Una aproximación a la percepción de los docentes sobre el aprendizaje cooperativo

XXI Jornades de Foment de la Investigació de la Facultat de Ciències Humanes i Socials (Any 2016)Según Johnson, Johnson y Holubec (1999), el aprendizaje cooperativo es el uso didáctico de grupos reducidos de alumnos y alumnas, de entre tres y cinco personas, para aprovechar al máximo su interacción con el fin de maximizar el aprendizaje de todos. El objetivo de este trabajo será documentarse sobre la información de que se dispone actualmente respecto a dicha estructura de trabajo y contrastarlo con la percepción que los docentes tienen de ella. Conocer la opinión de aquellos que hoy en día forman a los niños dentro de las aulas y la formación que reciben respecto al aprendizaje cooperativo. Para ello se cuenta con la colaboración de los tutores de educación primaria del CEIP Pío XII de Nules (Castellón), que han contestado a un cuestionario propuesto. En los resultados obtenidos se observa que la formación de los docentes respecto a este tema es casi inexistente si no se acercan a él por interés propio, y que hay puntos en los que su percepción coincide con lo escrito sobre el aprendizaje cooperativo y otros en los que no. Con este trabajo se realiza un acercamiento a la realidad de nuestras aulas y a la situación de nuestros docentes respecto a la estructura del aprendizaje cooperativo

