On the Optical Response of Tellurium Activated Zinc Selenide ZnSe:Te Single Crystal

Luminescence Efficiency of Cerium Bromide Single Crystal under X-ray Radiation

A rare-earth trihalide scintillator, CeBr3, in 1 cm edge cubic monocrystal form, is examined with regard to its principal luminescence and scintillation properties, as a candidate for radiation imaging applications. This relatively new material exhibits attractive properties, including short decay time, negligible afterglow, high stopping power and emission spectrum compatible with several commercial optical sensors. In a setting typical for X-ray radiology (medical X-ray tube, spectra in the range 50–140 kVp, human chest equivalent filtering), the crystal’s light energy flux, absolute efficiency (AE) and X-ray luminescence efficiency (XLE) were determined. Light energy flux results are superior in comparison to other four materials broadly used in modern medical imaging (slope of the linear no-threshold fit was 29.5). The AE is superior from 90 kVp onwards and reaches a value of 29.5 EU at 140 kVp. The same is true for the XLE that, following a flat response, reaches 9 × 10−3 at 90 kVp. Moreover, the spectral matching factors and the respective effective efficiencies (EE) are calculated for a variety of optical sensors. The material exhibits full compatibility with all the flat-panel arrays and most of the photocathodes and Si PMs considered in this work, a factor that proves its suitability for use in state-of-the-art medical imaging applications, such as CT detectors and planar arrays for projection imaging.

Efficiency Properties of Cerium-Doped Lanthanum Chloride (LaCl3:Ce) Single Crystal Scintillator under Radiographic X-ray Excitation

The aim of this study is to evaluate the suitability of crystalline scintillator LaCl3:Ce for possible use in hybrid medical imaging systems, such as PET/CT and SPECT/CT scanners. For this purpose, a single crystal (10 × 10 × 10 mm3) was irradiated by X-rays within the tube voltage range from 50 to 150 kVp, and the absolute efficiency (AE) was measured experimentally. The energy absorption efficiency (EAE), quantum detection efficiency (QDE), and the spectral compatibility with various optical detectors were also calculated with the use of mathematical formulas. The results were compared with published data for Bi4Ge3O12 (BGO), Lu2SiO5:Ce (LSO), and CdWO4 single crystals of equal dimensions, commonly used in medical imaging applications. The luminescence efficiency values of the examined crystal were found to be higher than those of LSO, BGO, and CdWO4 crystals, within the whole X-ray tube voltage range. In the matter of EAE, LaCl3:Ce demonstrated reduced performance with respect to LSO and CdWO4 crystals. The emission spectrum of LaCl3:Ce was found to be compatible with various types of photocathodes and silicon photomultipliers (SiPMs). Considering these properties, LaCl3:Ce crystal could be considered suitable for use in hybrid medical imaging systems.

On the Response of a Micro Non-Destructive Testing X-ray Detector

Certain imaging performance metrics are examined for a state-of-the-art 20 μm pixel pitch CMOS sensor (RadEye HR), coupled to a Gd₂O₂S:Tb scintillator screen. The signal transfer property (STP), the modulation transfer function (MTF), the normalized noise power spectrum (NNPS) and the detective quantum efficiency (DQE) were estimated according to the IEC 62220-1-1:2015 standard. The detector exhibits excellent linearity (coefficient of determination of the STP linear regression fit, R² was 0.9978), while its DQE peaks at 33% and reaches 10% at a spatial frequency of 3 cycles/mm, for the measured with a Piranha RTI dosimeter (coefficient of variation CV = 0.03%) exposure value of 28.1 μGy DAK (detector Air Kerma). The resolution capabilities of the X-ray detector under investigation were compared to other commercial CMOS sensors, and were found in every case higher, except from the previous RadEye HR model (CMOS-Gd₂O₂S:Tb screen pair with 22.5 μm pixel pitch) version which had slightly better MTF. The present digital imager is designed for industrial inspection applications, nonetheless its applicability to medical imaging, as well as dual-energy is considered and certain approaches are discussed in this respect.