The main aim of the thesis is the development of a gamma camera for prompt gamma monitoring in proton therapy. The strength of this particular type of radiotherapy is the possibility to release the dose in a well limited area, without damaging healthy tissues. However these treatments have uncertainties in determining the deep of penetration of the beam in the patient. To solve this problem and guarantee safer treatments, several projects are investigating beam monitoring, through the revelation of prompt gamma emitted after nuclear interactions of protons with tissues. The gamma camera of interest is based on the concept of slit camera, which allows to obtain a 1-D projection on the scintillator of the beam path in the target. The project was funded by IBA (Ion Beam Applications), with the aim to develop a compact gamma camera with high spatial resolution for use during the treatment. The camera would allow the beam monitoring in cancer treatment. The project phases covered different issues, from the choice of scintillator material and geometry and the choice of photo-detectors for scintillation light revelation to the design of electronics for signal readout and a digital section for their elaboration. The thesis, in particular, begins from the start of year 2012, and involved primarily in the design of electronics and firmware for signal readout. First some Matlab simulations were done in order to understand input pulses features, using specification of crystal and photo-detector. After that Orcad simulations of the analog front-end were performed and optimal components selected for the system to work properly with maximum dynamic range. Then the work moved to the firmware of microcontroller, used for electronics settings and data acquisition. The last task was to program TCP/IP communication protocol in Labview between FPGA and pc in order to provide user interface. The thesis is structured as follows: The first chapter concentrates on general introduction about different Therapy systems. It includes purpose of Proton therapy, how Proton therapy is different from standard radiation therapy. It also explains different mechanisms and comparison of radiation treatments including Neutron therapy, Electron therapy, Particle therapy and some Multimodality systems. The main physical phenomenon of interaction of photon, neutron and ions with matter is also discussed. Finally the different systems that can be employed for proton therapy and specially for prompt gammas based on detection mechanism are also reviewed. 9 Page Second chapter is concern about different schemes that could be used for prompt gamma monitoring. Multiple factors such as gamma event rate, camera geometry parameters, crystal and photo-detector were considered. It listed the information for the optimization of good design and finally then selection choice is made. The third chapter concern about the design and operation of complete system. It mentions the Matlab simulated results of the input that is coming to the first stage of readout circuit. It also discusses about the simulation of front-end readout electronics, component selection for design and the result obtained with each stage of front-end electronics. Finally the fourth chapter is devoted to Digital design and firmware implementation. It talks about all the design parameters regarding the Circuit Board, Microcontroller and the user-interface. This chapter also explains the noise analysis that is done in Matlab to get the signal and noise data points based on the parameters of scintillator, SiPM and first stage readout electronics and then simulated with orcad using piece-wise function in order to get optimal time constant for first stage amplifier based on maximum signal to noise ratio. This chapter also focuses on TCP/IP tranmission between Labview and FPGA that is required to provide user interface for first prototype of gamma camera.
L’obiettivo principale della tesi è lo sviluppo di una gamma camera per la rivelazione dei raggi gamma secondari emessi in adroterapia a protoni, particolare tipo di radioterapia per la cura del cancro. Il vantaggio di questo tipo di terapia è la possibilità di rilasciare la dose in modo circoscritto nello spazio. Tuttavia tali trattamenti, allo stato attuale di monitoraggio, presentano incertezze nella determinazione della profondità di penetrazione del fascio nel paziente, imponendo restrizioni in termini di profondità. Per far fronte a questa problematica ed effettuare trattamenti più sicuri, diversi progetti sono attualmente in via di sviluppo per il controllo del fascio di protoni, tramite la rivelazione dei gamma secondari emessi a seguito delle interazioni dei protoni con i tessuti. La gamma camera di interesse si basa sul concetto di collimatore a fenditura, che consente di ottenere una proiezione unidimensionale sullo scintillatore del percorso del fascio nel bersaglio. Il progetto è finanziato da IBA (Ion Beam Applications), con lo scopo di sviluppare una gamma camera compatta con alta risoluzione spaziale per utilizzo durante il trattamento. La camera consentirà il controllo del fascio in trattamenti di tumori in cui è necessaria un’alta risoluzione spaziale. Le fasi del progetto hanno coperto varie questioni, dalla scelta del materiale scintillatore e della sua geometra e la scelta dei fotorivelatori al progetto di un’elettronica analogica per la lettura dei segnali e di una sezione digitale per l’elaborazione degli stessi. Oggetto di questa tesi, iniziata nell’anno accademico 2011/2012, sono stati in particolare il progetto dell’elettronica analogica e lo sviluppo del firmware. Inizialmente sono state effettuate simulazioni Matlab riguardanti la catena scintillatore-fotorivelatore per comprendere la forma e l’ampiezza degli impulsi da leggere con l’elettronica analogica dedicata. Successivamente, gli stadi di lettura sono stati implementati, simulati e dimensionati in Orcad Capture in modo da sfruttare il range dinamico dell’elettronica alle energie di interesse. Terminata la fase di simulazione, il lavoro si è spostato sullo sviluppo del firmware del microcontrollore responsabile del controllo dell’elettronica e della raccolta dei dati acquisiti. Attività secondarie