117,390 research outputs found
Generalized EPID calibration for in-vivo transit dosimetry A. Fidanzio, S. Cilla, F. Greco, L. Azario, A. Piermattei
No full textMany researchers are studying new in vivo dosimetry methods based on the use of
Elelctronic portal imaging devices (EPIDs) that are simple and efficient in their daily use.
However the need of time consuming implementation measurements with solid water phantoms
for the in vivo dosimetry implementation can discourage someone in their use.
In this paper a procedure has been proposed to calibrate aSi EPIDs for in vivo transit dosimetry.
The dosimetric equivalence of three aSi Varian EPIDs has been investigated in terms of signal reproducibility
and long termstability, signal linearity withMUand dose per pulse and signaldependence
on the field dimensions. The signal reproducibility was within +/-0.5% (2SD), while the long term
signal stability has been maintained well within +/-2%. The signal linearity with the monitor units
(MU) waswithin +/-2% and within +/-0.5% for the EPIDs controlled by the IAS 2, and IAS 3 respectively.
In particular it was verified that the correction factor for the signal linearity with the monitor
units, klin, is independent of the beam quality, and the dose per pulse absorbed by the EPID.
For 6, 10 and 15 MV photon beams, a generalized set of correlation functions F(TPR,w,L) and
empirical factors f(TPR,d,L) as a function of the Tissue Phantom Ratio (TPR), the phantom thickness,
w, the square field side, L, and the distance, d, between the phantom mid-plane and the isocentre
were determined to reconstruct the isocenter dose.
The tolerance levels of the present in vivo dosimetry method ranged between +/-5% and +/-6% depending
on the tumor body location.
In conclusion, the procedure proposed, that use generalized correlation functions, reduces the
effort for the in vivo dosimetry method implementation for those photon beams with TPR within
+/-0.3% as respect those here used
Calibration of Elekta aSi EPIDs used as transit dosimeter S. Cilla, A. Fidanzio, F. Greco, L. Azario, A. Piermattei.
No full textCorrelation functions for Elekta aSi-EPIDs used as transit dosimeter for open fields. S. Cilla, A. Fidanzio, F. Greco, L. Azario, A. Piermattei.
No full textPreliminary results in solid state dosimetry of proton beams for ocular pathology treatment
No full textGeneralized EPID calibration for in vivo transit dosimetry
No full textMany researchers are studying new in vivo dosimetry methods based on the use of
Elelctronic portal imaging devices (EPIDs) that are simple and efficient in their daily use.
However the need of time consuming implementation measurements with solid water phantoms
for the in vivo dosimetry implementation can discourage someone in their use.
In this paper a procedure has been proposed to calibrate aSi EPIDs for in vivo transit dosimetry.
The dosimetric equivalence of three aSi Varian EPIDs has been investigated in terms of signal reproducibility
and long termstability, signal linearity withMUand dose per pulse and signaldependence
on the field dimensions. The signal reproducibility was within 0.5% (2SD), while the long term
signal stability has been maintained well within 2%. The signal linearity with the monitor units
(MU) waswithin 2% and within 0.5% for the EPIDs controlled by the IAS 2, and IAS 3 respectively.
In particular it was verified that the correction factor for the signal linearity with the monitor
units, klin, is independent of the beam quality, and the dose per pulse absorbed by the EPID.
For 6, 10 and 15 MV photon beams, a generalized set of correlation functions F(TPR,w,L) and
empirical factors f(TPR,d,L) as a function of the Tissue Phantom Ratio (TPR), the phantom thickness,
w, the square field side, L, and the distance, d, between the phantom mid-plane and the isocentre
were determined to reconstruct the isocenter dose.
The tolerance levels of the present in vivo dosimetry method ranged between 5% and 6% depending
on the tumor body location.
In conclusion, the procedure proposed, that use generalized correlation functions, reduces the
effort for the in vivo dosimetry method implementation for those photon beams with TPR within
0.3% as respect those here used
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
Square Dancing with the Stars to Enhance Dynamic Hirschman Linkages?
No full textIn this Presidential Address, the author takes the reader on a reconnaissance of his life and time as a regional scientist. He points out scenery he found scintillating along the way, hoping that some may pick up the banner and chew on a few of the ideas for a while. He suggests a revisit to Albert O. Hirschman’s notion of key sectors and more empirical analysis related to Marcus Berliant’s and Masahisa Fujita’s notion of knowledge creation and transfer.Presidential Address, San Antonio, Texas, March 29, 2014 (53rd Meetings of the Southern Regional Science Association
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe 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
Photon and electron beam dosimetry with a CVD diamond detector
No full textThe performance of a radiation detector based on a 43 mm thick polycrystalline diamond film, obtained by hot
filament CVD has been tested under realistic clinical conditions of irradiation generated by conventional photon and
electron beams generally used for radiotherapy purposes. The linearity of the collected charge with the dose was verified
and the sensitivity per unit of the detector sensitive volume was evaluated to be 20 nC Gy1mm3 with an applied
electric field of 23 kV/cm. This value is of the same order as that reported for PTW natural diamond detectors
(50–135 nC Gy1mm3). A correction factor D 1⁄4 0:94 was found for the detector current dependence on the dose rate
working under the conditions of maximum signal-to-noise ratio. However, even a D 1⁄4 1:00 may be obtained when
working with higher polarization electric field but at the expense of a lower signal-to-noise ratio.
When the diamond detector signals were corrected for the dose rate dependence, the Percentage Depth Signal and the
Output Factor values were in agreement with the results obtained with an ionization chamber well within the
experimental uncertainty (1% 1s)
Letter from unknown writer to Jesse L. Boyce
No full textLetter to Jesse L. Boyce from unknown author (possibly Jack) about the investigation into the powder magazine located in the Grand Canyon. Some personal news is included in the letter such as the writer's marriage to the daughter of C.A. Taylor, former Supervisor of Cochise County
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