González Martínez, Antonio Javier
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- PublicaciónCharacterization of protons accelerated from a 3 TW table-top laser system(IOP Publishing, 2017-05) Bellido-Millán, Pablo Jesús; Lera, Roberto; Seimetz, Michael; Ruiz-de la Cruz, Alexandro; Torres Peiró, Salvador; Galán, M.; Mur, P.; Sánchez, I.; Zaffino, R.; Vidal San Sebastián, Luis Fernando; Soriano Asensi, Antonio; Sánchez-Góez, Sebastián; Sánchez Martínez, Filomeno; Rodríguez Álvarez, María José; Rigla, J.P.; Moliner Martínez, Laura; Iborra Carreres, Amadeo; Hernández Hernández, Liczandro; Grau-Ruiz, Daniel; González Martínez, Antonio Javier; García Garrigós, Juan José; Díaz Caballero, Elena; Conde-Castellanos, Pablo Eloy; Aguilar-Talens, Albert; Roso, Luis; Benlloch Baviera, Jose María; Departamento de Matemática Aplicada; Escuela Técnica Superior de Ingeniería Informática; Instituto de Instrumentación para Imagen Molecular; Ministerio de Economía y Competitividad; Ministerio de Ciencia e Innovación[EN] We report on benchmark tests of a 3 TW/50 fs, table-top laser system specifically developed for proton acceleration with an intrinsic pump rate up to 100 Hz. In two series of single-shot measurements differing in pulse energy and contrast the successful operation of the diode pumped laser is demonstrated. Protons have been accelerated up to 1.6 MeV in interactions of laser pulses focused on aluminium and mylar foils between 0.8 and 25 mu m thickness. Their spectral distributions and maximum energies are consistent with former experiments under similar conditions. These results show the suitability of our system and provide a reference for studies of laser targets at high repetition rate and possible applications.
- PublicaciónEffect of noise in CT image reconstruction using QR- Decomposition algorithm(IEEE, 2013-11-02) Iborra, A.; Rodríguez Álvarez, María José; Soriano, A.; Sánchez Martínez, Filomeno; Bellido, P.; Conde, P.; Crespo, E.; González Martínez, Antonio Javier; Martos, F.; Moliner Martínez, Laura; Rigla, J. P.; Seimetz, Michael; Vidal San Sebastián, Luis Fernando; Benlloch Baviera, Jose María; Departamento de Matemática Aplicada; Escuela Técnica Superior de Ingeniería Informática; Instituto de Instrumentación para Imagen Molecular; Generalitat Valenciana; Ministerio de Ciencia e Innovación[EN] The QR-Decomposition algorithm for CT 3D image reconstruction uses a linear system of equations to model the CT system response. Linear systems have a condition number that can be used to estimate the image noise. In this work the number of projections and the number of pixels in the detector have been studied to characterize the CT and the linear system of equations. The condition number of the system is estimated for the previous parameters used to generate the CT model with the aim of characterizing how these parameters affect the condition number and therefore bound the image noise level. It is shown that the condition number mainly depends on the size of pixels of the detector rather than the number of projections and this algorithm can be applied to low dose CT 3D image reconstruction without compromising image quality
- PublicaciónMotion Correction of Multi-Frame PET Data(IEEE, 2019-11-02) Cañizares, Gabriel; Espinós-Morató, Héctor; Santos Blasco, Joaquín; Hernández, Ángel; Moliner Martínez, Laura; Álvarez-Gómez, Juan Manuel; González Martínez, Antonio Javier; Sánchez Martínez, Filomeno; Rodríguez Álvarez, María José; Benlloch Baviera, Jose María; Departamento de Matemática Aplicada; Escuela Técnica Superior de Ingeniería Informática; Instituto de Instrumentación para Imagen Molecular[EN] Motion correction algorithms are necessary in PET studies where the patient cannot remain totally static. Otherwise, artifacts appear in the final reconstructed image, degrading the spatial resolution or even misplacing the radiation distribution source. In this work we propose a new enhanced motion correction algorithm (EMAF) based on the multiple acquisition frames (MAF). This methodology can be applied to two PET system geometries (a ring and a multi-panel system). Using simulated data, the comparison of static and motion corrected profiles shows minimum differences keeping more than 99% of the events after the process, with a minimal inter-frame error (the maximum range of loss counts is around 0.6%). To measure the quality of the correction method, two error metrics as peak signal to noise ratio (PSNR) and intensity matching precision (IMP) are proposed. A Mini-Derenzo in a ring PET system reveals a remarkable improvement both for these two metrics (44.5 dB and 98.7%) when compared to the uncorrected images (41.1 dB and 56%, respectively). An equivalent analysis for a point-like source also shows a sizeable enhancement both in contrast and resolution (64 dB and 98% versus 62.5 dB and 17.9%, PSNR and IMP correspondingly). The proposed algorithm minimizes the image artifacts and its simplicity, independency of PET configuration system and rapid reconstruction and registration times, makes it a useful tool in preclinical PET studies.
