The aim of this study was to experimentally assess the luminescence efficiency of a cerium fluoride (CeF₃) inorganic scintillator in crystal form as a possible alternative to high-luminescence but hygroscopic cerium bromide (CeBr₃). The experiments were performed under typical diagnostic radiology X-rays (50–140 kVp). Parameters such as the crystal’s absolute luminescence efficiency (AE) and the spectral matching with a series of optical detectors were examined. The replacement of bromine with fluorine appeared to drastically reduce the AE of CeF₃ compared to CeBr₃ and other commercially available inorganic scintillators such as bismuth germanate (Bi₄Ge₃O₁₂-BGO). CeF₃ reaches a maximum luminescence efficiency value of only 0.8334 efficiency units (EUs) at 140 kVp, whereas the corresponding values for CeBr₃ and BGO were 29.49 and 3.41, respectively. Furthermore, the emission maximum (at around 313 nm) moved towards the lower part of the visible spectrum, making CeF₃ suitable for spectral coupling with various photocathodes and photomultipliers applied in nuclear medicine detectors, but completely unsuitable for spectral matching with CCDs and CMOS. The obtained luminescence efficiency results denote that CeF₃ cannot be applied in medical imaging applications covering the range 50–140 kVp; however, examination of its luminescence output in the nuclear medicine energy range (~70 to 511 keV) could reveal possible applicability in these modalities.

In this study, the luminescence efficiency of a crystal-form barium fluoride (BaF₂) inorganic scintillator was assessed for medical imaging applications. For the experiments, we used a typical medical X-ray tube (50–140 kVp) for estimating the absolute luminescence efficiency (AE). Furthermore, we examined the spectral matching of the inorganic scintillator with a series of optical detectors. BaF₂ showed a higher AE than cerium fluoride (CeF₃), comparable to that of commercially available bismuth germanate (Bi₄Ge₃O₁₂-BGO), but lower than that of the gadolinium orthosilicate (Gd₂SiO₅:Ce-GSO:Ce) inorganic scintillator. The maximum AE of BaF₂ was 2.36 efficiency units (EU is the S.I. equivalent μWm⁻²/(mR/s) at 140 kVp, which is higher than that of the corresponding fluoride-based CeF₃ (0.8334 EU)) at the same X-ray energy. GSO:Ce and BGO crystals, which are often integrated in commercial positron emission tomography (PET) scanners, had AE values of 7.76 and 3.41, respectively. The emission maximum (~310 nm) of BaF₂ is adequate for coupling with flat-panel position-sensitive (PS) photomultipliers (PMTs) and various photocathodes. The luminescence efficiency results of BaF₂ were comparable to those of BGO; thus, it could possibly be used in medical imaging modalities, considering its significantly lower cost.

Background: In this research, the response of a 10 × 10 × 10 mm³ commercially available PbF₂ crystal was experimentally assessed under X-ray and gamma ray radiation to verify the possible application of this material in X-ray medical imaging. Methods: The measurements were performed under X-ray from 50 to 130 kVp and gamma ray excitation (Tc-99m 140 keV and I-131 365 keV). The PbF₂ response was experimentally assessed by the determination of the absolute luminescence efficiency (AE), X-ray luminescence efficiency (XLE), and the stopping power of this scintillating crystal in terms of the energy absorption efficiency (EAE). The results were compared with bismuth germanate (BGO) crystal, which is commonly used in medical imaging modalities. Results: The AE of PbF₂ gradually decreased from 50 kVp up to 130 kVp. The maximum value was 0.61 efficiency units (EU) at 140 keV, and the minimum value was 0.03 EU at 71 keV (130 kVp). Similarly, low values appeared for the XLE, where the maximum value was 16.9 × 10⁻⁵ at 140 keV. Conclusions: These findings show that the PbF₂ scintillator has unacceptably low luminescence efficiency. Although PbF₂ can effectively absorb radiation, the scintillation light, at room temperatures, is negligible, and, thus, it could not be used in medical imaging applications in the examined energy range.

This study examines the luminescence performance of two single-crystal scintillators under X-ray excitation, as a function of temperature. Two identical cubic samples of bismuth germanate (Bi₄Ge₃O₁₂-BGO) and barium fluoride (BaF₂) crystals are irradiated by a medical-type X-ray source, and their luminescence output is collected and measured while they are heated from room temperature up to 174 °C. The luminescence efficiencies of BGO and BaF₂ scintillators decreased by 87.5% and 79.48%, respectively, with increasing temperature. BGO showed higher luminescence efficiency results in most of the examined temperature range; however, BaF₂ minimized the differences at temperatures approaching 174 °C. The combination of economic accessibility and thermal performance at higher temperatures renders BaF₂ a good choice for harsh environments and large-scale applications where budget and durability are as critical as performance.