A method for the production of composite scintillators for dosimetry in diagnostic radiology

Plastic scintillators are used in the dosimetry of photons in radiotherapy. Their use in diagnostic radiology is affected by the drop in response at lower photon energies due to inadequate composition ( effective atomic number) and chemical quenching. To compensate for this deficiency, a method for the production of composite polystyrene-based plastic scintillators was devised allowing the incorporation of inorganic scintillation powder. Disks of 10 mm diameter and 1 mm thickness optimized for a flat energy response referred to kerma in air were produced using CaWO(4), ZnS: Ag and CaF(2):Eu as additives. In an HVL range of 2.26-13.69 mmAl, the response was within an interval of +/- 2.8% for CaF(2):Eu as additive, +/- 3.2% for CaWO(4) and +/- 10.9% for ZnS:Ag, respectively. The response of a commercial plastic scintillator (BC470) stays within +/- 13.6%. The temperature dependence of the composite scintillator using CaF(2): Eu is lowest with a variation of + 3.7% to - 3.6% in an interval from 5 degrees C to 45 degrees C. The deficiency in photon absorption at lower energies due to the effective atomic number is reduced but not fully compensated by the additive scintillators. The optimized concentrations were established for the scintillator dimensions used.