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An effective correction algorithm for off-axis portal dosimetry errors
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10.1118/1.3187785
/content/aapm/journal/medphys/36/9/10.1118/1.3187785
http://aip.metastore.ingenta.com/content/aapm/journal/medphys/36/9/10.1118/1.3187785

Figures

Image of FIG. 1.
FIG. 1.

Original half-detector open field as captured by the EPID and displayed for analysis in the TPS. Center and corners of the EPID detecting surface are marked with cross hairs. Diagonal profile (as shown) corresponds to the dimension along which measurements were taken in constructing the diagonal beam profile during beam commissioning and was used for the analysis shown in Figs. 2 and 3.

Image of FIG. 2.
FIG. 2.

EPID measured/predicted along the diagonal profile shown in Fig. 1 for the photon beam. Beyond approximately , the percent difference linearly increases with respect to the distance from the origin, according to the equation shown.

Image of FIG. 3.
FIG. 3.

EPID measured/predicted along the diagonal profile shown in Fig. 1 for the photon beam. Beyond approximately , the percent difference increases linearly with respect to distance from the origin, according to the equation shown.

Image of FIG. 4.
FIG. 4.

Comparison of predicted dose vs measured dose (both uncorrected and corrected) for the half-detector open field of Fig. 1. Gamma evaluation (3% ) pass rate: Uncorrected, 52.0%; corrected, 91.0%.

Image of FIG. 5.
FIG. 5.

Comparison of predicted dose vs measured dose (both uncorrected and corrected) for the half-detector open field of Fig. 1. Gamma evaluation (3%, ) pass rate: Uncorrected, 28.3%; corrected, 97.4%.

Image of FIG. 6.
FIG. 6.

An example image of a breast tangent IMRT fluence captured in the upper right quadrant of the EPID and displayed for analysis in the TPS. The cross hairs mark the center and upper right corner of the EPID detecting surface. The bottom graph displays a comparison between predicted, uncorrected, and corrected portal doses along the cross-plane dose profile shown above. Gamma evaluation (3% ) pass rate: Uncorrected, 61.2%; corrected, 99.1%.

Image of FIG. 7.
FIG. 7.

An example image of a breast tangent IMRT fluence captured in the lower right quadrant of the EPID and displayed for analysis in the TPS. The cross hairs mark the center and lower right corner of the EPID detecting surface. The bottom graph displays a comparison between predicted, uncorrected, and corrected portal doses along the cross-plane dose profile shown above. Gamma evaluation (3%, ) pass rate: Uncorrected, 60.0%; corrected, 99.5%.

Image of FIG. 8.
FIG. 8.

An example of brain fluence captured in the extreme lower left quadrant of the EPID and displayed for analysis in the TPS. The cross hairs mark the lower left corner of the EPID detecting surface, and the dimensions shown are measured from that corner. The bottom graph displays a comparison between predicted, uncorrected, and corrected portal doses along the in-plane dose profile shown above. Gamma evaluation (3%, ) pass rate: Uncorrected, 50.8%; corrected, 98.9%.

Image of FIG. 9.
FIG. 9.

An example of head and neck fluence captured with the EPID and displayed for analysis in the TPS. The central cross hairs mark the CAX, and the shown dimensions are measured from that point. The bottom graph displays a comparison between predicted, uncorrected, and corrected portal doses along the in-plane dose profile shown above. Gamma evaluation (3%, ) pass rate: Uncorrected, 68.7%; corrected, 92.9%.

Tables

Generic image for table
TABLE I.

Clinical examples: Asymmetric breast EComp.

Generic image for table
TABLE II.

Clinical examples: Head and neck IMRT. Comparison of three head and neck IMRT plans imaged with both the uncorrected and corrected diagonal profiles. Data only include those fluences that extend beyond roughly beyond the CAX (the number of these fluences is shown in the first column). Of all off-axis fluences within one plan, the fourth column shows the highest improvement in gamma evaluation of 3%, for a single fluence due to EPID calibration using the corrected profile.

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/content/aapm/journal/medphys/36/9/10.1118/1.3187785
2009-08-12
2014-04-16
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: An effective correction algorithm for off-axis portal dosimetry errors
http://aip.metastore.ingenta.com/content/aapm/journal/medphys/36/9/10.1118/1.3187785
10.1118/1.3187785
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