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Despite recent intensive study on scintillators, several fundamental questions on scintillator properties are still unknown. In this work, we use ab-initio calculations to determine the energy dependent group velocity of the hot electrons from the electronic structures of several typical scintillators. Based on the calculated group velocities and optical phonon frequencies, a Monte-Carlo simulation of hot electron transport in scintillators is carried out to calculate the thermalization time and diffusion range in selected scintillators. Our simulations provide physical insights on a recent trend of improved proportionality and light yield from mixed halide scintillators. (© 2016 WILEY-VCH Verlag GmbH &Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Purpose: Flexible radioluminescence imaging (Flex-RLI) is an optical method for imaging 18Ffluorodeoxyglucose (FDG)-avid tumors. The authors hypothesize that a gadolinium oxysulfide: terbium (GOS:Tb) flexible scintillator, which loosely conforms to the body contour, can enhance tumor signal-to-background ratio (SBR) compared with RLI, which utilizes a flat scintillator. The purpose of this paper is to characterize flex-RLI with respect to alternative modalities including RLI, beta-RLI (RLI with gamma rejection), and Cerenkov luminescence imaging (CLI). Methods: The photon sensitivity, spatial resolution, and signal linearity of flex-RLI were characterized with in vitro phantoms. In vivo experiments utilizing 13 nude mice inoculated with the head and neck (UMSCC1-Luc) cell line were then conducted in accordance with the institutional Administrative Panel on Laboratory Animal Care. After intravenous injection of 18F-FDG, the tumor SBR values for flex-RLI were compared to those for RLI, beta-RLI, and CLI using the Wilcoxon signed rank test. Results: With respect to photon sensitivity, RLI, beta-RLI, and flex-RLI produced 1216.2, 407.0, and 98.6 times more radiance per second than CLI. Respective full-width half maximum values across a 0.5 mm capillary tube were 6.9, 6.4, 2.2, and 1.5 mm, respectively. Flex-RLI demonstrated a near perfect correlation with 18F activity (r = 0.99). Signal uniformity for flex-RLI improved after more aggressive homogenization of the GOS powder with the silicone elastomer during formulation. In vivo, the SBR value for flex-RLI (median 1.29; interquartile range 1.18-1.36) was statistically greater than that for RLI (1.08; 1.02-1.14; p < 0.01) by 26%. However, there was no statistically significant difference in SBR values between flex-RLI and beta-RLI (p = 0.92). Furthermore, there was no statistically significant difference in SBR values between flex-RLI and CLI (p = 0.11) in a more limited dataset. Conclusions: Flex-RLI provides high quality images with SBRs comparable to those from CLI and beta-RLI in a single 10 s acquisition. [ABSTRACT FROM AUTHOR]

This study shows the first use of inorganic thin-film scintillators with optical pulse characteristics and light yield competitive with doped single crystal scintillators, while also providing improved structural and functional stability under extreme environmental conditions. Alpha-particle detections, cesium-copper-halides, detectors, ionizing radiations, perovskites, polycrystalline, scintillators Keywords: alpha-particle detections; cesium-copper-halides; detectors; ionizing radiations; perovskites; polycrystalline; scintillators EN alpha-particle detections cesium-copper-halides detectors ionizing radiations perovskites polycrystalline scintillators 1 1 1 11/29/22 20221124 NES 221124 B Alpha-Particle Detections b In article number 2206645, Csaba Janáky, Mátyás Hunyadi, and coworkers demonstrate the spectroscopic detection of charged particles with cesium copper halide thin films. [Extracted from the article]

Purpose: Plastic scintillation detectors are promising candidates for the dosimetry of low- to medium-energy photons but quantitative knowledge of their energy response is a prerequisite for their correct use. The purpose of this study was to characterize the energy dependent response of small scintillation detectors (active volume <1 mm³) made from the commonly used plastic scintillator BC400. Methods: Different detectors made from BC400 were calibrated at a number of radiation qualities ranging from 10 to 280 kV and at a 60Co beam. All calibrations were performed at the Physikalisch- Technische Bundesanstalt, the National Metrology Institute of Germany. The energy response in terms of air kerma, dose to water, and dose to the scintillator was determined. Conversion factors from air kerma to dose to water and to dose to the scintillator were derived from Monte Carlo simulations. In order to quantitatively describe the energy dependence, a semiempirical model known as unimolecular quenching or Birks' formula was fitted to the data and from this the response to secondary electrons generated within the scintillator material BC400 was derived. Results: The detector energy response in terms of air kerma differs for different scintillator sizes and different detector casings. It is therefore necessary to take attenuation within the scintillator and in the casing into account when deriving the response in terms of dose to water from a calibration in terms of air kerma. The measured energy response in terms of dose to water for BC400 cannot be reproduced by the ratio of mean mass energy-absorption coefficients for polyvinyl toluene to water but shows evidence of quenching. The quenching parameter kB in Birks' formula was determined to be kB = (12.3±0.9) mg MeV-1 cm-2. Conclusions: The energy response was quantified relative to the response to 60Co which is the common radiation quality for the calibration of therapy dosemeters. The observed energy dependence could be well explained with the assumption of ionization quenching as described by Birks' formula. Plastic scintillation detectors should be calibrated at the same radiation quality that they will be used at and changes of the spectrum within the application need to be considered. The authors results can be used to evaluate the range of validity of a given calibration. [ABSTRACT FROM AUTHOR]

Neutrons are known to be unique probes in situations where other types of radiation fail to penetrate samples and their surrounding structures. In this paper it is demonstrated how thermal and cold neutron radiography can provide time-resolved imaging of materials while they are being processed ( e.g. while growing single crystals). The processing equipment, in this case furnaces, and the scintillator materials are opaque to conventional X-ray interrogation techniques. The distribution of the europium activator within a BaBrCl:Eu scintillator (0.1 and 0.5% nominal doping concentrations per mole) is studied in situ during the melting and solidification processes with a temporal resolution of 5-7 s. The strong tendency of the Eu dopant to segregate during the solidification process is observed in repeated cycles, with Eu forming clusters on multiple length scales (only for clusters larger than ∼50 µm, as limited by the resolution of the present experiments). It is also demonstrated that the dopant concentration can be quantified even for very low concentration levels (∼0.1%) in 10 mm thick samples. The interface between the solid and liquid phases can also be imaged, provided there is a sufficient change in concentration of one of the elements with a sufficient neutron attenuation cross section. Tomographic imaging of the BaBrCl:0.1%Eu sample reveals a strong correlation between crystal fractures and Eu-deficient clusters. The results of these experiments demonstrate the unique capabilities of neutron imaging for in situ diagnostics and the optimization of crystal-growth procedures. [ABSTRACT FROM AUTHOR]

