González Martínez, Antonio Javier
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- PublicaciónCalibration of Gamma Ray Impacts in Monolithic-Based Detectors Using Voronoi Diagrams(Institute of Electrical and Electronics Engineers, 2020-05) Freire, Marta; Gonzalez-Montoro, Andrea; Sánchez Martínez, Filomeno; Benlloch Baviera, Jose María; González Martínez, Antonio Javier; Instituto de Instrumentación para Imagen Molecular; European Commission; Ministerio de Economía y Competitividad[EN] Molecular imaging systems, such as positron emission tomography (PET), use detectors providing energy and a 3-D interaction position of a gamma ray within a scintillation block. Monolithic crystals are becoming an alternative to crystal arrays in PET. However, calibration processes are required to correct for nonuniformities, mainly produced by the truncation of the scintillation light distribution at the edges. We propose a calibration method based on the Voronoi diagrams. We have used $50 \times 50 \times 15$ mm(3) LYSO blocks coupled to a $12\times 12$ SiPMs array. We have first studied two different interpolation algorithms: 1) weighted average method (WAM) and 2) natural neighbor (NN). We have compared them with an existing calibration based on 1-D monomials. Here, the crystal was laterally black painted and a retroreflector (RR) layer added to the entrance face. The NN exhibited the best results in terms of XY impact position, depth of Interaction, and energy, allowing us to calibrate the whole scintillation volume. Later, the NN interpolation has been tested against different crystal surface treatments, allowing always to correct edge effects. Best energy resolutions were observed when using the reflective layers (12%-14%). However, better linearity was observed with the treatments using black paint. In particular, we obtained the best overall performance when lateral black paint is combined with the RR.
- PublicaciónIn-depth evaluation of TOF-PET detectors based on crystal arrays and the TOFPET2 ASIC(Elsevier, 2020-10-11) Lamprou, Efthymios; Sánchez Martínez, Filomeno; Benlloch Baviera, Jose María; González Martínez, Antonio Javier; Instituto de Instrumentación para Imagen Molecular; European Commission; Generalitat Valenciana; Ministerio de Economía y Competitividad[EN] In recent years high efforts have been devoted to enhance spatial and temporal resolutions of PET detectors. However, accurately combining these two main features is, in most of the cases, challenging. Typically, a compromise has to be made between the number of readout channels, scintillator type and size, and photosensors arrangement if aiming for a good system performance, while keeping a moderate cost. In this work, we have studied several detector configurations for PET based on a set of 8x8 Silicon Photomultiplier (SiPMs) of 3x3 mm(2) active area, and LYSO crystal arrays with different pixel sizes. An exhaustive evaluation in terms of spatial, energy and timing resolution was made for all detector configurations. In some cases, when using pixel sizes different than SiPM active area, a significant amount of scintillation light may spread among several SiPMs. Therefore, we made use of a calibration method considering the different SiPM timing contributions. Best Detector Time Resolution (DTR) of 156 ps FWHM was measured when using 3x3 mm(2) crystal pixels directly coupled to the 3x3 mm(2) SiPMs. However, when using 1.5 mm crystal pixels with the same photosensor array, although we could clearly resolve all crystal pixels, an average DTR of 250 ps FWHM was achieved. We also shed light in this work on the timing dependency of the crystal pixel and photosensor alignment.
- PublicaciónFeasibility Study of a Small Animal PET Insert Based on a Single LYSO Monolithic Tube(Frontiers Media, 2018-11-28) González Martínez, Antonio Javier; Berr, Stuart S.; Cañizares-Ledo, Gabriel; Gonzalez-Montoro, Andrea; Orero Palomares, Abel; Correcher Salvador, Carlos; Rezaei, Ahmadreza; Nuyts, Johan; Sánchez Martínez, Filomeno; Majewski, Stan; Benlloch Baviera, Jose María; Instituto de Instrumentación para Imagen Molecular; European Commission; Ministerio de Economía y Competitividad; Research Foundation Flanders; University of Virginia[EN] There are drawbacks with using a Positron Emission Tomography (PET) scanner design employing the traditional arrangement of multiple detectors in an array format. Typically PET systems are constructed with many regular gaps between the detector modules in a ring or box configuration, with additional axial gaps between the rings. Although this has been significantly reduced with the use of the compact high granularity SiPM photodetector technology, such a scanner design leads to a decrease in the number of annihilation photons that are detected causing lower scanner sensitivity. Moreover, the ability to precisely determine the line of response (LOR) along which the positron annihilated is diminished closer to the detector edges because the spatial resolution there is degraded due to edge effects. This happens for both monolithic based designs, caused by the truncation of the scintillation light distribution, but also for detector blocks that use crystal arrays with a number of elements that are larger than the number of photosensors and, therefore, make use of the light sharing principle. In this report we present a design for a small-animal PET scanner based on a single monolithic annulus-like scintillator that can be used as a PET insert in high-field Magnetic Resonance systems. We provide real data showing the performance improvement when edge-less modules are used. We also describe the specific proposed design for a rodent scanner that employs facetted outside faces in a single LYSO tube. In a further step, in order to support and prove the proposed edgeless geometry, simulations of that scanner have been performed and lately reconstructed showing the advantages of the design.
