1,720,962 research outputs found
Gamma camera piatta a scintillazione, ad altissima risoluzione spaziale, a struttura modulare /Flat scintillation gamma camera with very high spatial resolution,with modular structure
No full textThe gamma camera, able to be developed in areas of any size and unlimited, presents such a thickness as to be considered flat and of minimal bulk and it can be assembled in individual modules to be attached one to the other solving the problem of dead zones between individual PSPMTS, with values of intrinsic spatial resolution in the order of 1 mm. The application of the present invention may range from the medical field (PET, SPECT, SPEM, PEM, etc.) to employment in astrophysics
Low-power charge division circuits for wireless applications based on silicon photomultipliers
No full textIn this paper, we present a dedicated charge division circuit (CDC) as readout system for wireless detectors based on silicon photomultiplier (SiPM) arrays coupled to scintillators. In the proposed readout circuit, the SiPM output current is split into two symmetric signals by a pair of diodes, so it was called diode coupled symmetric charge division (DCSCD). The circuit was investigated using LTSPICE, fabricated as a printed circuit board and characterized. Its performances were compared with that of the traditional discrete positioning circuit (DPC) scheme. Testing the two CDC networks on a 16× 28 array of SiPMs, we found that image reconstruction is significantly compromised when the DPC configuration is connected to few SiPMs, while the diode-based CDC configuration presents a very high-quality image histogram independently on the number of the connected photosensors. The proposed electronics features very low-power consumption when compared with commercial solutions and it is, therefore, suitable for battery-operated device, which requires a power-efficient design. Indeed, the DCSCD electronics requires less than 10 mW of static power to read out the 16× 28 array of SiPMs, demonstrating the efficacy of the proposed diode-based CDC as passive readout circuitry and opening the route for the development of wireless gamma camera systems
Low power readout circuits for large area silicon photomultiplier array
No full textIn this paper we present modeling and experimental characterization of two passive charge division circuits as low power readout systems for large area silicon photomultiplier (SiPM) array. The first configuration is the traditional discrete positioning circuit (DPC), while the second one is a symmetric charge division circuit where the SiPM output current is split into two symmetric signals by a pair of diodes. Testing the two CDC networks on a 16 × 28 array of SiPMs, we found that image reconstruction is significantly compromised when the DPC configuration is connected to few SiPMs, while the diode-based CDC configuration presents a very high quality image histogram independently on the number of the connected photosensors. These results demonstrate the efficacy of the proposed diode-based CDC as passive readout circuitry and open the route for the development of effective low-power consumption, portable gamma camera systems
Radioisotope guided surgery with imaging probe, a hand-held high-resolution gamma camera
No full textSince 1997, our group of Physics together with Nuclear Physicians studies imaging probes (IP), hand-held, high-resolution gamma cameras for radio-guided surgery (RGS). Present work is aimed to verify the usefulness of two updated IP in different surgical operations. Forty patients scheduled for breast cancer sentinel node (SN) biopsy, five patients with nodal recurrence of thyroid cancer, seven patients with parathyroid adenomas, five patients with neuroendocrine tumours (NET), were operated under the guide of IP. We 2 used two different IP with field of view of 1 and 4in.(2), respectively and intrinsic spatial resolution of about 2mm. Radioisotopes were (99m)Tc, (123)I and (111)In. The 1 in.(2) IP detected SN in all the 40 patients and more than one node in 24, whereas anger camera (AC) failed locating SN in four patients and detected true positive second nodes in only nine patients. The 4 in.(2) IP was used for RGS of thyroid, parathyroid and NETs. It detected eight latero-cervical nodes. In the same patients, AC detected five invaded nodes. Parathyroid adenomas detected by IP were 10 in 7 patients, NET five in five patients. One and 4 in.(2) IPs showed usefulness in all operations. Initial studies on SN biopsy were carried out on small series of patients to validate IP and to demonstrate the effectiveness and usefulness of IP alone or against conventional probes. We propose the use of the IP as control method for legal documentation and surgeon strategy guide before and after lesion(s) removal. (c) 2007 Elsevier B.V. All rights reserved
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
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