Dissertations / Theses on the topic 'In-beam monitoring'

[EN] The Compact Linear Collider (CLIC) is an electron-positron collider conceived for the study of High-Energy Physics in the TeV center of mass energy region, is based on a two-beam operation principle: instead of using active elements (klystrons), the necessary RF power to accelerate the Main Beam (MB) is obtained from the deceleration of a high-current, moderate energy Drive Beam (DB) in the so-called Power Extraction and Transfer Structures (PETS). These structures emit an RF signal of about 130 MW power at 12 GHz. As this frequency is above the cut-o ff frequency of the fundamental mode for the specified beam pipe dimensions (7.6 GHz), the inference propagates from the PETS to the neighboring devices, including the Beam Position Monitors (BPM). According to the CLIC Conceptual Design Report (CDR), an ef ficient beam position monitoring system for the CLIC DB decelerator needs to meet the following requirements: - It should be as simple and economic as possible, as 41580 units are required, amounting to 75% of all CLIC BPMs. - The signal processing scheme should not be a ffected by the PETS interference. This rules out processing the signals at the beam bunching frequency (12 GHz). - The resulting position signal should detect changes in the beam position whose duration is 10 ns or longer. - The required spatial resolution is 2 um for a 23 mm diameter vacuum pipe. - Wide dynamic range: the electronic acquisition system must be able to process signals with extreme levels, induced by either very high (100 A) or very low (3 A) current beams. This PhD thesis describes the electromagnetic and mechanical design of the first prototype BPM developed for the CLIC Drive Beam and its characterization tests in laboratory and with beam. The first two chapters introduce the CLIC project and review the state-of-the-art beam position monitoring techniques. Chapter 3 presents the design of the BPM. The stripline technology has been selected, as it is the only one among the most commonly used BPM techniques to present a suitable frequency response to filter out the RF interference caused by the PETS. Choosing an appropriate length for the electrodes, it is possible to tune one the periodic notches in the stripline frequency response to 12 GHz. The influence of di erent electromagnetic and geometrical aspects is also studied, such as beam coupling impedance or the ratio between longitudinal and transverse dimensions. The design of the electronic acquisition system is presented in Chapter 4, considering the project requirements in terms of resolution (2 u m), accuracy (20 um) and time resolution (10 ns). Due to the high amount of units required, the number of electronics components has been minimized. As the designed signal processing scheme is based on charge integration, it can be adapted to di erent stripline pick-ups by simply modifying the attenuator settings according to the required output signal levels. The laboratory characterization tests of the prototype stripline BPM, in the low and the high frequency ranges, performed with a thin wire and a coaxial waveguide, respectively, are described in Chapter 5. The measurement results are compared with the theoretical estimation and the electromagnetic field simulations. In addition, the high-frequency test reveals that the first prototype stripline BPM does not provide su cient suppression of the 12 GHz PETS RF interference. An additional study proposed several modifications and guidelines for a second prototype stripline BPM. Finally, Chapter 6 presents the beam tests of the prototype stripline BPM at the CLIC Test Facility 3 (CTF3) in the Test Beam Line (TBL), a scaled version of the CLIC Drive Beam decelerator. Two types of tests were performed: linearity/sensivity and resolution. These results are compared to the ones in the laboratory characterization tests. An upper bound of the resolution is estimated performing a Singular Value Decomposition (SVD) analysis.
[ES] El Colisionador Lineal Compacto (Compact Linear Collider, CLIC), un colisionador de electrones y positrones concebido en el CERN para el estudio de la Física de Altas Energías en la región de los TeV, se basa en un principio de funcionamiento de doble haz: en lugar de emplear elementos activos (klystrons) para proporcionar la potencia RF requerida para acelerar el haz principal (Main Beam, MB), ésta se obtiene de la deceleración de un haz secundario (Drive Beam, DB), de alta corriente y energía moderada, en las llamadas estructuras de extracción y transferencia de potencia (Power Extraction and Transfer Structures, PETS). Estas estructuras emiten una señal interferente RF de más de 130 MW de potencia a 12 GHz, que, por estar localizada en una frecuencia superior a la de corte del modo fundamental en el tubo de vacío del haz (7.6 GHz), se propaga por éste hacia los dispositivos adyacentes, entre los cuales se encuentran los sistemas de monitorización de la posición (Beam Position Monitor, BPM). De acuerdo con el informe conceptual de diseño de CLIC (Conceptual Design Report, CDR) , un sistema eficiente de monitorización de la posición del haz en el decelerador del haz secundario deberá cumplir los siguientes requisitos: - Debe ser lo más sencillo y económico posible, ya que se precisan 41580 unidades: el 75% de todos los BPMs de CLIC. - El procesado de señal en el sistema de adquisición deberá ser inmune a la interferencia generada en las PETS. Esto excluye la solución habitual de procesar las señales del BPM a la frecuencia de pulsado del haz (12 GHz). - La señal de posición resultante del procesado debe ser capaz de detectar cambios en la posición del haz de duración igual o mayor a 10 ns (resolución temporal). - La resolución espacial requerida es de 2 um para un tubo de vacío de 23 mm de diámetro, con una calibración precisa. - Amplio rango dinámico: el sistema electrónico de adquisición del BPM debe poder resistir los altos valores de señal provocados por los casos de desviación extrema del haz nominal (se contempla una desviación máxima de la mitad del radio del tubo), así como detectar las señales inducidas por las configuraciones de haz con menor carga de todas las previstas, cuyos niveles serán muy débiles.
[CAT] El Col·lisionador Lineal Compacte (Compact Linear Collider, CLIC), un col·lisionador d'electrons i positrons concebut per l'estudi de la Física d'Altes Energies a la regió dels TeV (energía del centre de massa), es basa en un principi de funcionament de doble feix:en lloc de fer servir elements actius (klystrons) per proporcionar la potència RF requerida per accelerar el feix principal (Main Beam, MB), aquesta s'obtè de la desacceleració d'un feix secundari (Drive Beam, DB), d'alt corrent i energia moderada, a les anomenades estructures d'extracció i transferència de potència (Power Extraction and Transfer Structures, PETS). Aquestes estructures emeten una senyal interferent RF de més de 130 MW de potència a 12 GHz, que, pel fet d'estar localitzada a una freqüència superior a la de tall del mode fonamental al tub de buit del feix (7.6 GHz), es propaga a través d'aquest fins els dispositius adjacents, entre els quals trobem els sistemes de monitorització de la posició (Beam Position Monitor, BPM). D'acord amb l'informe conceptual de disseny de CLIC (Conceptual Design Report, CDR), un sistema eficient de monitorització de la posició del feix al desaccelerador del feix secundari haurà de complir els següents requisits: ¿ - Ha de ser el més senzill i econòmic possible, ja que es necessiten 41580 unitats: el 75% de tots els BPMs de CLIC. ¿ - El processat de la senyal al sistema d'adquisició haurà de ser inmune a la interferència generada als PETS. Això exclou la solució habitual de processar les senyals del BPM a la freqüència de pulsacions del feix (12 GHz). ¿- La senyal de posició resultant del processat ha de ser capaç de detectar canvis a la posició del feix de durada igual o més gran que 10 ns (resolució temporal). ¿- La resolució espaial necessària és de 2 um per a un tub de buit de 23 mm de diàmetre. ¿- Ampli rang dinàmic: el sistema electrònic d'adquisició del BPM ha de poder processar senyals amb nivells extrems, induïdes per feixos de molt alt (100 A) i molt baix (3 A) corrent.
Benot Morell, A. (2016). Beam position monitoring in the clic drive beam decelerator using stripline technology [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/64067
TESIS

La terapia adronica è una tecnica che usa protoni e ioni positivi per trattare il cancro. Essa permette di applicare distribuzioni di dose sul tessuto tumorale con precisioni irraggiungibili attraverso altre tecniche, come per esempio quelle radioterapiche convenzionali. Tale precisione fa sì che la tossicità sul tessuto sano circostante venga ridotta al minimo. Al fine di sfruttare a pieno le potenzialità della terapia adronica, è necessario disporre di una tecnica di monitoraggio in-vivo, che permetta di ridurre l'incertezza di range delle particelle e quindi i margini di sicurezza del trattamento. La tomografia ad emissione positronica (PET) è considerata una delle tecniche di imaging non invasivo in-vivo più mature per il monitoraggio del range nei trattamenti radioterapici. Quando l'acquisizione dei dati PET viene eseguita durante l'irraggiamento, il monitoraggio viene indicato come in-beam. Il problema del monitoraggio in-beam è che i dati acquisiti durante l'irraggiamento (in-spill) sono molto rumorosi mentre quelli acquisiti nelle pause (inter-spill) lo sono molto meno. Durante l'inter-spill, tuttavia, il segnale è anche molto debole perché molti degli emettitori β+ non sono stati ancora prodotti. Il rumore di fondo durante l'in-spill è dovuto alla forte radiazione rivelata mentre il fascio colpisce il tessuto bersaglio. Tale radiazione aumenta la probabilità di rivelazione di coincidenze random, a loro volta fonte di rumore nell'imaging PET. La radiazione di fondo può essere causata dal decadimento di emettitori β+ con vita media nell'ordine dei millisecondi, da raggi γ prodotti immediati (prompt) di reazioni nucleari non correlate al decadimento β+, da produzioni di coppie positrone-elettrone o da neutroni. Gli eventi random non possono essere discriminati dai decadimenti β+ utili, e non possono essere corretti con le tecniche convenzionali di stima delle coincidenze random a causa della mancanza di correlazione temporale tra i decadimenti β+ e i prodotti nucleari immediati. Allo stato dell'arte sono stati proposti due metodi per separare le coincidenze in-spill che si verificano durante la fase di estrazione dall'acceleratore da quelle che si verificano durante la fase di accelerazione. Le prime sono naturalmente più rumorose delle seconde, in quanto durante la fase di accelerazione sono assenti gli eventi prompt. Entrambi i metodi utilizzano informazioni sulla microstruttura del fascio da fonti esterne. Nel primo metodo, il segnale RF dall'acceleratore viene utilizzato per generare un segnale di gate all'interno del sistema di acquisizione PET. Nel secondo, il segnale di gate viene prodotto da un rivelatore di particelle inserito nel percorso del fascio prima del bersaglio. In questa tesi, le fasi della microstruttura del fascio vengono rivelate direttamente analizzando la distribuzione temporale degli eventi PET acquisiti in-spill. A tal fine, un nuovo algoritmo è stato sviluppato e validato in simulazione e sperimentalmente per il rilevamento della microstruttura temporale del fascio. I risultati di simulazione mostrano che e possibile implementare l'algoritmo su un FPGA e sfruttare le informazioni da esso prodotte per discriminare le coincidenze avvenute durante le fasi di estrazione da quelle avvenute durante le fasi di accelerazione. La distribuzione spaziale 3D ei profili di attività 1D degli eventi di coincidenza sono ricavati con un algoritmo di ricostruzione tomografica ML-EM per i dati interspill e in-spill. Il rumore di background è visibile nelle immagini ricostruite da dati sperimentali in-spill. Dopo aver filtrato i dati in-spill, scartando gli eventi di coincidenza che si verificano durante la fase di estrazione, si dimostra che l'immagine ricostruita migliora significativamente. Nel profilo di attività 1D si osserva una forte diminuzione della baseline del segnale, corrispondente al contributo delle coincidenze random. In particolare, il rapporto fra il picco di attività nel target diviso per il livello di fondo migliora di un fattore 4.8. Questa attività è stata sviluppata all'interno dei progetti INSIDE e INFIERI (FP7-PEOPLE-2012-ITN project number 317446), finanziati rispettivamente da MIUR e EU.
Hadron therapy is a widely employed technique that uses protons and heavy ions to treat cancer. It has the potential of delivering highly conformal dose distributions to the tumor volume while sparing the surrounding healthy tissue, thanks to the dose distribution characterized by the Bragg peak at the end of charged particles range. In order to exploit the full potential of hadron therapy, an in vivo monitoring technique is desirable in order to reduce the uncertainties and therefore the treatment safety margins. Positron emission tomography (PET) is considered one of the most promising in vivo non-invasive imaging techniques for monitoring the particle range in radiation treatments. One of the data acquisition methods is the so-called in-beam which is performed during irradiation at the treatment site. The problem of in-beam monitoring is that in-spill data are much noisier while inter-spill data for accelerators with high duty cycles, are much less due to the small number of acquired decays. During the spills, the noisy background is due to the presence of strong beam-induced radiation that increases the random coincidence rates. This background might originate from the decay of β+ emitters with half-lives in millisecond range and high endpoint energies, by γ-rays following nuclear reactions not related to β+ decay or by pair productions and neutrons. The noisy events cannot be separated from the usable decays of long-lived β+ emitters and cannot be corrected with standard random coincidence correction techniques because of the time-correlation of the beam-induced background with the ion beam microstructure. Until now, only two methods exist for identifying coincident events that occur during the microbunches in the spills. Both of them use information about the beam microstructure from external sources. In the first method, the RF signal from the accelerator is used externally and the data processing is done offline. In the second one, a fast particle detector placed in the beam path before the target is used and the process is triggered only when a particle arrives. With this thesis, the correlation between the beam microstructure and the RF of the synchrotron is confirmed by analyzing the events in the spills without the need of an external signal. An algorithm for the calculation of the period of the beam microstructure is developed. Small differences in the period between the spills impose the separate analysis for every spill. The period is calculated with 4 digits precision in nanosecond time scale, making a significant difference to the representation of the microbunch. In the end, the firmware related to the algorithm for the calculation of the period of the beam microstructure is developed using only the events in the spills. The simulation results show that it is possible the algorithm to be implemented in an FPGA and provide information about the period of the beam microstructure in real time. Moreover, a coincidence sorter is developed in order to provide real time coincidence detection. The simulation results for the two different architectures of the sorter that uses comparators with two and three inputs, are presented. The 3D spatial distribution and the 1D activity profiles of the coincidence events are constructed for inter-spill and in-spill data. The strong radiation background is visible in the reconstructed images, especially before the entrance surface of the phantom and at the end of the activity range with a tail. After filtering out the in-spill data by discarding the coincidence events that occur in a sub-interval of the microbunch, it is shown that the reconstructed image improves severely. In the 1D activity profile, one can observe that the number of coincidence events before the entrance surface of the phantom decreases significantly. This might happen because neutrons are discarded since they are detected a few ns later after the interaction of the beam with the nuclei. Results show that the signal to noise ratio (SNR), defined as the activity peak in the phantom divided by the background level, is improved by a factor of about 4.8 with respect to the in-spill signal. In the end, it is important to mention that this activity has been developed within the projects INSIDE and INFIERI (FP7-PEOPLE-2012-ITN project number 317446) funded by MIUR and EU respectively.