Time-resolved luminescence properties of Ce3+ doped Y3Al5O12 (YAG) nanocrystals have been studied by means of vacuum-ultraviolet excitation spectroscopy. It was discovered that additionally to the regular Ce3+ yellow-green emission which is well-known luminescence in YAG, new emission covering a broad spectral range from 2.7 eV to 3.5 eV was revealed in the luminescence spectra for all YAG:Ce nanocrystals studied. This blue-UV emission has fast decay time about 7 ns as well as intensive well-resolved excitation band peaking at 5.9 eV and, in contrast to green Ce3+ emission, practically is not excited at higher energies. The origin of the blue-UV emission is tentatively suggested and discussed. (© 2016 WILEY-VCH Verlag GmbH &Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Purpose: High-spatial-resolution x-ray imaging in the few-ten-keV range is becoming increasingly important in several applications, such as small-animal imaging and phase-contrast imaging. The detector properties critically influence the quality of such imaging. Here the authors present a quantitative comparison of scintillator-based detectors for this energy range and at high spatial frequencies. Methods: The authors determine the modulation transfer function, noise power spectrum (NPS), and detective quantum efficiency for Gadox, needle CsI, and structured CsI scintillators of different thicknesses and at different photon energies. An extended analysis of the NPS allows for direct measurements of the scintillator effective absorption efficiency and effective light yield as well as providing an alternative method to assess the underlying factors behind the detector properties. Results: There is a substantial difference in performance between the scintillators depending on the imaging task but in general, the CsI based scintillators perform better than the Gadox scintillators. At low energies (16 keV), a thin needle CsI scintillator has the best performance at all frequencies. At higher energies (28–38 keV), the thicker needle CsI scintillators and the structured CsI scintillator all have very good performance. The needle CsI scintillators have higher absorption efficiencies but the structured CsI scintillator has higher resolution. Conclusions: The choice of scintillator is greatly dependent on the imaging task. The presented comparison and methodology will assist the imaging scientist in optimizing their high-resolution few-ten-keV imaging system for best performance. [ABSTRACT FROM AUTHOR]

The short pulse duration, small effective source size and high flux of synchrotron radiation is ideally suited for probing a wide range of transient deformation processes in materials under extreme conditions. In this paper, the challenges of high-resolution time-resolved indirect X-ray detection are reviewed in the context of dynamic synchrotron experiments. In particular, the discussion is targeted at two-dimensional integrating detector methods, such as those focused on dynamic radiography and diffraction experiments. The response of a scintillator to periodic synchrotron X-ray excitation is modelled and validated against experimental data collected at the Diamond Light Source (DLS) and European Synchrotron Radiation Facility (ESRF). An upper bound on the dynamic range accessible in a time-resolved experiment for a given bunch separation is calculated for a range of scintillators. New bunch structures are suggested for DLS and ESRF using the highest-performing commercially available crystal LYSO:Ce, allowing time-resolved experiments with an interframe time of 189 ns and a maximum dynamic range of 98 (6.6 bits). [ABSTRACT FROM AUTHOR]

Organic single crystals (OSCs) have ideal qualities (well defined structure and morphology, lack of grain boundaries, high purity, 3D long range order, good electronic transport properties) for several technological applications, in particular as key components for electronic devices. It is only recently that OSCs have been considered as ionizing radiation detectors, and the latest developments in this field are here reported. In the first section, various methods for OSC growth are described, with emphasis on cost-effective, solution-based approaches capable of delivering large volume, well performing crystals. The second section is focused on the use of solution-grown OSCs as scintillators (i.e., as high energy photon to UV-vis photon conversion), highlighting the ability of cm-scale OSCs to effectively detect neutrons and to carry out neutrons-gamma pulse-shape discrimination tasks. Finally, the third section describes the use of semiconducting, solution-grown OSCs as effective solid state direct detectors (i.e., directly converting high energy photons into charge carriers), evidencing extremely promising performances in terms of operability in environmental conditions (i.e., no need for encapsulation), radiation hardness, linear response and low operating voltage. [ABSTRACT FROM AUTHOR]

Purpose: Three-dimensional irradiation with a scanned carbon-ion beam has been performed from 2011 at the authors' facility. The authors have developed the rotating-gantry equipped with the scanning irradiation system. The number of combinations of beam properties to measure for the commissioning is more than 7200, i.e., 201 energy steps, 3 intensities, and 12 gantry angles. To compress the commissioning time, quick and simple range verification system is required. In this work, the authors develop a quick range verification system using scintillator and charge-coupled device(CCD)camera and estimate the accuracy of the range verification. Methods: A cylindrical plastic scintillator block and a CCDcamera were installed on the black box. The optical spatial resolution of the system is 0.2 mm/pixel. The camera control system was connected and communicates with the measurement system that is part of the scanning system. The range was determined by image processing. Reference range for each energy beam was determined by a difference of Gaussian (DOG) method and the 80% of distal dose of the depth-dose distribution that were measured by a large parallel-plate ionization chamber. The authors compared a threshold method and a DOG method. Results: The authors found that the edge detection method (i.e., the DOG method) is best for the range detection. The accuracy of range detection using this system is within 0.2 mm, and the reproducibility of the same energy measurement is within 0.1 mm without setup error. Conclusions: The results of this study demonstrate that the authors' range check system is capable of quick and easy range verification with sufficient accuracy. [ABSTRACT FROM AUTHOR]

Purpose: In this study, the authors introduce a new generation of finely structured scintillators with a very high spatial resolution (a few micrometers) compared to conventional scintillators, yet maintaining a thick absorbing layer for improved detectivity. Methods: Their concept is based on a 2D array of high aspect ratio pores which are fabricated by ICP etching, with spacings (pitches) of a few micrometers, on silicon and oxidation of the pore walls. The pores were subsequently filled by melting of powdered CsI(Tl), as the scintillating agent. In order to couple the secondary emitted photons of the back of the scintillator array to a CCD device, having a larger pixel size than the pore pitch, an open optical microscope with adjustable magnification was designed and implemented. By imaging a sharp edge, the authors were able to calculate the modulation transfer function (MTF) of this finely structured scintillator. Results: The x-ray images of individually resolved pores suggest that they have been almost uniformly filled, and the MTF measurements show the feasibility of a few microns spatial resolution imaging, as set by the scintillator pore size. Compared to existing techniques utilizing CsI needles as a structured scintillator, their results imply an almost sevenfold improvement in resolution. Finally, high resolution images, taken by their detector, are presented. Conclusions: The presented work successfully shows the functionality of their detector concept for high resolution imaging and further fabrication developments are most likely to result in higher quantum efficiencies. [ABSTRACT FROM AUTHOR]