Simulation Study for Designing a Dedicated Cardiac TOF-PET System

[EN] The development of dedicated positron emission tomography scanners is an active area of research, especially aiming at the improvement of lesion detection and in support of cancer treatment and management. Recently, dedicated Positron Emission Tomography (PET) systems with different configurations for specific organs have been developed for improving detection effectiveness. Open geometries are always subject to distortion and artifacts in the reconstructed images. Therefore, the aim of this work is to determine the optimal geometry for a novel cardiac PET system that will be developed by our team, and determine the time resolution needed to achieve reasonable image quality for the chosen geometry. The proposed geometries consist of 36 modules. These modules are arranged in two sets of two plates, each one with different configurations. We performed Monte Carlo simulations with different TOF resolutions, in order to test the image quality improvement in each case. Our results show, as expected, that increasing TOF resolution reduces distortion and artifact effects. We can conclude that a TOF resolution of the order of 200 ps is needed to reduce the artifacts, to acceptable levels, generated in the simulated cardiac-PET open geometries.This project has been co-financed by the Spanish Government Grants TEC2016-79884-C2 and RTC-2016-5186-1, by the European Union through the European Regional Development Fund (ERDF) and by the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (Grant Agreement No. 695536). The work of V.I. was supported by the Generalitat Valenciana APOSTD/2019/086 fellowship.Oliver-Gil, S.; Moliner, L.; Ilisie, V.; Benlloch Baviera, JM.; Rodríguez-Álvarez, M. (2020). Simulation Study for Designing a Dedicated Cardiac TOF-PET System. Sensors. 20(5):1-16. https://doi.org/10.3390/s20051311S116205Gaemperli, O., & Kaufmann, P. A. (2011). PET and PET/CT in cardiovascular disease. Annals of the New York Academy of Sciences, 1228(1), 109-136. doi:10.1111/j.1749-6632.2011.06030.xThackeray, J. T., & Bengel, F. M. (2018). Molecular Imaging of Myocardial Inflammation With Positron Emission Tomography Post-Ischemia. JACC: Cardiovascular Imaging, 11(9), 1340-1355. doi:10.1016/j.jcmg.2018.05.026Li, Z., Gupte, A. A., Zhang, A., & Hamilton, D. J. (2017). Pet Imaging and its Application in Cardiovascular Diseases. Methodist DeBakey Cardiovascular Journal, 13(1), 29. doi:10.14797/mdcj-13-1-29Juárez-Orozco, L. E., Tio, R. A., Alexanderson, E., Dweck, M., Vliegenthart, R., El Moumni, M., … Slart, R. H. J. A. (2017). Quantitative myocardial perfusion evaluation with positron emission tomography and the risk of cardiovascular events in patients with coronary artery disease: a systematic review of prognostic studies. European Heart Journal - Cardiovascular Imaging, 19(10), 1179-1187. doi:10.1093/ehjci/jex331Schelbert, H. R. (2009). Quantification of Myocardial Blood Flow: What is the Clinical Role? Cardiology Clinics, 27(2), 277-289. doi:10.1016/j.ccl.2008.12.009Knuuti, J., Kajander, S., Mäki, M., & Ukkonen, H. (2009). Quantification of myocardial blood flow will reform the detection of CAD. Journal of Nuclear Cardiology, 16(4), 497-506. doi:10.1007/s12350-009-9101-1Peng, H. (2015). Design study of a cardiac-dedicated PET system. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 779, 39-46. doi:10.1016/j.nima.2015.01.042Gonzalez, A. J., Sanchez, F., & Benlloch, J. M. (2018). Organ-Dedicated Molecular Imaging Systems. IEEE Transactions on Radiation and Plasma Medical Sciences, 2(5), 388-403. doi:10.1109/trpms.2018.2846745Moliner, L., Rodríguez-Alvarez, M. J., Catret, J. V., González, A., Ilisie, V., & Benlloch, J. M. (2019). NEMA Performance Evaluation of CareMiBrain dedicated brain PET and Comparison with the whole-body and dedicated brain PET systems. Scientific Reports, 9(1). doi:10.1038/s41598-019-51898-zAhmed, A. M., Tashima, H., Yoshida, E., Nishikido, F., & Yamaya, T. (2017). Simulation study comparing the helmet-chin PET with a cylindrical PET of the same number of detectors. Physics in Medicine and Biology, 62(11), 4541-4550. doi:10.1088/1361-6560/aa685cCho, Z.-H., Son, Y.-D., Kim, H.-K., Kwon, D.-H., Joo, Y.-H., Ra, J. B., … Kim, Y.