In-beam positron emission tomography (in-beam PET) is currently the only method for an in-situ monitoring of highly tumor-conformed charged hadron therapy. In such therapy, the clinical effect of deviations from treatment planning is highly minimized by implementing safety margins around the tumor and selecting proper beam portals. Nevertheless, in-beam PET is able to detect eventual, undesirable range deviations and anatomical modifications during fractionated irradiation, to verify the accuracy of the beam portal delivered and to provide the radiotherapist with an estimation of the difference in dosage if the treatment delivered differs from the planned one. In a first study within this work, a set of simulation and fully-3D reconstruction routines shows that minimizing the opening angle of a cylindrical camera is determinant for an optimum quality of the in-beam PET images. The study yields two favorite detector geometries: a closed ring or a dual-head tomograph with narrow gaps. The implementation of either detector geometry onto an isocentric, ion beam delivery (gantry) is feasible by mounting the PET scanner at the beam nozzle. The implementation of an in-beam PET scanner with the mentioned detector geometries at therapeutic sites with a fixed, horizontal beam line is also feasible. Nevertheless, knowing that previous in-beam PET research in Berkeley was abandoned due to detector activation (Bismuth Germanate, BGO), arising most probably from passive beam shaping contaminations, the proposed detector configurations had to be tested in-beam. For that, BGO was substituted with a state-of-the-art scintillator (lutetium oxyorthosilicate, LSO) and two position sensitive detectors were built. Each detector contains 32 pixels, consisting of LSO finger-like crystals coupled to avalanche photodiode arrays (APDA). In order to readout the two detectors operated in coincidence, either in standalone mode or at the GSI medical beam line, a multi-channel, zero-suppressing free, list mode data acquisition system was built.The APDA were chosen for scintillation detection instead of photomultiplier tubes (PMT) due to their higher compactness and magnetic field resistance. A magnetic field resistant detector is necessary if the in-beam PET scanner is operated close to the last beam bending magnet, due to its fringe magnetic field. This is the case at the isocentric, ion beam delivery planned for the dedicated, heavy ion hospital facility under construction in Heidelberg, Germany. In-beam imaging with the LSO/APDA detectors positioned at small target angles, both upbeam and downbeam from the target, was successful. This proves that the detectors provide a solution for the proposed next-generation, improved in-beam PET scanners. Further confirming this result are germanium-detector-based, spectroscopic gamma-ray measurements: no scintillator activation is observed in patient irradiation conditions. Although a closed ring or a dual-head tomograph with narrow gaps is expected to provide improved in-beam PET images, low count rates in in-beam PET represent a second problem to image quality. More importantly, new accelerator developments will further enhance this problem to the point of making impossible in-beam PET data taking if the present acquisition system is used. For these reasons, two random-suppression methods allowing to collect in-beam PET events even during particle extraction were tested. Image counts raised almost twofold. This proves that the methods and associated data acquisition technique provide a solution for next-generation, in-beam positron emission tomographs installed at synchrotron or cyclotron radiotherapy facilities.

In-beam positron emission tomography (in-beam PET) is currently the only method for an in-situ monitoring of highly tumor-conformed charged hadron therapy. In such therapy, the clinical effect of deviations from treatment planning is highly minimized by implementing safety margins around the tumor and selecting proper beam portals. Nevertheless, in-beam PET is able to detect eventual, undesirable range deviations and anatomical modifications during fractionated irradiation, to verify the accuracy of the beam portal delivered and to provide the radiotherapist with an estimation of the difference in dosage if the treatment delivered differs from the planned one. In a first study within this work, a set of simulation and fully-3D reconstruction routines shows that minimizing the opening angle of a cylindrical camera is determinant for an optimum quality of the in-beam PET images. The study yields two favorite detector geometries: a closed ring or a dual-head tomograph with narrow gaps. The implementation of either detector geometry onto an isocentric, ion beam delivery (gantry) is feasible by mounting the PET scanner at the beam nozzle. The implementation of an in-beam PET scanner with the mentioned detector geometries at therapeutic sites with a fixed, horizontal beam line is also feasible. Nevertheless, knowing that previous in-beam PET research in Berkeley was abandoned due to detector activation (Bismuth Germanate, BGO), arising most probably from passive beam shaping contaminations, the proposed detector configurations had to be tested in-beam. For that, BGO was substituted with a state-of-the-art scintillator (lutetium oxyorthosilicate, LSO) and two position sensitive detectors were built. Each detector contains 32 pixels, consisting of LSO finger-like crystals coupled to avalanche photodiode arrays (APDA). In order to readout the two detectors operated in coincidence, either in standalone mode or at the GSI medical beam line, a multi-channel, zero-suppressing free, list mode data acquisition system was built.The APDA were chosen for scintillation detection instead of photomultiplier tubes (PMT) due to their higher compactness and magnetic field resistance. A magnetic field resistant detector is necessary if the in-beam PET scanner is operated close to the last beam bending magnet, due to its fringe magnetic field. This is the case at the isocentric, ion beam delivery planned for the dedicated, heavy ion hospital facility under construction in Heidelberg, Germany. In-beam imaging with the LSO/APDA detectors positioned at small target angles, both upbeam and downbeam from the target, was successful. This proves that the detectors provide a solution for the proposed next-generation, improved in-beam PET scanners. Further confirming this result are germanium-detector-based, spectroscopic gamma-ray measurements: no scintillator activation is observed in patient irradiation conditions. Although a closed ring or a dual-head tomograph with narrow gaps is expected to provide improved in-beam PET images, low count rates in in-beam PET represent a second problem to image quality. More importantly, new accelerator developments will further enhance this problem to the point of making impossible in-beam PET data taking if the present acquisition system is used. For these reasons, two random-suppression methods allowing to collect in-beam PET events even during particle extraction were tested. Image counts raised almost twofold. This proves that the methods and associated data acquisition technique provide a solution for next-generation, in-beam positron emission tomographs installed at synchrotron or cyclotron radiotherapy facilities.

Additive Manufacturing (AM) is being embraced at a rapid rate, mainly due to its advantages over conventional machining. These include the possibility to create parts with complex geometries, while minimizing waste. The exponential growth of the technology has brought about challenges in quality assurance, which has proved a key barrier to large scale adoption. Developing in-process monitoring techniques for AM is an ongoing challenge, and is still a long way off from the more established techniques developed for conventional machining. Previous research has brought about instances, where the technology has been implemented, with the focus on titanium alloys. This study aims to contribute to the research being carried out within in-process monitoring, and focusses on the Electron Beam Melting (EBM) process. The material being monitored is Inconel 625, to increase the scope of research to higher temperature ranges. The most suitable monitoring technology and vendor for the equipment, is narrowed down through a review of previous literature and market research. Experimental trials to analyze the performance of the monitoring technique with Inconel 625 are carried out. The extracted data is then analyzed using image processing, which gives interesting results with regards to temperature fluctuations over successive layers of the build. The events within the build process for a layer, show interesting deviations in temperature, which are mapped and presented as graphs. The after-rake event, shows a particularly large deviation, which is then attributed to differential heating of the metal powder during the rake phase. This observation is supported by noticing ‘cold-spots’ in extracted images of the build. The results are discussed, and future scope for the study is conveyed. The intention of this study is to provide a base for further research into in-process monitoring for higher temperature ranges and contribute to the development of real-time process monitoring for AM.
“Additive manufacturing” (AM) eller “friformsframställning” har snabbt ökat i omfattning, främst tack vare dess fördelar jämfört med konventionell bearbetning. Fördelarna inkluderar möjligheten att tillverka delar med komplexa geometrier medan slöseri minimeras. Den exponentiella tillväxten av tekniken har medfört utmaningar inom kvalitetssäkring, vilket har visat sig vara ett hinder för storskalig anpassning.  Utveckling av processövervakningstekniker för AM är en pågående utmaning, och ligger efter i utveckling jämfört med de mer etablerade teknikerna som utvecklats för konventionell bearbetning. Tidigare forskning har visat fall där tekniken har implementerats med fokus på titanlegeringar. Denna studie syftar till att bidra till den forskning som genomförs inom processövervakning och fokuserar på EBM-processen (Electronic Beam Melting). Materialet som övervakas är Inconel 625, för att expandera forskningsområdet till högre temperaturområden. Den mest lämpliga övervakningstekniken och leverantör av utrustning väljs ut genom en gransking av tidigare litteratur och en marknadsundersökning. Experimentella försök för att analysera övervakningsteknikens prestanda med Inconel 625 utförs.  De extraherade data analyseras sedan med bildbehandling, vilket ger intressanta resultat med avseende på temperaturfluktuationer över successiva lager av byggobjektet. Händelserna inom byggprocessen för ett lager visar intressanta avvikelser i temperatur, vilka kartläggs och presenteras som grafer. Tillståndet efter räfsning visar en särskilt stor avvikelse, som sedan tillskrivs differentialvärme av metallpulvret under räfsningsfasen. Denna observation stöds genom att notera "cold-spots" i extraherade bilder av byggobjektet. Resultaten diskuteras och vidare omfång för studien framförs. Avsikten med denna studie är att ta fram en grund för vidare forskning i processövervakning för högre temperaturområden och bidra till utvecklingen av realtidsprocessövervakning för AM.

