Absolute Luminescence Efficiency Research Articles

Facile Construction of New Hybrid Conjugation via Boron Cage Extension.

Aromatic polycyclic systems have been extensively utilized as structural subunits for the preparation of various functional molecules. Currently, aromatics-based polycyclic systems are predominantly generated from the extension of two-dimensional (2D) aromatic rings. In contrast, polycyclic compounds based on the extension of three-dimensional (3D) aromatics such as boron clusters are less studied. Here, we report three types of boron cluster-cored tricyclic molecular systems, which are constructed from a 2D aromatic ring, a 3D aromatic nido-carborane, and an alkyne. These new tricyclic compounds can be facilely accessed by Pd-catalyzed B-H activation and the subsequent cascade heteroannulation of carborane and pyridine with an alkyne in an isolated yield of up to 85% under mild conditions without any additives. Computational results indicate that the newly generated ring from the fusion of the 3D carborane, the 2D pyridyl ring, and an alkyne is non-aromatic. However, such fusion not only leads to a 1H chemical shift considerably downfield shifted owing to the strong diatropic ring current of the embedded carborane but also devotes to new/improved physicochemical properties including increased thermal stability, the emergence of a new absorption band, and a largely red-shifted emission band and enhanced emission efficiency. Besides, a number of bright, color-tunable solid emitters spanning over all visible light are obtained with absolute luminescence efficiency of up to 61%, in contrast to aggregation-caused emission quenching of, e.g., Rhodamine B containing a 2D-aromatics-fused structure. This work demonstrates that the new hybrid conjugated tricyclic systems might be promising structural scaffolds for the construction of functional molecules.

Response of Lead Fluoride (PbF2) Crystal under X-ray and Gamma Ray Radiation

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.

Luminescence and Structural Characterization of Gd2O2S Scintillators Doped with Tb3+, Ce3+, Pr3+ and F for Imaging Applications

Radiodiagnostic technologies are powerful tools for preventing diseases and monitoring the condition of patients. Medicine and sectors such as industry and research all use this inspection methodology. This field demands innovative and more sophisticated systems and materials for improving resolution and sensitivity, leading to a faster, reliable, and safe diagnosis. In this study, a large characterization of gadolinium oxysulfide (Gd2O2S) scintillator screens for imaging applications has been carried out. Seven scintillator samples were doped with praseodymium (Pr3+), terbium (Tb3+) activators and co-doped with praseodymium, cerium, and fluorine (Gd2O2S:Pr,Ce,F). The sample screens were prepared in the laboratory in the form of high packing density screens, following the methodology used in screen sample preparation in infrared spectroscopy and luminescence. Parameters such as quantum detection efficiency (QDE), energy absorption efficiency (EAE), and absolute luminescence efficiency (ALE) were evaluated. In parallel, a structural characterization was performed, via XRD and SEM analysis, for quality control purposes as well as for correlation with optical properties. Spatial resolution properties were experimentally evaluated via the Modulation Transfer Function. Results were compared with published data about Gd2O2S:Pr,Ce,F screens produced with a standard method of a sedimentation technique. In particular, the ALE rose with the X-ray tube voltage up to 100 kVp, while among the different dopants, Gd2O2S:Pr exhibited the highest ALE value. When comparing screens with different thicknesses, a linear trend for the ALE value was not observed; the highest ALE value was measured for the 0.57 mm thick Gd2O2S:Pr,Ce,F sample, while the best MTF values were found in the thinner Gd2O2S:Pr,Ce,F screen with 0.38 mm thickness.

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

In this study, the light output of a zinc selenide activated with tellurium (ZnSe: Te) single crystal was measured for X-ray radiography applications. A cubic crystal (10 × 10 × 10 mm) was irradiated using X-rays with tube voltages from 50 to 130 kV. The resulting energy absorption efficiency, detective quantum efficiency, and absolute luminescence efficiency were compared to published data for equally sized GSO: Ce (gadolinium orthosilicate) and BGO (bismuth germanium oxide) crystals. The emitted light was examined to estimate the spectral compatibility with widely used optical sensors. Energy absorption efficiency and detective quantum efficiency of ZnSe: Te and BGO were found to be similar, within the X-ray energies in question. Light output of all three crystals showed a tendency to increase with increasing X-ray tube voltage, but ZnSe: Te stood at least 2 EU higher than the others. ZnSe: Te can be coupled effectively with certain complementary metal–oxide–semiconductors (CMOS), photocathodes, and charge-coupled-devices (CCD), as the effective luminescence efficiency results assert. These properties render the material suitable for various imaging applications, dual-energy arrays included.