A new polycrystalline ceramic scintillator is reported for potential use in radiation detection and medical imaging applications. The goal was to develop cerium-activated aluminum oxynitride (AlON:Ce3+) ceramics, which can be produced using ceramic processes in comparison to the high-cost, low-yield single-crystal growth technique. A phase pure AlON:Ce3+ powder with cubic symmetry was successfully synthesized at high temperature under a reducing atmosphere to convert Ce4+ to Ce3+ in the solid solution. Two different activator concentrations (0.5 and 1.0 mol%) were explored. Fully dense and transparent AlON:Ce3+ ceramics were produced by a liquid-phase-assisted pressureless sintering. The crystal field splitting around the Ce3+ activator in the AlON was comparable to the splitting induced by Br− and the Cl− ligands, which produced an emission spectrum perfectly matching the maximum quantum efficiency range of the photomultiplier tube for radiation detection. Both optical excitation and radiation ionizations in AlON:Ce3+ were demonstrated. Challenges and mechanisms related to the radioluminescence efficiency are discussed. [ABSTRACT FROM AUTHOR]

Purpose: To present a noninvasive technique for directly measuring the CT bow-tie filter attenuation with a linear array x-ray detector. Methods: A scintillator based x-ray detector of 384 pixels, 307 mm active length, and fast data acquisition (model X-Scan 0.8c4-307, Detection Technology, FI-91100 Ii, Finland) was used to simultaneously detect radiation levels across a scan field-of-view. The sampling time was as short as 0.24 ms. To measure the body bow-tie attenuation on a GE Lightspeed Pro 16 CT scanner, the x-ray tube was parked at the 12 o'clock position, and the detector was centered in the scan field at the isocenter height. Two radiation exposures were made with and without the bow-tie in the beam path. Each readout signal was corrected for the detector background offset and signal-level related nonlinear gain, and the ratio of the two exposures gave the bow-tie attenuation. The results were used in the GEANT4 based simulations of the point doses measured using six thimble chambers placed in a human cadaver with abdomen/pelvis CT scans at 100 or 120 kV, helical pitch at 1.375, constant or variable tube current, and distinct x-ray tube starting angles. Results: Absolute attenuation was measured with the body bow-tie scanned at 80-140 kV. For 24 doses measured in six organs of the cadaver, the median or maximum difference between the simulation results and the measurements on the CT scanner was 8.9% or 25.9%, respectively. Conclusions: The described method allows fast and accurate bow-tie filter characterization. [ABSTRACT FROM AUTHOR]

Single crystals of Gd3Ga3Al2O12:Ce with B codopants were successfully grown using the Czochralski technique. The timing characteristics of the crystal was measured by coupling the crystal to photomultiplier tubes (PMT) or silicon photodiodes [Si(PIN)]. The two prompt γ-rays emitted in a cascade from 60Co or 22Na source were detected in coincidence using Gd3Ga3Al2O12:Ce,B crystal detectors and a BaF2 detector. The time resolution of these crystals are observed to be better than that measured for CsI:Tl crystal coupled to PMT or Si(PIN) in an identical measurement setup. [ABSTRACT FROM AUTHOR]

Sensitive and fast detection of neutrons and gamma rays is vital for homeland security, high‐energy physics and proton therapy. However, efficient mixed‐field detection using a single material is highly challenging because fast‐neutron detectors rely on light organic scintillators, and γ‐ray detectors use heavy inorganic scintillators and semiconductors. In the cover, the authors (DOI: 10.1002/inf2.12325) illustrate organic‐inorganic hybrid perovskites that combine light organic cations and heavy inorganic skeletons at a molecular level to achieve unprecedented performance for mixed‐field radiation detection, so as to obtain the time information and energy information of the nuclear reaction process accurately. [ABSTRACT FROM AUTHOR]

Antisite defects (ADs) in nonstoichiometric Lu3Al5O12:Ce (LuAG:Ce) were studied systematically by a combination of first-principles calculation based on density functional theory (DFT), X-ray diffraction (XRD), and electron spin resonance (ESR) experiments. Calculations illustrated that LuAl,16a AD is dominant in LuAG when an Lu2O3 excess exists. Nonstoichiometric LuAG:Ce ceramic with different Lu2O3 excess were prepared to verify the calculation results. The retrieved XRD lattice constants of Lu2O3 excess LuAG:Ce ceramics fit well with DFT calculation results on LuAl,16a AD model, and the same distorted Ce sites in single crystals were also found in LuAG:Ce ceramics by ESR, which suggests the existence of LuAl,16a ADs and they are dominant in nonstoichiometric LuAG:Ce ceramics, and thus measurable concentrations of ADs were detected in ceramics. This revealed that the formation of ADs is related to both temperature and chemical stoichiometry. LuAl,16a antisite defects and nearest normal Lu sites. [ABSTRACT FROM AUTHOR]

A novel approach is reported to minimize various defect centers in Ce doped Gd3Ga3Al2O12 single crystals to improve the scintillation properties. The crystals of Gd3Ga3Al2O12 codoped with 0.2 at% Ce and B (GGAG:Ce,B) have been grown in air and argon ambient using the Czochralski technique. The scintillation light output of crystals grown in Ar ambient was significantly increased after annealing the crystals in air. The measured light output of 60000 ph/MeV for annealed crystals is the highest value reported among this class of materials. As a consequence, the energy resolution at 662 keV gamma-rays from a 137Cs source was improved from 8% for the crystals grown in air to 6% for crystals grown in Ar and subsequently annealed in air. Further, the thermal quenching energy of photoluminescence (PL) emission was increased to be 470 meV for the annealed crystals. The thermoluminescence (TL) measurements suggest that the crystals grown in Ar ambient and post-growth annealed in air may have a lesser concentration of trap centers which subsequently lead to the improvement in optical and scintillation properties leading to a superior detector performance. (© 2015 WILEY-VCH Verlag GmbH &Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

We report for the first time the optimized content and excellent scintillation properties of single crystalline film (SCF) scintillators of multicomponent Gd3- xLu x Al5- yGa y O12:Ce garnet compounds grown by liquid phase epitaxy (LPE) method. The Gd1.5Lu1.5Al2.75Ga2.25O12:Ce and Gd3Al2.75-2Ga2.25-3O12:Ce SCF show the light yield (LY) comparable with that of high-quality bulk crystal analogues of these garnets but faster scintillation decay and very low thermoluminescence in the above room temperature range. To our knowledge, these SCF possess the highest LY values ever obtained in LPE grown garnet SCF scintillators exceeding by at least 1.5-1.6 times the values previously reported for SCF scintillators. [ABSTRACT FROM AUTHOR]

