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Determination of output factors for small proton therapy fields
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10.1118/1.2428406
/content/aapm/journal/medphys/34/2/10.1118/1.2428406
http://aip.metastore.ingenta.com/content/aapm/journal/medphys/34/2/10.1118/1.2428406

Figures

Image of FIG. 1.
FIG. 1.

Schematic view of the simulation geometry of the beam delivery system showing the proton pencil beam (A), vacuum window (B), profile monitor (C), reference monitor (D), first scatterer-modulator (E), second scatterer (F), middle base plate (G), sub (H) and main dose (I) monitors, precollimator (J), snout base plate (K), and patient-specific aperture (L), adjustable snout (M), and patient-specific range compensator (N).

Image of FIG. 2.
FIG. 2.

Scale drawing of the target geometry used to investigate the influence of the range compensator on values. A passively scattered proton beam (p) is collimated with an aperture before passing through a radially symmetric range compensator (RC) of height, , and diameter, . The beam then enters a phantom comprised of a layer of bone, water, and a cylindrical heterogeneity (either bone or air) of height, , and diameter, . The region of interest (ROI) over which values were determined is also indicated.

Image of FIG. 3.
FIG. 3.

ratios as a function of lateral position for a sample well-shaped range compensator across the ROI. The error bars include contributions from statistical uncertainties, uncertainties in stopping power, and uncertainties due to dose gradients.

Image of FIG. 4.
FIG. 4.

ratios as a function of lateral position for a sample pedestal-shaped range compensator across the ROI. The error bars include contributions from statistical uncertainties, uncertainties in stopping power, and uncertainties due to dose gradients.

Image of FIG. 5.
FIG. 5.

Energy deposition distributions representative of those studied in this work, where a well-shaped range compensator was used to produce a homogeneous dose distribution in the patient (a). Measurements in a water phantom without the range compensator (c) provided more reliable estimates of than measuring with the range compensator (b).

Tables

Generic image for table
TABLE I.

Evaluation of the two quality assurance techniques—one with and one without the range compensator (RC)—using the metrics defined in Sec. II C for well-shaped range compensators. The acronyms in the top row represent the mean ratio (MR), standard deviation of the mean ratio (SDMR), mean relative uncertainty (RU), standard deviation of the mean relative uncertainty (SDRU), maximum deviation of the mean ratio from unity (MDU), and maximum relative uncertainty (MRU).

Generic image for table
TABLE II.

Evaluation of the two quality assurance techniques—one with and one without the range compensator (RC)—using the metrics defined in Sec. II C for pedestal-shaped range compensators. The acronyms in the top row represent the mean ratio (MR), standard deviation of the mean ratio (SDMR), mean relative uncertainty (RU), standard deviation of the mean relative uncertainty (SDRU), maximum deviation of the mean ratio from unity (MDU), and maximum relative uncertainty (MRU).

Generic image for table
TABLE III.

The total , clinical , variability , and worst-case figures of merit with (RC) and without (No RC) well-shaped range compensators for each tested parameter.

Generic image for table
TABLE IV.

The total , clinical , variability , and worst-case figures of merit with (RC) and without (No RC) pedestal-shaped range compensators for each tested parameter.

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/content/aapm/journal/medphys/34/2/10.1118/1.2428406
2007-01-17
2014-04-20
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Determination of output factors for small proton therapy fields
http://aip.metastore.ingenta.com/content/aapm/journal/medphys/34/2/10.1118/1.2428406
10.1118/1.2428406
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