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295 results on '"Pavia J"'

2. Exploring APOE genotype effects on Alzheimer's disease risk and amyloid β burden in individuals with subjective cognitive decline: The FundacioACE Healthy Brain Initiative (FACEHBI) study baseline results

Author

Abdelnour, C., Aguilera, N., Alegret, M., Berthier, M., Boada, M., Buendia, M., Bullich, S., Campos, F., Cañabate, P., Cuevas, C., de Rojas, I., Espinosa, A., Gailhajenet, A., Diego, S., Gil, S., Giménez, J., Gismondi, R., Gómez-Chiari, M., Guitart, M., Hernández-Olasagarre, B., Hernández, I., Ibarria, M., Lafuente, A., Lomeña, F., Martín, E., Martínez, J., Mauleón, A., Monté, G., Moreno, M., Moreno-Grau, S., Núñez, L., Orellana, A., Ortega, G., Páez, A., Pancho, A., Pavía, J., Pelejà, E., Pérez-Cordon, A., Pérez-Grijalba, V., Pesini, P., Preckler, S., Rodríguez-Gómez, O., Romero, J., Rosende-Roca, M., Ruiz, A., Ruiz, S., Sanabria, A., Sánchez-Ruiz, D., Santos-Santos, M.A., Sarasa, M., Sotolongo-Grau, O., Tárraga, L., Tejero, M.A., Torres, M., Valero, S., Vargas, L., Vivas, A., Moreno–Grau, Sonia, Rodríguez-Gómez, Octavio, Sanabria, Ángela, Pérez-Cordón, Alba, Sánchez-Ruiz, Domingo, Abdelnour, Carla, Valero, Sergi, Hernández, Isabel, Rosende-Roca, Maitée, Mauleón, Ana, Vargas, Liliana, Lafuente, Asunción, Gil, Silvia, Santos-Santos, Miguel Ángel, Alegret, Montserrat, Espinosa, Ana, Ortega, Gemma, Guitart, Marina, Gailhajanet, Anna, de Rojas, Itziar, Sotolongo-Grau, Óscar, Ruiz, Susana, Aguilera, Nuria, Papasey, Judith, Martín, Elvira, Peleja, Esther, Lomeña, Francisco, Campos, Francisco, Vivas, Assumpta, Gómez-Chiari, Marta, Tejero, Miguel Ángel, Giménez, Joan, Serrano-Ríos, Manuel, Orellana, Adelina, Tárraga, Lluís, Ruiz, Agustín, and Boada, Mercè

Published
2018
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5. QuantiDOPA: A Quantification Software for Dopaminergic Neurotransmission SPECT

Author

Niñerola, A., Marti, B., Esteban, O., Planes, X., Frangi, A. F., Ledesma-Carbayo, M. J., Santos, A., Cot, A., Lomeña, F., Pavia, J., Ros, D., Magjarevic, Ratko, Editor-in-chief, Ładyzynsk, Piotr, Series editor, Ibrahim, Fatimah, Series editor, Lacković, Igor, Series editor, Rock, Emilio Sacristan, Series editor, and Roa Romero, Laura M., editor

Published
2014
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13. Geometrical response modeling in fan-beam collimators--a numerical simulation

Author

Pareto, D., Cot, A., Falcon, C., Juvells, I., Pavia, J., and Ros, D.