Transparent (Ce,Gd)3Al3Ga2O12 (Ce:GAGG) ceramics are promising scintillators for use in high-energy particle detection application such as nuclear medical imaging. In this study, we report a novel method for the preparation of transparent Ce:GAGG ceramic in oxygen atmosphere without sintering aid. The highest transmittance of as prepared samples with thickness of 1 mm around wavelength of 558 nm reaches 62%, which is close to that value of its comparative single crystal. The average grain size of samples sintered at 1650°C for 10 h is about 11 μm. The spectroscopic properties have also been investigated. The emission peak around 558 nm, which is consistent with that of Ce:GAGG single crystals, matches well with the detection wavelength of photomultiplier. [ABSTRACT FROM AUTHOR]

Purpose: Breast specific gamma imaging or molecular breast imaging (BSGI) obtains 2D images of 99mTc sestamibi distribution in the breast. Molecular breast tomosynthesis (MBT) maps the tracer distribution in 3D by acquiring multiple projections over a limited angular range. Here, the authors compare the performance of the two technologies in terms of spatial resolution, lesion contrast, and contrast-to-noise ratio (CNR) in phantom studies under conditions of clinically relevant sestamibi dose and imaging time. Methods: The systems tested were a Dilon 6800 and a MBT prototype developed at the University of Virginia. Both systems comprise a pixelated sodium iodide scintillator, an array of position sensitive photomultipliers, and a parallel hole collimator. The active areas and energy resolution of the systems are similar. System sensitivity, spatial resolution, lesion contrast, and CNR were measured using a Petri dish, a point source phantom, and a breast phantom containing simulated lesions at two depths, respectively. A single BSGI projection was acquired. Five MBT projections were acquired over ±20°. For both modalities, the total scan count density was comparable to that observed for each in typical 10 min human scans following injection of 22 mCi (814 MBq) of 99mTc-sestamibi. To assess the impact of reducing the tracer dose, the pixel counts of projection images were later binomially subsampled by a factor of 2 to give images corresponding to an injected activity of approximately 11 mCi (407 MBq). Both unprocessed (pixelated) BSGI projections and interpolated (smoothed) BSGI images displayed by default on the Dilon 6800 workstation were analyzed. Volumetric images were reconstructed from the MBT projections using a maximum likelihood expectation maximization algorithm and extracted slices were analyzed. Results: Over a depth range of 1.5-7.5 cm, BSGI spatial resolution was 5.6-11.5 mm in unprocessed projections and 5.7-12.0 mm in interpolated images. Over the same range, the in-slice MBT spatial resolution was 6.7-9.4 mm. Lesion contrast was significantly improved with MBT relative to BSGI for five out of eight lesions imaged at either the 22 mCi or the 11 mCi dose level (p < 0.05). At both dose levels, significant improvements in CNR with MBT were also found for five out of eight lesions (9.8, 7.8, 6.2 mm lesions at water depth of 1.7 cm and 9.8, 7.8 mm lesions at water depth of 4.5 cm, p < 0.05). The 6.2 and 4.9 mm lesions located at 4.5 cm below the water surface were not visible in either modality at either activity level. Conclusions: Under conditions of equal dose, imaging time and similar detectors, compared to BSGI, MBT provided higher lesion contrast, higher CNR, and spatial resolution that was less depth dependent. [ABSTRACT FROM AUTHOR]

Gd2O2S: Pr ceramics were fabricated by spark plasma sintering using the powders synthesized by carbothermal reduction method. The calcination temperature, carbon content, and other preparation conditions of the powders are optimized. The results indicate that the carbon content in the raw mixture has a great influence on the final phases of the phosphor powders. A possible reaction process and mechanism are also proposed. The spectroscopic properties of Gd2O2S: Pr phosphors and ceramics are studied by the photoluminescence ( PL) and X-ray excitation luminescence ( XEL) spectra, in which show a green emission at 513 nm was detected as the main emission under the UV and X-ray excitation. [ABSTRACT FROM AUTHOR]

In this study, translucent CeF3 ceramics was firstly fabricated by hot-pressing, aiming to develop an economical, radiation hard scintillation material. After sintering at 950°C and pressure exertion of 300 MPa for 2 h, a transmittance of 10-25% was achieved in the visible region, through a thickness of 0.75 mm. Microstructure investigations indicated the average grain size was around 42.7 μm, with no obvious pores observed on the fracture surface. The X-ray luminescence spectra, decay time, and thermoluminescence spectra were measured, and the results of the ceramics were similar to its corresponding single crystals, which proved it to be a promising scintillation material. [ABSTRACT FROM AUTHOR]

The detector response function of X-ray and gamma-ray detectors is obtained from the convolution of the energy deposition spectrum with the detector resolution function. The energy deposition spectrum can be computed by using deterministic or Monte Carlo codes, while the energy resolution depends specifically on the detection mechanism, which is characteristic of the single detector. In a first approximation, the energy resolution can be modeled using a normalized Gaussian distribution having its full width at half maximum expressed in terms of specific semiempirical formulas for solid-state detectors, scintillators, and gas proportional counters. However, this approach is not sufficient with some solid-state detectors. It is frequent to find that the peaks show a deviation from the Gaussian shape: a long flat shelf structure from the peak centroid to the lower energies and an asymmetry that can be described with an exponential decay on the left side of the peak. These two effects have been introduced in the new tool RESOLUTION by adapting empirical models found in literature. RESOLUTION can be tailored to the specific detector by analyzing measured monochromatic peaks by means of the following strategies: (1) in a first approximation, a Gaussian shape is assumed in order to determine the full width at half maximum parameters, (2) if it is noted a flat background on the left side of the peak, then a shelf function is added, and (3) if a departure of the Gaussian is observed, then an exponential tail function is added. RESOLUTION gives a very precise description of the line shape. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

In this review, the major achievements and research and development (R&D) trends from the last decade in the field of single crystal scintillator materials are described. Two material families are included, namely, those of halide and oxide compounds. In most cases, the host crystals are doped with Ce3+, Pr3+ or Eu2+ rare earth ions. Their spin‐ and parity‐allowed 5d–4f transitions enable a rapid scintillation response, on the order of tens to hundreds of nanoseconds. Technological recipes, extended characterization by means of optical and magnetic spectroscopies, and theoretical studies are described. The latter provide further support to experimental results and provide a better understanding of the host electronic band structure, energy levels of specific defects, and the emission centers themselves. Applications in medical imaging and dosimetry, security measures, high‐energy physics and the high‐tech industry, in which X(γ)‐rays or particle beams are used and monitored, are recognized as the main driving factor for R&D activities in this field. [ABSTRACT FROM AUTHOR]

Caesium iodide is one of the most extensively studied scintillators. Here, we present X-ray luminescence spectra, scintillation light output and decay curves as a function of temperature, from room temperature down to below 10 K. Features of the observed intrinsic luminescence are explained in terms of radiative recombination of on- and off-center STE. A model permitting interpretation of the dynamics of luminescence changes in CsI with temperature is suggested. This model includes adiabatic potential energy surfaces (APES) associated with singlet and triplet states of self-trapped excitons (STE) and explains the variation of the luminescence spectra with temperature as a result of re-distribution in the population between on- and off-center STE. The temperature dependence of the scintillation light yield is discussed in the framework of the Onsager mechanism. [ABSTRACT FROM AUTHOR]

