RESUMEN

BACKGROUND: Pencil Beam Scanning proton therapy has many advantages from a therapeutic point of view, but raises technical constraints in terms of treatment verification. The treatment relies on a large number of planned pencil beams (PB) (up to thousands), whose delivery is divided in several low-intensity pulses delivered a high frequency (1 kHz in this study). PURPOSE: The purpose of this study was to develop a three-dimensional quality assurance system allowing to verify all the PBs' characteristics (position, energy, intensity in terms of delivered monitor unit-MU) of patient treatment plans on a pulse-by-pulse or a PB-by-PB basis. METHODS: A system named SCICOPRO has been developed. It is based on a 10 × 10 × 10 cm3 scintillator cube and a fast camera, synchronized with beam delivery, recording two views (direct and using a mirror) of the scintillation distribution generated by the pulses. A specific calibration and analysis process allowed to extract the characteristics of all the pulses delivered during the treatment, and consequently of all the PBs. The system uncertainties, defined here as average value + standard deviation, were characterized with a customized irradiation plan at different PB intensities (0.02, 0.1, and 1 MU) and with two patient's treatment plans of three beams each. The system's ability to detect potential treatment delivery problems, such as positioning errors of the treatment table in this work (1° rotations and a 2 mm translation), was assessed by calculating the confidence intervals (CI) for the different characteristics and evaluating the proportion of PBs within these intervals. RESULTS: The performances of SCICOPRO were evaluated on a pulse-by-pulse basis. They showed a very good signal-to-noise ratio for all the pulse intensities (between 2 × 10-3 MU and 150 × 10-3 MU) allowing uncertainties smaller than 580 µm for the position, 180 keV for the energy and 3% for the intensity on patients treatment plans. The position and energy uncertainties were found to be little dependent from the pulse intensities whereas the intensity uncertainty depends on the pulses number and intensity distribution. Finally, treatment plans evaluations showed that 98% of the PBs were within the CIs with a nominal positioning against 83% or less with the table positioning errors, thus proving the ability of SCICOPRO to detect this kind of errors. CONCLUSION: The high acquisition rate and the very high sensitivity of the system developed in this work allowed to record pulses of intensities as low as 2 × 10-3 MU. SCICOPRO was thus able to measure all the characteristics of the spots of a treatment (position, energy, intensity) in a single measurement, making it possible to verify their compliance with the treatment plan. SCICOPRO thus proved to be a fast and accurate tool that would be useful for patient-specific quality assurance (PSQA) on a pulse-by-pulse or PB-by-PB verification basis.

RESUMEN

Self-trapped exciton (STE) emission, typified by antimony (Sb), with broadband characteristics, represents the next generation of materials for solid-state lighting and radiation detection. However, little is known about the multiexciton behavior of the Sb emission center. Here, we proposed a general approach for designing antimony-centered multi-exciton emitting materials through self-assembly. Benefitting from controllable multiexciton behavior, dual-band white light emission spanning the entire visible spectrum was achieved. Relying on the reduction of an effective atomic number brought by self-assembly, excellent scintillation response to ß-rays was attained. This study offers unprecedented insight into hybrid single/triple STE emission and unveils new avenues for single-emitter white-light emission, as well as radiographic testing using low-risk ß-rays as sources.

