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Direct aperture optimization for IMRT using Monte Carlo generated beamlets
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10.1118/1.2336509
/content/aapm/journal/medphys/33/10/10.1118/1.2336509
http://aip.metastore.ingenta.com/content/aapm/journal/medphys/33/10/10.1118/1.2336509

Figures

Image of FIG. 1.
FIG. 1.

MC model of the Varian CL21EX linear accelerator head (a) Group A—target, primary collimator, monitor chamber, mylar mirror, and phase space A. (b) Group B—monitor chamber, mylar mirror, secondary collimation (jaws) and phase space B.

Image of FIG. 2.
FIG. 2.

Dose distribution from a single beamlet. Solid line: PTV.

Image of FIG. 3.
FIG. 3.

Open-field phase space is segmented into beamlets. Each beamlet, , contributes dose to a voxel, , within a structure-of-interest. This data is stored in a beamlet dose distribution matrix.

Image of FIG. 4.
FIG. 4.

Water equivalent AVID phantom with air cavity. (a) Structure set with C-shaped PTV and spinal cord-like OAR. (b) Field placement.

Image of FIG. 5.
FIG. 5.

Anterior bias beam arrangement for nasopharynx recurrence example.

Image of FIG. 6.
FIG. 6.

Open field percentage depth dose through air cavity. Dotted line: PBK algorithm (without inhomogeneity correction), Dashed line: PBK (with modified Batho correction), Solid line: Monte Carlo.

Image of FIG. 7.
FIG. 7.

3D representation of the 95% prescription isodose surface encompassing the C-shaped target. The air cavity surface rendering is not shown for clarity; however, the box drawing indicates its relative position. (a) PBK algorithm optimization/PBK final forward calculation (b) Same plan from (a) recalculated using MC simulation (c) MC-DAO plan with six apertures per field.

Image of FIG. 8.
FIG. 8.

DVHs for phantom example. (a) Eclipse TPS plan (solid line) is recalculated using MC (dashed line). (b) MC-DAO plan (solid line) compared to same dashed line in (a) (PBK optimized/MC forward calculation).

Image of FIG. 9.
FIG. 9.

Coronal dose plane MC-DAO plan: (a) film measurement (left) and Monte Carlo (right). Arrows show tongue and groove effect. Profiles (b) parallel and (c) perpendicular to leaf motion. Solid line: MC dose. Dashed line: Film measured dose. (d) Cropped film plane (e) Corresponding dose-difference (DD)/distance-to-agreement (DTA) map.36 or DD passed. . (Pass/Fail: DD max dose/DTA .)

Image of FIG. 10.
FIG. 10.

Nasopharynx recurrence: MC-DAO optimization/MC-forward calculation. Solid line: PTV contour. Dotted line: 95% isodose.

Image of FIG. 11.
FIG. 11.

Monte Carlo reveals 9.0% underdosage of PTV (mean dose) for this IMRT plan. Solid line: PBK optimized/PBK forward calculation. Dashed line: PBK optimized/MC forward calculation.

Image of FIG. 12.
FIG. 12.

The optimized DVH (before final calculation) and final DVH (after final dose calculation) are compared for the (a) fluence-based optimization and (b) DAO plans. Dashed DVH. Solid DVH.

Tables

Generic image for table
TABLE I.

Treatment field/optimization parameters for AVID phantom with C-shaped target.

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TABLE II.

DVH planning objectives—phantom example (C-shape).

Generic image for table
TABLE III.

Treatment field/optimization parameters for nasopharynx recurrence example.

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TABLE IV.

DVH planning objectives—Nasopharynx recurrence example.

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TABLE VI.

Phantom example: Comparison of monitor unit (MU) delivery efficiency for Varian Eclipse fluence-based plan and MC-DAO.

Generic image for table
TABLE VII.

Doses to structures of interest for nasopharynx example. Prescription .

Generic image for table
TABLE VIII.

Ion chamber point dose measurements in cylindrical verification phantom.

Generic image for table
TABLE IX.

Nasopharynx example: comparison of monitor unit (MU) delivery efficiency for Varian eclipse fluence-based plan and MC-DAO.

Generic image for table
TABLE V.

Doses to structures-of-interest for AVID phantom example.

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/content/aapm/journal/medphys/33/10/10.1118/1.2336509
2006-09-14
2014-04-19
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Direct aperture optimization for IMRT using Monte Carlo generated beamlets
http://aip.metastore.ingenta.com/content/aapm/journal/medphys/33/10/10.1118/1.2336509
10.1118/1.2336509
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