measured sensitivity decreases from 9 cps/μCi to 6 cps/μCi varying the slant angle from 5° to 45°. The measured IC and CNR of GT reconstructed images demonstrated that it was possible to improve the spatial resolution/sensitivity trade-off. Conclusions: The proposed GT based VAPHC demonstrated the potential for superior spatial resolution and contrast compared to planar and SPECT acquisitions. A conventional gamma camera equipped with the VAPHC could be located at the minimum distance from the patient, thus improving detection, localisation and characterisation of sub-centimetre lesions
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
Metabolic radiotherapy of benign thyroid diseases: study of dosimetry methods.
No full textreservedLa radioterapia metabolica con l’utilizzo di I -131 rappresenta un’opportunità efficace nel trattamento dell’ipertiroidismo delle patologie benigne della tiroide, offrendo una valida alternativa all’utilizzo dei farmaci antitiroidei e all’intervento chirurgico. Come lo iodio stabile, il radioiodio viene captato dalla ghiandola tiroidea e, grazie alla radiazione beta emessa da esso, riesce a distruggere le cellule follicolari tiroidee e a ridurre la sovrapproduzione di ormoni tipica dell’ipertiroidismo. Il trattamento può essere eseguito sia tramite la somministrazione di attività fissa o con un approccio dosimetrico previsionale, fortemente raccomandato. La dosimetria pre-terapia ha infatti un ruolo fondamentale nel garantire i principi di giustificazione, ottimizzazione sanciti dal D. Lgs. 101/2020. Nelle patologie benigne della tiroide, l’attività di I -131 da somministrare nell’approccio con dosimetria personalizzata dipende: dalla massa dell’organo bersaglio, dalla captazione massima dello iodio nel target, dalla dose di radiazioni necessaria per l’effetto terapeutico e dalla cinetica paziente-specifica del radioiodio. La iodocaptazione tiroidea consente di effettuare, prima della terapia, una stima della curva di assorbimento del radioiodio nel tempo dalla quale ricavare i parametri necessari al calcolo dell’attività da somministrare. Tale funzione di assorbimento nel tempo è calcolata con diversi formalismi e con l’utilizzo di diversi modelli che definiscono la cinetica del radionuclide nell’organismo del paziente. L’approccio più utilizzato è il modello a due compartimenti (ghiandola tiroidea e distribuzione ematica) che prevede, dopo somministrazione di una dose tracciante di I -131, l’acquisizione di almeno 4 misure sperimentali a diversi istanti temporali dei conteggi dell’attività della tiroide. Ulteriore approccio prevede l’utilizzo di un modello a un solo compartimento (tiroide) e la misura di punto sperimentale a 24 h e ulteriori a 4 o 8 giorni dalla somministrazione del radiofarmaco. Inoltre, può essere utilizzata una metodologia che non tiene conto dei compartimenti e considera soltanto una misura tardiva (>24 h) dalla somministrazione del tracciante. Il seguente elaborato propone di valutare le diverse metodologie dosimetriche e di confrontarle, valutando quelle più appropriate in termini di sia di esigenze cliniche che di efficienza, attraverso un’analisi retrospettiva del calcolo dei valori di attività da somministrare per il trattamento medico nucleare delle patologie benigne della tiroide. L’obiettivo è quello di analizzare le differenze e il potenziale di errore nei metodi comunemente utilizzati per il calcolo dell'attività di I - 131 da somministrare ed, eventualmente, suggerire nuovi approcci che consentano di raggiungere una migliore accuratezza del calcolo dosimetrico
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
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