Abstract

Dose to the total body from induced radiation resulting from primary exposure to radiotherapeutic beams is not detailed in routine treatment planning though this information is potentially important for better estimates of health risks including secondary cancers. This information can also allow better management of patient treatment logistics, suggesting better timing, sequencing, and conduct of treatment. Monte Carlo simulations capable of taking into account all interactions contributing to the dose to the total body, including neutron scattering and induced radioactivity, provide the most versatile and accurate tool for investigating these effects. MCNPX code version 2.2.6 with full IAEA library of photoneutron cross sections is particularly suited to trace not only photoneutrons but also protons and heavy ion particles that result from photoneutron interactions. Specifically, the MCNPX code is applied here to the problem of dose calculations in traditional (non-IMRT) photon beam therapy. Points of calculation are located in the head, where the primary irradiation has been directed, but also in the superior portion of the torso of the ORNL Mathematical Human Phantom. We calculated dose contributions from neutrons, protons, deutrons, tritons and He-3 that are produced at the time of photoneutron interactions in the body and that would not have been accounted for by conventional radiation oncology dosimetry. © 2003 American Association of Physicists in Medicine.

Key words: Photoneutron, neutron dosimetry, Monte Carlo simulations and internal dosimetry 87.53.Pb, 87.53.Wz, 87.53.Vb, 87.53.-j, 25.20.-x, 28.20.-v, 28.20.Gd

References

1. M. Cristy, "Mathematical phantoms representing children of various ages for use in estimates of internal dose," U.S. Nuclear Regulatory Commission Report No. NUREG/CR-1159 (also Oak Ridge National Laboratory Report No. ORNL/NUREG/TM-367) (1980).
2. L. Cozzi, F. M. Buffa, and A. Fogliata, "Dosimetric features of linac head and phantom scattered radiation outside the clinical beam: experimental measurements and comparison with treatment planning system calculations," Radiother. Oncol. 58, 193–200 (2001) (ScienceDirect). [INSPEC] [MEDLINE]
3. V. G. Nedoresov and Yu. H. Ranuk, Photo-division of Nuclei Above Giant Resonance, 1st ed. (Naukova Dumka, Kiev, 1989) (in Russian).
4. E. J. Hall, Radiobiology for the Radiologist, 4th ed. (Lippincott Williams & Wilkins, New York, 1993).
5. A. M. Kellerer and L. Walsh, "Solid cancer risk coefficient for fast neutrons in terms of effective dose," Radiat. Res. 158, 61–68 (2002). [INSPEC] [MEDLINE]
6. A. M. Kellerer and L. Walsh, "Risk estimation for fast neutrons with regard to solid cancer," Radiat. Res. 156, 708–717 (2001). [INSPEC] [MEDLINE]
7. D. Sheikh-Bagheri and D. W. O. Rogers, "Monte Carlo calculation of nine megavoltage photon beam spectra using the BEAM code," Med. Phys. 29, 391–402 (2002).
8. R. Mohan, C. Chui, and L. Lidofsky, "Energy and angular distributions of photons from medical linear accelerators," Med. Phys. 12, 592–597 (1985). [MEDLINE]
9. I. Gudowska, "Measurements of the neutron absorbed dose from medical accelerators," Internal Report, Dept. of Radiation Physics, The Karolinska Institute, Stockholm, RI 1984-04, pp. 1–87, 1984.
10. I. Gudowska and A. Brahme, "Neutron radiation from high-energy x-ray medical accelerators," Nukleonika 41, 99–112 (1996).
11. V. Moskvin, L. Papiez, C. DesRosiers, and X. Lu, "Specialized Monte Carlo codes versus general-purpose Monte Carlo codes," American Nuclear Society, 2001 Winter Meeting, Accelerator Applications/Accelerator Driven Transmission Technology and Application (AccApp/ADTTA'01), November 11–15, Reno, Nevada, 2001.
12. F. Salvat, J. M. Fernández-Varea, J. Baró, and J. Sempau, PENELOPE, an algorithm and computer code for Monte Carlo simulation of electron-photon showers, Informes Tecnicos CIEMAT Report No. 799, CIEMAT, Madrid, 1996.
13. Handbook on Photonuclear Data for Applications, IAEA–TECDOC, March 2000 (International Atomic Energy Agency, Vienna, Austria, 2000).
14. MCNPX User's Guide, edited by L. S. Waters (Los Alamos National Laboratory, Los Alamos, NM, 1999).
15. E. Glatstein, "The return of the snake oil salesman," Int. J. Radiat. Oncol., Biol., Phys. 55, 561–562 (2003) (ScienceDirect). [MEDLINE]