1,720,961 research outputs found
IAEA section of dosimetry and medical radiation physics (DMRP).
No full textPublished Article,The Dosimetry and Medical Radiation Physics (DMRP) section works on the Quality Assurance (QA) aspects of the use of radiation in medicine to ensure safety and effectiveness. Furthermore, it
contributes to the increase in scientific and technical capacity in medical physics worldwide by
fostering research and development in dosimetry techniques and playing a role in the education and
training of medical physicists. The primary beneficiaries of these activities are hospital patients
undergoing therapy and diagnosis with radiation, radiation workers who benefit from the
standardization of radiation protection measurements and the general public due to improved
dosimetry practice. DMRP also provides two types of service directly to Member States: dosimetry
calibration and dosimetry auditing
Detector to detector corrections: A comprehensive experimental study of detector specific correction factors for beam output measurements for small radiotherapy beams.
No full textPublished Journal Article,Purpose: The aim of the present study is to provide a comprehensive set of detector specific correction
factors for beam output measurements for small beams, for a wide range of real time and passive
detectors. The detector specific correction factors determined in this study may be potentially useful
as a reference data set for small beam dosimetry measurements.
Methods: Dose response of passive and real time detectors was investigated for small field sizes
shaped with a micromultileaf collimator ranging from 0.6 × 0.6 cm2 to 4.2 × 4.2 cm2 and the measurements
were extended to larger fields of up to 10 × 10 cm2. Measurements were performed at
5 cm depth, in a 6 MV photon beam. Detectors used included alanine, thermoluminescent dosimeters
(TLDs), stereotactic diode, electron diode, photon diode, radiophotoluminescent dosimeters
(RPLDs), radioluminescence detector based on carbon-doped aluminium oxide (Al2O3:C), organic
plastic scintillators, diamond detectors, liquid filled ion chamber, and a range of small volume air
filled ionization chambers (volumes ranging from 0.002 cm3 to 0.3 cm3). All detector measurements
were corrected for volume averaging effect and compared with dose ratios determined from alanine
to derive a detector correction factors that account for beam perturbation related to nonwater equivalence
of the detector materials.
Results: For the detectors used in this study, volume averaging corrections ranged from unity for the
smallest detectors such as the diodes, 1.148 for the 0.14 cm3 air filled ionization chamber and were
as high as 1.924 for the 0.3 cm3 ionization chamber. After applying volume averaging corrections,
the detector readings were consistent among themselves and with alanine measurements for several
small detectors but they differed for larger detectors, in particular for some small ionization chambers
with volumes larger than 0.1 cm3
Quality audits of small field output factors: a multi-centre pilot study.
No full textPublished Journal Article,A new co-ordinated research project (CRP) was launched by
the IAEA for the national audit networks for radiotherapy with
the purpose of developing the methodology for remotely
auditing IMRT related QA. The programme involves three audit
steps: (1) remote verification of TPS calculation of small field
output factors relevant for IMRT and audit of MLC positional
performance, (2) audit of single clinical IMRT field dose delivery
and (3) ‘end-to-end’ audit (imaging, planning, dose delivery) for
multiple field IMRT techniques. New procedures and phantoms
are being developed and examined through multi-centre pilot
studies involving CRP participants
A comparison of dosimetric properties of three solid state dosimetry systems for dosimetry audit in radiotherapy.
No full textPublished Article,The purpose of this study is to investigate
and compare characteristics of three solid
state dosimetry systems in order to determine
working parameters and corrections needed for
remote dosimetry audits of high energy photon
and electron beams. The following systems
were investigated: a thermo luminescent
dosimetry (TLD) system (TLD-100, PCL3 reader),
an optically stimulated luminescent dosimetry
(OSLD) system (nanoDots, microStar reader)
and a radiophoto luminescent dosimetry (RPLD)
system (GD 302M, FGD-1000 reader)
In vitro monitoring of rabbit anterior cruciate ligament damage by acoustic emission.
No full textPublished Journal Article,Anterior cruciate ligament (ACL) rupture is a major clinical problem leading to instability and degeneration of the knee joint.
The problem is compounded by the limited ability of the ACL to heal when ruptured. The existing knowledge regarding the way
the ACL ruptures is limited, and this investigation is an attempt to understand the nature of the ruptures using the rabbit as a model.
A total of 16 rabbit tibia–ACL–femur complexes were stretched in tension to complete rupture. Four specimens were stretched to
failure at a displacement rate of 0.5 mm/min and 12 specimens at 10 mm/min. Acoustic emission (AE) transducers were placed
on both the tibia and the femur, and stress wave signals generated during the tensile test were recorded. Fibre fractures produced
the highest amplitude signals with a relatively longer rise time. Other failure modes such as matrix failure and debonding produced
lower amplitude signals with shorter rise times. We also noted that few events were recorded during the initial period of tensile
loading (the elastic phase). The activity then increased significantly after maximum load was reached. The location information
provided by the acoustic emission system was consistent with the final site of rupture. We have shown that AE can be used to
characterise ligament damage, with fibre pull-outs and fibre fracture producing the highest signal amplitudes
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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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