Le travail présenté dans cette thèse a été effectué au sein de la collaboration internationale LHCb qui a conçue et qui exploite un détecteur pour la physique des particules auprès de l’accélérateur proton-proton, le LHC, au CERN à Genève. Ces travaux concerne l’opération de l’expérience dans son ensemble. Ils ont montré toutes leurs forces pendant la première année de prise de données qui a débutée fin 2009. Ils couvrent plusieurs systèmes qui sont très dépendant les uns des autres. Deux systèmes sont plus particulièrement étudiés. Le premier est en charge de la surveillance des faisceaux, du niveau des bruits de fond et de la luminosité. Le second permet la visualisation, l’analyse et l’optimisation des conditions expérimentales. Ces deux systèmes sont fortement interconnectés. En effet, l’amélioration de la qualité des faisceaux de la machine et la diminution du bruit de fond augmentent le nombre de collisions utiles pour la physique. En même temps, comprendre les paramètres clefs qui gouvernent l’opération de l’expérience permet de les optimiser et d’améliorer la qualité des données collectées
There are two main central topics in the thesis: the LHCb beam, background and luminosity monitoring systems and the LHCb optimization systems of experimental conditions. These systems are heavily connected to each other, as improving the machine beam, background and luminosity conditions will automatically improve global operation by maximizing the ratio of luminosity recorded over signal background. At the same time, improving the operation of the experiment will help improve luminosity, by studying more accurately the beam and background conditions and therefore improving the LHC machine settings. In this thesis, the systems to accomplish the requirements of these two main topics are described in detail

Ion beam therapy (IBT) is a promising treatment option in radiotherapy. The characteristic physical and biological properties of light ion beams allow for the delivery of highly tumour conformal dose distributions. Related to the sparing of surrounding healthy tissue and nearby organs at risk, it is feasible to escalate the dose in the tumour volume to reach higher tumour control and survival rates. Remarkable clinical outcome was achieved with IBT for radio-resistant, deep-seated, static and well fixated tumour entities. Presumably, more patients could benefit from the advantages of IBT if it would be available for more frequent tumour sites. Those located in the thorax and upper abdominal region are commonly subjected to intra-fractional, respiration related motion. Different motion compensated dose delivery techniques have been developed for active field shaping with scanned pencil beams and are at least available under experimental conditions at the GSI Helmholtzzentrum für Schwerionenforschung (GSI) in Darmstadt, Germany. High standards for quality assurance are required in IBT to ensure a safe and precise dose application. Both underdosage in the tumour and overdosage in the normal tissue might endanger the treatment success. Since minor unexpected anatomical changes e.g. related to patient mispositioning, tumour shrinkage or tissue swelling could already lead to remarkable deviations between planned and delivered dose distribution, a valuable dose monitoring system is desired for IBT. So far, positron emission tomography (PET) is the only in vivo, in situ and non-invasive qualitative dose monitoring method applied under clinical conditions. It makes use of the tissue autoactivation by nuclear fragmentation reactions occurring along the beam path. Among others, β+-emitting nuclides are generated and decay according to their half-life under the emission of a positron. The subsequent positron-electron annihilation creates two 511 keV photons which are emitted in opposite direction and can be detected as coincidence event by a dedicated PET scanner. The induced three-dimensional (3D) β+-activity distribution in the patient can be reconstructed from the measured coincidences. Conclusions about the delivered dose distribution can be drawn indirectly from a comparison between two β+-activity distributions: the measured one and an expected one generated by a Monte-Carlo simulation. This workflow has been proven to be valuable for the dose monitoring in IBT when it was applied for about 440 patients, mainly suffering from deep-seated head and neck tumours that have been treated with 12C ions at GSI. In the presence of intra-fractional target motion, the conventional 3D PET data processing will result in an inaccurate representation of the β+-activity distribution in the patient. Four-dimensional, time-resolved (4D) reconstruction algorithms adapted to the special geometry of in-beam PET scanners allow to compensate for the motion related blurring artefacts. Within this thesis, a 4D maximum likelihood expectation maximization (MLEM) reconstruction algorithm has been implemented for the double-head scanner Bastei installed at GSI. The proper functionality of the algorithm and its superior performance in terms of suppressing motion related blurring artefacts compared to an already applied co-registration approach has been demonstrated by a comparative simulation study and by dedicated measurements with moving radioactive sources and irradiated targets. Dedicated phantoms mainly made up of polymethyl methacrylate (PMMA) and a motion table for regular one-dimensional (1D) motion patterns have been designed and manufactured for the experiments. Furthermore, the general applicability of the 4D MLEM algorithm for more complex motion patterns has been demonstrated by the successful reduction of motion artefacts from a measurement with rotating (two-dimensional moving) radioactive sources. For 1D cos^2 and cos^4 motion, it has been clearly illustrated by systematic point source measurements that the motion influence can be better compensated with the same number of motion phases if amplitude-sorted instead of time-sorted phases are utilized. In any case, with an appropriate parameter selection to obtain a mean residual motion per phase of about half of the size of a PET crystal size, acceptable results have been achieved. Additionally, it has been validated that the 4D MLEM algorithm allows to reliably access the relevant parameters (particle range and lateral field position and gradients) for a dose verification in intra-fractionally moving targets even from the intrinsically low counting statistics of IBT-PET data. To evaluate the measured β+-activity distribution, it should be compared to a simulated one that is expected from the moving target irradiation. Thus, a 4D version of the simulation software is required. It has to emulate the generation of β+-emitters under consideration of the intra-fractional motion, their decay at motion state dependent coordinates and to create listmode data streams from the simulated coincidences. Such a revised and extended version that has been compiled for the special geometry of the Bastei PET scanner is presented within this thesis. The therapy control system provides information about the exact progress of the motion compensated dose delivery. This information and the intra-fractional target motion needs to be taken into account for simulating realistic β+-activity distributions. A dedicated preclinical phantom simulation study has been performed to demonstrate the correct functionality of the 4D simulation program and the necessity of the additional, motion-related input parameters. Different to the data evaluation for static targets, additional effort is required to avoid a potential misleading interpretation of the 4D measured and simulated β+-activity distribu- tions in the presence of deficient motion mitigation or data processing. It is presented that in the presence of treatment errors the results from the simulation might be in accordance to the measurement although the planned and delivered dose distribution are different. In contrast to that, deviations may occur between both distributions which are not related to anatomical changes but to deficient 4D data processing. Recommendations are given in this thesis to optimize the 4D IBT-PET workflow and to prevent the observer from a mis-interpretation of the dose monitoring data. In summary, the thesis contributes on a large scale to a potential future application of the IBT-PET monitoring for intra-fractionally moving target volumes by providing the required reconstruction and simulation algorithms. Systematic examinations with more realistic, multi-directional and irregular motion patterns are required for further improvements. For a final rating of the expectable benefit from a 4D IBT-PET dose monitoring, future investigations should include real treatment plans, breathing curves and 4D patient CT images
Die Ionenstrahltherapie (englisch: ion beam therapy, IBT) ist eine vielversprechende Behandlungsoption im Bereich der Strahlentherapie. Die charakteristischen physikalischen und biologischen Eigenschaften der Ionenstrahlen werden genutzt, um tumorkonformale Dosisverteilungen zu erzeugen. Die verbesserte Schonung des an den Tumor angrenzenden Normalgewebes und eventuell naheliegender Risikoorgane ermöglicht eine Dosissteigerung im Zielgebiet und somit potentiell höhere Tumorkontroll- und Überlebensraten. Für tiefliegende, gegenüber konventioneller Strahlung resistente, statische und gut fixierte Tumore wurden bereits beachtliche klinische Resultate erzielt. Wahrscheinlich könnten noch mehr Patienten von den Vorteilen der IBT profitieren, wenn diese auch für häufiger auftretende und intrafraktionell bewegliche Tumore uneingeschränkt nutzbar wäre. Verschiedene bewegungskompensierte Bestrahlungsmethoden wurden entwickelt und stehen zumindest unter experimentellen Bedingungen für weitere Untersuchungen am GSI Helmholtzzentrum für Schwerionenforschung (GSI) in Darmstadt zur Verfügung. Um eine sichere und präzise Dosisapplikation in der IBT zu ermöglichen, werden hohe Anforderungen an die Qualitätssicherung gesetzt. Sowohl auftretende Überdosierungen im Normalgewebe als auch Unterdosierungen im Tumor können den Therapieerfolg gefährden. Da bereits kleine, unerwartete anatomische Veränderungen, zum Beispiel durch Fehlpositionierung des Patienten, Schrumpfung des Tumors oder Schwellungen, zu erheblichen Abweichungen zwischen geplanter und applizierter Dosisverteilung führen können, gibt es Bestrebungen, die applizierte Dosis zumindest qualitativ zu verifizieren. Die Positronen-Emissions-Tomografie (PET) ist derzeit die einzige, bereits klinisch erprobte Methode für ein in vivo, in situ und nicht-invasives qualitatives Dosismonitoring. Diese Methode ist im Stande, die Autoaktivierung des bestrahlten Gewebes zu erfassen, welche aufgrund von Kernfragmentierungsprozessen entlang des Strahlweges erzeugt wird. Unter anderem werden in diesen Reaktionen instabile Nuklide erzeugt, die entsprechend ihrer Halbwertszeit unter Emission eines Positrons zerfallen. Bei der anschließenden Positron-Elektron-Annihilation werden zwei 511keV Photonen in entgegengesetzter Richtung emittiert und können mittels eines geeigneten PET-Scanners als Koinzidenzereignis detektiert werden. Die im Patienten induzierte dreidimensionale (3D) β+-Aktivitätsverteilung kann aus den gemessenen Koinzidenzen rekonstruiert werden. Ein Vergleich der gemessenen mit einer erwarteten, mittels Monte-Carlo Simulation erzeugten β+-Aktivitätsverteilung erlaubt es, Schlussfolgerungen über die tatsächlich im Patienten deponierte 3D Dosisverteilung zu ziehen. Diese Art der Datenauswertung wurde erfolgreich für die qualitative Dosisverifikation von über 440 Patienten eingesetzt, deren Tumore (vorwiegend im Kopf- und Halsbereich) an der GSI mit 12C-Ionen bestrahlt wurden. Bei der konventionellen 3D IBT-PET-Datenverarbeitung wird eine mögliche intrafraktionelle Bewegung des Zielgebietes nicht berücksichtigt und fehlerhaft rekonstruierte β+-Aktivitätsverteilungen sind die Folge. Daher werden vierdimensionale, zeitaufgelöste (4D) Rekonstruktionsalgorithmen benötigt, die für die spezielle Geometrie eines in-beam PET-Scanner adaptiert wurden und eine Kompensation der bewegungsinduzierten Artefakte ermöglichen. Im Rahmen der vorliegenden Arbeit wurde für den an der GSI installierten Doppelkopf-PET-Scanner Bastei ein 4D Maximum-Likelihood-Expectation-Maximization (MLEM) Algorithmus implementiert. Die Funktionsfähigkeit des Algorithmus sowie dessen verbesserte Reduktion von Bewegungsartefakten im Vergleich zu einem bereits vorhandenen Koregistrierungsansatz wurde anhand verschiedener Messungen mit bewegten radioaktiven Quellen und bestrahlten Phantomen sowie einer vergleichenden Simulationsstudie dargelegt. Für die Experimente wurden entsprechende Phantomgeometrien (zumeist aus Polymethylmethacrylat (PMMA)) sowie ein Bewegungstisch für reguläre eindimensionale (1D) Bewegungsmuster entworfen und gefertigt. Zudem wurde durch die erfolgreiche, quasi-statische und nahezu artefaktfreie Rekonstruktion einer rotierenden und sich damit zweidimensional bewegenden Aktivitätsverteilung die prinzipielle Anwendbarkeit des 4D MLEM Algorithmus für komplexere Bewegungsmuster gezeigt. Systematische Punktquellenmessungen mit 1D cos^2- und cos^4-förmigen Bewegungsmustern haben deutlich gemacht, dass der Bewegungseinfluss mit der gleichen Anzahl an Bewegungsphasen besser kompensiert werden kann, wenn die Bewegungsphasen entsprechend der Bewegungsamplitude anstelle der -phase unterteilt sind. In jedem Fall können aber zufriedenstellende Rekonstruktionsergebnisse erzielt werden, wenn durch geeignete Parameterwahl eine mittlere Restbewegung pro Bewegungsphase von maximal etwa der halben Größe eines Detektorkristalls eingestellt wird. Durch weitere Experimente konnte gezeigt werden, dass nach der Rekonstruktion mit dem 4D MLEM Algorithmus die relevanten Parameter für die qualitative Dosisverifikation (Teilchenreichweite, laterale Feldposition und -gradienten) zuverlässig erfasst werden können. Dies ist auch dann der Fall, wenn nur eine verminderte Anzahl an Koinzidenzereignissen, so wie sie unter klinischen Bedingungen zu erwarten ist, für die Auswertung verwendet wird. Um die gemessene β+-Aktivitätsverteilung besser zu beurteilen, sollte sie mit einer simulierten, für die bewegungskompensierte Bestrahlung erwarteten Verteilung verglichen werden und es bedarf deshalb einer 4D Version der Simulationssoftware. Diese muss die Erzeugung sowie den Zerfall der Positronenemitter unter Berücksichtigung der intrafraktionellen Bewegung simulieren und aus den gültigen Koinzidenzereignissen Listmode-Datensätze erstellen. Eine derart überarbeitet Version des Simulationsprogramms wurde für den Bastei PET-Scanner erstellt und wird in dieser Arbeit vorgestellt. Informationen über den exakten Verlauf der bewegungskompensierten Bestrahlung werden durch das Therapiekontrollsystem geliefert. Diese Informationen sowie die intrafraktionelle Bewegung werden in die Simulation realistischer β+-Aktivitätsverteilungen bzw. der zugehörigen Listmode-Datensätze einbezogen. Anhand einer präklinischen Phantom-Simulationsstudie wurde die korrekte Funktionsweise des Simulationsprogramms sowie die Notwendigkeit der zusätzlichen Parameter gezeigt. Im Gegensatz zur Datenauswertung für statische Zielvolumina bedarf es bei intrafraktioneller Bewegung gegebenenfalls zusätzlichen Aufwand, um eine Fehlinterpretation aus dem Vergleich der gemessenen und simulierten β+-Aktivitätsverteilung zu vermeiden. In der vorliegenden Arbeit wird beispielhaft gezeigt, dass sich bei fehlerhafter Bewegungskompensation die gemessene und simulierte β+-Aktivitätsverteilung einander ähneln können, obwohl die applizierte Dosisverteilung deutlich von der geplanten abweicht. Im Gegensatz dazu können auch Abweichungen zwischen Messung und Simulation auftreten, die nicht auf anatomische Veränderungen, sondern auf eine ungenaue 4D Datenverarbeitung zurückzuführen sind. Es werden Vorschläge unterbreitet, um den Prozess der 4D IBT-PET Datenauswertung zu optimieren und somit Fehlinterpretationen zu vermeiden. Die vorliegende Dissertationsschrift enthält durch die Bereitstellung der benötigten 4D Rekonstruktions- und Simulationsprogramme grundlegende Arbeiten für eine mögliche zukünftige Anwendung der 4D IBT-PET als qualitatives Dosismonitoring bei intrafraktionell bewegten Zielvolumina. Für weitere Verbesserungen des Verfahrens sind zusätzliche systematische Betrachtungen mit realistischeren, mehrdimensionalen und unregelmäßigen Bewegungsmustern notwendig. Zukünftige Untersuchungen sollten außerdem echte Bestrahlungspläne, Atemkurven sowie 4D Patienten-CT-Daten einschließen, um den erwartbaren Nutzen eines 4D IBT-PET Dosismonitorings besser abschätzen zu können

