1,720,961 research outputs found
Exposure to static magnetic fields in NMR research laboratories
No full textTo obtain cumulative exposure of workers to static magnetic fields in research laboratories, isotropic magnetic flux density values generated by MR spectrometers were integrated over time. One need only to consider that in a non medical environment, exposure limits are regulated only by international guidelines and by good practice, while in MR diagnostic environment there is a proper legislation. In this paper, the AA also introduced a weighting function, incorporating the international guidelines limits, and tested it with the Italian legislation existing for medical workers. The results were stored on a personal dose card, in order to evaluate the daily exposure of the worker and to better study the long term effects to static magnetic fields
Prove di funzionamento e controlli di qualità in radiodiagnostica tradizionale: considerazioni e proposte operative.
No full textQuality conservation of ultrasonography images in mobile devices
No full textMedical ultrasonography (US) is based on the correct evaluation of images. To guarantee the maintenance of consistent image quality over the lifetime of the device it is necessary to conduct periodic quality controls, consisting in image processing of images acquired from dedicated phantoms. At the present time mobile devices (e.g., iPad, Windows RT tablets, Android-based systems) are increasingly used for visualization of diagnostic images acquired by US machines, so images processing on this kind of hardware plays a crucial role in diagnostic imaging. In this paper we report an overview on the conservation of quality of the images transferred from the US consoles to remote electronic devices, in order to detect possible differences between homologous images. Moreover, always related to image quality controls, the Authors report about the development of an alternative procedure to quantitatively evaluate the US Functional Resolution (FR) parameter. To perform image conservation, image quality controls were conducted on eighteen different US systems and several parameters were evaluated by using a dedicated phantom, according to international and national technical protocols. The obtained images were analysed qualitatively and, if possible, quantitatively both on the US device (live analysis) and on a PC by using a dedicated LabView-based software (post processing). An iOS device was used for qualitative evaluations on the same images. The developed LabView-based application aims at measuring both directly and univocally the FR parameter, unlike the usual qualitative procedure that highly depends on medical staff capability. This alternative procedure allows to represent the anechoic structures as minima in the intensity vs. pixel graph. Thus, the measurement of the FR does not depend on the operator’s eye response
Slice thickness evaluation in CT and MRI: an alternative computerised procedure
No full textPurpose. The efficient use of computed tomography (CT) and magnetic resonance imaging (MRI) equipment necessitates establishing adequate quality-control (QC) procedures. In particular, the accuracy of slice thickness (ST) requires scan exploration of phantoms containing test objects (plane, cone or spiral). To simplify such procedures, a novel phantom and a computerised LabView-based procedure have been devised, enabling determination of full width at half maximum (FWHM) in real time. Materials and methods. The phantom consists of a polymethyl methacrylate (PMMA) box, diagonally crossed by a PMMA septum dividing the box into two sections. The phantom images were acquired and processed using the LabView-based procedure. Results. The LabView (LV) results were compared with those obtained by processing the same phantom images with commercial software, and the Fisher exact test (F test) was conducted on the resulting data sets to validate the proposed methodology. Conclusions. In all cases, there was no statistically significant variation between the two different procedures and the LV procedure, which can therefore be proposed as a valuable alternative to other commonly used procedures and be reliably used on any CT and MRI scanner
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
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