Development and Testing of a Portable Virtual Reality-Based Mirror Visual Feedback System with Behavioral Measures Monitoring

[EN] Virtual Reality (VR) is a technology that has been used to provide the Mirror Visual Feedback (MVF) illusion to patients with promising results. In the present work, the goal is to design, develop and test a portable VR-based MVF system that monitors behavioral information about the performance of a simple motor task. The developed application runs in a stand-alone VR system and allows the researcher to select the real and virtual hands used to perform the motor task. The system was evaluated with a group of twenty healthy volunteers (12 men and 8 women) with ages between 18 and 66 years. Participants had to repetitively perform a motor task in four different experimental conditions: two mirror conditions (performing real movements with the dominant and with the non-dominant hand) and two non-mirror conditions. A significant effect of the experimental condition on embodiment score (p < 0.001), response time (p < 0.001), performance time (p < 0.001), trajectory length (p < 0.004) and trajectory maximum horizontal deviation (p < 0.001) was observed. Furthermore, a significant effect of the experimental moment (initial, middle and final parts of the training) on the performance time was observed (p < 0.001). These results show that the monitored parameters provide relevant information to evaluate the participant's task performance in different experimental conditions.This research was funded by Conselleria de Innovacion, Universidades, Ciencia y Sociedad Digital, Comunitat Valenciana, Spain, grant number AICO/2019/029, and by MCIN/AEI/ 10.13039/501100011033, Spain, grant PID2020-114967GA-I00.Rey, B.; Oliver, A.; Monzó Ferrer, JM.; Riquelme, I. (2022). Development and Testing of a Portable Virtual Reality-Based Mirror Visual Feedback System with Behavioral Measures Monitoring. International Journal of Environmental research and Public Health (Online). 19(4):1-20. https://doi.org/10.3390/ijerph1904227612019

Micro-generador termoeléctrico basado en contactos eléctricos pasantes

Micro-generador termoeléctrico que comprende porciones (P, N) de material semiconductor alternadas entre sí, que definen filas (3) de material semiconductor agrupadas formando al menos dos capas horizontales (4) de material semiconductor, estando dichas filas separadas verticalmente entre sí por láminas (1) de sustrato eléctricamente aislante y térmicamente conductor provistas de orificios pasantes (5) que conectan eléctricamente las porciones (P, N) de material semiconductor de una capa (4), con las porciones (N, P) de material semiconductor de la capa (4) inmediatamente superior, creando columnas (8) verticales de termopares (7)Peer reviewedUniversidad Politécnica de Valencia, Centro de Transferencia de Tecnología, Consejo Superior de Investigaciones CientíficasB1 Patente sin examen previ

Improving FPGA Based Impedance Spectroscopy Measurement Equipment by Means of HLS Described Neural Networks to Apply Edge AI

[EN] The artificial intelligence (AI) application in instruments such as impedance spectroscopy highlights the difficulty to choose an electronic technology that correctly solves the basic performance problems, adaptation to the context, flexibility, precision, autonomy, and speed of design. Present work demonstrates that FPGAs, in conjunction with an optimized high-level synthesis (HLS), allow us to have an efficient connection between the signals sensed by the instrument and the artificial neural network-based AI computing block that will analyze them. State-of-the-art comparisons and experimental results also demonstrate that our designed and developed architectures offer the best compromise between performance, efficiency, and system costs in terms of artificial neural networks implementation. In the present work, computational efficiency above 21 Mps/DSP and power efficiency below 1.24 mW/Mps are achieved. It is important to remark that these results are more relevant because the system can be implemented on a low-cost FPGA.This work was supported in part by the Spanish MCIU under Project PID2020-116816RB-I00 (MCIU/FEDER) and in part by GVA under Project INNEST/2020/248.Fe, J.; Gadea Gironés, R.; Monzó Ferrer, JM.; Tébar Ruiz, Á.; Colom Palero, RJ. (2022). Improving FPGA Based Impedance Spectroscopy Measurement Equipment by Means of HLS Described Neural Networks to Apply Edge AI. Electronics. 11(13):1-14. https://doi.org/10.3390/electronics11132064114111

Evaluation of a Modular PET System Architecture with Synchronization over Data Links