-B. (2019). Development of Positron Emission Tomography With Wobbling and Zooming for High Sensitivity and High-Resolution Molecular Imaging. IEEE Transactions on Medical Imaging, 38(12), 2875-2882. doi:10.1109/tmi.2019.2916326Surti, S., & Karp, J. S. (2008). Design considerations for a limited angle, dedicated breast, TOF PET scanner. Physics in Medicine and Biology, 53(11), 2911-2921. doi:10.1088/0031-9155/53/11/010Surti, S., & Karp, J. S. (2016). Advances in time-of-flight PET. Physica Medica, 32(1), 12-22. doi:10.1016/j.ejmp.2015.12.007Grant, A. M., Deller, T. W., Khalighi, M. M., Maramraju, S. H., Delso, G., & Levin, C. S. (2016). NEMA NU 2-2012 performance studies for the SiPM-based ToF-PET component of the GE SIGNA PET/MR system. Medical Physics, 43(5), 2334-2343. doi:10.1118/1.4945416Van Sluis, J., de Jong, J., Schaar, J., Noordzij, W., van Snick, P., Dierckx, R., … Boellaard, R. (2019). Performance Characteristics of the Digital Biograph Vision PET/CT System. Journal of Nuclear Medicine, 60(7), 1031-1036. doi:10.2967/jnumed.118.215418Ito, M., Lee, M. S., & Lee, J. S. (2013). Continuous depth-of-interaction measurement in a single-layer pixelated crystal array using a single-ended readout. Physics in Medicine and Biology, 58(5), 1269-1282. doi:10.1088/0031-9155/58/5/1269Bugalho, R., Di Francesco, A., Ferramacho, L., Leong, C., Niknejad, T., Oliveira, L., … Varela, J. (2018). Experimental results with TOFPET2 ASIC for time-of-flight applications. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 912, 195-198. doi:10.1016/j.nima.2017.11.034Gundacker, S., Auffray, E., Frisch, B., Jarron, P., Knapitsch, A., Meyer, T., … Lecoq, P. (2013). Time of flight positron emission tomography towards 100ps resolution with L(Y)SO: an experimental and theoretical analysis. Journal of Instrumentation, 8(07), P07014-P07014. doi:10.1088/1748-0221/8/07/p07014A Code System for Monte Carlo Simulation of Electron and Photon Transporthttp://www.oecd-nea.org/lists/penelope.htmlStrydhorst, J., & Buvat, I. (2016). Redesign of the GATE PET coincidence sorter. Physics in Medicine and Biology, 61(18), N522-N531. doi:10.1088/0031-9155/61/18/n522Baró, J., Sempau, J., Fernández-Varea, J. M., & Salvat, F. (1995). PENELOPE: An algorithm for Monte Carlo simulation of the penetration and energy loss of electrons and positrons in matter. Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 100(1), 31-46. doi:10.1016/0168-583x(95)00349-5Sempau, J., Acosta, E., Baro, J., Fernández-Varea, J. M., & Salvat, F. (1997). An algorithm for Monte Carlo simulation of coupled electron-photon transport. Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 132(3), 377-390. doi:10.1016/s0168-583x(97)00414-xSempau, J., Fernández-Varea, J. M., Acosta, E., & Salvat, F. (2003). Experimental benchmarks of the Monte Carlo code penelope. Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 207(2), 107-123. doi:10.1016/s0168-583x(03)00453-1Reader, A. J., Ally, S., Bakatselos, F., Manavaki, R., Walledge, R. J., Jeavons, A. P., … Zweit, J. (2002). One-pass list-mode EM algorithm for high-resolution 3-D PET image reconstruction into large arrays. IEEE Transactions on Nuclear Science, 49(3), 693-699. doi:10.1109/tns.2002.1039550Spanoudaki, V. C., & Levin, C. S. (2010). Photo-Detectors for Time of Flight Positron Emission Tomography (ToF-PET). Sensors, 10(11), 10484-10505. doi:10.3390/s101110484Siddon, R. L. (1985). Fast calculation of the exact radiological path for a three-dimensional CT array. Medical Physics, 12(2), 252-255. doi:10.1118/1.595715Vandenberghe, S., Daube-Witherspoon, M. E., Lewitt, R. M., & Karp, J. S. (2006). Fast reconstruction of 3D time-of-flight PET data by axial rebinning and transverse mashing. Physics in Medicine and Biology, 51(6), 1603-1621. doi:10.1088/0031-9155/51/6/017Performance Measurements of Positron Emission Tomographshttps://www.nema.org/Standards/ComplimentaryDocuments/Contents%20and%20Scope%20NEMA%20NU%202%202012.pdfYu, W., & Zeng, L. (2014). A Novel Weighted Total Difference Based Image Reconstruction Algorithm for Few-View Computed Tomography. PLoS ONE, 9(10), e109345. doi:10.1371/journal.pone.0109345Tashima, H., Yamaya, T., Yoshida, E., Kinouchi, S., Watanabe, M., & Tanaka, E. (2012). A single-ring OpenPET enabling PET imaging during radiotherapy. Physics in Medicine and Biology, 57(14), 4705-4718. doi:10.1088/0031-9155/57/14/4705Yamaya, T., Inaniwa, T., Minohara, S., Yoshida, E., Inadama, N., Nishikido, F., … Murayama, H. (2008). A proposal of an open PET geometry. Physics in Medicine and Biology, 53(3), 757-773. doi:10.1088/0031-9155/53/3/015Miyake, K. K., Matsumoto, K., Inoue, M., Nakamoto, Y., Kanao, S., Oishi, T., … Togashi, K. (2014). Performance Evaluation of a New Dedicated Breast PET Scanner Using NEMA NU4-2008 Standards. Journal of Nuclear Medicine, 55(7), 1198-1203. doi:10.2967/jnumed.113.131565Yamamoto, S., Honda, M., Oohashi, T., Shimizu, K., & Senda, M. (2011). Development of a Brain PET System, PET-Hat: A Wearable PET System for Brain Research. IEEE Transactions on Nuclear Science, 58(3), 668-673. doi:10.1109/tns.2011.2105502Garibaldi, F., Capuani, S., Colilli, S., Cosentino, L., Cusanno, F., Leo, R. D., … Tamma, C. (2013). TOPEM: A PET-TOF endorectal probe, compatible with MRI for diagnosis and follow up of prostate cancer. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 702, 13-15. doi:10.1016/j.nima.2012.09.020González-Montoro, A., Sánchez, F., Martí, R., Hernández, L., Aguilar, A., Barberá, J., … González, A. J. (2018). Detector block performance based on a monolithic LYSO crystal using a novel signal multiplexing method. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 912, 372-377. doi:10.1016/j.nima.2017.10.09