RESUMEN

BACKGROUND: The accuracy of proton therapy and preclinical proton irradiation experiments is susceptible to proton range uncertainties, which partly stem from the inaccurate conversion between CT numbers and relative stopping power (RSP). Proton computed tomography (PCT) can reduce these uncertainties by directly acquiring RSP maps. PURPOSE: This study aims to develop a novel PCT imaging system based on scintillator-based proton range detection for accurate RSP reconstruction. METHODS: The proposed PCT system consists of a pencil-beam brass collimator with a 1 mm aperture, an object stage capable of translation and 360° rotation, a plastic scintillator for dose-to-light conversion, and a complementary metal oxide semiconductor (CMOS) camera for light distribution acquisition. A calibration procedure based on Monte Carlo (MC) simulation was implemented to convert the obtained light ranges into water equivalent ranges. The water equivalent path lengths (WEPLs) of the imaged object were determined by calculating the differences in proton ranges obtained with and without the object in the beam path. To validate the WEPL calculation, measurements of WEPLs for eight tissue-equivalent inserts were conducted. PCT imaging was performed on a custom-designed phantom and a mouse, utilizing both 60 and 360 projections. The filtered back projection (FBP) algorithm was employed to reconstruct the RSP from WEPLs. Image quality was assessed based on the reconstructed RSP maps and compared to reference and simulation-based reconstructions. RESULTS: The differences between the calibrated and reference ranges of 110-150 MeV proton beams were within 0.18 mm. The WEPLs of eight tissue-equivalent inserts were measured with accuracies better than 1%. Phantom experiments exhibited good agreement with reference and simulation-based reconstructions, demonstrating average RSP errors of 1.26%, 1.38%, and 0.38% for images reconstructed with 60 projections, 60 projections after penalized weighted least-squares algorithm denoising, and 360 projections, respectively. Mouse experiments provided clear observations of mouse contours and major tissue types. MC simulation estimated an imaging dose of 3.44 cGy for decent RSP reconstruction. CONCLUSIONS: The proposed PCT imaging system enables RSP map acquisition with high accuracy and has the potential to improve dose calculation accuracy in proton therapy and preclinical proton irradiation experiments.

RESUMEN

Combining rare earth elements with the halide perovskite structure offers valuable insights into designing nonlead (Pb) luminescent materials. However, most of these compositions tend to form zero-dimensional (0D) networks of metal-halide polyhedra, with higher-dimensional (1D, 2D, and 3D) structures receiving relatively less exploration. Herein, we present synthesis and optical properties of Cs3CeCl6·3H2O, characterized by its unique 1D crystal structure. The conduction band minimum of Cs3CeCl6·3H2O becomes less localized as a result of the increased structural dimension, making it possible for the materials to achieve an efficient electrical injection. For both Cs3CeCl6·3H2O single crystals and nanocrystals, we also observed remarkable luminescence with near-unity photoluminescence quantum yield and exceptional phase stability. Cs3CeCl6·3H2O single crystals demonstrate an X-ray scintillation light yield of 31900 photons/MeV, higher than that of commercial LuAG:Ce (22000 photons/MeV); electrically driven light-emitting diodes fabricated with Cs3CeCl6·3H2O nanocrystals yield the characteristic emission of Ce3+, indicating their potential use in next-generation violet-light-emitting devices.

RESUMEN

Investigating the mechanism of positron annihilation in liquid-scintillator based neutrino experiments could be helpful for positron reconstruction algorithms and positron-electron discrimination analysis. Based on this, we utilize a novel positron annihilation lifetime spectrometer to characterize a series of liquid scintillator samples without direct contact with the positron source by applying the anti-coincidence method, which facilitates the measurement of liquids with high accuracy and low background. We obtain an ortho-positronium (o-Ps) lifetime value of 3.02 ns for liquid scintillators composed of linear alkylbenzene and two solutes, and we also measure liquid scintillator samples by bubbling different gases to study the interaction of oxygen dissolved with positronium. The discussion of the annihilation behavior of o-Ps in liquid scintillators further clarify the factors affecting the lifetime and intensity of o-Ps, and the calculation of annihilation rate and free volume radius within the samples has potential applications in characterizing gas solubility and free volume in liquids with o-Ps as probe.

RESUMEN

Organic-inorganic hybrid manganese(II) halides (OIMnHs) have garnered tremendous interest across a wide array of research fields owing to their outstanding optical properties, abundant structural diversity, low-cost solution processibility, and low toxicity, which make them extremely suitable for use as a new class of luminescent materials for various optoelectronic applications. Over the past years, a plethora of OIMnHs with different structural dimensionalities and multifunctionalities such as efficient photoluminescence (PL), radioluminescence, circularly polarized luminescence, and mechanoluminescence have been newly created by judicious screening of the organic cations and inorganic Mn(II) polyhedra. Specifically, through precise molecular and structural engineering, a series of OIMnHs with near-unity PL quantum yields, high anti-thermal quenching properties, and excellent stability in harsh conditions have been devised and explored for applications in light-emitting diodes (LEDs), X-ray scintillators, multimodal anti-counterfeiting, and fluorescent sensing. In this review, the latest advancements in the development of OIMnHs as efficient light-emitting materials are summarized, which covers from their fundamental physicochemical properties to advanced optoelectronic applications, with an emphasis on the structural and functionality design especially for LEDs and X-ray detection and imaging. Current challenges and future efforts to unlock the potentials of these promising materials are also envisioned.