Purpose: Kilovoltage (kV) x-rays pose a significant challenge for radiation dosimetry. In the kV energy range, even small differences in material composition can result in significant variations in the absorbed energy between soft tissue and the detector. In addition, the use of electronic systems in light detection has demonstrated measurement losses at high photon fluence rates incident to the detector. This study investigated the feasibility of using a novel dual scintillator detector and whether its response to changes in beam energy from scatter and hardening is readily quantified. The detector incorporates a tissue-equivalent plastic scintillator and a gadolinium oxysulfide scintillator, which has a higher sensitivity to scatter x-rays. Methods: The detector was constructed by coupling two scintillators: (1) small cylindrical plastic scintillator, 500 jum in diameter and 2 mm in length, and (2) 100 micron sheet of gadolinium oxysulfide 500 um in diameter, each to a 2 m long optical fiber, which acts as a light guide to transmit scintillation photons from the sensitive element to a photomultiplier tube. Count rate linearity data were obtained from a wide range of exposure rates delivered from a radiological x-ray tube by adjusting the tube current. The data were fitted to a nonparalyzable dead time model to characterize the time response. The true counting rate was related to the reference free air dose air rate measured with a 0.6 cm3 Radcal® thimble chamber as described in AAPM Report No. 111. Secondary electron and photon spectra were evaluated using Monte Carlo techniques to analyze ionization quenching and photon energy-absorption characteristics from free-in-air and in phantom measurements. The depth/energy dependence of the detector was characterized using a computed tomography dose index QA phantom consisting of nested adult head and body segments. The phantom provided up to 32 cm of acrylic with a compatible 0.6 cm3 calibrated ionization chamber to measure the reference air kerma. Results: Each detector exhibited counting losses of 5% when irradiated at a dose rate of 26.3 mGy/s (Gadolinium) and 324.3 mGy/s (plastic). The dead time of the gadolinium oxysulfide detector was determined to be 48 ns, while the dead time of the plastic scintillating detector was unable to accurately be calculated due to poor counting statistics from low detected count rates. Noticeable depth/energy dependence was observed for the plastic scintillator for depths greater than 16 cm of acrylic that was not present for measurements using the gadolinium oxysulfide scintillator, leading us to believe that quenching may play a larger role in the depth dependence of the plastic scintillator than the incident x-ray energy spectrum. When properly corrected for dead time effects, the energy response of the gadolinium oxysulfide scintillator is consistent with the plastic scintillator. Using the integrated dual detector method was superior to each detector individually as the depth-dependent measure of dose was correctable to less than 8% between 100 and 135 kV. Conclusions: The dual scintillator fiber-optic detector accommodates a methodology for energy dependent corrections of the plastic scintillator, improving the overall accuracy of the dosimeter across the range of diagnostic energies. [ABSTRACT FROM AUTHOR]

Tb3+-, Eu3+-activated, and Eu3+/Tb3+-coactivated oxyfluoride borogermanate scintillating glasses with the density of about 6.50 g/cm³ were successfully synthesized by a melt-quenching method. The structure and optical properties including transmittance, photoluminescence (excitation and emission spectra), photoluminescence decay, and X-ray excited luminescence behaviors were studied in detail. Our results reveal that the energy-transfer efficiency from Tb3+ to Eu3+ ions increases with an increase in Eu3+ concentration. The energy-transfer mechanism is also discussed by Dexter's and Reisfeld's semiexperimental methods. [ABSTRACT FROM AUTHOR]

Strong oxygen dependence and limited penetration depth are the two major challenges facing the clinical application of photodynamic therapy (PDT). In contrast, ionizing radiation is too penetrative and often leads to inefficient radiotherapy (RT) in the clinic because of the lack of effective energy accumulation in the tumor region. Inspired by the complementary advantages of PDT and RT, we present herein the integration of a scintillator and a semiconductor as an ionizing-radiation-induced PDT agent, achieving synchronous radiotherapy and depth-insensitive PDT with diminished oxygen dependence. In the core-shell CeIII-doped LiYF4@SiO2@ZnO structure, the downconverted ultraviolet fluorescence from the CeIII-doped LiYF4 nanoscintillator under ionizing irradiation enables the generation of electron-hole (e−-h+) pairs in ZnO nanoparticles, giving rise to the formation of biotoxic hydroxyl radicals. This process is analogous to a type I PDT process for enhanced antitumor therapeutic efficacy. [ABSTRACT FROM AUTHOR]

The influence of different activator impurities on the scintillation yield of alkali halides has been investigated as a function of temperature. Luminescence spectra of pure and activated CsI and NaI scintillation crystals were measured under X-ray and VUV excitation at temperatures from 10 to 300 K. In indium- and thallium-doped crystals activator centers can capture electrons. Along with self-trapping of holes at low temperatures, electron capture by the dopant results in energy storage. This leads to a significant decrease of luminescence yield. In Eu-doped NaI and CsI crystals activator centers capture a hole first. In this way, at low temperatures electrons recombine either with self-trapped holes (yielding STE emission), or with holes trapped by the activator (giving rise to Eu emission band). No energy loss at low temperature is evident in CsI:Eu and NaI:Eu crystals. [ABSTRACT FROM AUTHOR]

Purpose: The most commonly used technology currently used for autoradiography is storage phosphor screens, which has many benefits such as a large field of view but lacks particle-counting detection of the time and energy of each detected radionuclide decay. A number of alternative designs, using either solid state or scintillator detectors, have been developed to address these issues. The aim of this study is to characterize the imaging performance of one such instrument, a double-sided silicon strip detector (DSSD) system for digital autoradiography. A novel aspect of this work is that the instrument, in contrast to previous prototype systems using the same detector type, provides the ability for user accessible imaging with higher throughput. Studies were performed to compare its spatial resolution to that of storage phosphor screens and test the implementation of multiradionuclide ex vivo imaging in a mouse preclinical animal study. Methods: Detector background counts were determined by measuring a nonradioactive sample slide for 52 h. Energy spectra and detection efficiency were measured for seven commonly used radionuclides under representative conditions for tissue imaging. System dead time was measured by imaging 18F samples of at least 5 kBq and studying the changes in count rate over time. A line source of 58Co was manufactured by irradiating a 10 μm nickel wire with fast neutrons in a research reactor. Samples of this wire were imaged in both the DSSD and storage phosphor screen systems and the full width at half maximum (FWHM) measured for the line profiles. Multiradionuclide imaging was employed in a two animal study to examine the intratumoral distribution of a 125I-labeled monoclonal antibody and a 131I-labeled engineered fragment (diabody) injected in the same mouse, both targeting carcinoembryonic antigen. Results: Detector background was 1.81 × 10-6 counts per second per 50 × 50 μm pixel. Energy spectra and detection efficiency were successfully measured for seven radionuclides. The system dead time was measured to be 59 μs, and FWHM for a 58Co line source was 154 ± 14 μm for the DSSD system and 343 ± 15 μm for the storage phosphor system. Separation of the contributions from 125I and 131I was performed on autoradiography images of tumor sections. Conclusions: This study has shown that a DSSD system can be beneficially applied for digital autoradiography with simultaneous multiradionuclide imaging capability. The system has a low background signal, ability to image both low and high activity samples, and a good energy resolution. [ABSTRACT FROM AUTHOR]

