Contribution of high energy physics techniques to the medical imaging field

The purpose of this study was to show how advanced concepts of compact, lossless and "Time Of Flight" (TOF) capable electronics similar to those foreseen for the LHC and ILC experiments could be fairly and easily transferred to the medical imaging field through Positron Emission Tomography (PET). As a wish of explanation, the two overriding weaknesses of PET camera readout electronics, namely dead-time and timing resolution, were investigated analytically and with a Monte-Carlo simulator presently dedicated to this task. Results have shown there was room left for count rate enhancement through a huge decrease of the timing resolution well below the nanosecond. The novel electronics scheme suggested for PET in this paper has been partly inspired by the long experience led in High Energy Physics where the latter requirement is compulsory. Its structure entirely pipelined combined to a pixelation of the whole detector should allow dead-times to be suppressed, while the absence of devoted timing channel would remove the preponderant contributions to the timing resolution. To the common solution for timing would substitute an optimal filtering method witch clearly appears as a good candidate as timing resolution of a few tens of picoseconds may be achieved provided the shape of the signal is known and sufficient samples are available with enough accuracy. First investigations have yield encouraging results as a sampling frequency of 50 MHz with a 7 bits precision appears sufficient to ensure the 500ps coincidence timing resolution planed. At this point, there will be a baby step ahead to draw benefice from a TOF implementation to the design and the enormous noise variance enhancement that would come with.Comment: presented at EuroMedIm 2006 : 1st European Conference on Molecular Imaging Technology, Marseille 9-12 May 2006, 6 pp, 4 figures, submitted to NI

Discutindo a educação ambiental no cotidiano escolar: desenvolvimento de projetos na escola formação inicial e continuada de professores

A presente pesquisa buscou discutir como a Educação Ambiental (EA) vem sendo trabalhada, no Ensino Fundamental e como os docentes desta escola compreendem e vem inserindo a EA no cotidiano escolar., em uma escola estadual do município de Tangará da Serra/MT, Brasil. Para tanto, realizou-se entrevistas com os professores que fazem parte de um projeto interdisciplinar de EA na escola pesquisada. Verificou-se que o projeto da escola não vem conseguindo alcançar os objetivos propostos por: desconhecimento do mesmo, pelos professores; formação deficiente dos professores, não entendimento da EA como processo de ensino-aprendizagem, falta de recursos didáticos, planejamento inadequado das atividades. A partir dessa constatação, procurou-se debater a impossibilidade de tratar do tema fora do trabalho interdisciplinar, bem como, e principalmente, a importância de um estudo mais aprofundado de EA, vinculando teoria e prática, tanto na formação docente, como em projetos escolares, a fim de fugir do tradicional vínculo “EA e ecologia, lixo e horta”.Facultad de Humanidades y Ciencias de la Educació

Differences between quark and gluon jets at LEP1

A report is ven here on the differences between quark and gluon initiated jets as measured in LEPl. Various measurements, agree qualitatively on the differences between quark and gluon jets. However a direct quantitative comparison among the measurements as well as comparisons between the measurements and analytical calculations are difficult. This is due to the dependence of the results on the selected event topologies and used jet finding algorithms. Topology dependence of the charged particle multiplicity in quark and gluon jets is studied by ALEPH and transverse momentum-like scales are proposed to account for it. OPAL produced the first quantitative test of QCD analytic prediction for the ratio of the mean particle multiplicity between gluon and quark jets valid, at least, for 39 GeV jets

Conception de circuits analogique-numérique pour le conditionnement de micro-capteurs embarqués

