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An MCNPX Monte Carlo model of a discrete spot scanning proton beam therapy nozzle
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10.1118/1.3476458
/content/aapm/journal/medphys/37/9/10.1118/1.3476458
http://aip.metastore.ingenta.com/content/aapm/journal/medphys/37/9/10.1118/1.3476458

Figures

Image of FIG. 1.
FIG. 1.

Components of the PTCH proton scanning beam nozzle. The and magnets were not used in the MC model described in this study. The beam direction was parallel to the axis, propagating from positive to negative axis values. For simulations in water, the position in the beam direction was specified in terms of depth in the water phantom.

Image of FIG. 2.
FIG. 2.

FWHM of Gaussian distributions used to simulate the spatial distribution of the proton sources using the new MCS algorithm. The full and dashed lines represent the and FWHM, respectively. The dotted lines represent the pencil beam energies used to adjust the size of the sources.

Image of FIG. 3.
FIG. 3.

(a) PDD profiles of pencil beams with energies ranging from 72.5 to 221.8 MeV. Simulations were performed using the new MCS algorithm. (b) Range as a function of pencil beam energy. The inset represents the DTA between the measured and simulated ranges (measured-MC). The error bars represent the experimental systematic uncertainty associated with the size of the sensitive volume of the ionization chamber. The circles and solid lines represent measured and simulated data, respectively. : Dose at depth in water ; : Dose at the Bragg peak; : Range; and : Beam energy.

Image of FIG. 4.
FIG. 4.

(a) In-air lateral profiles of pencil beams at the isocenter plane for 72.5, 148.8, and 221.8 MeV. The circles and solid lines represent measured and simulated data, respectively. The lateral profiles are normalized to dose at the central axis . (b) FWHM, FW0.01M, and FW0.001M of in-air lateral profiles of pencil beams at the isocenter plane as a function of the pencil beam’s energy. The circles represent measured data, the squares and solid line represent simulated data, and the dashed lines represent fits of the standard MCS algorithm simulated data.

Image of FIG. 5.
FIG. 5.

(a) In-air FWHM, FW0.01M, and FW0.001M of pencil beams at positions upstream and downstream of the isocenter plane for 72.5 MeV (, 0.0, −3.7, and −19.5 cm), 148.8 MeV (, 0.0, and −19.5 cm), and 221.8 MeV (, 0.0, −12.5, and −19.5 cm). The circles and lines represent measured and simulated data, respectively.

Image of FIG. 6.
FIG. 6.

(a) FWHM, (b) FW0.01M, and (c) FW0.001M for in-water lateral profiles of single pencil beams as a function of depth. The circles and lines represent measured and simulated data, respectively. For 148.8 MeV, the isocenter plane was at a depth of 20 cm in the water phantom, and for 72.5 and 221.8 MeV, the surface of the water phantom was located at the isocenter plane.

Image of FIG. 7.
FIG. 7.

PDD profiles of 3-D dose distributions with field sizes. The fields F1, F2, F3, and F4 used to create the dose distributions are given in Table I. The circles and lines represent measured and simulated data, respectively. The PDD profiles are normalized to the dose at the middle of the spread-out Bragg peak .

Image of FIG. 8.
FIG. 8.

Normalized in-water lateral profiles of 3-D dose distributions. The fields F1, F2, F3, and F4 used to create the 3-D dose distributions, with PDD profiles shown in Fig. 7, are given in Table I. The lateral profiles were measured and simulated at depths corresponding to the center of the volumes. F1: Depth of 6.0 cm; F2: Depth of 10.0 cm; F3: Depth of 15.5 cm; and F4: Depth of 25.6 cm. The circles and lines represent measured and simulated data, respectively. The measurements in F1 and F2 were obtained from EBT films and in F3 and F4 from ionization chambers.

Image of FIG. 9.
FIG. 9.

Energy deposition per particle as a function of depth in water simulated using the new MCS algorithm for the 221.8 MeV pencil beam. The solid, dashed, and dotted lines represent the integral energy deposition and the energy deposition in cylindrical tallies with radii 4.08 and 10 cm, respectively. The circles represent measurements using a commercially available ionization chamber with radius 4.08 cm. The inset represents the percentage deviation between the integral energy deposition and the energy deposition in the cylindrical tallies with radii 4.08 and 10 cm, respectively.

Tables

Generic image for table
TABLE I.

Fields used to create the 3-D dose distributions used in this study. The lateral extent of the fields was and the lateral spacing between the centers of adjacent spots at the isocenter plane was 0.5 cm. : Location of the 90% proximal dose level relative to the Bragg peak dose; : Location of the 90% distal dose level relative to the Bragg peak dose; : Lowest pencil beam energy; and : Highest pencil beam energy.

Generic image for table
TABLE II.

Differences between measure and simulated FWHM, FW0.01M, and FW0.001M for in-air lateral profiles at the isocenter plane.

Generic image for table
TABLE III.

Differences between measured and simulated FWHM, FW0.01M, and FW0.001M for in-air lateral profiles at positions downstream and upstream of the isocenter plane. The differences were obtained from the data represented in Fig. 5. See caption of Fig. 5 for positions.

Generic image for table
TABLE IV.

Differences between measured and simulated FWHM, FW0.01M, and FW0.001M for in-water lateral profiles at five depths for 72.5 and 148.8 MeV pencil beams and seven depths for the 221.8 MeV pencil beam. The differences were obtained from the data represented in Fig. 6.

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/content/aapm/journal/medphys/37/9/10.1118/1.3476458
2010-08-26
2014-04-20
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: An MCNPX Monte Carlo model of a discrete spot scanning proton beam therapy nozzle
http://aip.metastore.ingenta.com/content/aapm/journal/medphys/37/9/10.1118/1.3476458
10.1118/1.3476458
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