Abstract
The reference air kerma rate of an 192Ir high dose rate brachytherapy source is determined based broadly on the International Atomic Energy Agency (IAEA) TECDOC 1274 code of practice. Since the primary standards dosimetry laboratory at the Australian Radiation Protection and Nuclear Safety Agency (ARPANSA) does not maintain a standard at 192Ir quality, the air kerma calibration coefficient of an IBA FC65-G Farmer type ionisation chamber is calculated using coefficients determined at 300 kV and 60Co qualities. The methodology proposed by Mainegra-Hing and Rogers [1] at 250 kV and 137Cs qualities is used. The validity of this approach is tested by performing Monte Carlo simulations to determine the chamber’s air kerma calibration coefficient at 192Ir quality. Very good agreement is obtained between values using these two methods. The reference air kerma rate is measured using the Farmer chamber in an in air jig. In addition the necessary correction factors are applied to the measured value. The reference air kerma rate determined in this way is compared to the value stated by the vendor of the 192Ir source on the source calibration certificate. Differences are with one exception less than 1%. It is concluded that because of the agreement between the values from the methodology used in this study and the source calibration certificate values this methodology can be used clinically.
Notes
Schweda M, Personal communication, 2007.
Hovenkamp E, Personal communication, 2010.
References
Mainegra-Hing E, Rogers DWO (2006) On the accuracy of techniques for obtaining the calibration coefficient N K of 192Ir HDR brachytherapy sources. Med Phys 33:3340–3347
Kutcher GJ, Coia L, Gillin M, Hanson WF, Leibel S, Morton RJ, Palta JA, Purdy L, Reinstein E, Svensson GK, Weller M, Wingfield L (1994) Comprehensive QA for radiation oncology: Report of AAPM radiation therapy committee task group 40. Med Phys 21:581–618
International Atomic Energy Agency (2002) Calibration of photon and beta ray sources used in brachytherapy. Guidelines on standardized procedures at secondary standards dosimetry laboratories (SSDLs) and hospitals. IAEA-TECDOC-1274, Vienna
International Commission On Radiation Units And Measurements (1985) Dose and volume specification for reporting intracavitary therapy in gynaecology, ICRU report 38. ICRU Publications, Bethesda
Rivard MJ, Coursey BM, DeWerd LA, Hanson WF, Huq MS, Ibbott GS, Mitch MG, Nath R, Williamson WF (2004) Update of AAPM task group no. 43 report: a revised AAPM protocol for brachytherapy dose calculations. Med Phys 31:633–674
Goetsch SJ, Attix FH, Pearson DW, Thomadsen BR (1991) Calibration of 192Ir high-dose-rate afterloading systems. Med Phys 18:462–467
Podgorsak MB (1993) Radiation parameters of high dose rate iridium 192 sources. Thesis, University of Wisconsin
Drugge N (1995) Determination of the reference air kerma rate for clinical 192Ir sources. Thesis, University of Göteborg
Firestone RB, Ekström LP (1999) WWW table of radioactive isotopes. LBNL Isotopes Project: LUNDS Universitet. http://ie.lbl.gov/toi/nucSearch.asp
Douysset G, Gouriou J, Delauny F, DeWerd L, Stump K, Micka J (2005) Comparison of dosimetric standards of USA and France for HDR brachytherapy. Phys Med Biol 50:1961–1978
Butler D, Haworth A, Sander T, Todd S (2008) Comparison of 192Ir air kerma calibration coefficients derived at ARPANSA using the interpolation method and at the National Physical Laboratory using a direct measurement. Australas Phys Eng Sci Med 31:332–338
Bielajew AF (1990) Correction factors for thick-walled ionization chambers in point source photon beams. Phys Med Biol 35:501–516
Berg M, Noerrevang O (2004) Recombination factors for the cylindrical FC65-G ionization chamber in pulsed photon beams and the plane-parallel Roos ionization chamber in pulsed electron beams. Phys Med Biol 49:5309–5318
Butler D, Oliver C (2005) Calibration report on a therapy ionization chamber. ARPANSA Calibration Report No CAL00166/02, Melbourne
Rogers DWO et al (2005) BEAMnrc. National Research Council of Canada. http://irs.inms.nrc.ca/software/beamnrc/
Buckley LA, Kawrakow I, Rogers DWO (2003) An EGSnrc investigation of cavity theory for ion chambers measuring air kerma. Med Phys 30:1211–1218
Borg J, Kawrakow I, Rogers DWO, Seuntjens JP (2000) Monte Carlo study of correction factors for Spencer–Attix cavity theory at photon energies at or above 100 keV. Med Phys 27:1804–1813
International Atomic Energy Agency (1997) Absorbed dose determination in photon and electron beams. An international code of practice, 2nd edn. Technical Report Series No. 277, Vienna
Rogers DWO (1992) Fundamentals of high energy X-ray and electron dosimetry protocols. In: Purdy JA (ed) Advances in radiation oncology physics. AAPM, New York, pp 181–223
Borg J, Rogers DWO (1999) Spectra and air-kerma strength for encapsulated 192Ir sources. Med Phys 26:2441–2444
Büermann L, Kramer H-M, Schrader H, Selbach H-J (1994) Activity determination of 192Ir solid sources by ionization chamber measurements using calculated corrections for self-absorption. Nucl Instr Meth Phys Res A339:369–376
Acknowledgments
The authors wish to thank Aleksandra Kazi, Sylwia Zawlodzka-Bednarz and Guy Godwin for making the source calibration measurements and John Simpson for discussion on aspects of the Monte Carlo calculations. They also wish to thank Anne McNeale from Nucletron Pty. Limited for obtaining information on the Mallinckrodt Medical B. V. source calibration procedure.
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Fourie, O.L., Crabtree, T.G. A technique for calibrating a high dose rate 192Ir brachytherapy source. Australas Phys Eng Sci Med 35, 85–92 (2012). https://doi.org/10.1007/s13246-011-0120-2
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DOI: https://doi.org/10.1007/s13246-011-0120-2