RESUMEN

PURPOSE: This study investigated the potential of a commercially available plastic scintillator, the Exradin W2, as a real-time dosimeter for ultra-high-dose-rate (UHDR) electron beams. This work aimed to characterize this system's performance under UHDR conditions and addressed limitations inherent to other conventional dosimetry systems. METHODS AND MATERIALS: We assessed the W2's performance as a UHDR electron dosimeter using a 16 MeV UHDR electron beam from the FLASH research extension (FLEX) system. Additionally, the vendor provided a beta firmware upgrade to better handle the processing of the high signal generated in the UHDR environment. We evaluated the W2 regarding dose-per-pulse, pulse repetition rate, charge versus distance, and pulse linearity. Absorbed dose measurements were compared against those from a plane-parallel ionization chamber, optically stimulated luminescent dosimeters and radiochromic film. RESULTS: We observed that the 1 × 1 mm W2 scintillator with the MAX SD was more suitable for UHDR dosimetry compared to the 1 × 3 mm W2 scintillator, capable of matching film measurements within 2% accuracy for dose-per-pulse up to 3.6 Gy/pulse. The W2 accurately ascertained the inverse square relationship regarding charge versus virtual source distance with R2 of ∼1.00 for all channels. Pulse linearity was accurately measured with the W2, demonstrating a proportional response to the delivered pulse number. There was no discernible impact on the measured charge of the W2 when switching between the available repetition rates of the FLEX system (18-180 pulses/s), solidifying consistent beam output across pulse frequencies. CONCLUSIONS: This study tested a commercial plastic scintillator detector in a UHDR electron beam, paving the way for its potential use as a real-time, patient-specific dosimetry tool for future FLASH radiotherapy treatments. Further research is warranted to test and improve the signal processing of the W2 dosimetry system to accurately measure in UHDR environments using exceedingly high dose-per-pulse and pulse numbers.

Asunto(s)

RESUMEN

Organic scintillators are praised for their abundant element reserves, facile preparation procedures, and rich structures. However, the weak X-ray attenuation ability and low exciton utilization efficiency result in unsatisfactory scintillation performance. Herein, a new family of highly efficient organic phosphonium halide salts with thermally activated delayed fluorescence (TADF) are designed by innovatively adopting quaternary phosphonium as the electron acceptor, while dimethylamine group and halide anions (I-) serve as the electron donor. The prepared butyl(2-[2-(dimethylamino)phenyl]phenyl)diphenylphosphonium iodide (C4-I) exhibits bright blue emission and an ultra-high photoluminescence quantum yield (PLQY) of 100 %. Efficient charge transfer is realized through the unique n-π and anion-π stacking in solid-state C4-I. Photophysical studies of C4-I suggest that the incorporation of I accounts for high intersystem crossing rate (kISC) and reverse intersystem crossing rate (kRISC), suppressing the intrinsic prompt fluorescence and enabling near-pure TADF emission at room temperature. Benefitting from the large Stokes shift, high PLQY, efficient exciton utilization, and remarkable X-ray attenuation ability endowed by I, C4-I delivers an outstanding light yield of 80721 photons/MeV and a low limit of detection (LoD) of 22.79 nGy ⋅ s-1. This work would provide a rational design concept and open up an appealing road for developing efficient organic scintillators with tunable emission, strong X-ray attenuation ability, and excellent scintillator performance.

RESUMEN

In this study we have synthesized polystyrene based plastic scintillators (PS) loaded with commercially available fluorophores like p-Terphenyl and 1,4-bis(5-phenyloxazol-2-yl) benzene (POPOP). Optimum concentration of the fluorophores in the synthesized PS was determined. The PS exhibited 1.55 ± 0.05 times better light output than UPS-923A, a commercial PS. Emission maxima were obtained at 423 nm with an energy linearity of 99.78% up to 1.061 MeV. Radiation damage of PS by Co-60 irradiation led to 22.3% loss of light yield at 50 kGy radiation dose which is better than the commercial one. The loss of light output in the PS due to radiation damage was because of the degradation of polystyrene matrix rather than the fluorophores.