Le domaine de l'instrumentation des capteurs est en constante évolution. Ce travail propose la conception des éléments clefs qui constituent les chaines d'instrumentations de capteurs d'aujourd'hui au travers de 3 applications concrètes. La première application est la mesure de vitesse et de position, par exemple dans un roulement. Nous présentons la conception et la réalisation d'un circuit analogique pour le conditionnement d'un capteur de type magnétorésistif. Ce capteur mesure le champ magnétique généré par les pôles magnétiques d'une roue codeuse. Le circuit est optimisé en bruit, en consommation et travaille sur une bande passante de plusieurs kHz. Pour compenser la dispersion des capteurs, le circuit permet des réglages d'offset et une calibration de gains. Il contient également une mémoire de type OTP (One Time Programmable Memory) qui sauvegarde les réglages associés au capteur. La deuxième application est la mesure de signaux de type EcoG afin d'interfacer le cerveau humain. Nous décrivons la conception et la réalisation d'un convertisseur Analogique/Numérique de type SAR. Il possède un convertisseur numérique analogique capacitif avec une capacité d'atténuation afin de réduire le nombre total de condensateur et ainsi la consommation. Le comparateur possède une entrée rail-to-rail et un système de préamplification avec auto zéro pour diminuer l'offset. Sa consommation est de 86 W pour une vitesse de 24Ks/S et 12bits de résolution. Enfin la troisième application est la mesure de pression stationnaire sur la voilure des avions afin d'en connaître les contraintes. Nous décrivons l'étude architecturale d'un convertisseur sigma-delta permettant d'atteindre une grande résolution pour des signaux de faible fréquence. Il sera de type incrémentale et répondra à des applications de type instrumentation de capteur. Sa résolution est de 16bits ENOB pour une fréquence maximale d'entrée de 100Hz et minimale de sortie d'1Ks/S. Le mode incrémental permettra d'obtenir une sortie en réponse à une requête de manière asynchrone. Une modélisation de chaque élément du système complet convertisseur plus capteur a été effectuée sous Matlab. L'étude de la partie filtrage numérique du convertisseur et l'optimisation de son implémentation numérique sont présentées. Cette étude architecturale complète aboutit au dimensionnement de chaque élément pour répondre au cahier des charges de l'application .The domain of sensors instrumentation is constantly evolving. The present work proposes the design of the key elements conception which constitute the instrumentations chains of current sensors through 3 concrete applications. The first application is speed and position measurement, for example in a wheel bearing. We present the design and realization of an analogical circuit for the conditioning of magneto resistive sensor. This sensor measures the magnetic field generated by the coding wheel magnetic poles inside the bearing. The circuit is noise and power consumption optimized on a bandwidth of few kHz. To compensate sensors variability, the circuit includes offset regulations and gains. It also contains an OTP (One Time Programmable) memory which backs up the associated sensor regulations. The second application is the measurement of EcoG's signals to interface with the human brain. We describe the design and realization of SAR ADC. It is composed of a capacitive DAC with an attenuation capacitor to reduce the total number of condensers and, in doing so, to reduce power consumption. The comparator is composed by a rail-to-rail input and multistage preamplification and output offset storage. ADC total power consumption is 86 W for 24Ks/S speed and 12bits resolution. Finally the third application is the pressure measurement on aircraft wings. We describe the architectural study sigma-delta incremental ADC which reaches high resolution for low band pass signals. Its resolution is 16bits ENOB for a maximal input frequency of 100Hz and an output speed of 1Ks/S. The incremental mode leads to obtain output code in answer to asynchronous requests. Each system element (converter plus sensors) has been matlab modelled. The converter digital filtering study and its digital implementation optimization are presented. This complete architectural study concludes with the sizing of each element in order to answer the technical specifications of the application.SAVOIE-SCD - Bib.électronique (730659901) / SudocGRENOBLE1/INP-Bib.électronique (384210012) / SudocGRENOBLE2/3-Bib.électronique (384219901) / SudocSudocFranceF

Contribution à l'étude des processus nucléaires en hadronthérapie et de leur impact sur la délocalisation du dépôt de dose