Benchmark of the PenRed Monte Carlo framework for HDR brachytherapy

[EN] Purpose: The purpose of this study is to validate the PenRed Monte Carlo framework for clinical applications in brachytherapy. PenRed is a C++ version of Penelope Monte Carlo code with additional tallies and utilities. Methods and materials: Six benchmarking scenarios are explored to validate the use of PenRed and its improved bachytherapy-oriented capabilities for HDR brachytherapy. A new tally allowing the evaluation of collisional kerma for any material using the track length kerma estimator and the possibility to obtain the seed positions, weights and directions processing directly the DICOM file are now implemented in the PenRed distribution. The four non-clinical test cases developed by the Joint AAPM-ESTRO-ABG-ABS WG-DCAB were evaluated by comparing local and global absorbed dose differences with respect to established reference datasets. A prostate and a palliative lung cases, were also studied. For them, absorbed dose ratios, global absorbed dose differences, and cumulative dose-volume histograms were obtained and discussed. Results: The air-kerma strength and the dose rate constant corresponding to the two sources agree with the reference datatests within 0.3% (Sk) and 0.1% (¿). With respect to the first three WG-DCAB test cases, more than 99.8% of the voxels present local (global) differences within ±1%(±0.1%) of the reference datasets. For test Case 4 reference dataset, more than 94.9%(97.5%) of voxels show an agreement within ±1%(±0.1%), better than similar benchmarking calculations in the literature. The track length kerma estimator scorer implemented increases the numerical efficiency of brachytherapy calculations two orders of magnitude, while the specific brachytherapy source allows the user to avoid the use of error-prone intermediate steps to translate the DICOM information into the simulation. In both clinical cases, only minor absorbed dose differences arise in the low-dose isodoses. 99.8% and 100% of the voxels have a global absorbed dose difference ratio within ±0.2% for the prostate and lung cases, respectively. The role played by the different segmentation and composition material in the bone structures was discussed, obtaining negligible absorbed dose differences. Dose-volume histograms were in agreement with the reference data. Conclusions: PenRed incorporates new tallies and utilities and has been validated for its use for detailed and precise high-dose-rate brachytherapy simulations.This work is partially supported by the Ministerio de Ciencia e Innovación of Spain (MCIN) grants PID2020- 113126RB-I00 and PID2021-125096NB-I00 funded by MCIN/AEI/10.13039/501100011033. V. G. acknowledges partial support from AEI-MICINN under grant PID2020-1 13334GB-I00/AEI/10.13039/501100011033 and by Generalitat Valenciana through the project PROMETEO/2019/087. The work has also been supported by the Natural Sciences and Engineering Research Council of Canada (NSERC) grant RGPIN-2019-05038. Francisco Berumen acknowledges support by the Fonds de Recherche du Québec ¿ Nature et Technologies (FRQNT). J.V. and F.B. would like to acknowledge funding by MCIN/ AEI/10.13039 and the Generalitat Valenciana (GVA) grant PROMETEO/2021/064. Our colleague Prof. Vicent Giménez Gómez passed away on November 16, 2022, during the proofs of this study. We dedicate it to his memory. The Universitat de València lost a dedicated and accomplished physicist.Oliver-Gil, S.; Giménez-Alventosa, V.; Berumen, F.; Giménez, V.; Beaulieu, L.; Ballester, F.; Vijande, J. (2023). Benchmark of the PenRed Monte Carlo framework for HDR brachytherapy. Zeitschrift für Medizinische Physik. 33(4):511-528. https://doi.org/10.1016/j.zemedi.2022.11.00251152833