A DAQ architecture for a PET system is presented that focuses on modularity, scalability and reusability. The system defines two basic building blocks: data acquisitors and concentra- tors, which can be replicated in order to build a complete DAQ of variable size. Acquisition modules contain a scintillating crystal and either a position-sensitive photomultiplier (PSPMT) or an array of silicon photomultipliers (SiPM). The detector signals are processed by AMIC, an integrated analog front-end that generates programmable analog outputs which contain the first few statistical moments of the light distribution in the scintillator. These signals are digitized at 156.25 Msamples/s with free-run- ning ADCs and sent to an FPGA which detects single gamma events, extracts position and time information online using digital algorithms, and submits these data to a concentrator module. Concentrator modules collect single events from acquisition modules and perform coincidence detection and data aggregation. A synchronization scheme over data links is implemented that calibrates each link s latency independently, ensuring that there are no limitations on module mobility, and that the architecture is arbitrarily scalable. Prototype boards with both acquisition and concentration functionality have been built for evaluation pur- poses. The performance of a small PET system with two detectors based on continuous scintillators is presented. A synchronization error below 50 ps rms is measured, and energy resolutions of 19% and 24% and timing resolutions of 2.0 ns and 4.7 ns FWHM are obtained for PMT and SiPM photodetectors, respectively.Manuscript received June 25, 2013; revised November 06, 2013; accepted January 03, 2014. Date of publication January 29, 2014; date of current version February 06, 2014. This work was supported in part by the Spanish Ministry of Science and Innovation under CICYT Grant FIS2010-21216-C02-02.Aliaga Varea, RJ.; Herrero Bosch, V.; Monzó Ferrer, JM.; Ros García, A.; Gadea Gironés, R.; Colom Palero, RJ. (2014). Evaluation of a Modular PET System Architecture with Synchronization over Data Links. IEEE Transactions on Nuclear Science. 61(1):88-98. https://doi.org/10.1109/TNS.2014.2298399S889861

From specialized to core course in Telecommunications degree: Experiences from digital electronic design and verification

[EN] The European Higher Education Area (EHEA) defines the competences for professional practice of a Telecommunications Engineer. The School of Telecommunication Engineering of the Universitat Politècnica de València (Valencia, Spain) provides an integrated education program consisting of a Graduate (GITST) + Master (MUIT). The GITST course offers four specialization tracks: Electronics, Telematics, Communication Systems and Multimedia for the proper acquisition of knowledge and competences of the future Telecommunications Engineers. In 2018, the graduate program has implemented a structural change in the organization of subjects for reinforcing important skills, in which a course on digital electronics design and verification (Integration of Digital Systems, ISDIGI) has been transformed into a core subject of the study plan. In this paper, we describe the methodology and adaptation of ISDIGI (i.e. a project-based learning intermediate HDL course that includes design and verification abilities) to the new GITST Curriculum. In addition, this paper describes the process of moving from specialized to core subject.Martínez Millana, A.; Liberos Mascarell, A.; Monzó Ferrer, JM.; Martínez Peiró, MA.; Martínez Pérez, JD.; Gadea Gironés, R. (2020). From specialized to core course in Telecommunications degree: Experiences from digital electronic design and verification. Editorial Universitat Politècnica de València. 229-238. https://doi.org/10.4995/INN2019.2019.10133OCS22923

PET System Synchronization and Timing Resolution Using High-Speed Data Links

Current PET systems with fully digital trigger rely on early digitization of detector signals and the use of digital processors, usually FPGAs, for recognition of valid gamma events on single detectors. Timestamps are assigned and later used for coincidence analysis. In order to maintain a decent timing resolution for events detected on different acquisition boards, it is necessary that local timestamps on different FPGAs be synchronized. Sub-nanosecond accuracy is mandatory if we want this effect to be negligible on overall timing resolution. This is usually achieved by connecting all boards to a common backplane with a precise clock delivery network; however, this approach forces a rigid structure on the whole PET system and may pose scalability problems. © 2006 IEEE.Manuscript received June 14, 2010; revised November 18, 2010; accepted March 31, 2011. Date of publication April 21, 2011; date of current version August 17, 2011. This work was supported in part by the Spanish Ministry of Science and Innovation under FPU Grant AP2006-04275 and CICYT Grant FIS2010-21216-C02-02.Aliaga Varea, RJ.; Monzó Ferrer, JM.; Spaggiari, M.; Ferrando Jódar, N.; Gadea Gironés, R.; Colom Palero, RJ. (2011). PET System Synchronization and Timing Resolution Using High-Speed Data Links. IEEE Transactions on Nuclear Science. 58(4):1596-1605. https://doi.org/10.1109/TNS.2011.2140130S1596160558

