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Evaluation of the Gafchromic® EBT2 film for the dosimetry of radiosurgical beams
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10.1118/1.4752211
/content/aapm/journal/medphys/39/10/10.1118/1.4752211
http://aip.metastore.ingenta.com/content/aapm/journal/medphys/39/10/10.1118/1.4752211

Figures

Image of FIG. 1.
FIG. 1.

A photograph of the poly(methyl methacrylate) frames used to hold the film in the scanner tank system (a). The films are attached to the frame by using black tape after immersion to avoid air bubbles (b).

Image of FIG. 2.
FIG. 2.

(a) The film calibration curve for the EBT2 film model. The fitting curve was obtained using an in-house program based on MATLAB ®. (b) An estimation of the total uncertainty (1σ) of the film as a dose detector as a function of the dose delivered to the film (solid line). This uncertainty was the result of the sum in the quadrature of σ cal, σ linac, σ fit and the expansion of the uncertainty in netOD according to Refs. 19 and 27 .

Image of FIG. 3.
FIG. 3.

A comparison of the total scatter factors with the EBT2 and SFD daisy-chained measurements. The uncertainty of the SFD measurements is less than 0.7%. In overall, the observed EBT film measurements from Ref. 9 were within 3% of the SFD measured ones and differed by up to 6.1% with the EBT2 film for the smallest field.

Image of FIG. 4.
FIG. 4.

(a) A comparison of the TMRs between the EBT2 and SFD (dashed line) detectors. There are differences between the detectors for depths beyond dmax. (b) The difference between EBT2 and SFD in the buildup region can be better observed when their respective tissue-phantom ratios are compared (normalized) at 5.0 cm. The buildup region exhibits differences greater than 5%, especially for the 4.0-mm circular collimator, which can be attributed to the film's energy dependence.

Image of FIG. 5.
FIG. 5.

A comparison of the measured off-axis ratios between the EBT2 (solid line) and SFD (open circles) detectors. Differences can be observed in the penumbra region. However, these differences are not significant based on the metrics used for their evaluation in this work.

Tables

Generic image for table
TABLE I.

The scatter factors measured with the diode and radiochromic film. The percent differences and the p-values obtained with the statistical analysis are also shown.

Generic image for table
TABLE II.

The gamma-index analysis between the off-axis ratios measured with the SFD diode and the EBT2 film. The percentage of points with γδ, ΔD) < 1 is shown.

Generic image for table
TABLE III.

The values of the 80%–20% penumbra of the circular collimators measured with the SFD diode. The differences with the EBT2-measured penumbra and the p-values used for the statistical analysis are shown.

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/content/aapm/journal/medphys/39/10/10.1118/1.4752211
2012-09-21
2014-04-25
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Evaluation of the Gafchromic® EBT2 film for the dosimetry of radiosurgical beams
http://aip.metastore.ingenta.com/content/aapm/journal/medphys/39/10/10.1118/1.4752211
10.1118/1.4752211
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