RESUMEN

BACKGROUND: Good timing resolution in medical imaging applications such as TOF-CT or TOF-PET can boost image quality or patient comfort significantly by reducing the influence of background noise. However, the timing resolution of state-of-the-art detectors in CT and PET are limited by their light emission process. Core-valence cross-luminescence is an alternative, but well-known compounds (e.g. BaF2) pose several problems for medical imaging applications, such as their emission wavelength in the deep UV. CsZnCl-based materials show promise to solve this issue, as they provide fast decay times of 1-2 ns and an emission wavelength around 300 nm. RESULTS: In this work, we investigated two CsZnCl-compounds: Cs2ZnCl4 and Cs3ZnCl5. We validated the previously published decay times on a time-correlated single-photon counting setup with 1.786 ± 0.016 ns for Cs2ZnCl4 and 1.034 ± 0.013 ns for Cs3ZnCl5. The setup's high resolution enabled the discovery of an additional prompt emission component with a significant abundance of 98 ± 18 (Cs2ZnCl4) and 86 ± 14 (Cs3ZnCl5) photons/MeV energy deposit. In a PET coincidence experiment, we measured the best coincidence time resolution (CTR) of 62 ps (FWHM) for Cs2ZnCL4 coupled to FBK VUV SiPMs with silicon oil. To assess the CTR for lower energies, we filtered the energy along the Compton continuum and found a deteriorated CTR that seems to be mainly influenced by photon statistics. Furthermore, this study gave us a rough estimate of e.g. 150 ps (FWHM) CTR at 100 keV energy for Cs2ZnCL4. From measurements with high activity of 14 MBq to check for pile-up effects we assume that Cs2ZnCl4 is better suited for high-rate time-of-flight applications than lutetium-based oxides. Simulations demonstrated that the stopping power of Cs2ZnCl4 is lower than for LSO:Ce,Ca, meaning that a high amount of material would be needed for TOF-PET applications. However, the stopping power seems acceptable for applications in TOF-CT. CONCLUSIONS: The fast decay time, state-of-the-art CTR in benchtop experiments and high-rate suitability make CsZnCl materials a promising candidate for time-of-flight experiments. We consider especially TOF-CT a suitable application due to its relatively low X-ray energies (~ 100 keV) and the thusly acceptable stopping power of Cs2ZnCl4. Currently, further exploration of the prompt emission and its creation mechanism is planned, as well as investigating the light transport of Cs2ZnCl4 in longer crystals.

RESUMEN

In order to adapt to the rapid development of high-speed imaging technology in recent years, it is very important to develop scintillators with an ultrafast time response. Because of its radiation-induced ultrafast decay time, ZnO has become an important material for radiation detection and dosimetry. According to different detection sources and application scenarios, ZnO is used in various radiation detectors in different structures, including nanoarrays and nanocomposites. In this paper, the synthesis methods and research status of various nanostructured ZnO-based materials and their applications in the detection of high-energy rays (X-rays, γ-rays) and high-energy particles (α, ß and neutron) are reviewed. The performance discussion mainly includes spatial resolution, decay time and detection efficiency.

RESUMEN

Manganese halides are one of the most potential candidates for large-area flat-panel detection owing to their biological safety and all-solution preparation. However, reducing photon scattering and enhancing the efficient luminescence of scintillator screens remains a challenge due to their uncontrollable crystallization and serious nonradiative recombination. Herein, an organic cation modulation is reported to control the crystallization process and enhance the luminescence properties of manganese halides. Given the industrial requirements of the X-ray flat-panel detector, the large-area A2MnBr4 screen (900 cm2) with excellent uniformity is blade-coated at 60 °C. Theoretical calculations and in situ measurements reveal that organic cations with larger steric hindrance can slow down the crystallization of the screen, thus neatening the crystal arrangement and reducing the photon scattering. Moreover, larger steric hindrance can also endow the material with higher exciton binding energy, which is beneficial for restraining nonradiative recombination. Therefore, the BPP2MnBr4 (BPP = C25H22P+) screen with larger steric hindrance exhibits a superior spatial resolution (>20 lp mm-1) and ultra-low detection limit (< 250 nGyair s-1). This is the first time steric hindrance modulation is used in blade-coated scintillator screens, and it believes this study will provide some guidance for the development of high-performance manganese halide scintillators.