The methods of analysis with a focused ion beam, commonly termed as nuclear microscopy, include quantitative physical processes like PIXE and RBS. The element concentrations in a sample can be quantitatively mapped with a sub-micron spatial resolution and a sub-ppm sensitivity. Its fully quantitative and non-destructive nature makes it particularly suitable for analysing biological samples. The applications in biomedical research are manifold. The iron overload hypothesis in Parkinson\\\'s disease is investigated by a differential analysis of human substantia nigra. The trace element content is quantified in neuromelanin, in microglia cells, and in extraneuronal environment. A comparison of six Parkinsonian cases with six control cases revealed no significant elevation in iron level bound to neuromelanin. In fact, a decrease in the Fe/S ratio of Parkinsonian neuromelanin was measured, suggesting a modification in its iron binding properties. Drosophila melanogaster, or the fruit fly, is a widely used model organism in neurobiological experiments. The electrolyte elements are quantified in various organs associated with the olfactory signalling, namely the brain, the antenna and its sensilla hairs, the mouth parts, and the compound eye. The determination of spatially resolved element concentrations is useful in preparing the organ specific Ringer\\\'s solution, an artificial lymph that is used in disruptive neurobiological experiments. The role of trace elements in the progression of atherosclerosis is examined in a pilot study. A differential quantification of the element content in an induced murine atherosclerotic lesion reveals elevated S and Ca levels in the artery wall adjacent to the lesion and an increase in iron in the lesion. The 3D quantitative distribution of elements is reconstructed by means of stacking the 2D quantitative maps of consecutive sections of an artery. The feasibility of generating a quantitative elemental rodent brain atlas by Large Area Mapping is investigated by measuring at high beam currents. A whole coronal section of the rat brain was measured in segments in 14 h. Individual quantitative maps of the segments are pieced together to reconstruct a high-definition element distribution map of the whole section with a subcellular spatial resolution. The use of immunohistochemical staining enhanced with single elements helps in determining the cell specific element content. Its concurrent use with Large Area Mapping can give cellular element distribution maps.

Proton radiation therapy allows for delivering a high dose to a well-confinedregion of interest due to the characteristic proton dose deposition. Due to protonrange straggling, anatomic variations in patients and small patient setup errors,treatment plans needs to account for proton range uncertainties of up to 3.5% invivo.Therefore, it is highly desirable to measure the proton range on-line in orderto minimize margins in the treatment plan. Initially, the feasibility of on-linerange monitoring through prompt gamma imaging and Positron EmissionTomography (PET) at different proton energies is evaluated using GEANT4Application for Tomographic Emission (GATE) Monte Carlo (MC) simulations.In the second phase, the performance of a lead knife-edge slit system for promptgamma imaging was evaluated with MC simulations. Results from simulationsindicate that prompt gamma emission and PET isotope production is correlatedwith proton range, with discrete prompt gamma emission lines from Carbon (4.4MeV) showing good correlation. The evaluated system was able to image thepeak gamma emission location at three different slit positions with promisingprecision ± 1 mm, ± 0.7 mm and ± 1.3 mm, and average shifts of -2 mm, -3 mmand -4 mm, respectively. The proton range was resolved with mean profile shiftsof -12 ± 1 mm, -13 ± 0.7 mm and -14 ± 1.3 mm, following prompt gamma crosssectionbehavior with peak emission- and threshold energies. The results providean indication of the potential of the knife-edge slit system and future work willinclude more extensive MC simulations and experimental measurements at the Skandion clinic to determine its clinical validity.
Strålbehandling av cancer med hjälp av protoner är fördelaktigt jämfört medkonventionell strålterapi då protonerna kan leverera en hög dos till ett välavgränsat område samtidigt som dosen till intilliggande vävnad effektivtreduceras. Tack vare statistiska variationer i protoners dosfördelning, anatomiskaavvikelser i patienter samt små fel vid patientfixering måste behandlingsplanerinnehålla marginaler som motsvarar ca 3.5% avvikelse i protonräckvidd. Att irealtid kunna mäta protoners räckvidd i patienten skulle vara tills stor nytta ochskulle bidra till att minska marginalerna i behandlingsplanen. I ett första skede avarbetet undersöktes möjligheten att avbilda protonräckvidden med promptgammaemission och Positron Emissions Tomografi (PET) genom GEANT4Application for Tomographic Emission (GATE) Monte Carlo (MC) simuleringar.Resultatet från MC simuleringarna användes sedan för att utvärdera ettdetektorsystem för prompt-gamma avbildning. Simuleringarna indikerade attproduktion av både prompt-gamma och PET isotoper är korrelerade medprotonernas räckvidd, särskilt 4.4 MeV emissionslinjen från Kol. Positionen förmaximal gamma emission kunde avbildas för tre olika positioner idetektorsystemet med en medelförskjutning på -2 ± 1 mm, -3 ± 0.7 mm och -4 ±1.3 mm. Detektorprofilen var förskjuten -12 ± 1 mm, -13 ± 0.7 mm och -14 ± 1.3mm jämfört med protonräckvidden p.g.a. interaktionernas energiberoende.Resultatet påvisar detektorsystemets potential att avbilda prompt-gamma fotoneroch framtida arbete omfattar ytterligare MC simuleringar och experimentellamätningar på Skandionklinken.

Feedback On Nanosecond Timescales (FONT) is a feedback system being developed to correct the beam position jitter in the extraction line and final focus system at the Accelerator Test Facility (ATF2), Tsukuba, Japan. FONT5 is currently being tested and is used to correct the intra-train jitter for a 3-bunch train; the bunch spacing is 154ns. This system measures the position of an electron bunch, using beam position monitors (BPMs). From this measurement, digital feedback electronics calculate the required correction, and sends a pulse to a feedback kicker. The feedback kicker then deflects the next bunch in the train in order to correct its position. Stripline BPMs are used at ATF2, and analogue processors manipulate the BPM signals before they are interpreted by the feedback electronics. The BPM system has been modelled and tested so that it can be parameterised and optimised. The BPMs are calibrated regularly, and the resolution of the system measured. Both of these properties have been analysed and modelled. This has allowed the resolution to be minimised. The resolution is an important factor which limits the achievable feedback correction. Several other factors have also been investigated; these include the feedback gain and the bunch-bunch correlation. To allow the feedback electronics to be controlled remotely, several data acquisition systems (DAQs) have been developed to allow data flow both to and from the digital board. The DAQs have been designed specically for the firmware on the FONT digital board.

