González Martínez, Antonio Javier
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- 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.
- PublicaciónPilot performance of a dedicated prostate PET suitable for diagnosis and biopsy guidance(SpringerOpen (part of Springer Nature), 2020-06-05) Cañizares-Ledo, Gabriel; Gonzalez-Montoro, Andrea; Freire, Marta; Lamprou, Efthymios; Barrio, John; Sánchez Martínez, Filomeno; Benlloch Baviera, Jose María; Hernandez, Liczandro; Moliner Martínez, Laura; Vidal San Sebastián, Luis Fernando; Torres, Irene; Sopena, Pablo; Vera-Donoso, Cesar D.; Bello, Pilar; Barbera, Julio; González Martínez, Antonio Javier; Instituto de Instrumentación para Imagen Molecular; European Commission; Generalitat Valenciana; European Regional Development Fund; Ministerio de Economía y Competitividad[EN] Background: Prostate cancer (PCa) represents one of the most common types of cancers facing the male population. Nowadays, to confirm PCa, systematic or multiparametric MRI-targeted transrectal or transperineal biopsies of the prostate are required. However, due to the lack of an accurate imaging technique capable to precisely locate cancerous cells in the prostate, ultrasound biopsies sample random parts of the prostate and, therefore, it is possible to miss regions where those cancerous cells are present. In spite of the improvement with multiparametric MRI, the low reproducibility of its reading undermines the specificity of the method. Recent development of prostatespecific radiotracers has grown the interest on using positron emission tomography (PET) scanners for this purpose, but technological improvements are still required (current scanners have resolutions in the range of 4¿5 mm). Results: The main goal of this work is to improve state-of-the-art PCa imaging and diagnosis. We have focused our efforts on the design of a novel prostate-dedicated PET scanner, named ProsPET. This system has small scanner dimensions defined by a ring of just 41 cm inner diameter. In this work, we report the design, implementation, and evaluation (both through simulations and real data) of the ProsPET scanner. We have been able to achieve < 2 mm resolution in reconstructed images and high sensitivity. In addition, we have included a comparison with the Philips Gemini-TF scanner, which is used for routine imaging of PCa patients. The ProsPET exhibits better contrast, especially for rod sizes as small as 4.5 mm in diameter. Finally, we also show the first reconstructed image of a PCa patient acquired with the ProsPET. Conclusions: We have designed and built a prostate specific PET system, with a small footprint and improved spatial resolution when compared to conventional whole-body PET scanners. The gamma ray impact within each detector block includes accurate DOI determination, correcting for the parallax error. The potential role of combined organdedicated prostate-specific membrane antigen (PSMA) PET and ultrasound devices, as a prebiopsy diagnostic tool, could be used to guide sampling of the most aggressive sites in the prostate.
- 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.
- PublicaciónDetector block performance based on a monolithic LYSO crystal using a novel signal multiplexing method(Elsevier, 2018-12-21) González, A.; Sánchez Martínez, Filomeno; Martí, Rosana; Hernández Hernández, Liczandro; Aguilar-Talens, Albert; BARBERA BALLESTER, JULIO; CATRET MASCARELL, JUAN VICENTE; Cañizares-Ledo, Gabriel; Conde-Castellanos, Pablo Eloy; Lamprou, Efthymios; Martos Pedrosa, Francisco; Sánchez-Góez, Sebastián; Vidal San Sebastián, Luis Fernando; Benlloch Baviera, Jose María; González Martínez, Antonio Javier; Instituto de Instrumentación para Imagen Molecular; Ministerio de Economía y Competitividad[EN] Organ dedicated PET devices provide improved imaging performance when compared to whole body systems. The present study summarizes the test carried out to study a new detector block designed for an organ dedicated PET system. This block includes three novel components namely the scintillator geometry and a retroreflector layer coupled to the entrance face, the photosensor and the readout electronics. We used arrays of 12 x 12 SiPM photosensors with 3 x 3 mm(2) active area each and a pitch of 4.2 mm. We are proposing a new readout electronics that permits to reduce the 12 row and columns signals to only 8 without significant detector performance degradation. This approach also allows for resolving radioactive sources in the whole volume of the proposed crystal, significantly reducing the edge effect that typically rejects these events. An overall spatial resolution of about 1.8 mm FWHM is obtained for the whole scintillation volume, with an average energy resolution of 13% FWHM and a photon depth of interaction resolution (FWHM) of 3.7 mm. (C) 2018 Elsevier B.V. All rights reserved.