RESUMEN

Designing and synthesizing multifunctional hybrid copper halides with near ultraviolet (NUV) light-excited high-energy emission (<500 nm) remains challenging. Here, a pair of broadband-excited high-energy emitting isomers, namely, α-/ß-(MePh3P)2CuI3 (MePh3P=methyltriphenylphosphonium), were synthesized. α-(MePh3P)2CuI3 with blue emission peaking at 475 nm is firstly discovered wherein its structure contains regular [CuI3]2- triangles and crystallizes in centrosymmetric space group P21/c. While ß-(MePh3P)2CuI3 featuring distorted [CuI3]2- planar triangles shows inversion symmetry breaking and crystallizes in the noncentrosymmetric space group P21, which exhibits cyan emission peaking at 495 nm with prominent near-unity photoluminescence quantum yield and the excitation band ranging from 200 to 450 nm. Intriguingly, ß-(MePh3P)2CuI3 exhibits phase-matchable second-harmonic generation response of 0.54×KDP and a suitable birefringence of 0.06@1064 nm. Furthermore, ß-(MePh3P)2CuI3 also can be excited by X-ray radioluminescence with a high scintillation light yield of 16193 photon/MeV and an ultra-low detection limit of 47.97 nGy/s, which is only 0.87 % of the standard medical diagnosis (5.5 µGy/s). This work not only promotes the development of solid-state lighting, laser frequency conversion and X-ray imaging, but also provides a reference for constructing multifunctional hybrid metal halides.

RESUMEN

PURPOSE: Although plastic scintillator detectors (PSDs) are considered ideal dosimeters for small field dosimetry in conventional linear accelerators (linacs), the impact of the magnetic field strength on the response of the PSD must be investigated. METHODS: A linac Monte Carlo (MC) head model for a low-field MR-linac was validated for small field dosimetry and utilized to calculate field output factors (OFs). The MC-calculated OFs were compared with the treatment planning system (TPS)-calculated OFs and measured OFs using a Blue Physics (BP) Model 10 commercial PSD and a synthetic diamond detector. The field-specific correction factors, [Formula: see text] , were calculated for the PSD in the presence of a 0.35 T and magnetic field. The impact of the source focal spot size and initial electron energy on the MC-calculated OFs was investigated. RESULTS: Good agreement to within 2 % was found between the MC-calculated OFs and BP PSD OFs except for the 0.415 × 0.415 cm2 field size. The BP PSD [Formula: see text] correction factors were calculated to be within 1 % of unity. For field sizes ≥1.66 × 1.66 cm2, the MC-calculated OFs were relatively insensitive to the focal spot size and initial electron energy to within 2.5 %. However, for smaller field sizes, the MC-calculated OFs were found to differ up to 9.50 % and 7.00 % when the focal spot size and initial electron energy was varied, respectively. CONCLUSIONS: The BP PSD was deemed suitable for small field dosimetry in MR-linacs without requiring any [Formula: see text] correction factors.

Asunto(s)

