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A Monte Carlo model for out-of-field dose calculation from high-energy photon therapy
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10.1118/1.2756940
/content/aapm/journal/medphys/34/9/10.1118/1.2756940
http://aip.metastore.ingenta.com/content/aapm/journal/medphys/34/9/10.1118/1.2756940

Figures

Image of FIG. 1.
FIG. 1.

Photon dose profile in the in-plane direction. Lines are simulated data, points are measured data. Fields are and with the MLC retracted and defined by the MLC (jaws set to ). “Calc” and “Meas” refer to calculated and measured profiles. Statistical uncertainty in the simulated doses ranged between and approximately , depending on the dose.

Image of FIG. 2.
FIG. 2.

Photon dose profile in the cross-plane direction. The line is calculated data, and the points are measured data. The field is defined by the MLC (jaws set to ). Statistical uncertainty in the simulated doses ranged between and approximately , depending on the dose.

Image of FIG. 3.
FIG. 3.

Photon dose profile in the in-plane direction from a field with the MLC retracted. Depths in the acrylic phantom were 3.75 and 11.25 cm. Lines are the simulated data, and the points are measured data. “3.75 Calc” refers to the calculated data at 3.75 cm depth, while “3.75 Meas” refers to the measured data at 3.75 cm depth.

Image of FIG. 4.
FIG. 4.

Percentage difference between the photon dose at 3.75 cm depth and the dose at 11.25 cm depth. “Measured” refers to the percentage difference in the TLD data of Fig. 3, while “Simulated” refers to the percentage difference in the simulated data of Fig. 3.

Image of FIG. 5.
FIG. 5.

Simulated photon spectra from a field in an acrylic phantom at a depth of 3.0 cm on the central axis (CAX) and at a 3.75 cm depth at 10, 30, and 50 cm from the central axis.

Image of FIG. 6.
FIG. 6.

Photon dose from a field in the in-plane direction between the central axis and 50 cm toward the gantry and at depths up to 30 cm. The gray scale is logarithmic and shows the dose in per MU.

Image of FIG. 7.
FIG. 7.

Neutron spectra at 40 cm from the central axis. “Monte Carlo” refers to the data simulated in the current study from a field, while “Measured” refers to data measured by Howell et al.(Ref. 7) from a prostate IMRT therapy.

Image of FIG. 8.
FIG. 8.

Neutron dose equivalent from a field in the in-plane direction between central axis and 50 cm toward the gantry and at depths up to 30 cm. The gray scale is logarithmic and shows the dose equivalent in per MU.

Image of FIG. 9.
FIG. 9.

Percentage of the total dose equivalent contributed by neutrons from a field in the in-plane direction between the central axis and 50 cm toward the gantry and at depths up to 30 cm. The gray scale is linear and shows percent neutron contribution.

Image of FIG. 10.
FIG. 10.

Conversion factor converting between neutron fluence ( particle) to dose equivalent (Sv/MU) as a function of depth in a water phantom. The various data series are labeled by two numbers and represent different field sizes and distances from the central axis. The first number is the size of one side of the square field and the second number is the distance from the central axis (i.e., “20–25” is the conversion factors for a field at 25 cm from the central axis).

Image of FIG. 11.
FIG. 11.

Photon dose in the cross-plane direction. Solid line (Monte Carlo) is simulated data from the current study; points refer to measurements by Mutic and Klein (Ref. 46) and Stern (Ref. 47) that have been modified to be of the same geometry.

Tables

Generic image for table
TABLE I.

Measured and calculated neutron fluence in the patient plane for various field sizes and distances from the central axis.

Generic image for table
TABLE II.

Neutron spectra characteristics at 40 cm from the central axis for two field sizes. Values calculated in the current study are compared with previously measured data.

Generic image for table
TABLE III.

Neutron fluence , excluding thermal neutrons, as simulated in the current study and measured in the literature using a Varian 2100 accelerator operated at 18 MV.

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/content/aapm/journal/medphys/34/9/10.1118/1.2756940
2007-08-09
2014-04-17
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: A Monte Carlo model for out-of-field dose calculation from high-energy photon therapy
http://aip.metastore.ingenta.com/content/aapm/journal/medphys/34/9/10.1118/1.2756940
10.1118/1.2756940
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