Subjects
Collimators (Optical instrument) -- Models, Algorithms -- Analysis, SPECT imaging -- Analysis, Business, Electronics, Electronics and electrical industries
Abstract

Iterative reconstruction algorithms require modeling of the point spread function (PSF) of the collimator in order to correct the loss of resolution in single photon emission computed tomography (SPECT). A method for modeling the geometric response of a fan-beam collimator is proposed. The geometric PSF is obtained by numerical simulation based on ray-tracing techniques. The versatility of the numerical simulation allows us to generate the array of holes with a distance between them varying as an angular function. This enables us to reproduce the real distribution of holes. The integral of the simulated PSF was calculated in order to determine the relative sensitivity and Gaussian functions were fitted to obtain the resolution. Functions depending on the intrinsic collimator parameters and on the coordinates of the source were fitted to the individual PSF. To validate the functions proposed, a comparison-between the predicted values and those obtained from experimental measures was made. Our findings show that the predicted values for relative sensitivity and resolution accurately match the experimental ones, with a correlation coefficient of 0.992 for the sensitivity and 0.994 for the resolution. Index Terms--Collimator modeling, fan beam, geometric point spread function, ray tracing, single photon emission computed tomography (SPECT).

Published
2002

14. Evaluation of the geometric, scatter, and septal penetration components in fan-beam collimators using Monte Carlo simulation

Author

Cot, A., Sempau, J., Pareto, D., Bullich, S., Pavia, J., Calvino, F., and Ros, D.

Subjects
Nuclear engineering -- Research, Monte Carlo method -- Usage, Collimators (Optical instrument) -- Research, SPECT imaging -- Research, Business, Electronics, Electronics and electrical industries
Abstract

The quantitative analysis of single-photon emission computed tomography data requires an accurate determination of the collimator point spread function (PSF). The aim of this paper is to characterize fan-beam collimators' PSFs by using Monte Carlo simulation. Given a particular collimator configuration, a detailed hexagonal hole array was generated and information describing its geometry was stored in a lookup table. When a photon crossed the collimator front plane, a hole array was placed around its impact position using this table. Each photon was then tracked up to the detector surface by using the Monte Carlo code PENELOPE and its associated geometry handling routines. Particle counters were defined that score the probability of impact on the detector as a function of the final photon position. Four sets of counters were employed so as to differentiate contributions to the geometric, septal penetration, coherent (Rayleigh), and incoherent (Compton) scatter components. Furthermore, sensitivity quantification was calculated for different source locations. Monte Carlo results were compared with sensitivity values obtained experimentally, and good agreement was found. Our results show that for [sup.99m]Tc imaging, the geometric component represents about 95% of the fan-beam PSF, whereas the incoherent scattering component is negligible. Index Terms--Fan-beam collimator, Monte Carlo simulation, single photon emission computed tomography (SPECT).

Published
2002

35. Correlación de la captación de 18 F-FDG de la PET/TC con el Ki67 de la inmunohistoquímica en el cáncer epitelial de ovario pretratamiento

Author

Mayoral, M., primary, Paredes, P., additional, Saco, A., additional, Fusté, P., additional, Perlaza, P., additional, Tapias, A., additional, Fernandez-Martinez, A., additional, Vidal, L., additional, Ordi, J., additional, Pavia, J., additional, Martinez-Roman, S., additional, and Lomeña, F., additional

Published
2018
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42. Reduced myocardial F-18-FDG uptake after calcium channel blocker administration. Initial observation for a potential new method to improve plaque detection

Author

Gaeta, C, Fernandez, Y, Pavia, J, Flotats, A, Artigas, C, Deportos, J, Geraldo, L, and Carrio, I

Subjects
F-18-FDG, Calcium channel blocker, Mice, PET, Coronary atherosclerosis
Abstract