- PublicaciónTOF studies for dedicated PET with open geometries(IOP Publishing, 2019-02) Moliner Martínez, Laura; Ilisie, V.; González Martínez, Antonio Javier; Oliver Gil, Sandra; Gonzalez, A.; Giménez-Alventosa, Vicent; Cañizares, G.; Lamprou, E.; Alamo, J.; Rodríguez Álvarez, María José; Sánchez Martínez, Filomeno; Benlloch Baviera, Jose María; Departamento de Física Aplicada; Departamento de Matemática Aplicada; Escuela Técnica Superior de Ingeniería Industrial; Instituto Universitario de Seguridad Industrial, Radiofísica y Medioambiental; Escuela Técnica Superior de Ingeniería Informática; Instituto de Instrumentación para Imagen Molecular; European Commission; Ministerio de Economía y Competitividad[EN] Recently, two novel PET devices have been developed with open geometries, namely: breast and prostate-dedicated scanners. The breast-dedicated system comprises two detector rings of twelve modules with a field of view of 170 mm x 170 mm x 94 mm. Each module consists of a continuous trapezoidal LYSO crystal and a PSPMT. The system has the capability to vary the opening of the rings up to 60 mm in order to allow the insertion of a needle to perform a biopsy procedure. The prostate system has an open geometry consisting on two parallel plates separated 28 cm. One panel includes 18 detectors organized in a 6 x 3 matrix while the second one comprises 6 detectors organized in a 3 x 2 matrix. All detectors are formed by continuous LYSO crystals of 50 mm x 50 mm x15 mm, and a SiPM array of 12 x 12 individual photo-detectors. The system geometry is asymmetric maximizing the sensitivity of the system at the prostate location, located at about 2/3 in the abdomen-anus distance. The reconstructed images for PET scanners with open geometries present severe artifacts due to this peculiarity. These artifacts can be minimized using Time Of Flight information (TOF). In this work we present a TOF resolution study for open geometries. With this aim, the dedicated breast and prostate systems have been simulated using GATE (8.1 version) with different TOF resolutions in order to determine the image quality improvements that can be achieved with the existing TOF-dedicated electronics currently present in the market. The images have been reconstructed using the LMOS algorithm including TOF modeling in the calculation of the voxel-Line Of Response emission probabilities.
- PublicaciónExploring TOF Capabilities of PET Detector Blocks Based on Large Monolithic Crystals and Analog SiPMs(Elsevier, 2020-02) Lamprou, Efthymios; González Martínez, Antonio Javier; Sánchez Martínez, Filomeno; Benlloch Baviera, Jose María; Instituto de Instrumentación para Imagen Molecular; European Commission; Ministerio de Economía y Competitividad[EN] Monolithic scintillators are more frequently used in PET instrumentation due to their advantages in terms of accurate position estimation of the impinging gamma rays both planar and depth of interaction, their increased efficiency, and expected timing capabilities. Such timing performance has been studied when those blocks are coupled to digital photosensors showing an excellent timing resolution. In this work we study the timing behaviour of detectors composed by monolithic crystals and analog SiPMs read out by an ASIC. The scintillation light spreads across the crystal towards the photosensors, resulting in a high number of SiPMs and ASIC channels fired. This has been studied in relation with the Coincidence Timing Resolution (CTR). We have used LYSO monolithic blocks with dimensions of 50 x 50 x 15 mm(3) coupled to SiPM arrays (8 x 8 elements with 6 x 6 mm(2) area) which compose detectors suitable for clinical applications. While a CTR as good as 186 ps FWHM was achieved for a pair of 3 x 3 x 5 mm(3) LYSO crystals, when using the monolithic block and the SiPM arrays, a raw CTR over 1 ns was observed. An optimal timestamp assignment was studied as well as compensation methods for the time-skew and time-walk errors. This work describes all steps followed to improve the CTR. Eventually, an average detector time resolution of 497 ps FWHM was measured for the whole thick monolithic block. This improves to 380 ps FWHM for a central volume of interest near the photosensors. The timing dependency with the photon depth of interaction and planar position are also included.
