Thermoluminescent characteristics of LiF:Mg,Cu,P and CaSO$_4$:Dy for low dose measurement

Abstract

Thermoluminescence (TL) characteristics for LiF:Mg,Cu,P, and CaSO$_4$:Dy under the homogeneous field of X-ray beams of diagnostic irradiation and its verification using thermoluminescence dosimetry is presented. The irradiation were performed utilizing a conventional X-ray equipment installed at the Hospital Ju\'arez Norte of M\'exico. Different thermoluminescence characteristics of two material were studied, such as batch homogeneity, glow curve, linearity, detection threshold, reproducibility, relative sensitivity and fading. Materials were calibrated in terms of absorbed dose to the standard calibration distance and they were positioned in a generic phantom. The dose analysis, verification and comparison with the measurements obtained by the TLD-100 were performed. Results indicate that the dosimetric peak appears at 202$^o$C and 277.5$^o$C for LiF:Mg,Cu,P and CaSO$_4$:Dy, respectively. TL response as a function of X-ray dose showed a linearity behavior in the very low dose range for all materials. However, the TLD-100 is not accurate for measurements below $4mGy$. CaSO$_4$:Dy is 80\% more sensitive than TLD-100 and it show the lowest detection threshold, whereas LiF:Mg,Cu,P is 60\% more sensitive than TLD-100. All material showed very good repeatability. Fading for a period of one month at room temperature showed low fading LiF:Mg,Cu,P, medium and high for TLD-100 and CaSO$_4$:Dy. The results suggest that CaSO$_4$:Dy and LiF:Mg,Cu,P are suitable for measurements at low doses used in radiodiagnostic.