High resolution and sensitivity gamma camera with active septa. A first Monte Carlo study

[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.This project has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (Grant Agreement No. 695536). This work was supported in part by the Spanish Government Grants Generalitat Valenciana, APOSTD/2019/086 and TEC2016-79884-C2 and RTC-2016-5186-1.Ilisie, V.; Moliner, L.; Oliver-Gil, S.; Sánchez Martínez, F.; González Martínez, AJ.; Seimetz, M.; Rodríguez Álvarez, MJ.... (2019). High resolution and sensitivity gamma camera with active septa. A first Monte Carlo study. Scientific Reports. 9:1-9. https://doi.org/10.1038/s41598-019-54934-0S199Mok, G. S. P., Tsui, B. M. W. & Beekman, F. J. The effects of object activity distribution on multiplexing multi-pinhole SPECT. Phys. Med. Biol. 56, 2635–2650 (2011).Johnson, C., Shokouhi, S. & Peterson, T. E. Reducing Multiplexing artifacts in Multi-Pinhole SPECT with a Stacked Silicon-Germanium System: a Simulation Study. IEEE Trans Med Imaging. 33(12), 2342–2351 (2014).Mok, G. S. P., Wang, Y. & Tsui, B. M. W. Quantification of the Multiplexing Effects in Multi-Pinhole Small Animal SPECT: A Simulation Study. IEEE Trans Nucl Sci. 56(5), 2636–2643 (2009).Vunckx, K., Suetens, P. & Nuyts, J. Effect of Overlapping Projections on Reconstruction Image Quality in Multipinhole SPECT. IEEE Transactions on Medical Imaging. 27(7) (2008).Ivashchenko, O. et al. Quarter-Millimeter-Resolution Molecular Mouse Imaging with U-SPECT+. Mol Imaging. 2014. 13 (2014).Gal, O. et al. Development of a portable gamma camera with coded apertura. Nuclear Instruments and Methods in Phys. Res. A. 563, 233–237 (2006).Accorsi, R., Gasparini, F. & Lanza, R. C. A Coded Aperture for High-Resolution Nuclear Medicine Planar Imaging With a Conventional Anger Camera: Experimental Results. IEEE Transactions on Nuclear Science. 48, 2411–2417 (2001).Fuji, H. et al. Optimization of Coded Aperture Radioscintigraphy for Sentinel Lymph Node Mapping. Mol. Imaging Biol. 14, 173–182 (2012).Accorsi, R., Gasparini, F. & Lanza, R. C. Optimal coded aperture patterns for improved SNR in nuclear medicine imaging. Nucl. Instrum. Methods Phys. Res. A. 474, 273–284 (2001).Lee, T. & Lee, W. Portable Active Collimation Imager Using URA Patterned Scintillator. IEEE Transactions on Nuclear Science. 61, 654–662 (2014).Lee, T. & Lee, W. A cubic gamma camera with an active collimator. Applied Radiation and Isotopes. 90, 102–108 (2014).Accorsi, R. & Lanza, R. C. Near-field artifact reduction in coded aperture imaging. Appl. Opt. 40, 4697–4705 (2001).Ilisie, V., Sánchez, F., González, A. J. & Benlloch, J. M. Dispositivo Para la Detección de Rayos Gamma con Tabiques Activos (Device for Gamma Ray Detection with Active Septa), Patent application Ref. P201831058/PT-018004.González, A. J. et al. Detector block based on arrays of 144 SiPMs and monolithic scintillators: A performance study. Nuclear Instruments and Methods in Physics Research A. 787, 42–45 (2015).Pani, R. et al. Preliminary evaluation of a monolithic detector module for integrated PET/MRI scanner with high spatial resolution. JINST. 10, C06006 (2015).Pani, R. et al. Continuous DOI determination by Gaussian modelling of linear and non-linear scintillation light distributions. Proc. IEEE NSS-MIC. 3386–3389 (2011).Shepp, L. A. & Vardi, Y. Maximum likelihood reconstruction for emission tomography. IEEE Transactions on Medical Imaging. 2, 113 (1982).Hudson, H. M. & Larkin, R. S. Accelerated Image Reconstruction Using Ordered Subsets of projection Data. IEEE Transactions on Medical Imaging. 13, 601 (1994).Reader, A. J. et al. Accelerated list-mode EM algorithm. IEEE Transactions on Nuclear Science. 49, 42 (2002).Rahmim, A., Ruth, T. & Sossi, V. Study of a convergent subsetized list-mode EM reconstruction algorithm. FILTR SEP. 6. 3978–3982. 6, 10.1109 (2004).Siddon, R. L. Fast calculation of the exact radiological path for a three-dimensional CT array. Medical Physics. 12, 252 (1985).Sundermann, E., Jacobs, F., Christiaens, M., De Sutter, B. & Lemahieu, I. A Fast Algorithm to Calculate the Exact Radiological Path Through a Pixel Or Voxel Space. Journal of Computing and Information Technology. 6 (1998).Reader, A. J. et al. One-pass list-mode EM algorithm for high-resolution 3-D PET image reconstruction into large arrays. IEEE Transactions on Nuclear Science. 49(3), 693–699 (2002).Agostinelli, S. et al. Geant4 - a simulation toolkit. Nuclear Instruments and Methods in Physics Research A. 506, 250–303 (2003).Jan, S. et al. GATE - Geant4 Application for Tomographic Emission: a simulation toolkit for PET and SPECT. Phys. Med. Biol. 49(19), 4543–4561 (2004)

