Evaluating the effect of energy on calibration of thermo-luminescent dosimeters 7-LiF:Mg,Cu,P (GR-207A)

Background: 7-LiF: Mg,Cu,P (GR-207A) is one kind of thermo-luminescent dosimeters (TLD) which can be used in diagnostic radiology and radiotherapy applications. Because of having suitable properties such as good sensitivity, small size and being tissue equivalent, thermo-luminescent dosimetry has been one of the most important techniques in medicine over many years. Choosing a correct energy for TLDs’ calibratioon is one of the most important factors in the accuracy of the absorbed dose. Materials and Methods: In order to evaluate the effect of calibration energy on the response of GR-207A TLDs, calibration of the TLDs were done with 120kVp, 200kVp, 6MV, 18MV and 60 ^Co beams. Then the responses of TLDs were normalized to 60^Co and energy dependence was calculated for each dose step. Results: The results confirmed that this kind of TLD dose not have the same response in different energies and reference dose affects on the amount of energy dependence.Discussion: Energy dependence of this type of TLDs is more significant atlower energies compared to megavoltage beams. Relative response to 60^Co illustrates that GR-207A dose not have uniform response to different steps ofenergies and the amount of energy dependence is totally different in variousdose levels.