Luminescence Efficiency of Cadmium Tungstate (CdWO4) Single Crystal for Medical Imaging Applications

Abstract

Background: In this study, the light output of a cadmium tungstate (CdWO₄) single crystal was measured under various X-ray radiographic energies. Methods: A CdWO₄ single crystal (10 × 10 × 10 mm³) was exposed to X-rays in the 50–130 kVp range. Measurements were evaluated against published data for single crystals of equal dimensions (CaF₂:Eu and Lu₃Al₅O₁₂:Ce). Since the crystal was examined for application in medical imaging detectors, the emitted optical spectrum was classified with respect to the spectral compatibility of numerous commercial optical sensors. Results: The luminescence efficiency (LE) was found to constantly increase with X-ray energy and was higher than that of CaF₂:Eu for energies above 90 kVp. However, the efficiency of the previously published Lu₃Al₅O₁₂:Ce was found to be constantly higher than that of CdWO₄. The light emitted from CdWO₄ can be optimally detected by certain charge-coupled devices (CCDs), amorphous silicon photodiodes, and photocathodes. Conclusions: The high density (7.9 g/cm³) of CdWO₄ and the luminescence signal of this material make it suitable for medical imaging (such as dual energy), high-energy physics or for applications of scintillators in harsh environments.