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’ calibration 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 60Co beams. Then the responses of TLDs were normalized to 60Co 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 at lower energies compared to megavoltage beams. Relative response to 60Co illustrates that GR-207A dose not have uniform response to different steps of energies and the amount of energy dependence is totally different in various dose levels.