- PublicaciónPerformance Evaluation of the Dual Ring MAMMI breast PET(IEEE, 2013-11-02) Soriano, A.; Sánchez Martínez, Filomeno; Carrilero, V.; Pardo, A.; Vidal San Sebastián, Luis Fernando; Vazquez, C.; Barbera, J.; Seimetz, Michael; Rodríguez Álvarez, María José; Rigla, J. P.; Moliner Martínez, Laura; Iborra, A.; Hernández, L.; González Martínez, Antonio Javier; Crespo, E.; Conde, P.; Bellido, P.; Caballero, L.; Benlloch Baviera, Jose María; Departamento de Matemática Aplicada; Escuela Técnica Superior de Ingeniería Informática; Instituto de Instrumentación para Imagen Molecular; Generalitat Valenciana; Ministerio de Ciencia e Innovación[EN] MAMMI is a dedicated breast positron emission tomograph (PET) based on monolythic LYSO crystals, with a transaxial field of view (FOV) of 170 mm. It has been upgraded by adding a second ring of detectors that extends the axial FOV from 40 mm to 94.4 mm, in order to improve its sensitivity and reduce the acquisition time. In this work we present the performance evaluation of the dual ring MAMMI breast PET and a discussion about the contribution of the addition of a second ring of detectors, the compensation of the detector blur and the increase of the scintillator thickness. Experimental measurements suggested on NEMA NU 4-2008 and NEMA NU 2-2007 have been conveniently adapted to the dimensions of the MAMMI. The addition of the second ring of detectors leads to a rise of the sensitivity from 1.8% to 3.6%. The spatial resolution at one-fourth of the axial FOV (1.5 mm axial, 1.6 mm tangential, 1.7 mm radial) is slightly better than that measured at the axial center (1.9 mm axial, 1.8 mm tangential and radial), because of the 14 mm gap in between detection rings. The results obtained after the evaluation reflect a substantial performance improvement, specially in the absolute sensitivity, because of the changes introduced in the MAMMI PET.
- PublicaciónTime reconstruction study using tubes of response backprojectors in List Mode algorithms, applied to amonolithic crystals based breast PET(IEEE, 2013-11-02) Moliner Martínez, Laura; Correcher, C.; González Martínez, Antonio Javier; Conde, P.; Crespo, E.; Hernandez, L.; Rigla, J. P.; Rodríguez Álvarez, María José; Sánchez Martínez, Filomeno; Soriano, A.; Iborra, A.; Bellido, P.; Seimetz, Michael; Vidal San Sebastián, Luis Fernando; Benlloch Baviera, Jose María; Departamento de Matemática Aplicada; Escuela Técnica Superior de Ingeniería Informática; Instituto de Instrumentación para Imagen Molecular; Generalitat Valenciana; Ministerio de Ciencia e Innovación[EN] The LM-EM algorithm has the advantage to calculate the emission probabilities needed for the reconstruction process on the fly, without the need of a pre-calculated system matrix. The reconstruction time for this algorithm strongly depends on the used backprojector and the available statistics. This algorithm when implemented in systems using monolithic crystals to detect gamma radiation allows one to extensively exploit the virtual pixilation feature, not available for systems based on pixilated crystals. In this work we present a backprojector for LM-EM, the TOR method, which achieves a tradeoff between computational efficiency and image quality. Its temporal subset algorithm optimization (LM-OS) has also been implemented in order to achieve real-time reconstructions. To evaluate the performances of LM-OS algorithm with the TOR method backprojector and only with one iteration on the datasets, studies based on the system spatial resolution, uniformity, and contrast coefficients were carried out and they were compared with those obtained with LM-EM and MLEM algorithms using twelve iteration. Finally, a study on reconstruction time using LM-OS has been performed with breast patients data
- PublicaciónEM tomographic image reconstruction using polarvoxels(Institute of Physics: Hybrid Open Access, 2013-01) Soriano Asensi, Antonio; Rodríguez Álvarez, María José; Iborra Carreres, Amadeo; Sánchez Martínez, Filomeno; Carles Fariña, Montserrat; Conde Castellanos, Pablo Eloy; González Martínez, Antonio Javier; Hernández Hernández, Liczandro; Moliner Martínez, Laura; Orero Palomares, Abel; Vidal San Sebastián, Luis Fernando; Benlloch Baviera, Jose María; Departamento de Matemática Aplicada; Escuela Técnica Superior de Ingeniería Informática; Instituto de Instrumentación para Imagen Molecular; Comisión Interministerial de Ciencia y Tecnología; Generalitat Valenciana; Ministerio de Ciencia e Innovación[EN] The splitting of the field of view (FOV) in polar voxels is proposed in this work in order to obtain an efficient description of a cone-beam computed tomography (CT) scanner. The proposed symmetric-polar pixelation makes it possible to deal with the 3D iterative reconstruction considering a number of projections and voxel sizes typical in CT preclinical imaging. The performance comparison, between the filtered backprojection (FBP) and 3D maximum likelihood expectation maximization (MLEM) reconstruction algorithm for CT, is presented. It is feasible to achieve the hardware spatial resolution limit with the considered pixelation. The image quality achieved with MLEM and FBP have been analyzed. The results obtained with both algorithms in clinical images have been compared too. Although the polar-symmetric pixelation is presented in the context of CT imaging, it can be applied to any other tomographic technique as long as the scan comprises the measurement of an object under several projection angles.