L hadronthérapie consiste en l utilisation des particules lourdes dans le but de soigner certains cancers inopérables et/ou résistants aux radiothérapies conventionnelles. L objectif est de déposer la dose nécessaire dans la tumeur afin de la stériliser, tout en limitant le dépôt de dose dans les tissus sains environnants. Le dépôt de dose est dû en grande partie à l ionisation de la cible directement par le faisceau incident, mais aussi dans une moindre mesure aux fragments produits par les interactions nucléaires entre les noyaux des projectiles et les noyaux des atomes de la cible. Ces processus nucléaires et leur contribution à la délocalisation de la distribution volumique du dépôt de dose sont difficilement quantifiables du fait de la mauvaise connaissance de leurs sections efficaces aux énergies utilisées en hadronthérapie. Le sujet principal de la thèse est de développer une méthodologie pour la quantification des incertitudes sur la dose effectivement délivrée, étant données les conditions d irradiation. Ce travail s est articulé autour de deux axes : une approche phénoménologique et une approche expérimentale. L approche phénoménologique a consisté en une étude bibliographique et une compilation des données expérimentales existantes, suite auxquelles le modèle empirique développé par Sihver et al. a été amélioré, permettant ainsi une meilleure description des sections efficaces de réaction totales et différentielles noyau-noyau pour un nombre de masse inférieur à 26. L approche expérimentale a consisté en deux prises de données: tout d abord la mesure du profil des émetteurs b+ dans une cible d eau irradiée par des ions carbone en utilisant la technique de tomographie à émission de positons au GANIL , puis la mesure de profils transversaux et longitudinaux de dépôt de dose dans des cible de graphite et de PMMA irradiées par des protons au PSI. Une méthode d analyse de données consistant à comparer les prédictions des simulations Monte Carlo aux mesures physiques a été ensuite développéeHadrontherapy consists of the use of heavy particles (hadrons) for treatment of radio-resistant or/and inoperable cancerous tumors. The aim is to deposit the necessary dose, in the tumor volume, to sterilize the cancerous cells while spearing the surrounding volumes. Dose deposition is mainly due to the electromagnetic interactions between the incoming beam particles and the target material leading principally to ionizations of the target molecular or atomic constituents. However, light nuclear fragments, issued from the nuclear interactions between the projectile and the target nuclei, do also contribute to the dose deposition. Even thought the amount of the later is small (few % of the total dose), its quantification is crucial since it is the main contribution to the dose delocalization out of the aimed target volume. This quantification is difficult because of the lack of experimental cross-sections at the energies used in hadrontherapy: a few tens or hundreds of MeV per nucleon of the projectile. The principal aim of this work is to develop a method in order to predict the dose distribution effectively delivered in the real conditions of therapeutic irradiation. Two complementary approaches were followed for this work. The first, phenomenological, consists of the study and the compilation of the existing experimental data available in the literature and the improvement of an empirical nuclear fragmentation cross-sections model. The second approach is purely experimental and concisted in two campaigns of data acquisition, mesaurement of b+ emitters profile in a water target irradiated by carbon ions at GANIL (Caen) using techniques of positron emission tomography, and acquisition of longitudinal and transversal dose distributions in carbon and water equivalent (PMMA) targets irradiated by protons at the PSI (Villigen) facility. Then a method of data analysis to compare the predictions of the Monte Carlo simulations to the measurements were developpedLYON1-BU.Sciences (692662101) / SudocSudocFranceF

Mechatronics for real time quality control in hadrontherapy

International audienc

Studies of the reaction π-p→η′π0n at 38 and 100 GeV/c

The production of η′π0 system in π-p charge-exchange interactions at π- momenta 38 GeV/c and 100 GeV/c has been studied. The 2γ and ηπ0π0 decay modes of η′ leading to 4γ and 8γ final states respectively have been detected. No statistically significant peak is observed in the η′π0 mass spectrum in the range of 1.2 GeV÷2.1 GeV. An upper limit of 6·10-3 has been established for the a20(1320)→η′π0 branching ratio. © 1992 Springer-Verlag.SCOPUS: ar.jinfo:eu-repo/semantics/publishe