svolte durante il lavoro di tesi sono state la partecipazione al debug dell’intera catena dell’elettronica di lettura, implementata in una scheda di prova. Infine mi sono dedicato allo sviluppo dell’interfaccia utente del sistema in ambiente Labview. La tesi è strutturata come segue: il primo capitolo fornisce un’introduzione generale sull’adroterapia, spiegandone gli scopi e le differenze rispetto alla radioterapia tradizionale. Sono illustrati i vari tipi di adroterapia e i fenomeni fisici riguardanti l’interazione di fotoni, neutroni e ioni con la materia. Infine sono elencati i vari metodi di monitoraggio del fascio, soffermandosi in particolare sul monitoraggio dei gamma secondari, tecnica presa in considerazione nel progetto oggetto di questa tesi. 11 Page Il secondo capitolo riassume la fase di studio preliminare che ha portato al disegno della gamma camera, in base alle specifiche richieste per un utilizzo clinico della stessa. Fattori determinanti nella definizione delle caratteristiche della camera sono stati in particolare il rate degli eventi gamma e la sensitività in termini di dose. La scelta della geometria, dei materiali e dei dispositivi scelti è illustrata e motivata. Il terzo capitolo riguarda il progetto dell’elettronica supportato da simulazioni Matlab del segnale in ingresso all’elettronica e simulazioni Spice del front-end sviluppato a tale scopo. Il quarto capitolo è dedicato allo sviluppo della sezione digitale del progetto e all’implementazione del firmware del microcontrollore per il controllo dell’elettronica. Sono inoltre riportate simulazioni di rumore dei fotorivelatori con lo scopo di dimensionare l’elettronica di lettura per ottenere il massimo rapporto segnale-rumore. Il capitolo si chiude con la presentazione dell’interfaccia Labview sviluppata per la gestione da parte dell’utente della gamma camera finale.
Development of a prompt gamma camera for beam range control in proton therapy : design of readout electronics and firmware implementation
ZAHEER, RIFAQAT
2012/2013
Abstract
The main aim of the thesis is the development of a gamma camera for prompt gamma monitoring in proton therapy. The strength of this particular type of radiotherapy is the possibility to release the dose in a well limited area, without damaging healthy tissues. However these treatments have uncertainties in determining the deep of penetration of the beam in the patient. To solve this problem and guarantee safer treatments, several projects are investigating beam monitoring, through the revelation of prompt gamma emitted after nuclear interactions of protons with tissues. The gamma camera of interest is based on the concept of slit camera, which allows to obtain a 1-D projection on the scintillator of the beam path in the target. The project was funded by IBA (Ion Beam Applications), with the aim to develop a compact gamma camera with high spatial resolution for use during the treatment. The camera would allow the beam monitoring in cancer treatment. The project phases covered different issues, from the choice of scintillator material and geometry and the choice of photo-detectors for scintillation light revelation to the design of electronics for signal readout and a digital section for their elaboration. The thesis, in particular, begins from the start of year 2012, and involved primarily in the design of electronics and firmware for signal readout. First some Matlab simulations were done in order to understand input pulses features, using specification of crystal and photo-detector. After that Orcad simulations of the analog front-end were performed and optimal components selected for the system to work properly with maximum dynamic range. Then the work moved to the firmware of microcontroller, used for electronics settings and data acquisition. The last task was to program TCP/IP communication protocol in Labview between FPGA and pc in order to provide user interface. The thesis is structured as follows: The first chapter concentrates on general introduction about different Therapy systems. It includes purpose of Proton therapy, how Proton therapy is different from standard radiation therapy. It also explains different mechanisms and comparison of radiation treatments including Neutron therapy, Electron therapy, Particle therapy and some Multimodality systems. The main physical phenomenon of interaction of photon, neutron and ions with matter is also discussed. Finally the different systems that can be employed for proton therapy and specially for prompt gammas based on detection mechanism are also reviewed. 9 Page Second chapter is concern about different schemes that could be used for prompt gamma monitoring. Multiple factors such as gamma event rate, camera geometry parameters, crystal and photo-detector were considered. It listed the information for the optimization of good design and finally then selection choice is made. The third chapter concern about the design and operation of complete system. It mentions the Matlab simulated results of the input that is coming to the first stage of readout circuit. It also discusses about the simulation of front-end readout electronics, component selection for design and the result obtained with each stage of front-end electronics. Finally the fourth chapter is devoted to Digital design and firmware implementation. It talks about all the design parameters regarding the Circuit Board, Microcontroller and the user-interface. This chapter also explains the noise analysis that is done in Matlab to get the signal and noise data points based on the parameters of scintillator, SiPM and first stage readout electronics and then simulated with orcad using piece-wise function in order to get optimal time constant for first stage amplifier based on maximum signal to noise ratio. This chapter also focuses on TCP/IP tranmission between Labview and FPGA that is required to provide user interface for first prototype of gamma camera.| File | Dimensione | Formato | |
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2012_12_ZAHEER.pdf
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Descrizione: Thesis text
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https://hdl.handle.net/10589/72790