Evaluation of a timing integrated circuit architecture for continuous crystal and SiPM based PET systems

[EN] Improving timing resolution in positron emission tomography (PET), thus having fine time information of the detected pulses, is important to increase the reconstructed images signal to noise ratio (SNR) [1]. In the present work, an integrated circuit topology for time extraction of the incoming pulses is evaluated. An accurate simulation including the detector physics and the electronics with different configurations has been developed. The selected architecture is intended for a PET system based on a continuous scintillation crystal attached to a SiPM array. The integrated circuit extracts the time stamp from the first few photons generated when the gamma-ray interacts with the scintillator, thus obtaining the best time resolution. To get the time stamp from the detected pulses, a time to digital converter (TDC) array based architecture has been proposed as in [2] or [3]. The TDC input stage uses a current comparator to transform the analog signal into a digital signal. Individually configurable trigger levels allow us to avoid false triggers due to signal noise. Using a TDC per SiPM configuration results in a very area consuming integrated circuit. One solution to this problem is to join several SiPM outputs to one TDC. This reduces the number of TDCs but, on the other hand, the first photons will be more difficult to be detected. For this reason, it is important to simulate how the time resolution is degraded when the number of TDCs is reduced. Following this criteria, the best configuration will be selected considering the trade-off between achievable time resolution and the cost per chip. A simulation is presented that uses Geant4 for simulation of the physics process and, for the electronic blocks, spice and Matlab. The Geant4 stage simulates the gamma-ray interaction with the scintillator, the photon shower generation and the first stages of the SiPM. The electronics simulation includes an electrical model of the SiPMarray and all the integrated circuitry that generates the time stamps. Time resolution results are analyzed using Matlab. The goal is to analyze the best resolution achievable with the SiPM and its degradation due to different circuitry configurations.This work was supported by local government Conselleria d’Educacio — Generalitat Valenciana research program GV/2011/068.Monzó Ferrer, JM.; Ros García, A.; Herrero Bosch, V.; Perino Vicentini, IV.; Aliaga Varea, RJ.; Gadea Gironés, R.; Colom Palero, RJ. (2013). Evaluation of a timing integrated circuit architecture for continuous crystal and SiPM based PET systems. Journal of Instrumentation. 8. https://doi.org/10.1088/1748-0221/8/03/C03017S8Moses, W. W. (2003). Time of flight in pet revisited. IEEE Transactions on Nuclear Science, 50(5), 1325-1330. doi:10.1109/tns.2003.817319Fang, X., Ollivier-Henry, N., Gao, W., Hu-Guo, C., Colledani, C., Humbert, B., … Hu, Y. (2011). IMOTEPAD: A mixed-signal 64-channel front-end ASIC for small-animal PET imaging. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 634(1), 106-112. doi:10.1016/j.nima.2011.01.082Abidi, M., Koua Calliste, K., Kanoun, M., Panier, S., Arpin, L., Tetraul, M.-A., … Fontaine, R. (2010). A Delay Locked Loop for fine time base generation in a positron emission tomography scanner. 5th International Conference on Design & Technology of Integrated Systems in Nanoscale Era. doi:10.1109/dtis.2010.5487578Karp, J. S., Surti, S., Daube-Witherspoon, M. E., & Muehllehner, G. (2008). Benefit of Time-of-Flight in PET: Experimental and Clinical Results. Journal of Nuclear Medicine, 49(3), 462-470. doi:10.2967/jnumed.107.044834Monzo, J. M., Aliaga, R. J., Herrero, V., Martinez, J. D., Mateo, F., Sebastia, A., … Pavon, N. (2008). Accurate Simulation Testbench for Nuclear Imaging Systems. IEEE Transactions on Nuclear Science, 55(1), 421-428. doi:10.1109/tns.2007.912878Avella, P., De Santo, A., Lohstroh, A., Sajjad, M. T., & Sellin, P. J. (2012). A study of timing properties of Silicon Photomultipliers. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 695, 257-260. doi:10.1016/j.nima.2011.11.049Seifert, S., van Dam, H. T., Huizenga, J., Vinke, R., Dendooven, P., Lohner, H., & Schaart, D. R. (2009). Simulation of Silicon Photomultiplier Signals. IEEE Transactions on Nuclear Science, 56(6), 3726-3733. doi:10.1109/tns.2009.2030728Corsi, F., Marzocca, C., Perrotta, A., Dragone, A., Foresta, M., Del Guerra, A., … Levi, G. (2006). Electrical Characterization of Silicon Photo-Multiplier Detectors for Optimal Front-End Design. 2006 IEEE Nuclear Science Symposium Conference Record. doi:10.1109/nssmic.2006.35607

