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On the output factor measurements of the CyberKnife iris collimator small fields: Experimental determination of the correction factors for microchamber and diode detectors
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10.1118/1.4736810
/content/aapm/journal/medphys/39/8/10.1118/1.4736810
http://aip.metastore.ingenta.com/content/aapm/journal/medphys/39/8/10.1118/1.4736810

Figures

Image of FIG. 1.
FIG. 1.

Photographs depicting [(a), (b)] the experimental setup for the polymer gel dosimetry and (c) the three irradiated gel phantoms (left to right: 650 mm SDD, 800 mm SDD, and 1000 mm SDD).

Image of FIG. 2.
FIG. 2.

Measured (left) and corrected (right) output factors for 650 mm SDD, plotted as a function of iris collimator size. Diode measurements were corrected using the MC derived correction factors for the 800 mm SDD given in Ref. 37, while PinPoint measurements were corrected using the corresponding, experimentally derived of this work. The alanine, TLD, EBT, and gel error weighted average output factor values are shown with a solid line. The insert figure on the right shows a more detailed comparison of the corrected output factors obtained using the most commonly used detectors (i.e., diodes and microchambers only) with the alanine, TLD, EBT, and gel weighted average.

Image of FIG. 3.
FIG. 3.

Measured (left) and corrected (right) output factors for 800 mm SDD, plotted as a function of iris collimator size. Diode and PinPoint measurements were corrected using the MC derived correction factors given in Ref. 37. The alanine, TLD, EBT, and gel error weighted average output factor values are shown with a solid line. The insert figure on the right shows a more detailed comparison of the corrected output factors obtained using the most commonly used detectors (i.e., diodes and microchambers only) with the alanine, TLD, EBT, and gel weighted average.

Image of FIG. 4.
FIG. 4.

Measured (left) and corrected (right) output factors for 1000 mm SDD, plotted as a function of iris collimator size. Diode measurements were corrected using the MC derived correction factors for the 800 mm SDD given in Ref. 37, while PinPoint measurements were corrected using the corresponding, experimentally derived of this work. The alanine, TLD, EBT, and gel error weighted average output factor values are shown with a solid line. The insert figure on the right shows a more detailed comparison of the corrected output factors obtained using the most commonly used detectors (i.e., diodes and microchambers only) with the alanine, TLD, EBT, and gel weighted average.

Image of FIG. 5.
FIG. 5.

Volume averaging correction factors for the 5 mm, 7.5 mm, 10 mm, 12.5 mm, and 15 mm iris collimators plotted as a function of detector diameter for (a) 650 mm, (b) 800 mm, and (c) 1000 mm SDD.

Image of FIG. 6.
FIG. 6.

Measured correction factors for 800 mm SDD plotted as a function of iris collimator size for the PinPoint 31014 microchamber, PTW-60017 unshielded, and PTW-60008 shielded diodes. Corresponding results calculated using MC simulation by Francescon et al. (Ref. 37) are plotted for comparison. The uncertainty, at 68% confidence level, of the presented correction factor results are depicted using error bars.

Tables

Generic image for table
TABLE I.

Measured output factors for the 5 mm, 7.5 mm, 10 mm, 12.5 mm, and 15 mm iris collimators for the 650 mm, 800 mm, and 1000 mm SDD values. Corresponding uncertainties at the 68% level are shown in parentheses.

Generic image for table
TABLE II.

Alanine volume averaging correction factors for the 5 mm, 7.5 mm, 10 mm, 12.5 mm, and 15 mm iris collimators, and the 650 mm, 800 mm, and 1000 mm SDD values. Corresponding uncertainties at the 68% level are shown in parentheses.

Generic image for table
TABLE III.

Microchamber and diode detector correction factors for the 5 mm, 7.5 mm, 10 mm, 12.5 mm, and 15 mm iris collimators, for the 650 mm, 800 mm, and 1000 mm SDD values. Corresponding uncertainties at the 68% level are shown in parentheses.

Generic image for table
TABLE IV.

Corrected output factors, , for the 5 mm, 7.5 mm, 10 mm, 12.5 mm, and 15 mm iris collimators for the 650 mm, 800 mm, and 1000 mm SDD values. Diode measurements were corrected using the corresponding MC derived correction factors of Francescon et al. (Ref. 37) PinPoint measurements at 800 mm SDD were corrected using the MC derived correction factors, while at 650 mm and 1000 mm SDD were corrected using the experimentally derived correction factors of Table III. Corresponding uncertainties at the 68% level are shown in parentheses.

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/content/aapm/journal/medphys/39/8/10.1118/1.4736810
2012-07-20
2014-04-23
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: On the output factor measurements of the CyberKnife iris collimator small fields: Experimental determination of the kQ clin ,Q msr f clin ,f msr correction factors for microchamber and diode detectors
http://aip.metastore.ingenta.com/content/aapm/journal/medphys/39/8/10.1118/1.4736810
10.1118/1.4736810
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