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Fast transit portal dosimetry using density-scaled layer modeling of aSi-based electronic portal imaging device and Monte Carlo method
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10.1118/1.4764563
/content/aapm/journal/medphys/39/12/10.1118/1.4764563
http://aip.metastore.ingenta.com/content/aapm/journal/medphys/39/12/10.1118/1.4764563

Figures

Image of FIG. 1.
FIG. 1.

EPID model in XVMC. A simplified diagram of the homogeneous EPID model is provided in this figure and the actual modeling employed details (material content, thickness, and density) from the manufacturer. The Phosphor was based on Gadolinium Oxy Sulfide.

Image of FIG. 2.
FIG. 2.

Comparison of profiles in EPID that were corrected from measurements (E_corrected), processed thru convolution (E_convoluted), and Monte Carlo (MC)-calculated for 10 × 10 cm2.

Image of FIG. 3.
FIG. 3.

Computation setup of phantom and EPID in the XVMC code. Under the Rando phantom are EPID layers that are shown in detail in Fig. 1.

Image of FIG. 4.
FIG. 4.

Beam profile comparison of phosphor (a) and copper (b) layers with different thicknesses. The actual phosphor and copper thicknesses in EPID and 0.25 cm were compared. A beam of 6 MV and 10 × 10 cm2 was used.

Image of FIG. 5.
FIG. 5.

Beam profile comparison in the crossplane direction between calculations (XVMC) and measurements (E_corrected and E_convoluted) at 150 cm under a 20-cm flat phantom for various field sizes. The measured profiles have been processed through convolution. The phantom was placed at 90 cm SSD. The profiles are for field sizes of 5 × 5, 7 × 7, 10 × 10, 15 × 15, and 20 × 20 cm2.

Image of FIG. 6.
FIG. 6.

Beam profile comparison in the inplane direction between calculations (XVMC) and measurements (E_corrected and E_convoluted) in EPID at 150 cm for various field sizes under a 20-cm flat phantom. The measured profiles have been processed through convolution. The phantom was placed at 90 cm SSD. The profiles are for field sizes of 5 × 5, 7 × 7, 10 × 10, 15 × 15, and 20 × 20 cm2.

Image of FIG. 7.
FIG. 7.

Image-to-dose conversion factor of EPID dependent on phantom thicknesses. The data are normalized to the datum for 20 × 20 cm2 (set to one).

Image of FIG. 8.
FIG. 8.

Dose distribution comparison in EPID for an IMRT beam incident from 0° angle. Horizontal and vertical indexes are pixel numbers. (a) Measured dose distribution (E_corrected), (b) measured dose distribution after convolution (E_convoluted), (c) calculated dose distribution, (d) dose profile comparison at y = 49. The dose points above 10% isodose line were selected for quantitative dose evaluation.

Image of FIG. 9.
FIG. 9.

Dose distribution comparison on an isocentric plane in the Rando phantom for an IMRT beam incident from 0° angle. (a) Calculated dose distribution, (b) reconstructed dose distribution, (c) dose profile comparison at y = 49. The dose points above 10% isodose line were selected for quantitative dose evaluation.

Image of FIG. 10.
FIG. 10.

Comparison of the forwardly calculated dose distribution (thick) with the inversely reconstructed dose distribution (thin) for (a) small field plan and (b) large field plan.

Image of FIG. 11.
FIG. 11.

Dose volume histograms for (a) small prostate case and (b) large pelvis case.

Tables

Generic image for table
TABLE I.

Pass-rates(%) of forwardly calculated and reconstructed doses for IMRT beams. In EPID, both measured dose images (E_corrected and E_convoluted) were employed for comparison. The dose points above 10% isodose line were selected for quantitative dose evaluation. The criteria of 3% DD and 4.5 mm DTA were used for evaluation of forward-calculated dose in EPID at 150 cm. The criteria of 3% DD and 3.0 mm DTA were used for evaluation of reconstructed dose in an isocentric plane at 100 cm within the phantom.

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/content/aapm/journal/medphys/39/12/10.1118/1.4764563
2012-11-29
2014-04-19
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Fast transit portal dosimetry using density-scaled layer modeling of aSi-based electronic portal imaging device and Monte Carlo method
http://aip.metastore.ingenta.com/content/aapm/journal/medphys/39/12/10.1118/1.4764563
10.1118/1.4764563
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