Dual TLD-100/TLD-300 method to evaluate beam quality and absorbed dose in radiological imaging procedures

The relative intensity of high- and low-temperature peaks in the CaF2:Tm (TLD-300) glow curve depends on ionization density and has been previously reported as an indicator of beam quality for low-energy photons. On the other hand, absorbed dose measurements ideally require dosemeters that match the tissue density and effective atomic number. We propose a dual method that combines the photon field energy information given by TLD-300 glow curve shape and the tissue-similar response of TLD-100, in order to evaluate effective energy and dose within phantoms exposed to beams of use in pediatric radiology examinations. The TLD-300 high-to low-temperature signal ratio calibration as function of effective energy was established up to 64 keV. Results show that the photon effective energy can be determined with uncertainties lower than 12% for energies up to 33 keV, and lower than 16% up to 64 keV. The evolution of the effective energy, measured inside three pediatric-size PMMA phantoms, indicates that a 4% correction to the TLD-100 energy dependence is required in order to determine precisely the dose. Absorbed dose inside the phantoms decreases to half the surface value at depths between 3 and 5 cm, depending on the primary X-ray beam effective energy. Monte Carlo simulations described well the experimental results.