Spectral efficiency of lutetium aluminum garnet (Lu3Al5O12:Ce) with microelectronic optical sensors

The aim of the present work was to investigate the absolute luminescence efficiency (AE) of a lutetium aluminum Lu3Al5O12:Ce (LuAG:Ce) garnet, doped with cerium, combined with various microelectronic optical sensors. Two LuAG:Ce samples, with dimensions of 5 × 5 × 10 and 10 × 10 × 10 mm3 were examined. The light emitted by the crystals, was evaluated by performing measurements of the AE using X-rays from 50 to 130 kV. The spectral compatibility of the LuAG:Ce crystal, with various existing optical detectors, was investigated after emission spectra measurements. Results were compared with previously published data for commercially available lutetium based and cerium doped crystals, such as, (Lu,Gd)2SiO5:Ce and Lu2SiO5:Ce, frequently used in medical imaging applications. Absolute efficiency was found maximum at 130 kVp for the 5 × 5 × 10 mm3 LuAG:Ce crystal (31.86 efficiency units-E.U). AE of the 10 × 10 × 10 mm3 LuAG:Ce crystal was found higher than both LGSO:Ce and LSO:Ce crystals (of equal dimensions). The emission spectrum of LuAG:Ce is excellent matched with the spectral sensitivities of photocathodes, charge coupled devices (CCD), non-passivated amorphous hydrogenated silicon photodiodes (a-Si:H) and complementary metal-oxide semiconductors (CMOS) microelectronic devices employed in radiation detection. Considering the higher luminescence efficiency values than currently used crystals and the spectral compatibility with the various photodetectors, LuAG:Ce single crystal could be considered for use in imaging detectors, such as, PET/CT scanners.

Optical Characteristics of ZnCuInS/ZnS (Core/Shell) Nanocrystal Flexible Films Under X-Ray Excitation

The aim of this article is to evaluate optical characteristics, such as the intrinsic conversion efficiency and the inherent light propagation efficiency of three polymethyl methacrylate (PMMA)/methyl methacrylate (MMA) composite ZnCuInS/ZnS (core/shell) nanocrystal flexible films. The concentrations of these were 100 mg/mL, 150 mg/mL, and 250 mg/mL, respectively. Composite films were prepared by homogeneously diluting dry powder quantum dot (QD) samples in toluene and subsequently mixing these with a PMMA/MMA polymer solution. The absolute luminescence efficiency (AE) of the films was measured using X-ray excitation. A theoretical model describing the optical photon propagation in scintillator materials was used to calculate the fraction of the generated optical photons passed through the different material layers. Finally, the intrinsic conversion efficiency was calculated by considering the QD quantum yield and the optical photon emission spectrum.

Absolute Luminescence Efficiency of Europium-Doped Calcium Fluoride (CaF2:Eu) Single Crystals under X-ray Excitation

The absolute luminescence efficiency (AE) of a calcium fluoride (CaF2:Eu) single crystal doped with europium was studied using X-ray energies met in general radiography. A CaF2:Eu single crystal with dimensions of 10 × 10 × 10 mm3 was irradiated by X-rays. The emission light photon intensity of the CaF2:Eu sample was evaluated by measuring AE within the X-ray range from 50 to 130 kV. The results of this work were compared with data obtained under similar conditions for the commercially employed medical imaging modalities, Bi4Ge3O12 and Lu2SiO5:Ce single crystals. The compatibility of the light emitted by the CaF2:Eu crystal, with the sensitivity of optical sensors, was also examined. The AE of the 10 × 10 × 10 mm3 CaF2:Eu crystal peaked in the range from 70 to 90 kV (22.22 efficiency units; E.U). The light emitted from CaF2:Eu is compatible with photocathodes, charge coupled devices (CCD), and silicon photomultipliers, which are used as radiation sensors in medical imaging systems. Considering the AE results in the examined energies, as well as the spectral compatibility with various photodetectors, a CaF2:Eu single crystal could be considered for radiographic applications, including the detection of charged particles and soft gamma rays.

