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Response of TLD‐100 in mixed fields of photons and electrons
Author(s) -
Lawless Michael J.,
Junell Stephanie,
Hammer Cliff,
DeWerd Larry A.
Publication year - 2013
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.4773030
Subject(s) - thermoluminescent dosimeter , dosimeter , irradiation , linear particle accelerator , photon , laser beam quality , beam (structure) , dosimetry , dose profile , materials science , imaging phantom , absorbed dose , optics , physics , nuclear medicine , radiation , nuclear physics , laser , medicine , laser beams
Purpose: Thermoluminescent dosimeters (TLDs) are routinely used for dosimetric measurements of high energy photon and electron fields. However, TLD response in combined fields of photon and electron beam qualities has not been characterized. This work investigates the response of TLD‐100 (LiF:Mg,Ti) to sequential irradiation by high‐energy photon and electron beam qualities.Methods : TLDs were irradiated to a known dose by a linear accelerator with a 6 MV photon beam, a 6 MeV electron beam, and a NIST‐traceable 60 Co beam. TLDs were also irradiated in a mixed field of the 6 MeV electron beam and the 6 MV photon beam. The average TLD response per unit dose of the TLDs for each linac beam quality was normalized to the average response per unit dose of the TLDs irradiated by the 60 Co beam. Irradiations were performed in water and in a Virtual Water™ phantom. The 6 MV photon beam and 6 MeV electron beam were used to create dose calibration curves relating TLD response to absorbed dose to water, which were applied to the TLDs irradiated in the mixed field.Results: TLD relative response per unit dose in the mixed field was less sensitive than the relative response in the photon field and more sensitive than the relative response in the electron field. Application of the photon dose calibration curve to the TLDs irradiated in a mixed field resulted in an underestimation of the delivered dose, while application of the electron dose calibration curve resulted in an overestimation of the dose.Conclusions: The relative response of TLD‐100 in mixed fields fell between the relative response in the photon‐only and electron‐only fields. TLD‐100 dosimetry of mixed fields must account for this intermediate response to minimize the estimation errors associated with calibration factors obtained from a single beam quality.