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On the insensitivity of single field planar dosimetry to IMRT inaccuracies
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10.1118/1.3425781
/content/aapm/journal/medphys/37/6/10.1118/1.3425781
http://aip.metastore.ingenta.com/content/aapm/journal/medphys/37/6/10.1118/1.3425781

Figures

Image of FIG. 1.
FIG. 1.

(a) Axial plane of an IMRT plan that was determined by phantom measurements to be clinically acceptable. (b) Same plane of the IMRT plan, recast on the phantom used for ion chamber measurements to verify clinical acceptability of the plan. (c) Axial plane of an IMRT plan that was determined to be unacceptably inaccurate. (d) Same plane of the unacceptable IMRT plan, recast on the phantom used for ion chamber QA.

Image of FIG. 2.
FIG. 2.

Results of ion chamber measurements in the cumulative dose distributions for all IMRT plans. The deviation between measured and calculated dose is plotted against the dose calculated by the planning system. Deviations of greater than 4% between measurement and calculation (shaded regions) are qualified as failed results in the author’s center.

Image of FIG. 3.
FIG. 3.

(a) Single PDI measured by the EPID from plan that was determined by phantom measurements to be clinically acceptable. (b) The same field from an unacceptable plan for the same patient. (c) and (d) are gamma plots from comparison of measurements (a) and (b) to the predicted PDIs. Colored pixels are points that failed a 2%/2 mm gamma analysis.

Image of FIG. 4.
FIG. 4.

Field-by-field display of the gamma analysis results for EPID-based QA of six IMRT plans. The fraction of pixels passing the gamma analysis is plotted for each of the fields when using 2%/2 mm DTA criteria (top row) and 3%/3 mm DTA (bottom row). The solid lines connect the measurements of the unacceptable IMRT plans, while the dashed lines connect measurements of the acceptable plans. Missing points in the third column of plots correspond to fields which were delivered with a single MLC carriage position.

Image of FIG. 5.
FIG. 5.

(a) Single dose plane measured by the MATRIXX ion chamber array for a plan that was determined by phantom measurements to be clinically acceptable. (b) The same field from an unacceptable plan for the same patient. (c) and (d) are binary gamma plots from comparison of measurements (a) and (b) to the calculated dose planes. Red pixels are points that failed a 2%/2 mm gamma analysis.

Image of FIG. 6.
FIG. 6.

Field-by-field display of the gamma analysis results for QA of six IMRT plans performed with the MATRIXX ion chamber array. The fraction of pixels passing the gamma analysis is plotted for each of the fields when using 2%/2 mm DTA criteria (top row) and 3%/3 mm DTA (bottom row). The solid lines connect the measurements of the unacceptable IMRT plans, while the dashed lines connect measurements of the acceptable plans.

Tables

Generic image for table
TABLE I.

Summary of gamma analysis of IMRT plans measured field-by-field with an EPID. Scores for each plan are the percentage of pixels passing the gamma criteria, averaged over all fields in a plan. The standard deviations of the scores, calculated for all of fields in each plan, are reported in parentheses.

Generic image for table
TABLE II.

Summary of gamma analysis of IMRT plans measured field-by-field with a MATRIXX ion chamber array. Scores for each plan are the percentage of pixels passing the gamma criteria, averaged over all fields in a plan. The standard deviations of the scores, calculated for all of fields in each plan, are reported in parentheses.

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/content/aapm/journal/medphys/37/6/10.1118/1.3425781
2010-05-12
2014-04-18
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: On the insensitivity of single field planar dosimetry to IMRT inaccuracies
http://aip.metastore.ingenta.com/content/aapm/journal/medphys/37/6/10.1118/1.3425781
10.1118/1.3425781
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