González Martínez, Antonio Javier
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- PublicaciónA proof-of-concept of cross-luminescent metascintillators: testing results on a BGO: BaF2metapixel(IOP Publishing, 2023-01-21) Konstantinou, G.; Latella, Riccardo; Moliner Martínez, Laura; Zhang, L.; Benlloch Baviera, Jose María; González Martínez, Antonio Javier; Lecoq, Paul; Instituto de Instrumentación para Imagen Molecular; European Commission[EN] Objective: Time-of-flight positron emission tomography (PET)is the next frontier in improving the effective sensitivity. To achieve superior timing for time-of-flight PET, combined with high detection efficiency and cost-effectiveness, we have studied the applicability of BaF2 in metascintillators driven by the timing of cross-luminescence photon production. Approach: Based on previous simulation studies of energy sharing and analytic multi-exponential scintillation pulse, as well as sensitivity characteristics, we have experimentally tested a pixel of 3 × 3 × 15 mm3 based on 300 ¿m BGO and 300 ¿m BaF2 layers. To harness the deep ultraviolet cross-luminescent light component, which carries improved timing, we use the FBK VUV SiPM. Metascintillator energy sharing is addressed through a double integration approach. Main results: We reach an energy resolution of 22%, comparable to an 18% resolution of simple BGO pixels using the same readout, through the optimized use of the integrals of the metascintillator pulse in energy sharing calculation. We measure the energy sharing extent of each pulse with a resolution of 25% and demonstrate that experimental and simulation results agree well. Based on the energy sharing, a timewalk correction is applied, exhibiting significant improvements for both the coincidence time resolution (CTR) and the shape of the timing histogram. We reach 242 ps CTR for the entire photopeak, while for a subset of 13% of the most shared events, the CTR value improves to 108 ps, comparable to the 3 × 3 × 5 mm3 LYSO:Ce:Ca reference crystal. Significance: While we are considering different ways to improve further these results, this proof-ofconcept demonstrates the applicability of cross-luminescence for metascintillator designs through the application of VUV compatible SiPM coupling, and easily implementable digital algorithms. This is the first test of BaF2-based metascintillators of sufficient stoppng power to be included in a PET scanner, demonstrating the industrial applicability of such cross-luminescent metascintillators.
- PublicaciónExploiting Cherenkov Radiation With BGO-Based Metascintillators(Institute of Electrical and Electronics Engineers, 2023-11) Latella, Riccardo; González Martínez, Antonio Javier; Bonifacio, Daniel A. B.; Kovylina Zabyako, Miroslavna; Griol Barres, Amadeu; Benlloch Baviera, Jose María; Lecoq, Paul; Konstantinou, Georgios; Instituto Universitario de Telecomunicación y Aplicaciones Multimedia; Instituto Universitario de Tecnología Nanofotónica; Instituto de Instrumentación para Imagen Molecular; European Commission; European Research Council; Universitat Politècnica de València; Conselho Nacional de Desenvolvimento Científico e Tecnológico, Brasil[EN] In time-of-flight positron emission tomography (TOF-PET), the timing capabilities of the scintillation-based detector play an important role. An approach for fast timing is using the so-called metascintillators, which combine two materials leading to the synergistic blending of their favorable characteristics. An added effect for BGO-based metascintillators is taking advantage of better transportation of Cherenkov photons through UV-transparent materials such as plastic (type EJ232). To prove this, we use an optimized Coincidence Time Resolution (CTR) setup based on electronic boards with two output signals (timing and energy) and near-ultraviolet (NUV) and vacuum-ultraviolet (VUV) silicon photomultipliers (SiPMs) from Fondazione Bruno Kessler (FBK), along with different coupling materials. As a reference detector, we employed a 3x3x5-mm(3) LYSO:Ce,Ca crystal pixel coupled with optical grease to an NUV-HD SiPM. The evaluation is based on low-threshold rise time, energy and time of arrival of event datasets. Timing results of a BGO/EJ232 3x3x15-mm(3) metapixel show detector time resolutions (DTRs) of 159 ps for the full photopeak. We demonstrate the possibility of event discrimination using subsets with different DTR from the rise time distributions (RTDs). Finally, we present the synergistic capability of metascintillators to enhance Cherenkov photons detection when used along with VUV-sensitive SiPMs.