S100-A9 protein in exosomes from chronic lymphocytic leukemia cells promotes NF-κB activity during disease progression

Chronic lymphocytic leukemia (CLL) is an incurable disease characterized by accumulation of clonal B lymphocytes, resulting from a complex balance between cell proliferation and apoptotic death. Continuous crosstalk between cancer cells and local/distant host environment is required for effective tumor growth. Among the main actors of this dynamic interplay between tumoral cells and their microenvironment are the nano-sized vesicles called exosomes. Emerging evidence indicates that secretion, composition, and functional capacity of exosomes are altered as tumors progress to an aggressive phenotype. In CLL, no data exist exploring the specific changes in the proteomic profile of plasma-derived exosomes from patients during disease evolution. We hereby report for the first time different proteomic profiles of plasma exosomes, both between indolent and progressive CLLs as well as within the individual patients at the onset of disease and during its progression. Next, we focus on the changes of the exosome protein cargoes, which are found exclusively in patients with progressive CLL after disease progression. The alterations in the proteomic cargoes underline different networks specific for leukemia progression related to inflammation, oxidative stress, and NF-κB and phosphatidylinositol 3-kinase/AKT pathway activation. Finally, our results suggest a preponderant role for the protein S100-A9 as an activator of the NFκB pathway during CLL progression and suggest that the leukemic clone can generate an autoactivation loop through S100-A9 expression, NF-κB activation, and exosome secretion. Collectively, our data propose a new pathway for NF-κB activation in CLL and highlight the importance of exosomes as extracellular mediators promoting tumor progression in CLL

TOF studies for dedicated PET with open geometries

[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.This work was supported in part by the Spanish Government Grants TEC2016-79884-C2 and RTC-2016-5186-1 and by the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (Grant Agreement No. 695536).Moliner, L.; Ilisie, V.; González Martínez, AJ.; Oliver-Gil, S.; Gonzalez, A.; Giménez-Alventosa, V.; Cañizares, G.... (2019). TOF studies for dedicated PET with open geometries. Journal of Instrumentation. 14:1-8. https://doi.org/10.1088/1748-0221/14/02/C02006S181

Deep learning for MRI-based CT synthesis: a comparison of MRI sequences and neural network architectures