Nonstoichiometric LuAG: Ce Ceramics ([ Lu(1- x) Ce x]3 Al5 O12, x = 0.005) with different excess of Lu3+ were designed on the basis of Lu2 O3- Al2 O3 phase diagram and fabricated by a solid-state reaction method. Without using any traditional sintering aids, pure phase and good optical performance were obtained in such a Lu-rich LuAG: Ce ceramics. In addition, scintillation efficiency and light yield of 1% excess of Lu3+ ceramic sample were found 16 times and 1.82 times higher than that of commercial Bi4 Ge3 O12 ( BGO) single crystals, respectively. Such values are comparable or even better than those in most of LuAG: Ce single crystals. However, antisite defects were also induced by excess of Lu doping, whose luminescence was found at 350-410 nm in Lu-rich LuAG: Ce ceramics. The relationship of excess content of Lu and the microstructure, optical quality, and scintillation performance were clarified and discussed. Furthermore, by utilizing X-ray absorption near edge spectroscopy technique, the charge state stability of cerium in Lu-rich LuAG: Ce ceramics was examined. It appears that the excess of isovalence Lu3+ doping has a negligible effect on the cerium valence instability and creation of stable Ce4+ center. [ABSTRACT FROM AUTHOR]

Singulett ‐ Biradikaloide der Hauptgruppenelemente wurden in den letzten 20 Jahren gründlich untersucht, insbesondere Derivate des Cyclobutan ‐ 1,3 ‐ diyls. Jedoch sind in jedem der bekannten Beispiele die Radikalzentren äquivalent. Daher wollten wir ein gemischtes Dipniktadiazandiyl herstellen, in dem P und As den Radikalcharakter tragen. Um das Ziel zu erreichen, musste zunächst das Dichlorcycloarsaphosphadiazan [ClP(μ ‐ NTer)2AsCl] synthetisiert werden. Durch Chloridabstraktion von [ClP(μ ‐ NTer)2AsCl] wurde das cyclische Kation [P(μ ‐ NTer)2AsCl]+ erhalten, während die Reduktion mit Magnesium zum Arsaphosphadiazandiyl [P(μ ‐ NTer)2As] führte. Wenn man zu zweit ist, kann man nicht zu radikal sein: Das erste Biradikaloid mit unterschiedlichen Radikalzentren, das heteroatomare Biradikaloid [P(μ ‐ NR)2As], wurde durch Reduktion des entsprechenden Dichlorarsaphosphadiazans mit Magnesium erhalten. Die Molekülstruktur weist für den planaren viergliedrigen N2PAs ‐ Ring eine charakteristische Drachenform mit zwei gleichen P ‐ N ‐ und As ‐ N ‐ Abständen auf. CASSCF ‐ Rechnungen belegen einen Biradikalcharakter von 28 %. [ABSTRACT FROM AUTHOR]

Purpose: Metal package photomultiplier tubes (PMTs) with a metal channel dynode structure have several advanced features for devising such time-of-flight (TOF) and high spatial resolution positron emission tomography (PET) detectors, thanks to their high packing density, large effective area ratio, fast time response, and position encoding capability. Here, we report on an investigation of new metal package PMTs with high quantum efficiency (QE) for high-resolution PET and TOF PET detector modules. Methods: The latest metal package PMT, the Hamamatsu R11265 series, is served with two kinds of photocathodes that have higher quantum efficiency than normal bialkali (typical QE ≈ 25%), super bialkali (SBA; QE ≈ 35%), and ultra bialkali (UBA; QE ≈ 43%). In this study, the authors evaluated the performance of the new PMTs with SBA and UBA photocathodes as a PET detector by coupling various crystal arrays. They also investigated the performance improvements of high QE, focusing in particular on a block detector coupled with a lutetium-based scintillator. A single 4 x 4 x 10 mm³ LYSO, a 7 x 7 array of 3 x 3 x 20 mm³ LGSO, a 9 x 9 array of 1.2 x 1.2 x 10 mm³ LYSO, and a 6 x 6 array of 1.5 x 1.5 x 7 mm³ LuYAP were used for evaluation. All coincidence data were acquired with a DRS4 based fast digitizer. Results: This new PMT shows promising crystal positioning accuracy, energy and time discrimination performance for TOF, and high-resolution PET applications. The authors also found that a metal channel PMT with SBA was enough for both TOF and high-resolution application, although UBA gave a minor improvement to time resolution. However, significant performance improvement was observed in relative low light output crystals (LuYAP) coupled with UBA. Conclusions: The results of this study will be of value as a useful reference to select PMTs for high-performance PET detectors. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the main characteristics of the Exradin W1 scintillator as a dosimeter and to estimate measurement uncertainties when used in radiotherapy. Methods: We studied the calibration procedure, energy and modality dependence, short-term repeatability, dose-response linearity, angular dependence, temperature dependence, time to reach thermal equilibrium, dose-rate dependence, water-equivalent depth of the effective measurement point, and long-term stability. An uncertainty budget was derived for relative and absolute dose measurements in photon and electron beams. Results: Exradin W1 showed a temperature dependence of -0.225% °C-1. The loss of sensitivity with accumulated dose decreased with use. The sensitivity of Exradin W1 was energy independent for high-energy photon and electron beams. All remaining dependencies of Exradin W1 were around or below 0.5%, leading to an uncertainty budget of about 1%. When a dual channel electrometer with automatic trigger was not used, timing effects became significant, increasing uncertainties by one order of magnitude. Conclusions: The Exradin W1 response is energy independent for high energy x-rays and electron beams, and only one calibration coefficient is needed. A temperature correction factor should be applied to keep uncertainties around 2% for absolute dose measurements and around 1% for relative measurements in high-energy photon and electron beams. The Exradin W1 scintillator is an excellent alternative to detectors such as diodes for relative dose measurements. [ABSTRACT FROM AUTHOR]

