Clinical use of LiF:Mg,Cu,P: Critical evaluation of an ultrasensitive material for thermoluminescence dosimetry

Abstract

Radiation dosimetry is an essential part of optimization in medical exposures. However there are medical procedures that are particularly challenging for existing dosimetric techniques: neonatal radiography (low dose), mammography (low energy), cardiac catheterization (moving radiation fields), and brachytherapy using implanted radionuclides (steep dose gradients). Hence, the objectives of this thesis were to study the dosimetric characteristics of ultrasensitive LiF:Mg,Cu,P thermoluminescence dosimeters (TLDs) in radiation beams typical for both diagnostics and therapy, and develop procedures to implement this dosimeter into clinical practice for those selected scenarios. GR‐200 (SDDML, China) and MCP‐N (TLD Poland) TLDs were compared to other TLD materials (LiF:Mg,Ti, and tested for reproducibility, dose response (1 μGy to 500 Gy), photon energy response (10 keV to 18 MVp), light sensitivity (240–800 nm), long‐term stability (6 months) using different annealing cycles and glow curve deconvolution. A miniaturized TLD form (MCP‐Np) was developed by TLD Poland for the present investigations. Detection limit of GR‐200 and MCP‐Np was found to be less than 1 and 8 μGy, respectively, with dose response linear up to 18 Gy. To obtain adequate detection limits and precision, accurate temperature calibration of heating cycles and a dual‐anneal technique with dose history monitoring was performed. Energy response was similar for both materials within 5% and essentially uniform except for a minimum of 0.82 at 185 keV. LiF:Mg,Cu,P proved to be more suitable than LiF:Mg,Ti for dosimetry in low dose medical applications particularly when kilovoltage photons are to be used. The high sensitivity and resulting scope for miniaturization provided the opportunity to perform unique in vivo measurements within brachytherapy implants and for mammography.