[Otros] Synthetic computed tomography (CT) images derived from magnetic resonance images (MRI) are of interest for radiotherapy planning and positron emission tomography (PET) attenuation correction. In recent years, deep learning implementations have demonstrated improvement over atlasbased and segmentation-based methods. Nevertheless, several open questions remain to be addressed, such as which is the best of MRI sequences and neural network architectures. In this work, we compared the performance of different combinations of two common MRI sequences (T1- and T2-weighted), and three state-of-the-art neural networks designed for medical image processing (Vnet, HighRes3dNet and ScaleNet). The experiments were conducted on brain datasets from a public database. Our results suggest that T1 images perform better than T2, but the results further improve when combining both sequences. The lowest mean average error over the entire head (MAE = 101.76 ± 10.4 HU) was achieved combining T1 and T2 scans with HighRes3dNet. All tested deep learning models achieved significantly lower MAE (p < 0.01) than a well-known atlas-based method.This work was supported by the Spanish Government grants TEC2016-79884-C2 and RTC-2016-5186-1, and by the European Union through the European Regional Development Fund (ERDF)Larroza, A.; Moliner, L.; Álvarez-Gómez, JM.; Oliver-Gil, S.; Espinós-Morató, H.; Vergara-Díaz, M.; Rodríguez-Álvarez, MJ. (2019). Deep learning for MRI-based CT synthesis: a comparison of MRI sequences and neural network architectures. IEEE. 1-4. https://doi.org/10.1109/NSS/MIC42101.2019.9060051S1

Monte Carlo flattening filter design to high energy intraoperative electron beam homogenization

[EN] Intraoperative radiotherapy using mobile linear accelerators is used for a wide variety of malignancies. However, when large fields are used in combination with high energies, a deterioration of the flatness dose profile is measured with respect to smaller fields and lower energies. Indeed, for the LIAC HWL of Sordina, this deterioration is observed for the 12 MeV beam combined with 10 cm (or larger) diameter applicator. Aimed to solve this problem, a flattening filter has been designed and validated evaluating the feasibility of its usage at the upper part of the applicator. The design of the filter was based on Monte Carlo simulations because of its accuracy in modeling components of clinical devices, among other purposes. The LIAC 10 cm diameter applicator was modeled and simulated independently by two different research groups using two different MC codes, reproducing the heterogeneity of the 12 MeV energy beam. Then, an iterative process of filter design was carried out. Finally, the MC designed conical filter with the optimal size and height to obtain the desired flattened beam was built in-house using a 3D printer. During the experimental validation of the applicator-filter, percentage depth dose, beam profiles, absolute and peripheral dose measurements were performed to demonstrate the effectiveness of the filter addition in the applicator. These measurements conclude that the beam has been flattened, from 5.9% with the standard configuration to 1.6% for the configuration with the filter, without significant increase of the peripheral dose. Consequently, the new filter-applicator LIAC configuration can be used also in a conventional surgery room. A reduction of 16% of the output dose and a reduction of 1.1 mm in the D50 of the percentage depth dose was measured with respect to the original configuration. This work is a proof-of-concept that demonstrates that it is possible to add a filter able to flatten the beam delivered by the Sordina LIAC HWL. Future studies will focus on more refined technical solutions fully compatible with the integrity of the applicator, including its sterilization, to be safely introduced in the clinical practice.The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Giuseppe Felici reports a relationship with S.I.T. Sordina IORT Technologies S.p.A. that includes: employment. We thank the professionals and facilities at the 3D printing and metrology department in the Mechanics Unit at IFIC. JV thanks I. Diaz for measuring the PLA density. We thank S.I.T. SORDINA IORT Tech-nologies SpA for providing the applicator used for testing the filter during the measurements. JV, FB, and JP would like to acknowledge the Spanish "Ministerio de Ciencia e Innovacion" (MCIN) grant PID2021-125096NB-I00 funded by MCIN/AEI/10.13039 and the "Generalitat Valenciana" (GVA) grant PROMETEO/2021/064.Oliver-Gil, S.; Vijande, J.; Tejedor-Aguilar, N.; Miró Herrero, R.; Rovira-Escutia, JJ.; Ballester, F.; Juste-Vidal, B.... (2023). Monte Carlo flattening filter design to high energy intraoperative electron beam homogenization. Radiation Physics and Chemistry. 212. https://doi.org/10.1016/j.radphyschem.2023.11110221