The Effect of Neutron Contamination on Probability of Secondary Cancer in Radiotherapy of Pelvic Region with 18-MV Photons

Document Type : Original Article (s)

Authors

1 MSc Student, Department of Medical Physics, Student Research Committee, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran

2 Assistant Professor, Department of Medical Physics, School of Medicine, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran

3 Assistant Professor, Department of Nuclear Engineering, School of Advanced Sciences and Technologies, University of Isfahan, Isfahan, Iran

4 Assistant Professor, Department of Physics, Isfahan University of Technology, Isfahan, Iran

Abstract

Background: Todays, radiotherapy with high-energy photons is used as a common modality for cancer treatment. Unfortunately, high-energy photons can produce unwanted neutrons, and subsequently lead to increase the risk of secondary cancer in unshielded healthy organs.Methods: Using Monte Carlo (MC) code (MCNPX®), the main parts of a typical Medical Linear Accelerator (LINAC) was modeled in 18 MV. Then, neutron source strength (Q) of the LINAC and neutron mean energy were evaluated for different treatment fields, and also different points at the treatment table. Additionally, to estimate the probability of secondary cancer risk, the neutron equivalent dose was calculated at some of the human’s critical organs. For this purpose, the female medical internal radiation dosimetry (MIRD) phantom was included in the MC simulations.Findings: The Q was found as 1.25-1.38 (all in 1012 n/Gy) for different treatment fields meaning significant portion of neutrons with a mean energy of 0.59-0.90 MeV around the LINAC. Additionally, the total secondary cancer risk in unshielded healthy organs was calculated as 0.0924% which maximum and minimum were related to stomach (0.0216%) and thyroid (0.0005%), respectively.Conclusion: Regarding the estimated values for the probability of secondary cancer risk, it is suggested that in conventional radiotherapy of deeply seated tumors, the 15-MV photons are preferred instead of using 18-MV photons due to their less biological side effects.

Keywords

References

  1. Das IJ, Kase KR. Higher energy: Is it necessary, is it worth the cost for radiation oncology? Med Phys 1992; 19(4): 917-25.
  2. Shahbazi-Gahrouei D, Khosravi M, Jabbari K, Gheisari R. Measurement of photoneutron dose in the linear accelerator at the radiation therapy section of Seyed-Al-Shohada Hospital, Isfahan, Iran. J Isfahan Med Sch 2012; 29(166): 2330-9. [In Persian].
  3. Vega-Carrillo HR, de Leon-Martinez HA, Rivera-Perez E, Luis Benites-Rengifo J, Gallego E, Lorente A. Induced radioisotopes in a linac treatment hall. Appl Radiat Isot 2015; 102: 103-8.
  4. Chegeni N, Karimi AH, Jabbari I, Arvandi S. Photoneutron dose estimation in grid therapy using an anthropomorphic phantom: A Monte Carlo study. J Med Signals Sens 2018; 8(3): 175-83.
  5. Chibani O, Ma CM. Photonuclear dose calculations for high-energy photon beams from Siemens and Varian linacs. Med Phys 2003; 30(8): 1990-2000.
  6. Karimi AH, Brkic H, Shahbazi-Gahrouei D, Haghighi SB, Jabbari I. Essential considerations for accurate evaluation of photoneutron contamination in Radiotherapy. Appl Radiat Isot 2019; 145: 24-31.
  7. Mohammadi A, Afarideh H, Abbasi Davani F, Arbabi A. New aspect determination of photoneutron contamination in 18 MV medical linear accelerator. Radiat Meas 2016; 95: 55-61.
  8. Mohammadi N, Miri-Hakimabad SH, Rafat-Motavalli L. A Monte Carlo study for photoneutron dose estimations around the high-energy linacs. J Biomed Phys Eng 2014; 4(4): 127-40.
  9. Mohammadi N, Miri-Hakimabad H, Rafat-Motavalli L, Akbari F, Abdollahi S. Patient-specific voxel phantom dosimetry during the prostate treatment with high-energy linac. J Radioanal Nucl Chem 2015; 304(2): 785-92.
  10. Khabaz R, Boodaghi R, Benam MR, Zanganeh V. Estimation of photoneutron dosimetric characteristics in tissues/organs using an improved simple model of linac head. Appl Radiat Isot 2018; 133: 88-94.
  11. Pelowitz DB, Durkee JW, Elson JSLANL, Fensin ML, Hendricks JSLANL, James MR, et al. MCNPX 2.7.0 extensions. Los Alamos, NM: Los Alamos National Lab (LANL); 2011.
  12. Alem-Bezoubiri A, Bezoubiri F, Badreddine A, Mazrou H, Lounis-Mokrani Z. Monte Carlo estimation of photoneutrons spectra and dose equivalent around an 18MV medical linear accelerator. Radiat Phys Chem 2014; 97: 381-92.
  13. Barati B, Zabihzadeh M, Tahmasebi Birgani MJ, Chegini N, Fatahiasl J, Mirr I. Evaluation of the effect of source geometry on the output of miniature X-ray tube for electronic brachytherapy through simulation. J Biomed Phys Eng 2018; 8(1): 29-42.
  14. Brkic H, Kasabasic M, Ivkovic A, Agic D, Krpan I, Faj D. Influence of head cover on the neutron dose equivalent in Monte Carlo simulations of high energy Medical linear accelerator. Nuclear Technology and Radiation Protection 2018; 33(2): 217-22.
  15. Low DA, Harms WB, Mutic S, Purdy JA. A technique for the quantitative evaluation of dose distributions. Med Phys 1998; 25(5): 656-61.
  16. McGinley PH, Wood M, Mills M, Rodriguez R. Dose levels due to neutrons in the vicinity of high-energy medical accelerators. Med Phys 1976; 3(6): 397-402.
  17. Han EY, Bolch WE, Eckerman KF. Revisions to the ORNL series of adult and pediatric computational phantoms for use with the MIRD schema. Health Phys 2006; 90(4): 337-56.
  18. The 2007 Recommendations of the International Commission on Radiological Protection. ICRP publication 103. Ann ICRP 2007; 37(2-4): 1-332.
  19. National Council on Radiation Protection and Measurements (NCRP). Report No. 116 - Limitation of exposure to ionizing radiation. Bethesda, MD: NCRP; 1993.
  20. Brkic H, Ivkovic A, Kasabasic M, Poje Sovilj M, Jurkovic S, Stimac D, et al. The influence of field size and off-axis distance on photoneutron spectra of the 18 MV Siemens Oncor linear accelerator beam. Radiat Meas 2016; 93: 28-34.
  21. International Commission on Radiological Protection (ICRP). Conversion coefficients for use in radiological protection against external radiation. Adopted by the ICRP and ICRU in September 1995. Ann ICRP 1996; 26(3-4): 1-205.
Journal of Isfahan Medical School
Volume 37, Issue 519 - Serial Number 519
January and February 2019
Pages 222-227

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History

  • Receive Date: 16 March 2019
  • Revise Date: 02 November 2024
  • Accept Date: 06 April 2022

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