Evaluation of the Electron Contamination in Photon Therapy Using BEAMnrc Code

Document Type : Original Article (s)

Authors

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

2 MSc Student, Department of Medical Physics, Student Research Committee, School of Medicine, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran

3 Associate Professor, Department of Radiotherapy, School of Medicine, Golestan Hospital, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran

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

Abstract

Background: Today, high-energy photon beams are widely used in the treatment of all types of cancers. However, the production of electrons as contaminants in the photon pathway provides the necessity for research in this field.Methods: Using BEAMnrc code, a Varian2100C/D accelerator head was simulated with 6 MV energy. Applying the advanced techniques of the variance reduction, Depth Dose curves at the Isocenter were obtained and compared to the measurements. We used DOSXYZ code to calculate the Percentage depth dose (PDD) and profile curves. The effect of eliminating electron contamination by helium bag between the accelerator head and treatment bed, Vacuum, Al, Pb, Poly(methyl methacrylate) (PMMA) filters and their composition were also investigated.Findings: By increasing the source to surface distance (SSD) and the air column, we expected an increase in the contribution of electron contamination, but our results showed that increasing the height of air column acted like a filter and scattered low-energy electrons. The presence of helium instead of the air column reduced the surface dose by about 10% compared to the air column. Electron contamination increased for light elements such as Al and PMMA, and decreased by 3.5% for the lead filter.Conclusion: The use of materials with lower atomic numbers and high densities for filtration of electron contamination of the head of the device and secondary collimators and helium bag is simultaneously proposed.

Keywords

References

  1. Lopez MA, Teijeiro A, Garcia J, Esperon J, Terron JA, Ruiz DP, et al. Characterization of electron contamination in megavoltage photon beams. Med Phys 2005; 32(5): 1281-92.
  2. Allahverdi M, Zabihzadeh M, Ay M, Mahdavi S, Shahriari M, Mesbahi A et al . Monte Carlo estimation of electron contamination in a 18 MV clinical photon beam. Int J Radiat Res 2011; 9(1): 15-28.
  3. Butson MJ, Cheung T, Yu PKN. Calculation of electron contamination doses produced using blocking trays for 6MV X-rays. Radiation Measurements 2002; 35(2): 99-102.
  4. Kumar M, Sahani G, Chourasiya G. Magnetic removal of electron contamination for 60Co panoramic gamma ray exposure--Investigations with CaSO4:Dy and LiF based dosimeters. Appl Radiat Isot 2010; 68(6): 1173-6.
  5. Chetty IJ, Curran B, Cygler JE, DeMarco JJ, Ezzell G, Faddegon BA, et al. Report of the AAPM Task Group No. 105: Issues associated with clinical implementation of Monte Carlo-based photon and electron external beam treatment planning. Med Phys 2007; 34(12): 4818-53.
  6. Yani S, Dirgayussa IGE, Rhani MF, Soh RCX, Haryanto F, Arif I. Monte Carlo study on electron contamination and output factors of small field dosimetry in 6 MV photon beam. Smart Science 2016; 4(2): 87-94.
  7. Chegeni N, Hosseini K, Shahbazian H, Maskani R, Hoseini Ghafarokhi M, Mirkhaghani F, et al. Validation of the linac varian simulated using BEAMnrc code for 6mv photon energy. Jundishapur Sci Med J 2016; 15(5): 551-61. [In Persian].
  8. Kawrakow I, Rogers DW, Walters BR. Large efficiency improvements in BEAMnrc using directional bremsstrahlung splitting. Med Phys 2004; 31(10): 2883-98.
  9. Sheikh-Bagheri D, Rogers DW, Ross CK, Seuntjens JP. Comparison of measured and Monte Carlo calculated dose distributions from the NRC linac. Med Phys 2000; 27(10): 2256-66.
  10. Butson MJ, Cheung T, Yu PKN, Carolan M, Metcalfe PE. Simulation and measurement of air generated electron contamination in radiotherapy. Radiation Measurements 2000; 32(2): 105-11.
  11. Shukla R, Patel N, Yadav H, Kaushal V. A Monte Carlo simulation study on the effectiveness of electron filters designed for telecobalt radiation therapy treatment. Int J Radiat Res 2019; 17(2): 217-27.
  12. Rao BM, Prasad SG, Parthasaradhi K, Lee Y, Ruparel R, Garces R. Investigations on the near surface dose for three 10-MV x-ray beam accelerators with emphasis on the reduction of electron contamination. Med Phys 1988; 15(2): 246-9.
  13. Parthasaradhi K, Prasad SG, Rao BM, Lee Y, Ruparel R, Garces R. Investigation on the reduction of electron contamination with a 6-MV x-ray beam. Med Phys 1989; 16(1): 123-5.
  14. Kosunen A, Rogers DW. Beam quality specification for photon beam dosimetry. Med Phys 1993; 20(4): 1181-8.
  15. Rogers DW, Faddegon BA, Ding GX, Ma CM, We J, Mackie TR. BEAM: A Monte Carlo code to simulate radiotherapy treatment units. Med Phys 1995; 22(5): 503-24.
  16. Bahreyni Toosi MT, Saberi H, Hashemian A, Salek R. Application of an optimum filter for a neptune 10 PC linac to reduce electron contamination. Proceedings of the 2nd European IRPA congress on radiation protection - Radiation Protection: from Knowledge to Action; 2006 May 15-19; Paris, France.
  17. Nilsson B. Electron contamination from different materials in high energy photon beams. Phys Med Biol 1985; 30(2): 139-51.
  18. Khan FM. Use of electron filter to reduce skin dose in cobalt teletherapy. Am J Roentgenol Radium Ther Nucl Med 1971; 111(1): 180-1.
  19. Padikal TN, Deye JA. Electron contamination of a high-energy X-ray beam. Phys Med Biol 1978; 23(6): 1086-92.
Journal of Isfahan Medical School
Volume 37, Issue 535 - Serial Number 535
May and June 2019
Pages 839-844

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History

  • Receive Date: 06 August 2019
  • Revise Date: 01 November 2024
  • Accept Date: 06 April 2022

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