Luminescence efficiency of calcium tungstate (CaWO4) under X-ray radiation: Comparison with Gd2O2S:Tb

The aim of the present study was to investigate the absolute luminescence efficiency (AE) of a CaWO4 screen, under X-ray irradiation and to compare it with a custom made PMMA/Gd2O2S:Tb composite film screen. The emitted light was evaluated by performing measurements of the AE under X-ray exposure conditions, with tube voltages ranging from 50 to 125 kV. The spectral compatibility of the CaWO4 screen, with various existing optical detectors, was investigated after emission spectra measurements. AE was found maximum at 50 kVp (2.34 Efficiency Units-E.U) which was slightly lower than the corresponding “gold standard” Gd2O2S:Tb (2.67 E.U), at the same X-ray energy. The emission spectrum of CaWO4 is excellent matched with the spectral sensitivities of photocathodes and silicon photomultipliers often employed in radiation detectors, and with good matching with amorphous silicon photodiodes. Considering the adequate luminescence efficiency values and the spectral compatibility with various photodetectors, CaWO4 could be also considered for use in X-ray imaging devices such as charged-coupled devices (CCD) and complementary metal oxide semiconductors (CMOS).

Structural Characterization and Absolute Luminescence Efficiency Evaluation of Gd2O2S High Packing Density Ceramic Screens Doped with Tb3+ and Eu3+ for further Applications in Radiology

Rare earth activators are impurities added in the phosphor material to enhance probability of visible photon emission during the luminescence process. The main activators employed are rare earth trivalent ions such as Ce+3, Tb+3, Pr3+ and Eu+3. In this work, four terbium-activated Gd2O2S (GOS) powder screens with different thicknesses (1049 mg/cm2, 425.41 mg/cm2, 313 mg/cm2 and 187.36 mg/cm2) and one europium-activated GOS powder screen (232.18 mg/cm2) were studied to investigate possible applications for general radiology detectors. Results presented relevant differences in crystallinity between the GOS:Tb doped screens and GOS:Eu screens in respect to the dopant agent present. The AE (Absolute efficiency) was found to rise (i) with the increase of the X-ray tube voltage with the highest peaking at 110kVp and (ii) with the decrease of the thickness among the four GOS:Tb. Comparing similar thickness values, the europium-activated powder screen showed lower AE than the corresponding terbium-activated.

Grains size and shape dependence of luminescence efficiency of Lu2O3:Eu thin screens

The aim of this work is to provide a comparative evaluation of luminescence efficiency of Lu2O3:Eu phosphors screens, in transmission mode, prepared with different grain shape and size, and manufactured by the sedimentation method. More specific, three screens were prepared with spherical grains of size 50nm, 200nm and 5μm. Furthermore, two screens with rod-like shape grains and size of 500nm and 1–8μm. The behavior of Absolute Luminescence Efficiency (AE) at low energy X-rays (50kVp) appeared to differ with the grains size and shape. Furthermore the rod-like grain screens appeared with reduced luminescence efficiency values.

Luminescence efficiency of (Lu,Gd)2SiO5:Ce (LGSO:Ce) crystals under X-ray radiation

The aim of the present study was to investigate the absolute luminescence efficiency (AE) of mixed oxyorthosilicate (Lu,Gd)2SiO5:Ce (LGSO:Ce) single crystals, under X-ray irradiation. Six (Lu,Gd)2SiO5:Ce crystal samples, with dimensions of 3 × 3 × 5, 3 × 3 × 6, 3 × 3 × 10, 3 × 3 × 15, 10 × 10 × 10 and 10 × 10 × 20 mm3 were examined. The light emitted by the crystals, was evaluated by performing measurements of the AE under X-ray exposure conditions, with tube voltages ranging from 50 to 130 kV. Results were compared with previously published data for GSO:Ce and LSO:Ce crystals. The spectral compatibility of the (Lu,Gd)2SiO5:Ce crystal, with various existing optical detectors, was investigated after emission spectra measurements. Absolute efficiency was found maximum at 130 kVp for the 3 × 3 × 15 mm3 (Lu,Gd)2SiO5:Ce crystal (25.40 E.U). AE of the 10 × 10 × 10 mm3 (Lu,Gd)2SiO5:Ce crystal was found higher than both GSO:Ce and LSO:Ce crystals, in the whole X-ray tube range. The emission spectrum of (Lu,Gd)2SiO5:Ce is excellent matched with the spectral sensitivities of photocathodes and silicon photomultipliers often employed in radiation detectors. Considering the high luminescence efficiency values and the spectral compatibility with the various photodetectors, (Lu,Gd)2SiO5:Ce crystal could be considered for use in combined medical imaging detectors i.e. integrated PET/CT detectors.

