SUFT376: The Efficiency of Calculating Photonuclear Reaction On HighEnergy Photon Therapy by Monte Carlo Method
Abstract
Purpose: Secondaryneutrons having harmful influences to a human body are generated by photonuclear reaction on highenergy photon therapy. Their characteristics are not known in detail since the calculation to evaluate them takes very long time. PHITS(Particle and Heavy Ion Transport code System) Monte Carlo code since versions 2.80 has the new parameter “pnimul” raising the probability of occurring photonuclear reaction forcibly to make the efficiency of calculation. We investigated the optimum value of “pnimul” on highenergy photon therapy. Methods: The geometry of accelerator head based on the specification of a Varian Clinac 21EX was used for PHITS ver. 2.80. The phantom (30 cm * 30 cm * 30 cm) filled the composition defined by ICRU(International Commission on Radiation Units) was placed at sourcesurface distance 100 cm. We calculated the neutron energy spectra in the surface of ICRU phantom with “pnimal” setting 1, 10, 100, 1000, 10000 and compared the total calculation time and the behavior of photon using PDD(Percentage Depth Dose) and OCR(OffCenter Ratio). Next, the cutoff energy of photon, electron and positron were investigated for the calculation efficiency with 4, 5, 6 and 7 MeV. Results: The calculation total time until the errors of neutron fluence become within 1%more »
 Authors:
 Department of Health Sciences, Graduate School of Medical Sciences, Kyushu University (Japan)
 Department of Health Sciences, Faculty of Medical Sciences, Kyushu University (Japan)
 Publication Date:
 OSTI Identifier:
 22648974
 Resource Type:
 Journal Article
 Resource Relation:
 Journal Name: Medical Physics; Journal Volume: 43; Journal Issue: 6; Other Information: (c) 2016 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA)
 Country of Publication:
 United States
 Language:
 English
 Subject:
 61 RADIATION PROTECTION AND DOSIMETRY; 60 APPLIED LIFE SCIENCES; DEPTH DOSE DISTRIBUTIONS; EFFICIENCY; ENERGY SPECTRA; HEAVY IONS; MEV RANGE 0110; MONTE CARLO METHOD; NEUTRON FLUENCE; PHOTONUCLEAR REACTIONS; RADIOTHERAPY
Citation Formats
Hirayama, S, and Fujibuchi, T. SUFT376: The Efficiency of Calculating Photonuclear Reaction On HighEnergy Photon Therapy by Monte Carlo Method. United States: N. p., 2016.
Web. doi:10.1118/1.4956561.
Hirayama, S, & Fujibuchi, T. SUFT376: The Efficiency of Calculating Photonuclear Reaction On HighEnergy Photon Therapy by Monte Carlo Method. United States. doi:10.1118/1.4956561.
Hirayama, S, and Fujibuchi, T. 2016.
"SUFT376: The Efficiency of Calculating Photonuclear Reaction On HighEnergy Photon Therapy by Monte Carlo Method". United States.
doi:10.1118/1.4956561.
@article{osti_22648974,
title = {SUFT376: The Efficiency of Calculating Photonuclear Reaction On HighEnergy Photon Therapy by Monte Carlo Method},
author = {Hirayama, S and Fujibuchi, T},
abstractNote = {Purpose: Secondaryneutrons having harmful influences to a human body are generated by photonuclear reaction on highenergy photon therapy. Their characteristics are not known in detail since the calculation to evaluate them takes very long time. PHITS(Particle and Heavy Ion Transport code System) Monte Carlo code since versions 2.80 has the new parameter “pnimul” raising the probability of occurring photonuclear reaction forcibly to make the efficiency of calculation. We investigated the optimum value of “pnimul” on highenergy photon therapy. Methods: The geometry of accelerator head based on the specification of a Varian Clinac 21EX was used for PHITS ver. 2.80. The phantom (30 cm * 30 cm * 30 cm) filled the composition defined by ICRU(International Commission on Radiation Units) was placed at sourcesurface distance 100 cm. We calculated the neutron energy spectra in the surface of ICRU phantom with “pnimal” setting 1, 10, 100, 1000, 10000 and compared the total calculation time and the behavior of photon using PDD(Percentage Depth Dose) and OCR(OffCenter Ratio). Next, the cutoff energy of photon, electron and positron were investigated for the calculation efficiency with 4, 5, 6 and 7 MeV. Results: The calculation total time until the errors of neutron fluence become within 1% decreased as increasing “pnimul”. PDD and OCR showed no differences by the parameter. The calculation time setting the cutoff energy like 4, 5, 6 and 7 MeV decreased as increasing the cutoff energy. However, the errors of photon become within 1% did not decrease by the cutoff energy. Conclusion: The optimum values of “pnimul” and the cutoff energy were investigated on highenergy photon therapy. It is suggest that using the optimum “pnimul” makes the calculation efficiency. The study of the cutoff energy need more investigation.},
doi = {10.1118/1.4956561},
journal = {Medical Physics},
number = 6,
volume = 43,
place = {United States},
year = 2016,
month = 6
}

As cancer therapy becomes more efficacious and patients survive longer, the potential for late effects increases, including effects induced by radiation dose delivered away from the treatment site. This outoffield radiation is of particular concern with highenergy radiotherapy, as neutrons are produced in the accelerator head. We recently developed an accurate Monte Carlo model of a Varian 2100 accelerator using MCNPX for calculating the dose away from the treatment field resulting from lowenergy therapy. In this study, we expanded and validated our Monte Carlo model for highenergy (18 MV) photon therapy, including both photons and neutrons. Simulated outoffield photon dosesmore »

A highorder photon Monte Carlo method for radiative transfer in direct numerical simulation
A highorder photon Monte Carlo method is developed to solve the radiative transfer equation. The statistical and discretization errors of the computed radiative heat flux and radiation source term are isolated and quantified. Up to sixthorder spatial accuracy is demonstrated for the radiative heat flux, and up to fourthorder accuracy for the radiation source term. This demonstrates the compatibility of the method with highfidelity direct numerical simulation (DNS) for chemically reacting flows. The method is applied to address radiative heat transfer in a onedimensional laminar premixed flame and a statistically onedimensional turbulent premixed flame. Modifications of the flame structure withmore »