- PublicaciónMetascintillators: New Results for TOF-PET Applications(Institute of Electrical and Electronics Engineers, 2022-05) Lecoq, Paul; Konstantinou, Georgios; Latella, Riccardo; Moliner Martínez, Laura; Nuyts, Johan; Zhang, Lei; Barrio Toala, John; Benlloch Baviera, Jose María; González Martínez, Antonio Javier; Departamento de Ingeniería Electrónica; Escuela Técnica Superior de Ingeniería de Telecomunicación; Instituto de Instrumentación para Imagen Molecular; European Commission; European Research Council[EN] We report on the progress on a first generation of realistic size metascintillators for time-of-flight PET. These heterostructures combine dense LYSO or BGO plates, interleaved with fast scintillator layers producing a bunch of prompt photons from the energy leakage of the recoil photoelectric electron. From a Geant4 simulation of the energy sharing distribution between the dense and the fast scintillator on 42 LYSO-based and 42 BGO-based configurations, a detailed study of the timing performance has been performed on a selection of the most promising 12 LYSO-based and 14 BGO-based metascintillators. A Monte Carlo simulation was first performed to extrapolate from direct measurements of the performance of the metascintillator components, the detector time resolution (DTR), and sensitivity on the basis of the simulated amount of energy leakage to the fast scintillator. An analytic algorithm was then applied to determine an equivalent coincidence time resolution (CTR) from the random association of the DTR distributions from two metapixels in coincidence. This equivalent CTR is calculated in order to obtain the same variance in the reconstructed image as the combination of the DTR distributions of 2 metapixels. Preliminary results confirm that with these simple and still nonoptimized configurations, an equivalent CTR of 150 ps for BGO-based and 140 ps for LYSO-based metapixels of realistic size can be obtained
- PublicaciónSemi-Monolithic Meta-Scintillator Simulation Proof-of-Concept, Combining Accurate DOI and TOF(Institute of Electrical and Electronics Engineers, 2024-05) Konstantinou, Georgios; Zhang, Lei; Bonifacio, Daniel; Latella, Riccardo; Benlloch Baviera, Jose María; González Martínez, Antonio Javier; Lecoq, Paul; Instituto de Instrumentación para Imagen Molecular; European Commission[EN] In this study, we propose and examine a unique semimonolithic metascintillator (SMMS) detector design, where slow scintillators (BGO or LYSO) are split into thin slabs and read by an array of SiPM, offering depth-of-interaction (DOI) information. These are alternated with thin segmented fast scintillators (plastic EJ232 or EJ232Q), also read by single SiPMs, which provides pixel-level coincidence time resolution (CTR). The structure combines layers of slow scintillators of size 0.3 x 25.5 x (15 or 24) mm(3) with fast scintillators of size 0.1 x 3.1 x (15 or 24) mm(3). We use a Monte Carlo Gate simulation to gauge this novel semimonolithic detector's performance. We found that the time resolution of SMMS is comparable to pixelated metascintillator designs with the same materials. For example, a 15-mm deep LYSO-based SMMS yielded a CTR of 121 ps before applying timewalk correction (after correction, 107-ps CTR). The equivalent BGO-based SMMS presented a CTR of 241 ps, which is a 15% divergence from metascintillator pixel experimental findings from previous works. We also applied neural networks to the photon distributions and timestamps recorded at the SiPM array, following guidelines on semimonolithic detectors. This led to determining the DOI with less than 3-mm precision and a confidence level of 0.85 in the best case, plus more than 2 standard deviations accuracy in reconstructing energy sharing and interaction energy. In summary, neural network prediction capabilities outperform standard energy calculation methods or any analytical approach on energy sharing, thanks to the improved understanding of photon distribution.
- PublicaciónFast Timing in Medical Imaging(Institute of Electrical and Electronics Engineers, 2023-05) Lecoq, Paul; González Martínez, Antonio Javier; Auffray, E.; Konstantinou, G.; Nuyts, J.; Prior, J. O.; Turtos, R. M.; Varela, J.; Instituto de Instrumentación para Imagen Molecular; Generalitat Valenciana[EN] We report in this article on the Fast Timing in Medical Imaging workshop, (Valencia, 2 June 2022). The workshop gathered 104 attendees from all over the world, with representatives from the academic and industrial sectors. During three very dense days, nuclear medicine physicians, radiologists, oncologists, immunologists, and biologists have debated with physicists, engineers, technologists of different disciplines, as well as with medical imaging industry representatives to devise about the importance of improving the timing performance of a new generation of medical imaging instrumentation, with a special focus on positron emission tomography scanners toward the ultimate goal of 10-ps coincidence time resolution (CTR), allowing a millimeter 3-D spatial resolution on an event-to-event basis by time-of-flight (TOF) techniques. This article summarizes the most up-to-date developments on the roadmap toward the 10-ps time of flight challenge based on the contributions to this workshop.