Measurement of the luminescence properties of Gd2O2S:Pr,Ce,F powder scintillators under X-ray radiation

The aim of the present study was to investigate the absolute luminescence efficiency of gadolinium oxysulfide powder scintillators, doped with praseodymium, cerium and fluorine (Gd2O2S:Pr,Ce,F). Gd2O2S:Pr,Ce,F is a non-hygroscopic material, emitting green light with short decay time. For the purposes of this study, two scintillating screens with coating thicknesses 35.7 and 71.2 mg/cm2, were prepared in our laboratory from Gd2O2S:Pr,Ce,F powder (Phosphor Technology, Ltd) by sedimentation on silica substrates. The light emitted by the phosphors under investigation was evaluated by performing measurements of the absolute efficiency under X-ray exposure conditions with tube voltages ranging from 50 to 130 kV. Results were compared with previously published data for Gd2O2S:Eu screens. The spectral compatibility of Gd2O2S:Pr,Ce,F with various existing optical detectors, was investigated after emission spectra measurements. Particle size and morphology parameters of the Gd2O2S:Pr,Ce,F powder phosphor were verified via scanning electron microscope (SEM) micrographs. Absolute efficiency was found to maximize at 60 kVp for the 71.2 mg/cm2 and at 90 kVp for the 35.7 mg/cm2 Gd2O2S:Pr,Ce,F screens. Absolute efficiency of the 71.2 mg/cm2 Gd2O2S:Pr,Ce,F screen was higher in the whole X-ray tube voltage range showing potential interest for non-CT medical imaging (i.e. dental radiology) or industrial digital radiography.

On the response of GdAlO3:Ce powder scintillators

The aim of the present study was to investigate the luminescence efficiency (XLE) of gadolinium aluminum perovskite (GdAlO3:Ce) powder scintillator. This powder phosphor, also known as GAP:Ce scintillator, is a non-hygroscopic material, emitting blue light with short decay time. For the purposes of this study, five scintillating screens with coating thicknesses, 14.7, 31.0, 53.7, 67.2 and 121.1mg/cm2, were prepared in our laboratory from GdAlO3:Ce powder (Phosphor Technology, Ltd) by sedimentation on silica substrates. The light emitted by the phosphors under investigation was evaluated by performing measurements of the absolute luminescence efficiency (AE), X-ray luminescence efficiency and detector quantum gain (DQG) under X-ray exposure conditions with tube voltages ranging from 50 to 140kV. The quantum detection efficiency (QDE) and energy absorption efficiency (EAE) were also evaluated. The spectral compatibility of GdAlO3:Ce, with various existing optical detectors, was investigated after emission spectra measurements. A theoretical model, describing radiation and light transfer, was used to fit experimental AE data. This has allowed the estimation of optical attenuation coefficients of the scintillator. GdAlO3:Ce exhibited higher QDE and EAE values, compared to aluminium perovskite (YAlO3:Ce) but lower absolute efficiency values. Absolute efficiency was found to increase with increasing X-ray tube voltage, although for values higher than 120kVp a decrease was observed.

Light emission efficiency and imaging performance of powder scintillator under x‐ray radiography conditions

To evaluate Gd2O2S:Eu powder phosphor as a radiographic image receptor and to compare it to phosphors often used in radiography. Gd2O2S:Eu is nonhygroscopic, emitting red light with decay time close to that of Gd2O2S:Tb. The light intensity emitted per unit of x-ray exposure rate (absolute luminescence efficiency) was measured for laboratory prepared screens with coating thicknesses of 33.1, 46.4, 63.1, 78.3, and 139.8 mg/cm2 and tube voltages ranging from 50 to 140 kVp. Parameters related to image quality such as the modulation transfer function (MTF) and the detective quantum efficiency (DQE) were also experimentally examined. In addition, a previously validated Monte Carlo code was used to estimate intrinsic x-ray absorption and optical properties, as well as the MTF and the Swank factor (I) of the Gd2O2S:Eu scintillators. Gd2O2S:Eu light intensity was found higher than that of single CsI:T1 crystal for tube voltages up to 100 kVp. The MTF and the DQE were found to be comparable with those of Gd2O2S:Tb and CsI:T1 screens. MTF estimated by the Monte Carlo code was found very close to the experimental MTF values. Gd2O2S:Eu showed peak emission in the wavelength range 620-630 nm. Its emission spectrum was excellently matched to various optical detectors (photodiodes, photocathodes, CCDs, and CMOS) employed in flat panel detectors. Gd2O2S:Eu is an efficient phosphor potentially well suited to radiography and especially to some digital detectors sensitive to red light.

