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Feasibility of 3D printed air slab diode caps for small field dosimetry

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Abstract

Commercial diode detectors used for small field dosimetry introduce a field-size-dependent over-response relative to an ideal, water-equivalent dosimeter due to high density components in the body of the detector. An air gap above the detector introduces a field-size-dependent under-response, and can be used to offset the field-size-dependent detector over-response. Other groups have reported experimental validation of caps containing air gaps for use with several types of diodes in small fields. This paper examines two designs for 3D printed diode air caps for the stereotactic field diode (SFD)—a cap containing a sealed air cavity, and a cap with an air cavity at the face of the SFD. Monte Carlo simulations of both designs were performed to determine dimensions for an air cavity to introduce the desired dosimetric correction. Various parameter changes were also simulated to estimate the dosimetric uncertainties introduced by 3D printing. Cap layer dimensions, cap density changes due to 3D printing, and unwanted air gaps were considered. For the sealed design the optimal air gap size for water-equivalent cap material was 0.6 mm, which increased to 1.0 mm when acrylonitrile butadiene styrene in the cap was simulated. The unsealed design had less variation, a 0.4 mm air gap is optimal in both situations. Unwanted air pockets in the bore of the cap and density changes introduced by the 3D printing process can potentially introduce significant dosimetric effects. These effects may be limited by using fine print resolutions and minimising the volume of cap material.

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References

  1. Das IJ, Ding GX, Ahnesjö A (2008) Small fields: nonequilibrium radiation dosimetry. Med Phys 35(1):206–215

    Article  PubMed  Google Scholar 

  2. Charles PH, Cranmer-Sargison G, Thwaites DI, Crowe SB, Kairn T, Knight RT, Kenny J, Langton CM, Trapp JV (2014) A practical and theoretical definition of very small field size for radiotherapy output factor measurements. Med Phys 41(4):041707

    Article  CAS  PubMed  Google Scholar 

  3. Alfonso R, Andreo P, Capote R, Huq MS, Kilby W, Kjäll P, Mackie TR, Palmans H, Rosser K, Seuntjens J et al (2008) A new formalism for reference dosimetry of small and nonstandard fields. Med Phys 35(11):5179–5186

    Article  CAS  PubMed  Google Scholar 

  4. McEwen M, DeWerd L, Ibbott G, Followill D, Rogers DWO, Seltzer S, Seuntjens J (2014) Addendum to the AAPM’s TG-51 protocol for clinical reference dosimetry of high-energy photon beams. Med Phys 41(4):041501

    Article  PubMed  PubMed Central  Google Scholar 

  5. Capote R, Sánchez-Doblado F, Leal A, Lagares JI, Arráns R, Hartmann GH (2004) An EGSnrc Monte Carlo study of the microionization chamber for reference dosimetry of narrow irregular IMRT beamlets. Med Phys 31(9):2416–2422

    Article  CAS  PubMed  Google Scholar 

  6. Bouchard H, Seuntjens J (2004) Ionization chamber-based reference dosimetry of intensity modulated radiation beams. Med Phys 31(9):2454–2465

    Article  CAS  PubMed  Google Scholar 

  7. Scott AJD, Kumar S, Nahum AE, Fenwick JD (2012) Characterizing the influence of detector density on dosimeter response in non-equilibrium small photon fields. Phys Med Biol 57(14):4461

    Article  PubMed  Google Scholar 

  8. Fenwick JD, Kumar S, Scott AJD, Nahum AE (2013) Using cavity theory to describe the dependence on detector density of dosimeter response in non-equilibrium small fields. Phys Med Biol 58(9):2901

    Article  PubMed  Google Scholar 

  9. Underwood TSA, Winter HC, Hill MA, Fenwick JD (2013) Detector density and small field dosimetry: integral versus point dose measurement schemes. Med Phys 40(8):082102

    Article  CAS  PubMed  Google Scholar 

  10. Cranmer-Sargison G, Weston S, Evans JA, Sidhu NP, Thwaites DI (2012) Monte Carlo modelling of diode detectors for small field MV photon dosimetry: detector model simplification and the sensitivity of correction factors to source parameterization. Phys Med Biol 57(16):5141

    Article  CAS  PubMed  Google Scholar 

  11. Francescon P, Kilby W, Satariano N, Cora S (2012) Monte Carlo simulated correction factors for machine specific reference field dose calibration and output factor measurement using fixed and iris collimators on the cyberknife system. Phys Med Biol 57(12):3741

    Article  CAS  PubMed  Google Scholar 

  12. Charles PH, Cranmer-Sargison G, Thwaites DI, Kairn T, Crowe SB, Pedrazzini G, Aland T, Kenny J, Langton CM, Trapp JV (2014) Design and experimental testing of air slab caps which convert commercial electron diodes into dual purpose, correction-free diodes for small field dosimetry. Med Phys 41(10):101701