Simulation study of resistor networks applied to an array of 256 SiPMs

[EN] In this work we describe a procedure to reduce the number of signals detected by an array of 256 Silicon Photo-multipliers (SiPMs) using a resistor network to divide the signal charge into few readout channels. Several configurations were modeled, and the pulsed signal at the readout contacts were simulated. These simulation results were experimentally tested on a specifically designed and manufactured set of printed circuit boards. Three network configurations were modeled. The modeling provided encouraging results for all three configurations. The measurements on the prototypes constructed for this study, however, provided useful position-sensitivity for only one of the network configurations. The lack of input signal amplification into the networks, the SiPM dark current, as well as the complexity of an eight layers board with parasitic capacitances, could have caused the degradation of resolving the impact photon position. This is hard to overcome with external printed circuit boards and components.This work was supported by the Spanish Plan Nacional de Investigación Científica, Desarrollo e Innovación Tecnológica (I+D+I) under Grant FIS2010-21216-CO2-01, the Valencian Local Government under Grant PROMETEO 2008/114 and through the JAE-Predoc grant from CSIC (BOE 29/01/2010).Gonzalez, A. J., Moreno, M., Barbera, J., Conde, P., Hernandez, L., Moliner, L., . . . Benlloch, J. M. (2013). Simulation study of resistor networks applied to an array of 256 SiPMs. IEEE Transactions on Nuclear Science, 60(2), 592-598. doi:10.1109/TNS.2012.2226051S59259860

PET detector block with accurate 4D capabilities

[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.This project has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (grant agreement No 695536). It has also been supported by the Spanish Ministerio de Economia, Industria y Competitividad under Grants No. FIS2014-62341-EXP and TEC2016-79884-C2-1-R.Lamprou, E.; Aguilar -Talens, A.; Gonzalez-Montoro, A.; Monzó Ferrer, JM.; Cañizares-Ledo, G.; Iranzo-Egea, S.; Vidal San Sebastian, LF.... (2018). PET detector block with accurate 4D capabilities. Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment. 912:132-136. https://doi.org/10.1016/j.nima.2017.11.002S13213691

Estudio e implementación de algoritmos digitales para la mejora de la resolución temporal en sistemas de tomografía por emisión de positrones