- PublicaciónHigh resolution and sensitivity gamma camera with active septa. A first Monte Carlo study(Nature Publishing Group, 2019-12-05) Ilisie, Victor; Moliner Martínez, Laura; Oliver Gil, Sandra; Sánchez Martínez, Filomeno; González Martínez, Antonio Javier; Seimetz, Michael; Rodríguez Álvarez, María José; 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; Generalitat Valenciana; Ministerio de Economía y Competitividad[EN] Gamma cameras are of great interest due to their high potential in the field of Nuclear Medicine Imaging. They allow for an early diagnosis of reduced size tumors, and also for a wide variety of preclinical studies with the aim of designing more effective treatments against cancer. In this work we propose a significantly improved multi-pinhole collimator gamma camera and perform a first Monte Carlo analysis of its characteristics. Maintaining the configuration of a multi-pinhole collimator with a high degree of overlapping (thus with a high sensitivity), we add a new element, an active septa, that besides acting as a collimator, is able to measure the impact coordinates of the incident photon. This way one is able to unambiguously identify through which pinhole any gamma ray passes before being detected. The result is a high sensitivity and resolution multi-pinhole gamma camera with an arbitrarily large field of view. As a consequence, the final reconstructed image does not suffer from the undesired artifacts or truncation associated to the multiplexing phenomenon. In this study we focus on the development of a system able to visualize in 3D tumors, nodes and metastasis in real time in the operating room with very low dose. We also briefly analyse and propose a novel design for a Single Photon Emission Computed Tomography system.
- PublicaciónBuilding blocks of a multi-layer PET with time sequence photon interaction discrimination and double Compton camera(Elsevier, 2018) Ilisie, V.; Giménez-Alventosa, Vicent; Moliner Martínez, Laura; Sánchez Martínez, Filomeno; González Martínez, Antonio Javier; Rodríguez Álvarez, María José; Benlloch Baviera, Jose María; Departamento de Matemática Aplicada; Escuela Técnica Superior de Ingeniería Informática; Instituto de Instrumentación para Imagen Molecular; Ministerio de Economía y Competitividad; European Commission[EN] Current PET detectors have a very low sensitivity, of the order of a few percent. One of the reasons is the fact that Compton interactions are rejected. If an event involves multiple Compton scattering and the total deposited energy lays within the photoelectric peak, then an energy-weighted centroid is the given output for the coordinates of the reconstructed interaction point. This introduces distortion in the final reconstructed image. The aim of our work is to prove that Compton events are a very rich source of additional information as one can improve the resolution of the detector and implicitly the final reconstructed image. This could be a real breakthrough for PET detector technology as one should be able to obtain better results with less patient radiation. Using a PET as a double Compton camera, by means of Compton cone matching i.e., Compton cones coming from the same event should be compatible, is applied to discard randoms, patient scattered events and also, to perform a correct matching among events with multiple coincidences. In order to fully benefit experimentally from Compton events using monolithic scintillators a multi-layer configuration is needed and a good time-of-flight resolution.
- 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.
- PublicaciónStatistical moments of scintillation light distribution analysis with dSiPMs and monolithic crystals(IEEE, 2013-11-02) Conde, P.; González Martínez, Antonio Javier; Hernández, L.; Bellido, P.; Crespo, E.; Iborra, A.; Moliner Martínez, Laura; Rigla, J. P.; Rodríguez Álvarez, María José; Sánchez Martínez, Filomeno; Seimetz, Michael; Soriano, A.; Vidal San Sebastián, Luis Fernando; Benlloch Baviera, Jose María; Departamento de Matemática Aplicada; Escuela Técnica Superior de Ingeniería Informática; Instituto de Instrumentación para Imagen Molecular; Generalitat Valenciana; Ministerio de Ciencia e Innovación[EN] Monolithic scintillation crystals offer the possibility to preserve the scintillation light distribution, specially when black painted. Furthermore, the statistical moments of that distribution can provide accurate information about the three spatial components. Nevertheless, for monolithic crystal the moments estimation has an associated error due to the symmetry truncation of the light distribution towards the crystal borders. For the 2-D impact coordinates determination, this error is called compression as it is accentuated near the edges. The computation of all centered moments is, therefore, affected by this error. Digital SiPMs (dSiPMs) can offer complete information about the light distribution, since all cells are purely digital detectors, so that other ways to obtain ¿-impact coordinates can be performed. In this work, a comparison between the statistical moments analysis and an alternative fitting the light distribution for each event to a theoretical distribution has been made. With the fitted approach, compression is avoided and an approximately constant spatial resolution is obtained for the entire photodetection area. Moreover, DOI information is improved and preserved all over the crystal.