    Article  CAS  PubMed  Google Scholar 

  13. P Andreo, DT Burns, K Hohlfeld, MS Huq, T Kanai, F Laitano, VG Smyth, S Vynckier (2000) Absorbed dose determination in external beam radiotherapy. Technical Report TRS 398. International Atomic Energy Agency, Vienna

  14. Charles PH, Crowe SB, Kairn T, Kenny J, Lehmann J, Lye J, Dunn L, Hill B, Knight RT, Langton CM et al (2012) The effect of very small air gaps on small field dosimetry. Phys Med Biol 57(21):6947

    Article  CAS  PubMed  Google Scholar 

  15. Charles PH, Crowe SB, Kairn T, Knight RT, Hill B, Kenny J, Langton CM, Trapp JV (2013) Monte Carlo-based diode design for correction-less small field dosimetry. Phys Med Biol 58(13):4501

    Article  CAS  PubMed  Google Scholar 

  16. Charles PH, Crowe SB, Kairn T, Knight R, Hill B, Kenny J, Langton CM, Trapp JV (2013) The influence of Monte Carlo source parameters on detector design and dose perturbation in small field dosimetry. J Phys 489:012006

  17. Underwood TSA, Winter HC, Hill MA, Fenwick JD (2013) Mass-density compensation can improve the performance of a range of different detectors under non-equilibrium conditions. Phys Med Biol 58(23):8295

    Article  CAS  PubMed  Google Scholar 

  18. Underwood TSA, Thompson J, Bird L, Scott AJD, Patmore P, Winter HC, Hill MA, Fenwick JD (2015) Validation of a prototype DiodeAir for small field dosimetry. Phys Med Biol 60(7):2939

    Article  CAS  PubMed  Google Scholar 

  19. Kairn T, Crowe SB, Markwell T (2015) Use of 3D printed materials as tissue-equivalent phantoms. In: IFMBE Proceedings 51. Springer, New York, pp 728–731

  20. Kawrakow I, Mainegra-Hing E, Tessier F (2009) BRB Walters. The EGSnrc C++ class library. NRC Report PIRS-898 (rev A)

  21. Kairn T, Aland T, Franich RD, Johnston PN, Kakakhel MB, Kenny J, Knight RT, Langton CM, Schlect D, Taylor ML et al (2010) Adapting a generic BEAMnrc model of the BrainLAB m3 micro-multileaf collimator to simulate a local collimation device. Phys Med Biol 55(17):N451

    Article  CAS  PubMed  Google Scholar 

  22. Kairn T, Kenny J, Crowe SB, Fielding AL, Franich RD, Johnston PN, Knight RT, Langton CM, Schlect D, Trapp JV (2010) Technical note: Modeling a complex micro-multileaf collimator using the standard BEAMnrc distribution. Med Phys 37(4):1761–1767

    Article  CAS  PubMed  Google Scholar 

  23. Kawrakow I, Fippel M (2000) Investigation of variance reduction techniques for Monte Carlo photon dose calculation using XVMC. Phys Med Biol 45(8):2163

    Article  CAS  PubMed  Google Scholar 

  24. Bits from Bytes, 3D systems (2012) Axon 2 user manual, 1.0.0 edn

  25. Ultimaker (2016) Ultimaker 3 installation and user manual, 1.0 edn

Download references

Acknowledgements

BFB 3D Touch and ABS printing material were provided by the Department of Nuclear Medicine, Royal Brisbane & Womens Hospital, Herston, Australia. Computational resources and services used in the work were provided by the High Performance Computing and Research Support Unit, QUT, Brisbane, Australia.

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Authors and Affiliations

  1. Science and Engineering Faculty, Queensland University of Technology, Brisbane, Queensland, Australia

    Benjamin Perrett, Paul Charles, Tanya Kairn & Scott Crowe

  2. Department of Radiation Oncology, Princess Alexandra Hospital, Ipswich Road, Woolloongabba, Queensland, 4102, Australia

    Benjamin Perrett & Paul Charles

  3. Mater Cancer Care Centre, Duncombe Building Level 2, Raymond Terrace, South Brisbane, Queensland, 4101, Australia

    Tim Markwell

  4. Genesis Cancer Care Queensland, The Wesley Medical Centre, Suite 1, 40 Chasely Street, Auchenflower, Queensland, 4066, Australia

    Tanya Kairn

  5. Cancer Care Services, Royal Brisbane and Womens Hospital, Butterfield Street, Herston, Queensland, 4029, Australia

    Scott Crowe

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  1. Benjamin Perrett
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  2. Paul Charles
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  3. Tim Markwell
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  4. Tanya Kairn
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  5. Scott Crowe
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Correspondence to Benjamin Perrett.

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Perrett, B., Charles, P., Markwell, T. et al. Feasibility of 3D printed air slab diode caps for small field dosimetry. Australas Phys Eng Sci Med 40, 631–642 (2017). https://doi.org/10.1007/s13246-017-0570-2

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  • DOI: https://doi.org/10.1007/s13246-017-0570-2

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