L'hadronthérapie joue un rôle de plus en plus important au sein des techniques de radiothérapie grâce aux propriétés balistiques des ions et, dans le cas de ceux plus lourds que les protons, à une augmentation de l'efficacité biologique dans la région tumorale. Ces caractéristiques permettent une meilleure conformation de la dose délivrée au volume tumoral et elles permettent en particulier de traiter des tumeurs radio-résistantes. Elles conduisent cependant à une grande sensibilité du parcours des ions aux incertitudes du traitement. C'est dans ce contexte qu'a été proposée la détection de radiations secondaires émises lors des interactions nucléaires induites par les ions incidents dans le patient. La tomographie par émission de positons et la détection des rayons gamma prompts ont notamment fait l'objet d'une recherche intense ces dernières années. Le réseau de formation européen ENTERVISION, soutenu par la communauté ENLIGHT, a été crée fin 2009 pour développer ce type d'imagerie et, plus généralement, traiter les incertitudes de traitement en hadronthérapie. Le travail présenté dans ce manuscrit et intitulé ≪ Modélisation et simulation des processus physiques pour l'imagerie en ligne de l'hadronthérapie ≫ est l'un des nombreux travaux issus de ce projet. Bien que le sujet soit particulièrement large, le fil conducteur de ce travail a été une étude systématique visant in fine une implémentation d'un dispositif d'imagerie ≪ gamma prompts ≫ utilisable à la fois en faisceau de protons et d'ions carbone
Hadrontherapy is taking an increasingly important role in radiotherapy thanks to the ballistic properties of ions and, for those heavier than protons, an enhancement in the relative biological effectiveness in the tumour region. These features allow for a higher tumour conformality possible and gives the opportunity to tackle the problem of radioresistant tumours. However, they may lead to a great sensitivity of ion range to treatment uncertainties, namely to morphological changes along their path. In view of this, the detection of secondary radiations emitted after nuclear interactions between the incoming ions and the patient have been long proposed as ion range probes and, in this regard, positron emitters and prompt gammas have been the matter of intensive research. The European training network ENTERVISION, supported by the ENLIGHT community, was created in the end of 2009 in order to develop such imaging techniques and more generally to address treatment uncertainties during hadrontherapy. The present work is one of the many resulting from this project, under the subject “Modelling and simulation of physics processes for in-beam imaging in hadrontherapy”. Despite the extensive range of the topic, the purpose was always to make a systematic study towards the clinical implementation of a prompt-gamma imaging device to be used for both proton and carbon ion treatments

Le procédé de fabrication additive par fusion sur lit de poudre par faisceau d’électrons (E-PBF) permet la réalisation de pièces métalliques par fusion sélective de couches successives. Il peut cependant générer des défauts dans les pièces fabriquées. Afin d’améliorer la fiabilité de ce procédé, le besoin de contrôles in situ (pendant la fabrication) est devenu une exigence forte. L’objectif de ce travail est de mettre en place des stratégies de suivi in situ de la fabrication additive E-PBF. L’outil sélectionné est une caméra proche infrarouge (NIR) permettant d’obtenir des images des pièces en cours de fabrication. Un dispositif expérimental permettant de réaliser les acquisitions à l’aide d’une caméra proche infrarouge de façon automatisée a été mis en place en prenant en compte l’environnement contraignant (haute température, vide, dépôt de métal sur les parois). Deux stratégies de contrôle sont proposées. La première vise à prendre une image de chaque couche fabriquée, en l’occurrence à l’issue de l’étape de fusion. Des routines d’analyse d’images ont été développées et permettent d’identifier et de localiser les défauts (distorsions géométriques, porosités) à partir de leur signature thermique sur les images NIR. Une méthode de contrôle non destructif (tomographie aux rayons X) permet de valider la détection des défauts internes. La seconde stratégie de caractérisation consiste à réaliser l’acquisition d’images en continu afin d’analyser l’évolution temporelle des niveaux de gris, cette dernière apportant des informations reliées aux changements de température. Une méthodologie permettant de détecter, voire d’anticiper certains défauts liés à l’apport d’énergie délivrée par le faisceau d’électrons est proposée. Les deux stratégies de caractérisation doivent permettre de repérer les défauts au plus vite afin de mettre en place une action corrective dans la cadre d’un futur contrôle du procédé par une boucle fermée
Electron beam Powder Bed Fusion (E-PBF) is an additive manufacturing process that allows metallic parts to be built by selectively melting successive layers of powder. However, this process can generate defects in the fabricated parts. To improve the reliability of this process, there is a need to develop in-situ monitoring imaging techniques. The main objective of this work is to set up strategies to characterize in-situ the E-PBF process. The selected tool is a near-infrared (NIR) camera employed to obtain images of the parts being manufactured. The first part of the work has been dedicated to setting up an experimental device allowing to acquire near-infrared images in an automated way and by taking into account the constrained environment of E-PBF (high temperature, vacuum, metal deposit on the walls). Two strategies of in-situ monitoring of E-PBF are suggested. The first one aims at taking one image per layer, just after the melting stage. Image analysis routines were developed and allow to identify and determine the spatial distribution of the defects (geometrical distortions, porosity) from their thermal signatures on the NIR-images. The detection of internal defects is validated with a non-destructive characterization (X-rays computed tomography). The second strategy consists of carrying out continuous image acquisition to analyze the temporal evolution of the grey level which is directly related to temperature changes. A methodology allowing to detect, even to anticipate given defects related to the energy delivered by the electron beam has been proposed. Those two approaches should allow the defects to be identified as quickly as possible to apply a correction within the framework of future closed-loop process control

Dehnungssensoren werden zur Überwachung von sicherheitsrelevanten Bauteilen, besonders in Bauteilen aus faserverstärkten Polymermatrixverbundwerkstoffen eingesetzt. Durch deren Integration in das Bauteilinnere werden sie vor schädigenden mechanischen sowie korrosiven Einwirkungen geschützt. Dies gewährleistet eine zuverlässige sowie dauerhafte Funktion. Verschiedene Ansätze zur Weiterentwicklung integrierbarer Dehnungssensoren werden international untersucht. Die Verringerung des Sensordurchmessers auf Abmaße im Bereich des Durchmessers von Verstärkungsfasern ist dabei ein bedeutendes Entwicklungsziel. Insbesondere bei der Integration in Bauteile aus faserverstärkten Kunststoffen sorgen zum Durchmesser von Fasern vergleichbare Sensordurchmesser für eine optimale Sensoranbindung. Die Bildung von Harznestern sowie schwächender Unstetigkeiten kann mittels dünner Sensoren verhindert werden. Dies gewährleistet eine artefaktefreie Dehnungsmessung. Drei verschiedene Ansätze für neuartige Dehnungssensoren mit kleinem Querschnitt wurden in dieser Arbeit untersucht
Strain sensors are used for structural health monitoring issues, certainly in parts with high safety requirements made of fibre-reinforced plastic composites. The integration of these sensors inside the parts protects them against any mechanical and corrosive impact. The sensor functionality can be enhanced by integration. There is a lot of international research effort to further develop integratable strain sensors. Different approaches are currently pursued. This thesis presents the results of investigations on three different approaches for novel strain sensors. The main goal of these investigations was to minimise the sensor diameter down to the diameter of reinforcing fibres. The small diameter allows for an optimum and artefact free integration of the sensors. The formation of resin nests and notches to the material structure can be prevented by integrating sensor with a smaller diameter. The strain measurement and monitoring is enhanced and more reliable then

Changes in load characteristics, deterioration with age, environmental influences and random actions may cause local or global damage in structures, especially in bridges, which are designed for long life spans. Continuous health monitoring of structures will enable the early identification of distress and allow appropriate retrofitting in order to avoid failure or collapse of the structures. In recent times, structural health monitoring (SHM) has attracted much attention in both research and development. Local and global methods of damage assessment using the monitored information are an integral part of SHM techniques. In the local case, the assessment of the state of a structure is done either by direct visual inspection or using experimental techniques such as acoustic emission, ultrasonic, magnetic particle inspection, radiography and eddy current. A characteristic of all these techniques is that their application requires a prior localization of the damaged zones. The limitations of the local methodologies can be overcome by using vibration-based methods, which give a global damage assessment. The vibration-based damage detection methods use measured changes in dynamic characteristics to evaluate changes in physical properties that may indicate structural damage or degradation. The basic idea is that modal parameters (notably frequencies, mode shapes, and modal damping) are functions of the physical properties of the structure (mass, damping, and stiffness). Changes in the physical properties will therefore cause changes in the modal properties. Any reduction in structural stiffness and increase in damping in the structure may indicate structural damage. This research uses the variations in vibration parameters to develop a multi-criteria method for damage assessment. It incorporates the changes in natural frequencies, modal flexibility and modal strain energy to locate damage in the main load bearing elements in bridge structures such as beams, slabs and trusses and simple bridges involving these elements. Dynamic computer simulation techniques are used to develop and apply the multi-criteria procedure under different damage scenarios. The effectiveness of the procedure is demonstrated through numerical examples. Results show that the proposed method incorporating modal flexibility and modal strain energy changes is competent in damage assessment in the structures treated herein.

Changes in load characteristics, deterioration with age, environmental influences and random actions may cause local or global damage in structures, especially in bridges, which are designed for long life spans. Continuous health monitoring of structures will enable the early identification of distress and allow appropriate retrofitting in order to avoid failure or collapse of the structures. In recent times, structural health monitoring (SHM) has attracted much attention in both research and development. Local and global methods of damage assessment using the monitored information are an integral part of SHM techniques. In the local case, the assessment of the state of a structure is done either by direct visual inspection or using experimental techniques such as acoustic emission, ultrasonic, magnetic particle inspection, radiography and eddy current. A characteristic of all these techniques is that their application requires a prior localization of the damaged zones. The limitations of the local methodologies can be overcome by using vibration-based methods, which give a global damage assessment. The vibration-based damage detection methods use measured changes in dynamic characteristics to evaluate changes in physical properties that may indicate structural damage or degradation. The basic idea is that modal parameters (notably frequencies, mode shapes, and modal damping) are functions of the physical properties of the structure (mass, damping, and stiffness). Changes in the physical properties will therefore cause changes in the modal properties. Any reduction in structural stiffness and increase in damping in the structure may indicate structural damage. This research uses the variations in vibration parameters to develop a multi-criteria method for damage assessment. It incorporates the changes in natural frequencies, modal flexibility and modal strain energy to locate damage in the main load bearing elements in bridge structures such as beams, slabs and trusses and simple bridges involving these elements. Dynamic computer simulation techniques are used to develop and apply the multi-criteria procedure under different damage scenarios. The effectiveness of the procedure is demonstrated through numerical examples. Results show that the proposed method incorporating modal flexibility and modal strain energy changes is competent in damage assessment in the structures treated herein.

Bridges are designed for long life spans and the slab-on-girder bridge is one of the most commonly used bridge types in Australia and also in the world. However, changes in load characteristics, random loading, deterioration with age and environmental influences may inflict damage to the structures. This research developed a method to detect, locate and quantify damage in the slab-on-girder bridge structure at an early stage before the problem becomes visible to human eyes. Findings of this research will help to enhance the safety and efficiency of slab-on-girder bridges.

In-beam Positron Emission Tomography (PET) is a system for monitoring high precision radiation therapy which is in the most cases applied to the tumors near organs at risk. High quality and fast availability of in-beam PET images are, therefore, extremely important for successful verification of the dose delivery. Two main problems make an in-beam PET monitoring a challenging task. Firstly, in-beam PET measurements result in a very low counting statistics. Secondly, an integration of the PET scanner into the treatment facility requires significant reduction of the sensitive surface of the scanner and leads to a dual-head form resulting in imaging artifacts. The aim of this work is to bring the imaging process by means of in-beam PET to optimum quality and time scale. The following topics are under consideration: - analysis of image quality for in-beam PET; - image reconstruction; - solutions for building, testing, and integration of a PET monitoring system into the dedicated treatment facility.

The Particle Therapy (PT) is a particular kind of radiation therapy in which accelerated light ions beams are exploited instead of photons, commonly used in conventional radiotherapy. One of the most advantageous PT features is its capability to achieve high localised dose distributions, allowing to concentrate most of the energy release in the tumour volume. As a results, the undesired amount of radiation absorbed by the healthy tissues is minimised, and the probability of side effects occurrence is reduced. One of the most important still open issue in PT is represented by the treatment quality assurance, since a control system capable to provide a real-time feedback on the dose distribution actually delivered to the patient is missing in the clinical practice. In PT the capability to deliver the dose at a certain depth depends from the capability to properly predict the beam range in the patient, then the scientific community have addressed several researches to develop on-line beam range verification techniques. In PT the primary beam particles does not escape from the patient, and the most followed approach consists of an indirect range measurement, exploiting the secondary particles produced due to the nuclear interaction between the beam projectiles and the crossed tissues nuclei. In this Ph.D. thesis an innovative range verification technique that exploits charged secondary fragments, particularly suitable for 12C ion treatments, is proposed. In particular, the development of a detector, named Dose Profiler (DP) and specifically designed for this purpose, is presented. The detector, assembled and tested using a proton beam in 2017, has been included in a clinical trial that will be performed at CNAO. The DP design and the performances measured using MIPs and protons are reviewed, as well the preliminary results obtained in a test with an anthropomorphic phantom. The feasibility of the proposed technique is discussed .