Cerium doped rare earths aluminum perovskites, (REAlO3) are widely used as highly efficient and fast scintillators matrix for γ-ray detection. The crystal structures of pure perovskites (YAlO3 (YAP) and LuAlO3 (LuAP)) and their mixed compound (Lu0,7Y0,3AlO3 (LuYAP)) needs to be free of structural defects in order to avoid unwelcome shallow or deep intragap energy levels that decreases light yield and can generates afterglow that further reduce the efficiency of the final devices. However in this paper we focus on the possibility to control and use such carrier traps to engineer new devices for optical memory storage. In this perspective, the optical and structural characterizations are presented and the effects of visible irradiation on the thermoluminescence measurements are discussed. Three trap levels are observed in nitrogen atmosphere grown monocrystals of LuYAP sample, and the selective effects of red, blue and deep blue irradiation show the feasibility in the near future of new promising transparent displays. [ABSTRACT FROM AUTHOR]

The article presents abstracts of the articles regarding chemistry including "Current Status on Plastic Scintillators Modifications," by G. H. V. Bertrand, M. Hamel and F. Sguerra, "Drug Screening Boosted by Hyperpolarized Long-Lived States in NMR," by R. Buratto and colleagues, and "Functional Redundancy of Microbial Anodes fed by Domestic Wastewater," by C. Koch, D. Popiel and F. Harnisch.

Purpose: Side readout of scintillation light from crystal elements in positron emission tomography (PET) is an alternative to conventional end-readout configurations, with the benefit of being able to provide accurate depth-of-interaction (DOI) information and good energy resolution while achieving excellent timing resolution required for time-of-flight PET. This paper explores different readout geometries of scintillation crystal elements with the goal of achieving a detector that simultaneously achieves excellent timing resolution, energy resolution, spatial resolution, and photon sensitivity. Methods: The performance of discrete LYSO scintillation elements of different lengths read out from the end/side with digital silicon photomultipliers (dSiPMs) has been assessed. Results: Compared to 3 x 3 x 20 mm³ LYSO crystals read out from their ends with a coincidence resolving time (CRT) of 162 ± 6 ps FWHM and saturated energy spectra, a side-readout configuration achieved an excellent CRT of 144 ± 2 ps FWHM after correcting for timing skews within the dSiPM and an energy resolution of 11.8% ± 0.2% without requiring energy saturation correction. Using a maximum likelihood estimation method on individual dSiPM pixel response that corresponds to different 511 keV photon interaction positions, the DOI resolution of this 3 x 3 x 20 mm³ crystal side-readout configuration was computed to be 0.8 mm FWHM with negligible artifacts at the crystal ends. On the other hand, with smaller 3 x 3 x 5 mm³ LYSO crystals that can also be tiled/stacked to provide DOI information, a timing resolution of 134 ± 6 ps was attained but produced highly saturated energy spectra. Conclusions: The energy, timing, and DOI resolution information extracted from the side of long scintillation crystal elements coupled to dSiPM have been acquired for the first time. The authors conclude in this proof of concept study that such detector configuration has the potential to enable outstanding detector performance in terms of timing, energy, and DOI resolution. [ABSTRACT FROM AUTHOR]

Recent developments of plastic scintillators are reviewed, from 2000 to March 2014, distributed in two different chapters. First chapter deals with the chemical modifications of the polymer backbone, whereas modifications of the fluorescent probe are presented in the second chapter. All examples are provided with the scope of detection of various radiation particles. The main characteristics of these newly created scintillators and their detection properties are given. [ABSTRACT FROM AUTHOR]

authoren We have employed a range of atomistic simulation methods to explore aspects of defect chemistry in ABO [ABSTRACT FROM AUTHOR]

Fast Ce3+-activated borogermanate scintillating glasses with the density of 5.58-5.67 g/cm3 were synthesized by melt quenching method in air atmosphere for the first time. The optical transmittance and X-ray absorption near edge spectroscopy results confirm that Ce4+ ions can be effectively reduced to Ce3+ ions by adding 0.31 mol% Si3 N4 as a strong reducing agent during glass synthesis. The luminescence behavior under both ultraviolet and X-ray excitations indicate that the proposed Ce3+-activated borogermanate scintillating glasses have a broad emission band centered at 430 nm and a decay time of less than 25 ns. This will be of great interest in high-energy physics and nuclear physics engineering. [ABSTRACT FROM AUTHOR]

The behavior of light yield in a wide range of inorganic scintillation crystals formed by isovalent substitution of anions or cations was investigated. The correlation between improvement of light yield in mixed crystals, and the ratios of volumes occupied by the competing atoms (ions) has been analyzed. A phenomenological approach to the prediction of light yield in mixed scintillation crystals allows us to predict the optimal combination of mixing components to reach the best scintillation performance. Relation between the rate of light-yield improvement and ratio of the volumes occupied by the substituted atoms. [ABSTRACT FROM AUTHOR]

Purpose: Because frame rates on current clinical available electronic portal imaging devices (EPID's) are limited to 7.5 Hz, a new commercially available PerkinElmer EPID (XRD 1642 AP19) with a maximum frame rate of 30 Hz and a new scintillator (Kyokko PI200) with improved sensitivity (light output) for megavolt (MV) irradiation was evaluated. In this work, the influence of MV pulse artifacts and pulsing artifact suppression techniques on fiducial marker and marker-less detection of a lung lesion was investigated, because target localization is an important component of uncertainty in geometrical verification of real-time tumor tracking. Methods: Visicoil™markers with a diameter of 0.05 and 0.075 cm were used forMVmarker tracking with a frame rate of, respectively, 7.5, 15, and 30 Hz. A 30 Hz readout of the detector was obtained by a 2×2 pixel binning, reducing spatial resolution. Static marker detection was conducted in function of increasing phantom thickness. Additionally, marker-less tracking was conducted and compared with the ground-truth fiducial marker motion. Performance of MV target detection was investigated by comparing the least-square sine wave fit of the detected marker positions with the predefined sine wave motion. For fiducial marker detection, a Laplacian-of-Gaussian enhancement was applied after which normalized cross correlation was used to find the most probable marker position. Marker-less detection was performed by using the scale and orientation adaptive mean shift tracking algorithm. For each MV fluoroscopy, a free running (FR-nF) (ignoring MV pulsing during readout) acquisition mode was compared with two acquisition modes intending to reduce MV pulsing artifacts, i.e., combined wavelet-FFT filtering (FR-wF) and electronic readout synchronized with respect to MV pulses. Results: A 0.05 cm Visicoil marker resulted in an unacceptable root-mean square error (RMSE) > 0.2 cm with a maximum frame rate of 30 Hz during FR-nF readout. With a 30 Hz synchronized readout (S-nF) and during 15 Hz readout (independent of readout mode), RMSE was submillimeter for a static 0.05 cm Visicoil. A dynamic 0.05 cm Visicoil was not detectable on the XRD 1642 AP19, despite a fast synchronized readout. For a 0.075 cm Visicoil, deviations of sine wave motion were submillimeter (RMSE < 0.08 cm), independent of the acquisition mode (FR, S). For marker-less tumor detection, FR-nF images resulted in RMSE > 0.3 cm, while for MV fluoroscopy in S-mode RMSE < 0.1 cm for 15 Hz and RMSE < 0.16 cm for 30 Hz. Largest consistency in target localization was experienced during 15 Hz S-nF readout. Conclusions: In general, marker contrast decreased in function of higher frame rates, which was detrimental for marker detection success. In this work, Visicoils with a thickness of 0.075 cm were showing best results for a 15 Hz frame rate, while non-MV compatible 0.05 cm Visicoil markers were not visible on the new EPID with improved sensitivity compared to EPID models based on a Kodak Lanex Fast scintillator. No noticeable influence of pulsing artifacts on the detection of a 0.075 cm Visicoil was observed, while a synchronized readout provided most reliable detection of a marker-less soft-tissue structure. [ABSTRACT FROM AUTHOR]

