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Verification of TG-61 dose for synchrotron-produced monochromatic x-ray beams using fluence-normalized MCNP5 calculations
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10.1118/1.4761870
/content/aapm/journal/medphys/39/12/10.1118/1.4761870
http://aip.metastore.ingenta.com/content/aapm/journal/medphys/39/12/10.1118/1.4761870

Figures

Image of FIG. 1.
FIG. 1.

Differential Compton cross section per gram molecular weight versus scattering angle for polyethylene at (a) 35 keV and (b) 25 keV. (Squares) Differential cross section calculated using the formulism described by Dugas et al. (Ref. 4) which ignores electron binding effects (BE not included). (Triangles) Differential cross section values obtained from xraylib (Ref. 7) which includes electron binding effects (BE included). Cross section values were determined for the case of x-rays 100% polarized in the plane of the synchrotron.

Image of FIG. 2.
FIG. 2.

Differential cross section per gram molecular weight versus scattering angle for Rayleigh and Compton scattering from polyethylene at (a) 35 keV and (b) 25 keV. Cross section values were obtained from xraylib for the case of x-rays 100% polarized in the plane of the synchrotron.

Image of FIG. 3.
FIG. 3.

Total and Compton differential cross sections per gram molecular weight versus scattering angle for polyethylene at (a) 35 keV and (b) 25 keV. (Diamonds) Total differential cross section obtained using Rayleigh and Compton cross section values obtained from xraylib (Ref. 7) which include electron binding effects (BE included). (Squares) Differential Compton cross section calculated using the formulism described by Dugas et al. (Ref. 4) which ignores electron binding effects (BE not included). Cross section values were determined for the case of x-rays 100% polarized in the plane of the synchrotron.

Image of FIG. 4.
FIG. 4.

Background-subtracted energy spectra measured at (a) 35 keV for θ = 45° and (b) 25 keV for θ = 60°. Spectra were acquired for live times of 170 and 135 s, respectively. In spectrum (a) the peaks at ∼35 keV and ∼6 keV (iodine escape peak) correspond to n = 1 photons which have been Compton or Rayleigh scattered from the target. The events at high energy correspond to n = 2 photons. In spectrum (b) the peaks at ∼25 keV and ∼50 keV correspond to n = 1 and n = 2 photons which have been Compton or Rayleigh scattered from the target.

Image of FIG. 5.
FIG. 5.

Dose to water versus PMMA depth at (a) 35 keV (1 of 2 data sets) and (b) 25 keV (1 of 3 data sets). Ion chamber measurements are compared with the product of a MCNP5 calculation and measured beam fluence for an exposure time of 320 s. Dose values were normalized to a synchrotron storage ring current of 100 mA.

Tables

Generic image for table
TABLE I.

TG-61 ion chamber calibration and correction factors used for dose calculations at 25 and 35 keV. Measurements of P TP, P ion, and P pol were repeated for each set of depth-dose measurements, and the range of values obtained are shown here.

Generic image for table
TABLE II.

Scatter factors and differential cross sections per gram molecular weight for polyethylene for E = 25 and 50 keV and E = 35 and 70 keV. The values shown were obtained from xraylib (Ref. 7).

Generic image for table
TABLE III.

% difference between the ion chamber and the fluence-normalized MCNP5 doses determined at PMMA depths 0.6–7.7 cm. Emono is the energy setting of the monochromator, and Emeas is the measured energy value obtained from the Si640c powder-diffraction measurements. Weighted average values for the % difference have been calculated for each nominal energy setting.

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/content/aapm/journal/medphys/39/12/10.1118/1.4761870
2012-11-27
2014-04-17
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Verification of TG-61 dose for synchrotron-produced monochromatic x-ray beams using fluence-normalized MCNP5 calculations
http://aip.metastore.ingenta.com/content/aapm/journal/medphys/39/12/10.1118/1.4761870
10.1118/1.4761870
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