In-beam positron emission tomography (in-beam PET) is currently the only method for an in-situ monitoring of highly tumor-conformed charged hadron therapy. In such therapy, the clinical effect of deviations from treatment planning is highly minimized by implementing safety margins around the tumor and selecting proper beam portals. Nevertheless, in-beam PET is able to detect eventual, undesirable range deviations and anatomical modifications during fractionated irradiation, to verify the accuracy of the beam portal delivered and to provide the radiotherapist with an estimation of the difference in dosage if the treatment delivered differs from the planned one. In a first study within this work, a set of simulation and fully-3D reconstruction routines shows that minimizing the opening angle of a cylindrical camera is determinant for an optimum quality of the in-beam PET images. The study yields two favorite detector geometries: a closed ring or a dual-head tomograph with narrow gaps. The implementation of either detector geometry onto an isocentric, ion beam delivery (gantry) is feasible by mounting the PET scanner at the beam nozzle. The implementation of an in-beam PET scanner with the mentioned detector geometries at therapeutic sites with a fixed, horizontal beam line is also feasible. Nevertheless, knowing that previous in-beam PET research in Berkeley was abandoned due to detector activation (Bismuth Germanate, BGO), arising most probably from passive beam shaping contaminations, the proposed detector configurations had to be tested in-beam. For that, BGO was substituted with a state-of-the-art scintillator (lutetium oxyorthosilicate, LSO) and two position sensitive detectors were built. Each detector contains 32 pixels, consisting of LSO finger-like crystals coupled to avalanche photodiode arrays (APDA). In order to readout the two detectors operated in coincidence, either in standalone mode or at the GSI medical beam line, a multi-channel, zero-suppressing free, list mode data acquisition system was built.The APDA were chosen for scintillation detection instead of photomultiplier tubes (PMT) due to their higher compactness and magnetic field resistance. A magnetic field resistant detector is necessary if the in-beam PET scanner is operated close to the last beam bending magnet, due to its fringe magnetic field. This is the case at the isocentric, ion beam delivery planned for the dedicated, heavy ion hospital facility under construction in Heidelberg, Germany. In-beam imaging with the LSO/APDA detectors positioned at small target angles, both upbeam and downbeam from the target, was successful. This proves that the detectors provide a solution for the proposed next-generation, improved in-beam PET scanners. Further confirming this result are germanium-detector-based, spectroscopic gamma-ray measurements: no scintillator activation is observed in patient irradiation conditions. Although a closed ring or a dual-head tomograph with narrow gaps is expected to provide improved in-beam PET images, low count rates in in-beam PET represent a second problem to image quality. More importantly, new accelerator developments will further enhance this problem to the point of making impossible in-beam PET data taking if the present acquisition system is used. For these reasons, two random-suppression methods allowing to collect in-beam PET events even during particle extraction were tested. Image counts raised almost twofold. This proves that the methods and associated data acquisition technique provide a solution for next-generation, in-beam positron emission tomographs installed at synchrotron or cyclotron radiotherapy facilities.

Proton therapy is a very attractive and promising modality in cancer treatment that relies on the depth dose distribution property known as Bragg peak. This localized and bettercontrolled dose distribution in comparison to X-rays, improves the therapeutic ratio while sparing the healthy tissue surrounding the tumors. The beam energy is one of the key parameters in proton therapy that defines the depth inside the patient (up to 30 cm) at which the radiation is deposited with the required clinical range accuracy of 1 mm. Range deviations alter the dose distribution, leading to under-dosage of the distal edge of the tumor or normal structure over-dosage. The beam range verification is mainly performed by measuring the integrated depth-dose profiles in water phantoms and using multi layers ionization chambers and just in the routine quality control checks. This thesis is focused on the development and the use of the Ultra-Fast Silicon Detector (UFSD), chosen as innovative proton beam monitor. UFSDs are thin silicon sensors based on the Low Gain Avalanche Diode technology (LGAD), which should overcome the limitations of ionization chambers. They can be used for the energy check during the irradiation, and for the development of new beam monitors for future delivery schemes employing fast energy modulation systems. The prototype consists of two thin UFSDs, aligned along the clinical proton beam direction in a telescope configuration that allows to measure the time-of-flight (TOF) of proton to determine the beam energy .