Evaluation of the Luminescence Efficiency of YAG:Ce Powder Scintillating Screens for Use in Digital Mammography Detectors

In the present study scintillating screens prepared from Y3Al5O12:Ce (YAG:Ce) powder phosphor were evaluated for use in digital mammography. YAG:Ce has never previously been used in X-ray medical imaging, however since it emits green light (i.e peak at 550 nm), it is expected to match well the spectral sensitivities of most photodetectors (photodiodes, CCDs and amorphous silicon sensors) incorporated in various digital mammography detectors. YAG:Ce was purchased in powder form and was used in order to prepare test screens in the laboratory. Screens were evaluated by determining the quantum detection efficiency (QDE), the energy absorption efficiency (EAE), the absolute luminescence efficiency, the X-ray luminescence efficiency (XLE), the light emission spectrum, the X-ray to light intrinsic conversion efficiency and the spectral compatibility with various photodetectors. Results were compared with phosphor materials commercially employed in X-ray imaging such as CsI:Tl and Gd2O2 S:Tb. Maximum YAG:Ce emission efficiency was observed for the 63 mg/cm2 screen at 49 kVp. The spectral compatibility with amorphous silicon photodiodes (0.93) and CCDs (0.95) was found to be very high, better than the corresponding compatibility of the CsI:Tl screen, mostly used in current digital radiography detectors. Taking into account the YAG:Ce overall performance, its short decay time as well as its spectral compatibility with amorphous silicon detectors and CCDs, YAG:Ce could be of interest for further investigation for applications in digital mammography.

Comparative Investigation of ${\rm Ce}^{3+}$ Doped Scintillators in a Wide Range of Photon Energies Covering X-ray CT, Nuclear Medicine and Megavoltage Radiation Therapy Portal Imaging Applications

The aim of the present work is to study the performance of scintillators currently used in PET and animal PET systems, under conditions met in radiation therapy and PET/CT imaging. The results of this study will be useful in applications where both CT and PET photons as well as megavoltage cone beam CT (MV CBCT) photons could be detected using a common detector unit. To this aim crystal samples of GSO, LSO, LYSO, LuYAP and YAP scintillators, doped with cerium (Ce+3) were examined under a wide energy range of photon energies. Evaluation was performed by determining the absolute luminescence efficiency (emitted light flux over incident X-ray exposure) in the energy range employed in X-ray CT, in Nuclear Medicine (70 keV up to 662 keV) and in radiotherapy 6 MV (approx. 2.0 MeV mean energy)-18 MV (approx. 4.5 MeV mean energy). Measurements were performed using an experimental set-up based on a photomultiplier coupled to a light integration sphere. The emission spectrum under X-ray excitation was measured, using an optical grating monochromator, to determine the spectral compatibility to optical photon detectors incorporated in medical imaging systems. Maximum absolute luminescence efficiency values were observed at 70 keV for YAP:Ce and LuYAP:Ce and at 140 keV for LSO:Ce, LYSO:Ce and GSO:Ce. Highest absolute efficiency between the scintillators examined was observed for LSO:Ce, followed by LYSO:Ce. The detector optical gain (DOG) exhibited a significant variation with the increase of energy between 70 keV to 2.0 MeV. All scintillators exhibited low compatibility when combined with GaAsP (G5645) photodetector.

