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Conservatism in linear accelerator bunker shielding


Conservatism in the shielding of linear accelerator bunkers is engrained in the methodology of international protocols and guidelines. However, the degree to which this cautious and prudent approach is necessary should be judged against the International Committee of Radiation Protection’s principles of exposure justification and optimisation. Radiation survey data from 75 concrete barriers was aggregated and compared to exposure predictions from three popular protocols in order to assess any conservatism in factors used to calculate scatter, leakage and beam penetration. These findings, in addition to a list of common conservative practices, were then used to tally the possible fiscal impact of an over-conservative approach to linear accelerator bunker shielding. While primary beam penetration was accurately predicted, stated conservatisms in scatter and leakage was found to be largely misplaced. An estimated total factor of conservatism calculated from a tally was found to be in agreement with literature values of radiotherapist occupational exposure. This factor amounted to a cost increase of 43% for a single bunker if all conservative assumptions were made. There are aspects of linear accelerator shielding design that have been shown to be overly conservative, beyond what is justifiable by the International Committee of Radiation Protection. Some adjustment to international protocol methodology may be required.

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  1. Abrath FG, Bello J, Purdy JA (1983) Attenuation of primary and scatter radiation in concrete and steel for 18 MV x-rays from a clinac-20 linear accelerator. Health Phys 45(5):969–973

    Article  CAS  PubMed  Google Scholar 

  2. ARPANSA (2016) Radiation protection in planned exposure situations. Radiation protection series C-1. Australian Radiation Protection and Nuclear Safety Agency, Miranda

    Google Scholar 

  3. Bhat M (2010) Fear of radiation is frightening. Aust Phys Eng Sci Med 33(3):215–217

    Article  Google Scholar 

  4. Biggs PJ (1996) Obliquity factors for 60 co and 4, 10, and 18 MV x rays for concrete, steel, and lead and angles of incidence between 0 and 70 degrees. Health Phys 70(4):527–536

    Article  CAS  PubMed  Google Scholar 

  5. Brodsky A, Kathren R (1989) Historical development of radiation safety practices in radiology. Radiographics 9(6):1267–1275

    Article  CAS  PubMed  Google Scholar 

  6. Coates R (2017) Prudence and conservatism in radiation protection: a case study. Radiat Prot Dosim 173(1–3):100–103

    Article  Google Scholar 

  7. Feinendegen LE (2016) Quantification of adaptive protection following low-dose irradiation. Health Phys 110(3):276–280

    Article  CAS  PubMed  Google Scholar 

  8. Hayton A, Litwin M (2019) O83 occupational radiation doses in medical professions—a review of 30 years of data from the ARPANSA PRMS database. Aust Phys Eng Sci Med 42(1):285–401

    Article  Google Scholar 

  9. IAEA (2006) Safety report series no. 47, radiation protection in the design of radiotherapy facilities. International Atomic Energy Agency, Vienna

    Google Scholar 

  10. ICRP (2007) The 2007 recommendations of the international commission on radiological protection. ICRP publication 103. ann. ICRP 37(2–4). International Commission on Radiological Protection, Ottawa

  11. IEC (2009) Medical electrical equipment–part 2-1: particular requirements for the safety of electron accelerators in the range 1 MeV to 50 MeV 60601-2-1, 2nd edn. International Electrotechnical Commission, Geneva

    Google Scholar 

  12. Inkret WC, Meinhold CB, Taschner JC (1995) Protection standards. Los Alamos Sci 25:117–123

    Google Scholar 

  13. IPEM (1997) Design and shielding of radiotherapy treatment facilities. IPEM report 75. Institute of Physics and Engineering in Medicine, New York

    Google Scholar 

  14. IPEM (2017) Design and shielding of radiotherapy treatment facilities. IPEM report 75, 2nd edn. Institute of Physics and Engineering in Medicine, New York

    Google Scholar 

  15. Kairn T, Crowe S, Trapp J (2013) Correcting radiation survey data to account for increased leakage during intensity modulated radiotherapy treatments. Med Phys.

    Article  PubMed  Google Scholar 

  16. Kragl G, Baier F, Lutz S, Albrich D, Dalaryd M, Kroupa B, Wiezorek T, Knöös T, Georg D (2011) Flattening filter free beams in SBRT and IMRT: dosimetric assessment of peripheral doses. Zeitschrift für Medizinische Physik 21(2):91–101

    Article  PubMed  Google Scholar 

  17. Kry SF, Howell RM, Polf J, Mohan R, Vassiliev ON (2009) Treatment vault shielding for a flattening filter-free medical linear accelerator. Phys Med Biol 54(5):1265

    Article  PubMed  Google Scholar 

  18. NCRP (1976) Structural shielding design and evaluation for medical use of x-rays and gamma-rays of energies up to 10 MeV, rep. 49. National Council on Radiation Protection and Measurements, Washington

    Google Scholar 

  19. NCRP (2005) Structural shielding design and evaluation for megavoltage x-and gamma-ray radiotherapy facilities: Recommendations of the national council on radiation protection and measurements. National Council on Radiation Protection and Measurements, Bethesda

    Google Scholar 

  20. Nelson WR, LaRiviere P (1983) Primary and leakage radiation calculations at 6-MeV, 10-MeV and 25-MeV. Health Phys 47(SLAC–PUB–3039):811

    Google Scholar 

  21. Pearson K (1895) Note on regression and inheritance in the case of two parents. Proc R Soc Lond 58:240–242

    Article  Google Scholar 

  22. Pollycove M, Feinendegen LE (2003) Radiation-induced versus endogenous dna damage: possible effect of inducible protective responses in mitigating endogenous damage. Human Exp Toxicol 22(6):290–306

    Article  CAS  Google Scholar 

  23. Rattan SI, Kyriazi M (2018) The science of hormesis in health and longevity. Academic Press, Cambridge

    Google Scholar 

  24. Taylor PL, Rodgers JE, Shobe J (1999) Scatter fractions from linear accelerators with x-ray energies from 6 to 24 MV. Med Phys 26(8):1442–1446

    Article  CAS  PubMed  Google Scholar 

  25. Yoshimoto K, Furuta H, Inoue K, Fukushi M, Kasagi F et al (2018) Occupational radiation exposure and leukemia mortality among nuclear workers in Japan: J-EPISODE, 1991–2010. Jpn J Health Phys 53(3):146–153

    Article  Google Scholar 

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Correspondence to James Rijken.

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Rijken, J., Bhat, M., Crowe, S. et al. Conservatism in linear accelerator bunker shielding. Australas Phys Eng Sci Med 42, 781–787 (2019).

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