Purpose Physiological glucose uptake by the myocardium may hamper visualization of coronary atherosclerotic plaques in F-18-FDG PET studies. Intracellular myocardial calcium relates to glucose influx. We assessed whether administration of a calcium channel blocker such as verapamil could decrease myocardial F-18-FDG uptake in mice. Methods Experiments were conducted on ten male C57BL/6JOlaHsd mice. The mice were studied by F-18-FDG PET/CT under basal conditions and after a single administration of verapamil injected 1 h prior to F-18-FDG administration at doses of 1 mg/kg (group A, n = 5) and 20 mg/kg (group B, n = 5). PET scanning was started 60 min after injection of F-18-FDG employing a dedicated small-animal PET/CT system (ARGUS-CT). In each mouse, post-verapamil PET images were coregistered with the basal PET images. Volumetric regions of interest (VOI) were drawn on the basal study containing the myocardium of the whole left ventricle and quantitatively compared with the same VOI applied to the post-verapamil scan. The SUVmean was used to express the mean myocardial F-18-FDG uptake. The relative coefficient of variation (RV) between the basal and post-verapamil conditions was calculated. Results Verapamil administration decreased myocardial F-18-FDG uptake in all animals. The median (range) SUVmean values in group A were 2.6 (1.6-4.1) under basal conditions and 1.7 (1.1-2.9) after verapamil administration (p = 0.043), and in group B were 1.6 (1.3-2.0) under basal conditions and 1.0 (0.9-1.4) after verapamil administration (p = 0.043). The median (range) RV values were -31% (-5%, -50%) in group A, and -37% (-10%, -51%) in group B (p = 0.6). Conclusion In this animal model there was a significant reduction in F-18-FDG uptake in the myocardium following verapamil administration. This type of intervention could facilitate the definition of coronary atherosclerotic plaque inflammation on F-18-FDG PET scans.

Published
2011

45. Key electoral institutions and rules influencing proportionality and partisan bias in Spanish politics

Author

Pavía José M. and Toboso Fernando

Subjects
institutions, institutional changes, spanish electoral rules, adapted swedish electoral rules, proportionality, partisan bias, quantitative estimations, Economic theory. Demography, HB1-3840
Abstract

The current paper focuses on the Spanish electoral rules governing political competition for the central “Congreso de los Diputados”. It is well-documented that the system as a whole has traditionally favoured one or the other of the two main political parties (PP and PSOE) at the expense of proportionality and the remaining political parties. This paper focuses on some key Spanish electoral rules and investigates how much the observed biases could be altered by introducing some alternative rules taken from the Swedish electoral system, ceteris paribus. Measures of disproportionality are made through the Loosemore-Hanby index and the Gallagher index. The electoral raw data used for our estimations comes from the 2011, 2015 and 2016 last three Spanish general elections. The basic contribution of the paper is an empirical one as it provides a new example that institutions matter for results.

Published
2021
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46. Evaluation of geometric, scatter and septal penetration components in fan beam collimators using Monte Carlo simulation

Author

Cot Sanz, Alberto, Pareto, D, Sempau, J, Bullich, S, Pavia, J, Calviño Tavares, Francisco, Ros, D, Universitat Politècnica de Catalunya. Departament de Física i Enginyeria Nuclear, and Universitat Politècnica de Catalunya. GREENER - Grup de recerca d'estudis energètics i de les radiacions

Subjects
Monte Carlo method, Física [Àrees temàtiques de la UPC], Mètode Monte Carlo, Collimators (Optical instrument)
Abstract

The quantitative analysis of SPECT data requires an accurate determination of the collimator point spread function (PSF). The aim of this work is to characterize the PSFs of fan beam and parallel collimators by using Monte Carlo simulation. Given a particular collimator configuration, a detailed hexagonal hole array is generated and information describing its geometry is stored in a look-up table. When a photon crosses the collimator front plane, a forty-hole array is placed around its impact position using this table. Each photon is then tracked up to the detector surface by using the Monte Carlo code PENELOPE and its associated geometry handling routines. Particle counters are defined that score the probability of impact on the detector as a function of the final photon position. Four sets of counters are employed so as to differentiate contributions to the geometric, septal penetration, coherent (Rayleigh) and incoherent (Compton) scatter components. Furthermore, sensitivity quantification and pulseheight energy spectra are calculated for different source locations. Monte Carlo results have been compared with sensitivity values obtained experimentally and good agreement was found. Our results show that for 99”Tc imaging, the geometric component represents about 95% of the fan beam PSF, whereas the incoherent scattering component is negligible.

Published
2000

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