- PublicaciónProgress report on the MEDAMI 2019 and CTR research at the DMIL in i3M(Società italiana di fisica, 2020-02) González Martínez, Antonio Javier; Barrio, J.; Lamprou, E.; Ilisie, Victor; Sánchez Martínez, Filomeno; Benlloch Baviera, Jose María; Instituto de Instrumentación para Imagen Molecular; European Commission; Ministerio de Economía y Competitividad[EN] This contribution reports on the recently held MEDAMI 2019 workshop in Valencia (15-17th May 2019). This workshop is about advanced molecular imaging and the main topic of this last edition was Imaging in Immunotherapy. Around 70 attenders met together during three days. This meeting made it possible to join medical doctors and instrumentalists. In MEDAMI 2019 it was exposed the new immunotherapies from a clinical and research point of view. It was shown the already observed improvements when using these therapies. At the same time, we heard about the difficulties and limitations of current molecular imaging in this particular field. It was clear that improvements in system sensitivity and resolution are demanded. Timing information can be utilized in different ways to improve the image quality in PET systems. Precise Coincidence Time Resolution (CTR) improves the signal-to-noise ratio and, therefore, the image contrast, allowing for instance to distinguish low uptake tumors, multicentric lesions, or tumor heterogeneity, to name but a few. Both high time resolution and angular coverage in a PET system can improve the effective sensitivity. An example of a system benchmarking the timing resolution is the Siemens Biograph Vision with 214 ps FWHM, enhancing the detectability. The Explorer total-body PET from UC Davis improves the system sensitivity by having a 2 meters long PET scanner. Deep investigations, from different research groups, are being carried out to further push the limits of timing resolution. This work also describes some of the projects on high timing performance that are being carried out at the Detector for Molecular Imaging Lab (DMIL) at the Institute for Instrumentation in Molecular Imaging (i3M) in Valencia. The DMIL group has extensively worked on detectors and implementation of PET systems enabling the use of accurate timing information. In this progress report we describe the results obtained at the DMIL regarding timing determination in gamma-ray detectors both based on monolithic and pixelated crystals. Although with 15 min thick LYSO blocks it was tough to obtain values of CTR below 500 ps when using analog SiPMs and ASIC-based readout, this was improved down to 250 ps if small 3 mm size and 6 mm height pixels under the one-to-one coupling approach were enabled. This type of approach, the one-to-one coupling, seems to benefit from the light collection in a single photosensor element and, therefore, to improve the timing properties. Monolithic blocks offer, on the contrary, advantages such as photon depth of interaction. In order to separate Compton and photoelectric events we have thought of a detector block design with a high aspect ratio, using LYSO crystals of 51 mm size vs. 3 mm thickness, read-out by the four lateral sides. We have demonstrated the possibility to reach below 2 mm FWHM spatial resolution with an energy resolution of 12%.
- PublicaciónA scintillator geometry suitable for very small PET gantries(IOP Publishing, 2017-12-11) González Martínez, Antonio Javier; Gonzalez-Montoro, A.; Aguilar, A.; Cañizares, G.; Martí, R.; Iranzo, S.; Lamprou, E.; Sánchez, S.; Sánchez Martínez, Filomeno; Benlloch Baviera, Jose María; Instituto de Instrumentación para Imagen Molecular; European Commission; Ministerio de Economía y Competitividad; Secretaría de Estado de Investigación, Desarrollo e Innovación