La Tomografía por emisión de positrones (PET, Positron Emission Tomography) es una técnica de diagnóstico médico que se encarga de mostrar imágenes de la distribución de radioisótopos dentro del cuerpo, permitiendo de esta forma observar procesos metabólicos que ocurren en su interior. Los sistemas PET se encargan de detectar pares de rayos gamma de 511KeV cada uno generados tras la aniquilación de un positrón con un electrón. De cada rayo gamma detectado, obtenemos su energía, la posición en la que el rayo es detectado y el tiempo exacto en el que el evento ha sido detectado. Denominamos tiempo de coincidencia a la diferencia de tiempos entre dos eventos. La resolución temporal de un sistema vendrá determinada por el error temporal cometido en la medida del tiempo de coincidencia. Una mejora en la resolución temporal implica una reducción del ruido de las imágenes generadas en el sistema PET. Tradicionalmente, las técnicas para la extracción del tiempo de un evento recibido han sido implementadas analógicamente. Estas técnicas permiten alcanzar una resolución temporal muy elevada. Sin embargo, la electrónica usada en las técnicas analógicas está muy adaptada a un detector específico, es compleja y poco configurable. La búsqueda de coincidencias en sistemas con muchos detectores que hacen uso de técnicas analógicas se vuelve un gran problema, pues hace necesario un incremento de la complejidad de la electrónica muchas veces inabordable. Existe una tendencia actual a reducir la electrónica analógica de los sistemas PET sustituyéndola por electrónica digital mediante una temprana digitalización de las señales de los detectores. Por tanto, deben proponerse y estudiarse algoritmos digitales para la extracción de una marca temporal de los eventos detectados. Por el momento, las técnicas digitales actuales no alcanzan las resoluciones temporales de las técnicas analógicas. El presente estudio se enmarca dentro del ámbito de los discriminadores de tiempo digitales. En el grupo de investigación, se dispone de un setup de medida con dos detectores de rayos gamma cuyas señales de salida se procesan en un front-end analógico. Las señales resultantes del front-end analógico son digitalizadas en un sistema de adquisición donde se procesan digitalmente. La búsqueda de una mejora en la resolución temporal del sistema y el hecho de que el procesado digital, todavía poco aplicado a los sistemas PET, puede proporcionar grandes mejoras en dicha resolución fueron la motivación inicial de la presente investigación. Durante la tesis, se proponen diferentes algoritmos digitales para la extracción de la información temporal de los pulsos recibidos. En un primer paso, se realiza un estado del arte a partir del cual se aportan diferentes posibles soluciones al problema. Los algoritmos propuestos están basados en bloques de procesado digital que pueden combinarse entre ellos. Estos algoritmos extraen la información temporal de las señales procesadas haciendo uso de versiones digitales adaptadas y configurables de discriminadores analógicos clásicos junto con bloques digitales que no poseen su análogo analógico. Uno de estos bloques digitales implementado se encarga de aumentar la frecuencia de muestreo mediante interpolación por filtro paso bajo, interpolando por factores x2 y x3 la señal de entrada. Entre los algoritmos analizados, el estudio propone nuevos discriminadores que se basan en hacer un cálculo digital de la carga de los pulsos recibidos, interpolados o no interpolados, obteniendo resultados mejores que con las configuraciones clásicas que trabajan con el pulso directamente adquirido y sin procesar. Para realizar el estudio del comportamiento de los discriminadores evaluados, se desarrolla una simulación que permite validar todo el sistema PET desde los detectores, generando pulsos lo más realistas posibles; la electrónica analógica, simulada mediante simuladores de tipo SPICE; y a nivel digital, estudiando el comportamiento de los algoritmos propuestos. Los algoritmos son simulados con distintas configuraciones, condiciones de jitter de reloj y ruido. Por último, todos los algoritmos propuestos son programados en la FPGA del sistema con arquitecturas que trabajan en tiempo real a medida que se vayan detectando eventos. Se definen y llevan a cabo una serie de experimentos que validan en condiciones reales en el setup de medida el funcionamiento de los discriminadores. Las medidas también permiten validar la simulación desarrollada. De esta forma, se dispone de una plataforma de test para futuras mejoras. Como conclusión final, en el trabajo se demuestra como un adecuado procesado digital de la señal permite mejorar la resolución temporal del sistema de forma considerable. El procesado digital, de gran flexibilidad frente al analógico, junto con el incremento de la velocidad de los dispositivos digitales programables y el incremento de la frecuencia de muestreo y de la integración de los convertidores analógicos-digitales (ADCs, "Analog to digital converters") hacen prever un aumento en el número de sistemas PET con estas características en un futuro no lejano y, por tanto, las soluciones investigadas en trabajos como el aquí presentado proporcionarán un aporte básico y necesario para futuros desarrollos.Monzó Ferrer, JM. (2012). Estudio e implementación de algoritmos digitales para la mejora de la resolución temporal en sistemas de tomografía por emisión de positrones [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/17226Palanci