This study describes the ability to use the melt-level control for stabilization of the crystallization rate during NaI crystal growth by the VGF technique with a skull layer. It is shown that a conventional linear decrease of the heater temperature leads to a nonuniform crystallization rate and deterioration of crystal quality. A method and algorithm of temperature control for the stabilization of the crystallization rate during crystal growth is proposed. The series of growth experiments with NaI(Tl) crystals proved the efficiency of this approach and ability to obtain scintillators with high registration efficiency, about 6.3% energy resolution for a 137Cs (662 keV) source. [ABSTRACT FROM AUTHOR]

The corrected abstract reads: "Cu halide materials with low electronic dimension show great scintillation properties with high photoluminescence quantum yield (PLQY) and large Stokes shift, which can result in reabsorption-free scintillators. In this regard, a high scintillation yield Cs SB 3 sb Cu SB 2 sb I SB 5 sb -PDMS flexible film utilizing ball-milled Cs SB 3 sb Cu SB 2 sb I SB 5 sb powder is developed. However, there is still a need for a large-scalable method to fabricate large amount of scintillation powder and large-size scintillation films. [Extracted from the article]

Purpose: Patient-specific quality assurance (QA) of dynamic radiotherapy delivery would gain from being performed using a 3D dosimeter. However, 3D dosimeters, such as gels, have many disadvantages limiting to quality assurance, such as tedious read-out procedures and poor reproducibility. The purpose of this work is to develop and validate a novel type of high resolution 3D dosimeter based on the real-time light acquisition of a plastic scintillator volume using a plenoptic camera. This dosimeter would allow for the QA of dynamic radiation therapy techniques such as intensity-modulated radiation therapy (IMRT) or volumetric-modulated arc therapy (VMAT). Methods: A Raytrix R5 plenoptic camera was used to image a 10 × 10 × 10 cm³ EJ-260 plastic scintillator embedded inside an acrylic phantom at a rate of one acquisition per second. The scintillator volume was irradiated with both an IMRT and VMAT treatment plan on a Clinac iX linear accelerator. The 3D light distribution emitted by the scintillator volume was reconstructed at a 2 mm resolution in all dimensions by back-projecting the light collected by each pixel of the light-field camera using an iterative reconstruction algorithm. The latter was constrained by a beam's eye view projection of the incident dose acquired using the portal imager integrated with the linac and by physical consideration of the dose behavior as a function of depth in the phantom. Results: The absolute dose difference between the reconstructed 3D dose and the expected dose calculated using the treatment planning software Pinnacle³ was on average below 1.5% of the maximum dose for both integrated IMRT and VMAT deliveries, and below 3% for each individual IMRT incidences. Dose agreement between the reconstructed 3D dose and a radiochromic film acquisition in the same experimental phantom was on average within 2.1% and 1.2% of the maximum recorded dose for the IMRT and VMAT delivery, respectively. Conclusions: Using plenoptic camera technology, the authors were able to perform millimeter resolution, water-equivalent dosimetry of an IMRT and VMAT plan over a whole 3D volume. Since no moving parts are required in the dosimeter, the incident dose distribution can be acquired as a function of time, thus enabling the validation of static and dynamic radiation delivery with photons, electrons, and heavier ions. [ABSTRACT FROM AUTHOR]

An array of monolayer of periodic nanospheres is used to efficiently extract the light from a scintillator of high refractive indexwith broadband capability. Compared with the plain sample without nanospheres, the enhancement of wavelength- and angleintegrated luminescence by 72 and 68% can be achieved under the excitation of ultraviolet and g-ray radiation, respectively. The whispering-gallery modes for the individual sphere and the periodic arrangement are responsible for the enhancement of light extraction. Such a photonic structure is advantageous over the traditional two-dimensional photonic crystal. [ABSTRACT FROM AUTHOR]

Purpose: Depth encoding detectors are required to improve the spatial resolution and spatial resolution uniformity of small animal positron emission tomography (PET) scanners, as well as dedicated breast and brain scanners. Depth of interaction (DOI) can be measured by using dual-ended readout of lutetium oxyorthosilicate (LSO) scintillator arrays with position-sensitive avalanche photodiodes. Inter-crystal reflectors and crystal surface treatments play important roles in determining the performance of dual-ended detectors. In this paper, the authors evaluated five LSO arrays made with three different intercrystal reflectors and with either polished or unpolished crystal surfaces. Methods: The crystal size in all arrays was 1.5 mm, which is typical of the detector size used in small animal and dedicated breast scanners. The LSO arrays were measured with dual-ended readout and were compared in terms of flood histogram, energy resolution, and DOI resolution performance. Results: The four arrays using enhanced specular reflector (ESR) and Toray reflector provided similar quality flood histograms and the array using Crystal Wrap reflector gave the worst flood histogram. The two arrays using ESR reflector provided the best energy resolution and the array using Crystal Wrap reflector yielded the worst energy resolution. All arrays except the polished ESR array provided good DOI resolution ranging from 1.9 mm to 2.9 mm. DOI resolution improved as the gradient in light collection efficiency with depth (GLCED) increased. The geometric mean energies were also calculated for these dual-ended readout detectors as an alternative to the conventional summed total energy. It was shown that the geometric mean energy is advantageous in that it provides more uniform photopeak amplitude at different depths for arrays with high GLCED, and is beneficial in event selection by allowing a fixed energy window independent of depth. A new method of DOI calculation that improved the linearity of DOI ratio vs depth and simplifies the DOI calibration procedure also was developed and tested. Conclusions: The results of these studies provide useful guidance in selecting the proper reflectors and crystal surface treatments when LSO arrays are used for high-resolution PET applications in small animal scanners or dedicated breast and brain scanners. [ABSTRACT FROM AUTHOR]