RESUMEN

Thanks to advancements in silicon photomultiplier sensors (SiPMs) and system-on-chip (SoC) technology, our INFN Roma1 group developed ArduSiPM in 2012, the first all-in-one scintillator particle detector in the literature. It used a custom Arduino Due shield to process fast signals, utilizing the Microchip Sam3X8E SoC's internal peripherals to control and acquire SiPM signals. The availability of radiation-tolerant SoCs, combined with the goal of reducing system space and weight, led to the development of an innovative second-generation board, a better-performing device called Cosmo ArduSiPM, suitable for space missions. The architecture of the new detector is based on the Microchip SAMV71 300 MHz, 32-bit ARM® Cortex®-M7 (Microchip Technology Inc., Chandler, AZ, USA). While the analog front-end is essentially identical to the ArduSiPM, it utilizes components with the smallest possible package. The board fits in a CubeSat module. Thanks to the compact design, the board has two independent channels, with a total weight of only 40 grams within a CubeSat form factor. The ArduSiPM architecture is based on a single microcontroller and fast discrete analog electronics. It benefits from the continued development of SoCs related to the IoT (Internet of Things) market. Compared with a system with a custom ASIC, this architecture based on software and SoC capabilities offers considerable advantages in terms of cost and development time. The ability to incorporate new commercial SoCs, continuously emerging from advancements in the aerospace and automotive industries, provides the system with a robust foundation for sustained growth over the years. A detailed characterization of the hardware and the system's response to different photon fluxes is presented in this article. Additionally, coupling the device with a scintillator was tested at the end of this article as a preliminary trial for future measurements, showing potential for further enhancement of the detector's capabilities.

RESUMEN

BACKGROUND: MRI-guided radiation therapy (MRgRT) requires unique quality assurance equipment to address MR-compatibility needs, minimize electron return effect, handle complex dose distributions, and evaluate real-time dosimetry for gating. Plastic scintillation detectors (PSDs) are an attractive option to address these needs. PURPOSE: To perform a comprehensive characterization of a multi-probe PSD system in a low-field 0.35 T MR-linac, including detector response assessment and gating performance. METHODS: A four-channel PSD system (HYPERSCINT RP-200) was assembled. A single channel was used to evaluate repeatability, percent depth dose (PDD), detector response as a function of orientation with respect to the magnetic field, and intersession variability. All four channels were used to evaluate repeatability, linearity, and output factors. The four PSDs were integrated into an MR-compatible motion phantom at isocenter and in gradient regions. Experiments were conducted to evaluate gating performance and tracking efficacy. RESULTS: For repeatability, the maximum standard deviation of repeated measurements was 0.13% (single PSD). Comparing the PSD to reference data, PDD had a maximum difference of 1.12% (10 cm depth, 6.64 × 6.64 cm2). Percent differences for rotated detector setups were negligible (< 0.3%). All four PSDs demonstrated linear response over 10-1000 MU delivered and the maximum percent difference between the baseline and measured output factors was 0.78% (2.49 × 2.49 cm2). Gating experiments had 400 cGy delivered to isocenter with < 0.8 cGy variation for central axis measures and < 0.7 cGy for the gradient sampled region. Real-time dosimetry measurements captured spurious beam-on incidents that correlated to tracking algorithm inaccuracies and highlighted gating parameter impact on delivery efficiency. CONCLUSIONS: Characterization of the multi-point PSD dosimetry system in a 0.35 T MR-linac demonstrated reliability in a low-field MR-Linac setting, with high repeatability, linearity, small intersession variability, and similarity to baseline data for PDD and output factors. Time-resolved, multi-point dosimetry also showed considerable promise for gated MR-Linac applications.

RESUMEN

Thermo-responsive smart materials have aroused extensive interest due to the particular significance of temperature sensing. Although various photoluminescent materials are explored in thermal detection, it is not applicable enough in X-ray radiation environment where the accuracy and reliability will be influenced. Here, a strategy is proposed by introducing the concept of radio-luminescent functional building units (RBUs) to construct thermo-responsive lanthanide metal-organic frameworks (Ln-MOFs) scintillators for self-calibrating thermometry. The rational designs of RBUs (including organic ligand and Tb3+/Eu3+) with appropriate energy levels lead to high-performance radio-luminescence. Ln-MOFs scintillators exhibit perfect linear response to X-ray, presenting low dose rate detection limit (min ≈156.1 nGyairs-1). Self-calibrating detection based on ratiometric XEL intensities is achieved with good absolute and relative sensitivities of 6.74 and 8.1%K-1, respectively. High relative light yield (max ≈39000 photons MeV-1), imaging spatial resolution (max ≈18 lp mm-1), irradiation stability (intensity ≈100% at 368 K in total dose up to 215 Gyair), and giant color transformation visualization benefit the applications, especially the in situ thermo-responsive X-ray imaging. Such strategy provides a promising way to develop the novel smart photonic materials with excellent scintillator performances.