Ion beam therapy (IBT) is a promising treatment option in radiotherapy. The characteristic physical and biological properties of light ion beams allow for the delivery of highly tumour conformal dose distributions. Related to the sparing of surrounding healthy tissue and nearby organs at risk, it is feasible to escalate the dose in the tumour volume to reach higher tumour control and survival rates. Remarkable clinical outcome was achieved with IBT for radio-resistant, deep-seated, static and well fixated tumour entities. Presumably, more patients could benefit from the advantages of IBT if it would be available for more frequent tumour sites. Those located in the thorax and upper abdominal region are commonly subjected to intra-fractional, respiration related motion. Different motion compensated dose delivery techniques have been developed for active field shaping with scanned pencil beams and are at least available under experimental conditions at the GSI Helmholtzzentrum für Schwerionenforschung (GSI) in Darmstadt, Germany. High standards for quality assurance are required in IBT to ensure a safe and precise dose application. Both underdosage in the tumour and overdosage in the normal tissue might endanger the treatment success. Since minor unexpected anatomical changes e.g. related to patient mispositioning, tumour shrinkage or tissue swelling could already lead to remarkable deviations between planned and delivered dose distribution, a valuable dose monitoring system is desired for IBT. So far, positron emission tomography (PET) is the only in vivo, in situ and non-invasive qualitative dose monitoring method applied under clinical conditions. It makes use of the tissue autoactivation by nuclear fragmentation reactions occurring along the beam path. Among others, β+-emitting nuclides are generated and decay according to their half-life under the emission of a positron. The subsequent positron-electron annihilation creates two 511 keV photons which are emitted in opposite direction and can be detected as coincidence event by a dedicated PET scanner. The induced three-dimensional (3D) β+-activity distribution in the patient can be reconstructed from the measured coincidences. Conclusions about the delivered dose distribution can be drawn indirectly from a comparison between two β+-activity distributions: the measured one and an expected one generated by a Monte-Carlo simulation. This workflow has been proven to be valuable for the dose monitoring in IBT when it was applied for about 440 patients, mainly suffering from deep-seated head and neck tumours that have been treated with 12C ions at GSI. In the presence of intra-fractional target motion, the conventional 3D PET data processing will result in an inaccurate representation of the β+-activity distribution in the patient. Four-dimensional, time-resolved (4D) reconstruction algorithms adapted to the special geometry of in-beam PET scanners allow to compensate for the motion related blurring artefacts. Within this thesis, a 4D maximum likelihood expectation maximization (MLEM) reconstruction algorithm has been implemented for the double-head scanner Bastei installed at GSI. The proper functionality of the algorithm and its superior performance in terms of suppressing motion related blurring artefacts compared to an already applied co-registration approach has been demonstrated by a comparative simulation study and by dedicated measurements with moving radioactive sources and irradiated targets. Dedicated phantoms mainly made up of polymethyl methacrylate (PMMA) and a motion table for regular one-dimensional (1D) motion patterns have been designed and manufactured for the experiments. Furthermore, the general applicability of the 4D MLEM algorithm for more complex motion patterns has been demonstrated by the successful reduction of motion artefacts from a measurement with rotating (two-dimensional moving) radioactive sources. For 1D cos^2 and cos^4 motion, it has been clearly illustrated by systematic point source measurements that the motion influence can be better compensated with the same number of motion phases if amplitude-sorted instead of time-sorted phases are utilized. In any case, with an appropriate parameter selection to obtain a mean residual motion per phase of about half of the size of a PET crystal size, acceptable results have been achieved. Additionally, it has been validated that the 4D MLEM algorithm allows to reliably access the relevant parameters (particle range and lateral field position and gradients) for a dose verification in intra-fractionally moving targets even from the intrinsically low counting statistics of IBT-PET data. To evaluate the measured β+-activity distribution, it should be compared to a simulated one that is expected from the moving target irradiation. Thus, a 4D version of the simulation software is required. It has to emulate the generation of β+-emitters under consideration of the intra-fractional motion, their decay at motion state dependent coordinates and to create listmode data streams from the simulated coincidences. Such a revised and extended version that has been compiled for the special geometry of the Bastei PET scanner is presented within this thesis. The therapy control system provides information about the exact progress of the motion compensated dose delivery. This information and the intra-fractional target motion needs to be taken into account for simulating realistic β+-activity distributions. A dedicated preclinical phantom simulation study has been performed to demonstrate the correct functionality of the 4D simulation program and the necessity of the additional, motion-related input parameters. Different to the data evaluation for static targets, additional effort is required to avoid a potential misleading interpretation of the 4D measured and simulated β+-activity distribu- tions in the presence of deficient motion mitigation or data processing. It is presented that in the presence of treatment errors the results from the simulation might be in accordance to the measurement although the planned and delivered dose distribution are different. In contrast to that, deviations may occur between both distributions which are not related to anatomical changes but to deficient 4D data processing. Recommendations are given in this thesis to optimize the 4D IBT-PET workflow and to prevent the observer from a mis-interpretation of the dose monitoring data. In summary, the thesis contributes on a large scale to a potential future application of the IBT-PET monitoring for intra-fractionally moving target volumes by providing the required reconstruction and simulation algorithms. Systematic examinations with more realistic, multi-directional and irregular motion patterns are required for further improvements. For a final rating of the expectable benefit from a 4D IBT-PET dose monitoring, future investigations should include real treatment plans, breathing curves and 4D patient CT images.:1 Motivation 1.1 Potential and obstacles of ion beam therapy 1.2 Objectives of the thesis 2 Ion beam therapy and moving targets 2.1 Physical and biological properties of ion beams 2.1.1 Dose deposition 2.1.2 Biological effectivity 2.2 Technical aspects of ion beam delivery 2.2.1 Active and passive beam delivery technique 2.2.2 Beam monitoring for pencil beam scanning 2.2.3 Considerations in treatment planning related to patient CT image 2.3 Organ motion in ion beam therapy 2.3.1 Types of organ motion 2.3.2 Detection of intra-fractional motion 2.3.3 Motion compensated ion beam therapy 2.4 Dose monitoring by means of positron emission tomography 2.4.1 Principle of PET imaging in ion beam therapy 2.4.2 In-beam PET at GSI 3 Reconstruction of in-beam PET data taken from moving targets 3.1 Reconstruction algorithm 3.1.1 3D MLEM reconstruction applied at GSI 3.1.2 4D in-beam PET reconstruction methods 3.1.3 Comparison of gated co-registration and 4D MLEM 3.2 Experiments with moving radioactive sources 3.2.1 Rotation of radioactive sources 3.2.2 One-dimensional point source motion 3.3 In-beam PET measurements with moving targets 3.3.1 Verification of lateral field position and gradients 3.3.2 Verification of particle range 3.4 Summary and discussion 4 Simulation of phase-sorted in-beam PET data for moving targets 4.1 Upgrading the IBT-PET simulation from 3D to 4D 4.1.1 General and motion-related simulation demands 4.1.2 Input parameters for the 4D simulation program 4.1.3 Workflow of the 4D simulation program 4.2 Verification of the 4D simulation code by means of a preclinical phantom study 4.2.1 Experiment design 4.2.2 4D in-beam PET data simulation 4.2.3 Comparison with 3D simulation 4.3 Summary and discussion 5 Interpretation of 4D IBT-PET data with respect to deficient motion mitigation or data processing 5.1 Detectability of failed motion mitigation 5.1.1 Failure in gated beam delivery 5.1.2 Failure in lateral target tracking 5.2 Deficient correlation between motion and PET data 5.3 Recommendations for the 4D IBT-PET workflow 6 Summary and outlook 7 Appendix A Transformation matrices A.1 Composition of transformation matrices A.2 Storage of transformation matrices A.3 Transformation matrices for rotation B Noise reduction in analogue signals by FFT-based filtering C Motion tables and corresponding motion patterns C.1 Rotational motion C.2 Motion table with stepping motor for precise 1D motion patterns C.3 Motion table enabling relative target movement D Synchronisation of PET, motion and beam monitoring data E Sorting PET data by time or amplitude and calculating corresponding mean offsets Bibliography
Die Ionenstrahltherapie (englisch: ion beam therapy, IBT) ist eine vielversprechende Behandlungsoption im Bereich der Strahlentherapie. Die charakteristischen physikalischen und biologischen Eigenschaften der Ionenstrahlen werden genutzt, um tumorkonformale Dosisverteilungen zu erzeugen. Die verbesserte Schonung des an den Tumor angrenzenden Normalgewebes und eventuell naheliegender Risikoorgane ermöglicht eine Dosissteigerung im Zielgebiet und somit potentiell höhere Tumorkontroll- und Überlebensraten. Für tiefliegende, gegenüber konventioneller Strahlung resistente, statische und gut fixierte Tumore wurden bereits beachtliche klinische Resultate erzielt. Wahrscheinlich könnten noch mehr Patienten von den Vorteilen der IBT profitieren, wenn diese auch für häufiger auftretende und intrafraktionell bewegliche Tumore uneingeschränkt nutzbar wäre. Verschiedene bewegungskompensierte Bestrahlungsmethoden wurden entwickelt und stehen zumindest unter experimentellen Bedingungen für weitere Untersuchungen am GSI Helmholtzzentrum für Schwerionenforschung (GSI) in Darmstadt zur Verfügung. Um eine sichere und präzise Dosisapplikation in der IBT zu ermöglichen, werden hohe Anforderungen an die Qualitätssicherung gesetzt. Sowohl auftretende Überdosierungen im Normalgewebe als auch Unterdosierungen im Tumor können den Therapieerfolg gefährden. Da bereits kleine, unerwartete anatomische Veränderungen, zum Beispiel durch Fehlpositionierung des Patienten, Schrumpfung des Tumors oder Schwellungen, zu erheblichen Abweichungen zwischen geplanter und applizierter Dosisverteilung führen können, gibt es Bestrebungen, die applizierte Dosis zumindest qualitativ zu verifizieren. Die Positronen-Emissions-Tomografie (PET) ist derzeit die einzige, bereits klinisch erprobte Methode für ein in vivo, in situ und nicht-invasives qualitatives Dosismonitoring. Diese Methode ist im Stande, die Autoaktivierung des bestrahlten Gewebes zu erfassen, welche aufgrund von Kernfragmentierungsprozessen entlang des Strahlweges erzeugt wird. Unter anderem werden in diesen Reaktionen instabile Nuklide erzeugt, die entsprechend ihrer Halbwertszeit unter Emission eines Positrons zerfallen. Bei der anschließenden Positron-Elektron-Annihilation werden zwei 511keV Photonen in entgegengesetzter Richtung emittiert und können mittels eines geeigneten PET-Scanners als Koinzidenzereignis detektiert werden. Die im Patienten induzierte dreidimensionale (3D) β+-Aktivitätsverteilung kann aus den gemessenen Koinzidenzen rekonstruiert werden. Ein Vergleich der gemessenen mit einer erwarteten, mittels Monte-Carlo Simulation erzeugten β+-Aktivitätsverteilung erlaubt es, Schlussfolgerungen über die tatsächlich im Patienten deponierte 3D Dosisverteilung zu ziehen. Diese Art der Datenauswertung wurde erfolgreich für die qualitative Dosisverifikation von über 440 Patienten eingesetzt, deren Tumore (vorwiegend im Kopf- und Halsbereich) an der GSI mit 12C-Ionen bestrahlt wurden. Bei der konventionellen 3D IBT-PET-Datenverarbeitung wird eine mögliche intrafraktionelle Bewegung des Zielgebietes nicht berücksichtigt und fehlerhaft rekonstruierte β+-Aktivitätsverteilungen sind die Folge. Daher werden vierdimensionale, zeitaufgelöste (4D) Rekonstruktionsalgorithmen benötigt, die für die spezielle Geometrie eines in-beam PET-Scanner adaptiert wurden und eine Kompensation der bewegungsinduzierten Artefakte ermöglichen. Im Rahmen der vorliegenden Arbeit wurde für den an der GSI installierten Doppelkopf-PET-Scanner Bastei ein 4D Maximum-Likelihood-Expectation-Maximization (MLEM) Algorithmus implementiert. Die Funktionsfähigkeit des Algorithmus sowie dessen verbesserte Reduktion von Bewegungsartefakten im Vergleich zu einem bereits vorhandenen Koregistrierungsansatz wurde anhand verschiedener Messungen mit bewegten radioaktiven Quellen und bestrahlten Phantomen sowie einer vergleichenden Simulationsstudie dargelegt. Für die Experimente wurden entsprechende Phantomgeometrien (zumeist aus Polymethylmethacrylat (PMMA)) sowie ein Bewegungstisch für reguläre eindimensionale (1D) Bewegungsmuster entworfen und gefertigt. Zudem wurde durch die erfolgreiche, quasi-statische und nahezu artefaktfreie Rekonstruktion einer rotierenden und sich damit zweidimensional bewegenden Aktivitätsverteilung die prinzipielle Anwendbarkeit des 4D MLEM Algorithmus für komplexere Bewegungsmuster gezeigt. Systematische Punktquellenmessungen mit 1D cos^2- und cos^4-förmigen Bewegungsmustern haben deutlich gemacht, dass der Bewegungseinfluss mit der gleichen Anzahl an Bewegungsphasen besser kompensiert werden kann, wenn die Bewegungsphasen entsprechend der Bewegungsamplitude anstelle der -phase unterteilt sind. In jedem Fall können aber zufriedenstellende Rekonstruktionsergebnisse erzielt werden, wenn durch geeignete Parameterwahl eine mittlere Restbewegung pro Bewegungsphase von maximal etwa der halben Größe eines Detektorkristalls eingestellt wird. Durch weitere Experimente konnte gezeigt werden, dass nach der Rekonstruktion mit dem 4D MLEM Algorithmus die relevanten Parameter für die qualitative Dosisverifikation (Teilchenreichweite, laterale Feldposition und -gradienten) zuverlässig erfasst werden können. Dies ist auch dann der Fall, wenn nur eine verminderte Anzahl an Koinzidenzereignissen, so wie sie unter klinischen Bedingungen zu erwarten ist, für die Auswertung verwendet wird. Um die gemessene β+-Aktivitätsverteilung besser zu beurteilen, sollte sie mit einer simulierten, für die bewegungskompensierte Bestrahlung erwarteten Verteilung verglichen werden und es bedarf deshalb einer 4D Version der Simulationssoftware. Diese muss die Erzeugung sowie den Zerfall der Positronenemitter unter Berücksichtigung der intrafraktionellen Bewegung simulieren und aus den gültigen Koinzidenzereignissen Listmode-Datensätze erstellen. Eine derart überarbeitet Version des Simulationsprogramms wurde für den Bastei PET-Scanner erstellt und wird in dieser Arbeit vorgestellt. Informationen über den exakten Verlauf der bewegungskompensierten Bestrahlung werden durch das Therapiekontrollsystem geliefert. Diese Informationen sowie die intrafraktionelle Bewegung werden in die Simulation realistischer β+-Aktivitätsverteilungen bzw. der zugehörigen Listmode-Datensätze einbezogen. Anhand einer präklinischen Phantom-Simulationsstudie wurde die korrekte Funktionsweise des Simulationsprogramms sowie die Notwendigkeit der zusätzlichen Parameter gezeigt. Im Gegensatz zur Datenauswertung für statische Zielvolumina bedarf es bei intrafraktioneller Bewegung gegebenenfalls zusätzlichen Aufwand, um eine Fehlinterpretation aus dem Vergleich der gemessenen und simulierten β+-Aktivitätsverteilung zu vermeiden. In der vorliegenden Arbeit wird beispielhaft gezeigt, dass sich bei fehlerhafter Bewegungskompensation die gemessene und simulierte β+-Aktivitätsverteilung einander ähneln können, obwohl die applizierte Dosisverteilung deutlich von der geplanten abweicht. Im Gegensatz dazu können auch Abweichungen zwischen Messung und Simulation auftreten, die nicht auf anatomische Veränderungen, sondern auf eine ungenaue 4D Datenverarbeitung zurückzuführen sind. Es werden Vorschläge unterbreitet, um den Prozess der 4D IBT-PET Datenauswertung zu optimieren und somit Fehlinterpretationen zu vermeiden. Die vorliegende Dissertationsschrift enthält durch die Bereitstellung der benötigten 4D Rekonstruktions- und Simulationsprogramme grundlegende Arbeiten für eine mögliche zukünftige Anwendung der 4D IBT-PET als qualitatives Dosismonitoring bei intrafraktionell bewegten Zielvolumina. Für weitere Verbesserungen des Verfahrens sind zusätzliche systematische Betrachtungen mit realistischeren, mehrdimensionalen und unregelmäßigen Bewegungsmustern notwendig. Zukünftige Untersuchungen sollten außerdem echte Bestrahlungspläne, Atemkurven sowie 4D Patienten-CT-Daten einschließen, um den erwartbaren Nutzen eines 4D IBT-PET Dosismonitorings besser abschätzen zu können.:1 Motivation 1.1 Potential and obstacles of ion beam therapy 1.2 Objectives of the thesis 2 Ion beam therapy and moving targets 2.1 Physical and biological properties of ion beams 2.1.1 Dose deposition 2.1.2 Biological effectivity 2.2 Technical aspects of ion beam delivery 2.2.1 Active and passive beam delivery technique 2.2.2 Beam monitoring for pencil beam scanning 2.2.3 Considerations in treatment planning related to patient CT image 2.3 Organ motion in ion beam therapy 2.3.1 Types of organ motion 2.3.2 Detection of intra-fractional motion 2.3.3 Motion compensated ion beam therapy 2.4 Dose monitoring by means of positron emission tomography 2.4.1 Principle of PET imaging in ion beam therapy 2.4.2 In-beam PET at GSI 3 Reconstruction of in-beam PET data taken from moving targets 3.1 Reconstruction algorithm 3.1.1 3D MLEM reconstruction applied at GSI 3.1.2 4D in-beam PET reconstruction methods 3.1.3 Comparison of gated co-registration and 4D MLEM 3.2 Experiments with moving radioactive sources 3.2.1 Rotation of radioactive sources 3.2.2 One-dimensional point source motion 3.3 In-beam PET measurements with moving targets 3.3.1 Verification of lateral field position and gradients 3.3.2 Verification of particle range 3.4 Summary and discussion 4 Simulation of phase-sorted in-beam PET data for moving targets 4.1 Upgrading the IBT-PET simulation from 3D to 4D 4.1.1 General and motion-related simulation demands 4.1.2 Input parameters for the 4D simulation program 4.1.3 Workflow of the 4D simulation program 4.2 Verification of the 4D simulation code by means of a preclinical phantom study 4.2.1 Experiment design 4.2.2 4D in-beam PET data simulation 4.2.3 Comparison with 3D simulation 4.3 Summary and discussion 5 Interpretation of 4D IBT-PET data with respect to deficient motion mitigation or data processing 5.1 Detectability of failed motion mitigation 5.1.1 Failure in gated beam delivery 5.1.2 Failure in lateral target tracking 5.2 Deficient correlation between motion and PET data 5.3 Recommendations for the 4D IBT-PET workflow 6 Summary and outlook 7 Appendix A Transformation matrices A.1 Composition of transformation matrices A.2 Storage of transformation matrices A.3 Transformation matrices for rotation B Noise reduction in analogue signals by FFT-based filtering C Motion tables and corresponding motion patterns C.1 Rotational motion C.2 Motion table with stepping motor for precise 1D motion patterns C.3 Motion table enabling relative target movement D Synchronisation of PET, motion and beam monitoring data E Sorting PET data by time or amplitude and calculating corresponding mean offsets Bibliography

