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A source model for modulated electron radiation therapy using dynamic jaw movements
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10.1118/1.4800492
/content/aapm/journal/medphys/40/5/10.1118/1.4800492
http://aip.metastore.ingenta.com/content/aapm/journal/medphys/40/5/10.1118/1.4800492

Figures

Image of FIG. 1.
FIG. 1.

Schematic diagram of the FLEC. The FLEC serves as a final collimation device on the accessory tray of an electron applicator.

Image of FIG. 2.
FIG. 2.

(a) The accelerator model of a Varian Clinac 21EX. The FLEC is explicitly included in the model. The beam can be characterized in various levels of the accelerator. (b) A decomposed version of the same accelerator. Only one FLEC leaf and its corresponding jaw leaf are kept during the simulation. Scattered beam characteristics are derived at the indicated collecting planes.

Image of FIG. 3.
FIG. 3.

A graphical explanation of the leaf-hit algorithm. During the MC simulation of the decomposed accelerator particles were allowed to pass through areas where normally leaves would be present. During the reconstruction phase particles are rejected on the various collimating levels based on their projected trajectory.

Image of FIG. 4.
FIG. 4.

Gaussian probability density functions when the leaf is placed +1 cm from the central axis and for energies of 6, 12, and 20 MeV. The distributions are used for sampling an original position on the edge of each leaf.

Image of FIG. 5.
FIG. 5.

Primary spatial fluence distributions as incident on plane 3 (before the FLEC leaves) for the case of a 2 × 2 cm field size. The modified FE scattering theory was used for the calculation.

Image of FIG. 6.
FIG. 6.

Spatial fluence [6 MeV (a) and 20 MeV (b)] and energy distributions [6 MeV (c) and 20 MeV (d)] for the FLEC-based reference field size of 8 × 8 cm and for a SSD = 100 cm as predicted by the SM-symbols and MC-lines.

Image of FIG. 7.
FIG. 7.

Spatial fluence [6 MeV (a) and 20 MeV (b)] and energy distributions [6 MeV (c) and 20 MeV (d)] for the FLEC-based reference field size of 2 × 2 cm and for a SSD = 100 cm as predicted by the SM-symbols and MC-lines.

Image of FIG. 8.
FIG. 8.

Scatterplot of the angle of final direction θ ( ) to the final position in the field (on the direction) for the FLEC source, as predicted by MC (top row) and the SM (bottom row) for energies of 6 and 20 MeV and field sizes of 2 × 2  and 8 × 8 cm. The number of histories varied from 2 × 10 to 2 × 10 depending on the field size and energy.

Image of FIG. 9.
FIG. 9.

Relative depth dose distributions in water for square field sizes and for a SSD = 100 cm as predicted by the SM-symbols and MC-lines. (a)–(c) The smallest field size of 2 × 2 cm and (d)–(f) the largest field size of 8 × 8 cm for energies of 6, 12, and 20 MeV, respectively.

Image of FIG. 10.
FIG. 10.

Relative profile dose distributions in water for square field sizes and for a SSD = 100 cm as predicted by the SM-symbols and MC-lines. (a)–(c) The smallest field size of 2 × 2 cm and (d)–(f) the largest field size of 8 × 8 cm for energies of 6, 12, and 20 MeV, respectively.

Image of FIG. 11.
FIG. 11.

Relative depth dose distributions in water for rectangular and off-axis field sizes and for a SSD = 100 cm as predicted by the SM-symbols and MC-lines. (a)–(c) A 2 × 2 cm off-axis field and (d)–(f) a rectangular 2 × 8 cm field for energies of 6, 12, and 20 MeV, respectively.

Image of FIG. 12.
FIG. 12.

Relative profile dose distributions in water for rectangular and off-axis field sizes and for a SSD = 100 cm as predicted by the SM-symbols and MC-lines. (a)–(c) A 2 × 2 cm off-axis field and (d)–(f) a rectangular 2 × 8 cm field for energies of 6, 12, and 20 MeV, respectively.

Tables

Generic image for table
TABLE I.

Dose output in water at depth of maximum dose as predicted by MC simulations and by the SM for field sizes of 2 × 2 cm, 2 × 2 cm (off-axis), 2 × 8 cm and energies of 6, 12, and 20 MeV at a SSD of 100 cm. The output is normalized to the maximum dose of the 8 × 8 cm field size for each energy and for each model independently.

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/content/aapm/journal/medphys/40/5/10.1118/1.4800492
2013-04-19
2014-04-17
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: A source model for modulated electron radiation therapy using dynamic jaw movements
http://aip.metastore.ingenta.com/content/aapm/journal/medphys/40/5/10.1118/1.4800492
10.1118/1.4800492
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