RESUMEN

BACKGROUND: In vivo dosimetry (IVD) is rarely performed in brachytherapy (BT), allowing potential dose misadministration to go unnoticed. This study presents a clinical routine-calibration method of detectors for IVD in high (HDR) and pulsed dose rate (PDR) Ir-192 BT. PURPOSE: To evaluate the dosimetric precision and feasibility of an in-clinic calibration routine of detectors for IVD in afterloading BT. METHODS: Calibrations were performed in a PMMA phantom with two needles inserted 20 mm apart. The source was loaded in one of the needles at 15 dwells for 10 s. The detector was placed in the other needle, and its signal was recorded. The mean signal at each dwell position was fitted to the expected dose rate with the calibration factor and the detector's longitudinal position being free parameters. The method was tested with an inorganic scintillation detector using one Ir-192 FlexiSource HDR and two Ir-192 GammaMedPlus PDR sources and followed by validation measurements in water. RESULTS: The standard measurement uncertainty (k = 1) of the calibration factor in absolute terms (Gy/s) was 3.2/3.4% for the HDR/PDR source. The uncertainty was dominated by source strength uncertainty, and the precision of the method was <1%. The mean ± 1SD of the difference in measured and expected dose rate during validation was 1.5 ± 4.7% (HDR) and 0.0 ± 4.1% (PDR) with a positional uncertainty in the setup of 0.33/0.23 mm (HDR/PDR) (k = 1). CONCLUSION: A precise and feasible in-clinic calibration method for IVD and source strength consistency tests in BT was presented.

Asunto(s)

RESUMEN

Scintillator-based ZnS:Ag/6LiF neutron detectors have been under development at ISIS for more than three decades. Continuous research and development aim to improve detector capabilities, achieve better performance and meet the increasingly demanding requirements set by neutron instruments. As part of this program, a high-efficiency 2D position-sensitive scintillator detector with wavelength-shifting fibres has been developed for neutron-diffraction applications. The detector consists of a double scintillator-fibre layer to improve detection efficiency. Each layer is made up of two orthogonal fibre planes placed between two ZnS:Ag/6LiF scintillator screens. Thin reflective foils are attached to the front and back scintillators of each layer to minimize light cross-talk between layers. The detector has an active area of 192 × 192 mm with a square pixel size of 3 × 3 mm. As part of the development process of the double-layer detector, a single-layer detector was built, together with a prototype detector in which the two layers of the detector could be read out separately. Efficiency calculations and measurements of all three detectors are discussed. The novel double-layer detector has been installed and tested on the SXD diffractometer at ISIS. The detector performance is compared with the current scintillator detectors employed on SXD by studying reference crystal samples. More than a factor of 3 improvement in efficiency is achieved with the double-layer wavelength-shifting-fibre detector. Software routines for further optimizations in spatial resolution and uniformity of response have been implemented and tested for 2D detectors. The methods and results are discussed in this manuscript.

RESUMEN

Metal halide perovskites, as a new class of attractive and potential scintillators, are highly promising in X-ray imaging. However, their application is limited by the sensitivity to moisture and irradiation. To address this issue, we reported a 2D layered double perovskite material Cs4Cd1-xMnxBi2Cl12 that exhibits high stability both under ambient condition and under X-ray irradiation. Cs4Cd1-xMnxBi2Cl12 demonstrates superior scintillation performance, including excellent X-ray response linearity and a high light yield (∼34,450 photons/MeV). More importantly, the X-ray excited emission intensity maintains 92% and 94% of its original value after stored at ambient condition for over two years and after X-ray irradiation with a total dose of 11.4 Gy, respectively. By mixing with PDMS (polydimethylsiloxane), we have successfully produced a high-quality flexible film that can be bent freely while maintaining its excellent scintillation properties. The scintillating screen exhibits outstanding imaging ability with a spatial resolution of up to 16.7 line pairs per millimeter (lp/mm), also, the superiority of this scintillation screen in flexible X-ray imaging is demonstrated. These results indicate the huge potential of this high-stability double perovskite scintillator in X-ray imaging.