- PublicaciónInnovative PET detector concept based on SiPMs and continuous crystals(Elsevier, 2012-12-11) González Martínez, Antonio Javier; Peiró Cloquell, Antonio; Sánchez Martínez, Filomeno; Vidal San Sebastián, Luis Fernando; Benlloch Baviera, Jose María; Instituto de Instrumentación para Imagen MolecularThe use of Silicon Photomultipliers (SiPM) has been proposed for Positron Emission Tomography (PET) readout because they are hardly affected by magnetic fields and their time response enables Time of Flight measurements. This work proposes an array of SiPM to be coupled to a monolithic LYSO crystal by means of a series of optical devices. The emitted light distribution by the scintillation crystal will be accurately determined using an Application Specific Integrated Circuit. The described sensor block aims to determine the planar coordinates and depth of interaction of the gamma ray with sub-millimetrical precision. In this work we present the initial studies regarding edge effects due to thick monolithic crystals and how to overcome these limitations by means of optical devices namely faceplates and light concentrators. We will also discuss on the alignment of such optical devices with the SiPMs
- PublicaciónPET detector block with accurate 4D capabilities(Elsevier, 2018-12-21) Lamprou, Efthymios; Aguilar -Talens, Albert; Gonzalez-Montoro, Andrea; Monzó Ferrer, José María; Cañizares-Ledo, Gabriel; Iranzo-Egea, Sofía; Vidal San Sebastián, Luis Fernando; Hernández Hernández, Liczandro; Conde-Castellanos, Pablo Eloy; Sánchez-Góez, Sebastián; Sánchez Martínez, Filomeno; González Martínez, Antonio Javier; Benlloch Baviera, Jose María; Departamento de Ingeniería Electrónica; Escuela Técnica Superior de Ingeniería de Telecomunicación; Instituto de Instrumentación para Imagen Molecular; European Commission; Ministerio de Economía y Competitividad[EN] In this contribution, large SiPM arrays (8 x 8 elements of 6 x 6 mm(2) each) are processed with an ASIC-based readout and coupled to a monolithic LYSO crystal to explore their potential use for TOF-PET applications. The aim of this work is to study the integration of this technology in the development of clinical PET systems reaching sub-300 ps coincidence resolving time (CRT). The SiPM and readout electronics have been evaluated first, using a small size 1.6 mm (6 mm height) crystal array (32 x 32 elements). All pixels were well resolved and they exhibited an energy resolution of about 20% (using Time-over-Threshold methods) for the 511 keV photons. Several parameters have been scanned to achieve the optimum readout system performance, obtaining a CRT as good as 330 +/- 5 ps FWHM. When using a black-painted monolithic block, the spatial resolution was measured to be on average 2.6 +/- 0.5 mm, without correcting for the source size. Energy resolution appears to be slightly above 20%. CRT measurements with the monolithic crystal detector were also carried out. Preliminary results as well as calibration methods specifically designed to improve timing performance, are being analyzed in the present manuscript.
- 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.
- PublicaciónCharacterization of a High-Aspect Ratio Detector With Lateral Sides Readout for Compton PET(Institute of Electrical and Electronics Engineers, 2020-09) Barrio, John; Cucarella, Neus; González Martínez, Antonio Javier; Freire, Marta; Ilisie, Victor; Benlloch Baviera, Jose María; Instituto de Instrumentación para Imagen Molecular; European Commission