A comparative study of the luminescence properties of LYSO:Ce, LSO:Ce, GSO:Ce and BGO single crystal scintillators for use in medical X-ray imaging

The present study is a comparative investigation of the luminescence properties of (Lu,Y) 2SiO 5:Ce (LYSO:Ce), Lu 2SiO 5:Ce (LSO:Ce), Gd 2SiO 5:Ce (GSO:Ce) and (Bi 4Ge 3O 12) BGO single crystal scintillators under medical X-ray excitation. All scintillating crystals have dimensions of 10 × 10 × 10 mm 3 are non-hygroscopic exhibiting high radiation absorption efficiency in the energy range used in medical imaging applications. The comparative investigation was performed by determining the absolute luminescence efficiency (emitted light flux over incident X-ray exposure) in X-ray energies employed in general X-ray imaging (40–140 kV) and in mammographic X-ray imaging (22–49 kV). Additionally, light emission spectra of crystals at various X-ray energies were measured, in order to determine the spectral compatibility to optical photon detectors incorporated in medical imaging systems and the overall efficiency (effective efficiency) of a scintillator–optical detector combination. The light emission performance of LYSO:Ce and LSO:Ce scintillators studied was found very high for X-ray imaging.

Investigation of luminescent properties of LSO:Ce, LYSO:Ce and GSO:Ce crystal scintillators under low-energy γ-ray excitation used in nuclear imaging

LSO:Ce, LYSO:Ce and GSO:Ce single-crystal scintillator light emission characteristics were studied in the low γ-ray energy range ( 99mTc source) used in nuclear medical imaging. The absolute luminescence efficiency and the optical emission spectrum of the three scintillators were measured, under γ-ray excitation using an integration sphere coupled to a photomultiplier and an optical spectrometer, respectively. Spectral compatibility of all scintillators to optical sensors was also estimated. The absolute luminescence efficiency of all crystals was found adequately high (8.7 μW m −2/μGy s −1 for GSO:Ce, 15.3 μW m −2/μGy s −1 for LYSO:Ce and 20.0 μW m −2/μGy s −1 for LSO:Ce). Their emission spectra were found compatible (57–94%) to currently employed optical photon detectors.

Light emission efficiency and imaging properties of YAP:Ce granular phosphor screens

Phosphor materials are used in medical imaging combined with radiographic film or other photodetectors. Cerium (Ce3+) -doped scintillators are of particular interest for medical imaging, because of their very fast response. YAP:Ce scintillator-based image detectors have already been evaluated in single-crystal form and under conditions of positron emission tomography and synchrotron or γ-ray irradiation. Furthermore, YAP:Ce phosphor has been evaluated in conjunction with radiographic films. The present work reports experimental and theoretical data concerning the light output absolute luminescence efficiency (AE) of the YAP:Ce screens under irradiation conditions employed in medical X-ray projection imaging (i.e., in diagnostic radiology). projection imaging (i.e., in diagnostic radiology). YAP:Ce phosphor screens with surface densities ranging between 53 and 110 mg/cm2 were prepared by sedimentation on fused silica substates in our laboratory. The resulted surface density of the screens was determined by dividing the phosphor mass deposited on the screen surface with the area of the surface. Additionally this work addresses the imaging performance of YAP:Ce by estimation of the detective quantum efficiency (DQE), i.e., the square of the signal to noise ratio transfer. Absolute efficiency was found to decrease with X-ray tube voltage for for YAP:Ce phosphor. The highest experimental efficiency was obtained for the 53.7 mg/cm2 and 88.0 mg/cm2 YAP:Ce screens. The highest DQE value was found for the 88.0 mg/cm2 screen irradiated at 60 kVp.

Comparative study of luminescence properties of LuYAP:Ce and LYSO:Ce single-crystal scintillators for use in medical imaging

The luminescence properties of Lu 0.7Y 0.3AlO 3:Ce (LuYAP:Ce) and (Lu 0.9,Y 0.1) 2SiO 5:Ce (LYSO:Ce) crystals were studied for use in medical X-ray imaging. LuYAP:Ce and LYSO:Ce are single-crystal scintillators of high density, non-hygroscopic, high light yield and short decay time. The two cerium doped crystals have dimensions of 2×2×8 mm 3 with all surfaces polished. Evaluation was performed by determining the absolute luminescence efficiency (emitted light flux over incident X-ray exposure) in X-ray energies employed in general medical X-ray imaging (40–140 kVp) and in mammographic X-ray imaging (22–49 kV). Additionally, the light emission spectrum at various X-ray energies was measured in order to determine the spectral compatibility to optical photon detectors, incorporated in medical imaging systems. The optical characteristics, such as emission spectra, were investigated and important correlations with the scintillation properties were pointed out. The light emission performance of the two scintillation materials studied was found adequately high for medical X-ray imaging.