Comparison of TLD calibration methods for 192Ir dosimetry

A. Haworth, D.J. Butler, L. Wilfert, Martin Ebert, S.P. Todd, A.J.M. Hayton, T. Kron

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    Abstract

    For the purpose of dose measurement using a high-dose rate 192Ir source, four methods of thermoluminescent dosimeter (TLD) calibration were investigated. Three of the four calibration methods used the 192Ir source. Dwell times were calculated to deliver 1 Gy to the TLDs irradiated either in air or water. Dwell time calculations were confirmed by direct measurement using an ionization chamber. The fourth method of calibration used 6 MV photons from a medical linear accelerator, and an energy correction factor was applied to account for the difference in sensitivity of the TLDs in 192Ir and 6 MV. The results of the four TLD calibration methods are presented in terms of the results of a brachytherapy audit where seven Australian centers irradiated three sets of TLDs in a water phantom. The results were in agreement within estimated uncertainties when the TLDs were calibrated with the 192Ir source. Calibrating TLDs in a phantom similar to that used for the audit proved to be the most practical method and provided the greatest confidence in measured dose. When calibrated using 6 MV photons, the TLD results were consistently higher than the 192Ir-calibrated TLDs, suggesting this method does not fully correct for the response of the TLDs when irradiated in the audit phantom.
    Original languageEnglish
    Pages (from-to)258-272
    JournalJournal of Applied Clinical Medical Physics
    Volume14
    Issue number1
    Publication statusPublished - 2013

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    Haworth, A., Butler, D. J., Wilfert, L., Ebert, M., Todd, S. P., Hayton, A. J. M., & Kron, T. (2013). Comparison of TLD calibration methods for 192Ir dosimetry. Journal of Applied Clinical Medical Physics, 14(1), 258-272.