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Field-size effect of physical doses in carbon-ion scanning using range shifter plates
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10.1118/1.3140586
/content/aapm/journal/medphys/36/7/10.1118/1.3140586
http://aip.metastore.ingenta.com/content/aapm/journal/medphys/36/7/10.1118/1.3140586

Figures

Image of FIG. 1.
FIG. 1.

Schematic view of experimental setup at the SBL in HIMAC.

Image of FIG. 2.
FIG. 2.

Schematics of frame experiments. The beam’s-eye-view positions of beam spots are indicated with dots for (a) frame A, (b) frame E, and (c) frame I. Corresponding dose distributions calculated at a depth of 24.26 mmWEL are shown with gray scale display for (d) frame A, (e) frame E, and (f) frame I. The Markus chamber (open circle) was placed at the center of concentric frames in the water phantom, and the dose contribution from the pencil beam scanned to the shape of the flat concentric squared frame is measured.

Image of FIG. 3.
FIG. 3.

Physical dose distributions along the beam axis for the target volumes of (open square), (open triangle), (cross), and (open rhombus) measured in a water phantom.

Image of FIG. 4.
FIG. 4.

Field-size dependence of the doses within the SOBP region of the target volumes of , , , and . The closed circles represent the averaged values of the measured physical dose, and the crosses and open squares represent those of the recalculated distribution with the two- and three-Gaussian beam models derived in the following sections, respectively.

Image of FIG. 5.
FIG. 5.

Doses measured in irradiations of frames A–J with no range shifter plates (symbols) are compared with the recalculated ones (lines) with the values of and obtained in the present study and incorporated into the treatment planning software.

Image of FIG. 6.
FIG. 6.

The lateral beam spreads of the first, second, and third components, , , and are shown with open squares, crosses and open triangles, respectively. The solid, dashed and dashed-dotted lines represent the calculated values for the range shifter thickness of 0, 50 and 100 mmWEL, respectively, with the simple formula derived in the present study.

Image of FIG. 7.
FIG. 7.

The fraction factors of the second and third components, and are shown with crosses and open triangles, respectively. The solid, dashed and dashed-dotted lines represent the calculated values for the range shifter thickness of 0, 50 and 100 mmWEL, respectively, with the simple formula derived in the present study.

Image of FIG. 8.
FIG. 8.

The measured physical dose distributions along the beam axis for the target volumes of (open square), (open triangle), (cross), and (open rhombus) are compared with the calculated ones using the three-Gaussian form of the pencil beam model.

Image of FIG. 9.
FIG. 9.

The measured physical dose distributions along the beam axis for the target volumes of (open square), (open triangle), (cross), and (open rhombus) are compared with the optimized ones using the three-Gaussian form of the pencil beam model.

Image of FIG. 10.
FIG. 10.

The measured physical dose distributions for the target volume of (open square) (a) along the beam axis and (b) on the axis. In both figures, the calculated distribution with the three-Gaussian pencil beam model is shown with a solid line.

Tables

Generic image for table
TABLE I.

The characteristics of the concentric squared frames. The inner and outer side lengths of the flat concentric squared frames and the number of spots required for the frame are summarized. The spot spacings in the and directions are 2 mm.

Generic image for table
TABLE II.

Standard deviations (Std.) of the derived parameters , , , , and for 500 data sets of doses are shown with their averages (Ave.) for three sets of five parameters assumed in the simulations (Ass.).

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/content/aapm/journal/medphys/36/7/10.1118/1.3140586
2009-06-09
2014-04-21
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Field-size effect of physical doses in carbon-ion scanning using range shifter plates
http://aip.metastore.ingenta.com/content/aapm/journal/medphys/36/7/10.1118/1.3140586
10.1118/1.3140586
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