During vibration of engineering structures, fatigue cracks may exhibit repetitive crack open-close breathing like phenomenon. In this thesis, the concept of entropy is employed to quantify this bi-linearity/irregularity of the vibration response so as to evaluate crack severity. To increase the sensitivity of the entropy calculation to detect the damage severity, entropy is merged with wavelet transformation (WT). A cantilever beam with a breathing crack is studied to asses proposed crack identification method under two vibration conditions: sinusoidal and random excitations. Through numerical simulations and experimental testing, the breathing crack identification under sinusoidal excitation is studied first and proven to be effective. Then, the crack identification sensitivity under lower excitation frequencies is further improved by parametric optimization of sample entropy and WT. Finally, breathing crack identification under general random excitations are experimentally studied and realized using frequency response functions (FRFs) as an add-in tool with the proposed crack identification technique.
October 2016

碩士
國立臺北科技大學
機械與自動化碩士外國學生專班
106
In the field of clean room systems, the need to have high standards of cleaning and environmental control has generated the creation of new equipment which can solve the different problems of monitoring in particle filtration. To carry out this research we aimed at the light scattering by particles, the light scattering by particles is the process by which small particles such as dust, planetary dust, and blood cells cause optical phenomena such as rainbows and color of the sky. The system proposed below has been developed based on new technologies like the evolution of camera sensors, the use of a beam laser to visualize particles, and the link between programming algorithms with free platforms. We use a green beam laser (a Ld Pumped All-Solid-State Green Laser) which it has been modified in order to control its aperture and angle of slide, the light is determined as a visible electromagnetic radiation having a wavelength λ between 0.4 (violet color) and 0.7 µm (red color), the center of the visible light region is green light, with a wavelength of approximately 0.5 µm, being it the range which we are going to handle, furthermore several holder designs were manufactured to create the suitable holder lens for the beam laser. In addition, to recognize the real wavelength of the laser we performed a test of stroboscopic measurement thereby we can filter the noise wavelength; a bandpass filter with the center point in 0.532 µm was chosen to clarify the image. We demonstrate the viability of using a high sensitivity camera to perform a Particle image visualization system after testing three different kinds of cameras which each one has a special feature. Canon EOS 650D which has a high resolution in photographs at long distances, Logitech ConferenceCam CC3000e USB camera used to test the communication between the program and the photography sensor. A high-speed camera such as Lumenera’s Lt225 2.2 Megapixel High-Speed CMOS Camera. With the purpose to figure out the advantages and disadvantages of each camera, strict tests were performed inside a controlled environment where the exposure of external diameter light was removed, we used a transparent FOUP (Front Opening Unified Pod) where the sample of white marble dust (Fumed Silica) was introduced to see its dispersion among the particles. Consequently, photographs were taken at different angles of incidence such as against the laser and 60 degrees with reference to the line of action of the laser. Moreover, other tests were carried out in an external diameter environment, where photographs of particles from the human body were taken. Herein when performing the different tests, the parameter to consider in order to create an efficient Particle Image Visualization system is to use a high sensitivity camera, such as the Hamamatsu Orca Flash camera, which has a high percentage of the spectrum response, its control of the resolution and frame per seconds, its the most powerful tool for Particle Image Visualization. The tests were performed using the fumed silica particles which have a diameter size of 12 µm, consequently the information was processed through the software programmed in visual studio and Matlab. Image processing using OpenCV libraries in such a case EmguCV. The fundamental principle of the image processing is the reading of each pixel (the intensities of each pixel) and in that event of processing black and white images and each pixel receives values from 0 to 255, with 0 being the value for black and 255 for white. The program algorithm responds to these values and will separate the high-intensity values from the low-intensity values. The green color will become an important value, which by means of mathematical filters; will generate a clearer image of where the particles are. In an additional way, this research included the applying image algorithms in Matlab to visualize particles in the air, in other words, we handled the image like a matrix where each pixel is a vector which has information, and this information is its location inside of the image and its trajectory. Moreover, The simulation using Ansys was achieved to contrast the result of the video and image processing, the comparison give us an accurate idea of the principal point to improve our system, such as speed of visualization and range of visualizing measure.

Dehnungssensoren werden zur Überwachung von sicherheitsrelevanten Bauteilen, besonders in Bauteilen aus faserverstärkten Polymermatrixverbundwerkstoffen eingesetzt. Durch deren Integration in das Bauteilinnere werden sie vor schädigenden mechanischen sowie korrosiven Einwirkungen geschützt. Dies gewährleistet eine zuverlässige sowie dauerhafte Funktion. Verschiedene Ansätze zur Weiterentwicklung integrierbarer Dehnungssensoren werden international untersucht. Die Verringerung des Sensordurchmessers auf Abmaße im Bereich des Durchmessers von Verstärkungsfasern ist dabei ein bedeutendes Entwicklungsziel. Insbesondere bei der Integration in Bauteile aus faserverstärkten Kunststoffen sorgen zum Durchmesser von Fasern vergleichbare Sensordurchmesser für eine optimale Sensoranbindung. Die Bildung von Harznestern sowie schwächender Unstetigkeiten kann mittels dünner Sensoren verhindert werden. Dies gewährleistet eine artefaktefreie Dehnungsmessung. Drei verschiedene Ansätze für neuartige Dehnungssensoren mit kleinem Querschnitt wurden in dieser Arbeit untersucht.
Strain sensors are used for structural health monitoring issues, certainly in parts with high safety requirements made of fibre-reinforced plastic composites. The integration of these sensors inside the parts protects them against any mechanical and corrosive impact. The sensor functionality can be enhanced by integration. There is a lot of international research effort to further develop integratable strain sensors. Different approaches are currently pursued. This thesis presents the results of investigations on three different approaches for novel strain sensors. The main goal of these investigations was to minimise the sensor diameter down to the diameter of reinforcing fibres. The small diameter allows for an optimum and artefact free integration of the sensors. The formation of resin nests and notches to the material structure can be prevented by integrating sensor with a smaller diameter. The strain measurement and monitoring is enhanced and more reliable then.

Composite structures provide opportunities for weight reduction, material tailoring and integrating control surfaces with embedded transducers, which are not possible in conventional metallic structures. As a result there is a substantial increase in the use of composite materials in aerospace and other major industries, which has necessitated the need for structural health monitoring(SHM) of aerospace structures. In the context of SHM of aircraft structures, there are many areas, which are still not explored and need deep investigation. Among these, one of the major areas is the development of efficient damage models for complex composite structures, like stiffened structures, box-type structures, which are the building blocks of an aircraft wing structure. Quantification of the defect due to porosity and especially the methods for identifying the porous regions in a composite structure is another such area, which demands extensive research. In aircraft structures, it is not advisable for the structures, to have high porosity content, since it can initiate common defects in composites such as, delamination, matrix cracks etc.. In fact, there is need for a high frequency analysis to detect defects in such complex structures and also to detect damages, where the change in the stiffness due to the damage is very small. Lamb wave propagation based method is one of the efficient high frequency wave based method for damage detection and are extensively used for detecting small damages, which is essentially needed in aircraft industry. However, in order, to develop an efficient Lamb wave based SHM system, we also need an efficient computational wave propagation model. Developing an efficient computational wave propagation model for complex structures is still a challenging area. One of the major difficulty is its computational expense, when the analysis is performed using conventional FEM. However, for 1D And 2D composite structures, frequency domain spectral finite element method (SFEM), which are very effective in sensing small stiffness changes due to a defect in a structure, is one of the efficient tool for developing computationally efficient and accurate wave based damage models. In this work, we extend the efficiency of SFEM in developing damage models, for detecting damages in built-up composite structures and porous composite structure. Finally, in reality, the nature of variability of the material properties in a composite structure, created a variety of structural problems, in which the uncertainties in different parameters play a major part. Uncertainties can be due to the lack of good knowledge of material properties or due to the change in the load and support condition with the change in environmental variables such as temperature, humidity and pressure. The modeling technique is also one of the major sources of uncertainty, in the analysis of composites. In fact, when the variations are large, we can find in the literatures available that the probabilistic models are advantageous than the deterministic ones. Further, without performing a proper uncertain wave propagation analysis, to characterize the effect of uncertainty in different parameters, it is difficult to maintain the reliability of the results predicted by SFEM based damage models. Hence, in this work, we also study the effect of uncertainty in different structural parameters on the performance of the damage models, based on the models developed in the present work. First, two SFEM based models, one based on the method of assembling 2D spectral elements and the other based on the concept of coupling 2D and 1D spectral elements, are developed to perform high frequency wave propagation analysis of some of the commonly used built-up composite structures. The SFEM model developed using the plate-beam coupling approach is then used to model wave propagation in a multiple stiffened structure and also to model the stiffened structures with different cross sections such as T-section, I-section and hat section. Next, the wave propagation in a porous laminated composite beam is modeled using SFEM, based on the modified rule of mixture approach. Here, the material properties of the composite is obtained from the modified rule of mixture model, which are then used in SFEM to develop a new model for solving wave propagation problems in porous laminated composite beam. The influence of the porosity content on the parameters such as wave number, group speed and also the effect of variation in theses parameters on the time responses are studied first. Next, the effect of the length of the porous region (in the propagation direction) and the frequency of loading, on the time responses, is studied. The change in the time responses with the change in the porosity of the structure is used as a parameter to find the porosity content in a composite beam. The SFEM models developed in this study is then used in the context of wave based damage detection, in the next study. First ,the actual measured response from a structure and the numerically obtained response from a SFEM model for porous laminated composite beam are used for the estimation of porosity, by solving a nonlinear optimization problem. The damage force indicator (DFI) technique is used to locate the porous region in a beam and also to find its length, using the measured wave propagation responses. DFI is derived from the dynamic stiffness matrix of the healthy structure along with the nodal displacements of the damaged structure. Next, a wave propagation based method is developed for modeling damage in stiffened composite structures, using SFEM, to locate and quantify the damage due to a crack and skin-stiffener debonding. The method of wave scattering and DFI technique are used to quantify the damage in the stiffened structure. In the uncertain wave propagation analysis, a study on the uncertainty in material parameters on the wave propagation responses in a healthy metallic beam structure is performed first. Both modulus of elasticity and density are considered uncertain and the analysis is performed using Monte-Carlo simulation (MCS) under the environment of SFEM. The randomness in the material properties are characterized by three different distributions namely normal, Weibul and extreme value distribution and their effect on wave propagation, in beam is investigated. Even a study is performed on the usage of different beam theories and their uncertain responses due to dynamic impulse load. A study is also conducted to analyze the wave propagation response In a composite structure in an uncertain environment using Neumann expansion blended with Monte-Carlo simulation (NE-MCS) under the environment of SFEM. Neumann expansion method accelerates the MCS, which is required for composites as there are many number of uncertain variables. The effect of the parameters like, fiber orientation, lay-up sequence, number of layers and the layer thickness on the uncertain responses due to dynamic impulse load, is thoroughly analyzed. Finally, a probabilistic sensitivity analysis is performed to estimate the sensitivity of uncertain material and fabrication parameters, on the SFEM based damage models for a porous laminated composite beam. MCS is coupled with SFEM, for the uncertain wave propagation analysis and the Kullback-Leibler relative entropy is used as the measure of sensitivity. The sensitivity of different input variables on the wave number, group speed and the values of DFI, are mainly considered in this study. The thesis, written in nine chapters, presents a unified document on wave propagation in healthy and defective composite structure subjected to both deterministic and highly uncertain environment.