Radiotherapy with high-energy charged particles has become an attractive therapeutic option for patients with several tumour types. The favourable physical properties of such particles justify their use. Unlike X-ray irradiation, the dose deposit of charged particles is characterized by a finite range in matter dependent on the starting energy, and by a sharp and narrow maximum reached towards the end of the range, the so called "Bragg peak". As a result, a high dose can be precisely delivered to the tumour area, while reducing the risk to surrounding healthy tissues. Because of these dosimetric benefits, charged particles such as protons, which are used in proton therapy, are currently being intensely investigated. Also neutrons, when used in neutron capture therapy, allow a highly selective therapeutic technique, providing an additional significant advantage due to their higher relative biological effectiveness (RBE). Neutron Capture Enhanced Particle Therapy (NCEPT), a new hybrid technique under development at The Australian Nuclear Science and Technology Organisation (ANSTO), arises from these considerations. This new type of radiotherapy is able to boost the effectiveness of particle therapy by capturing the thermal neutrons produced in and around the treatment site as a by-product of the particle therapy process, using neutron capture agent (10B or 157Gd-based) that concentrates in cancer cells. However, because of the large dose gradients which exist at the boundary between the treatment region and the surrounding healthy tissue, uncertainties in the determination of the range can heavily impact the applied dose distribution, preventing the techniques that used charged particles from exploiting their maximum potential. As regards NCEPT, the in vivo measurement can be performed by detecting the gamma rays emitted at highly specific wavelengths during the boron or gadolinium neutron capture reactions. Since they are emitted in situ and their emission rate is proportional to the reaction rate of the capture reactions, their detection makes it possible to monitor and quantify the delivered dose and its distribution during therapy. The goal of this thesis project is to design and develop a suitable detection system, the BENEdiCTE (Boron Enhanced NEutron CapTurE) module, capable of detecting the neutron-capture gamma photons, in order to estimate the dose delivered to the patient. The thesis is organized as follows: • Chapter 1 presents a brief overview on particle therapy, highlighting advantages and disadvantages of the different particles. Proton therapy is deeply explored, together with gamma radiation and radiation detectors, both for imaging and spectroscopy. It closes with an introduction of the GAMMA project, which has been the starting point for the BENEdiCTE module. • Chapter 2 describes neutron capture therapy, focusing in particular on boron neutron capture therapy. An introduction of the NCEPT technique follows, along with the ANSTO project and its main specifications and goals. • Chapter 3 defines the crystal and the photodetectors used. After an overview of the different photodetectors available, the choice of NUV-HD Silicon Photomultipliers (SiPMs) is justified, by describing their main figures of merit. Lastly, the readout ASIC is presented. • Chapter 4 describes in detail the detection system structure, composed of the scintillator crystal, the 64 NUV-HD SiPMs matrix, a metal enclosure and the DAQ system developed. Moreover, the VHDL firmware structure and the GUI developed for data acquisition are depicted. • Chapter 5 contains the characterizations and measurements performed with the instrument developed. First of all, the anticoincidence line is tested, then the spectroscopic capabilities of the detector are analyzed. • Chapter 6, lastly, presents a summary of the results and gives a view of the future perspective and challenges of the developed system.
La radioterapia che utilizza particelle ad alta energia è diventata un’interessante opzione terapeutica per molteplici tipologie di tumore. Le vantaggiose proprietà fisiche di questo tipo di particelle giustificano il loro utilizzo. A differenza che nei raggi X, la dose depositata dalle particelle cariche è caratterizzata da un percorso finito nella materia, che dipende dall’energia e raggiunge un picco massimo nel punto più profondo, il cosiddetto "picco di Bragg". Di conseguenza, un’alta dose può essere rilasciata precisamente nell’area tumorale, riducendo il rischio per i tessuti sani circostanti. Grazie a questi benefici nel rilascio di dose, le particelle cariche come i protoni, che sono usati nella protonterapia, sono attualmente oggetto di studio. Anche i neutroni, quando usati nelle terapie di cattura neutronica, permettono una tecnica terapeutica altamente selettiva, fornendo inoltre un vantaggio aggiuntivo dato dalla loro elevata efficacia biologica relativa (RBE). Da queste considerazioni nasce la Neutron Capture Enhanced Particle Therapy (NCEPT), una nuova tecnica ibrida in via di sviluppo all’ Australian Nuclear Science and Technology Organisation (ANSTO). Questa nuova tecnica di radioterapia è in grado di aumentare l’efficacia dell’adroterapia catturando i neutroni termici generati all’interno ed intorno all’area di trattamento, come prodotti delle reazioni di adroterapia, grazie all’utilizzo di agenti di cattura neutronica (a base di 10B o 157Gd) concentrati nelle cellule tumorali. A causa degli elevati gradienti di dose che esistono al confine fra l’area di trattamento ed i tessuti sani circostanti, però, incertezze nella determinazione della profondità possono modificare pesantemente la distribuzione di dose, impedendo quindi alle tecniche che utilizzano particelle pesanti di sfruttare al massimo il loro potenziale. In particolare, nella NCEPT, il monitoraggio in vivo può essere effettuato detectando i raggi gamma emessi a specifiche lunghezze d’onda durante le reazioni di cattura neutronica del boro o del gadolinio. Poichè questi raggi sono emessi in situ ed il loro tasso di emissione è proporzionale al tasso di emissione delle reazioni di cattura, la loro rivelazione rende possible monitorare e quantificare la dose rilasciata e la sua distribuzione durante la terapia. L’obiettivo di questo progetto di tesi è il design e lo sviluppo di un adeguato sistema, il modulo BENEdiCTE (Boron Enhanced NEutron CapTurE), capace di rivelare i fotoni gamma derivanti dalle catture neutroniche, col fine di stimare la dose rilasciata al paziente. La tesi è strutturata come segue: • Capitolo 1 presenta una breve panoramica sull’adroterapia, evidenziando vantaggi e svantaggi dei diversi tipi di particelle. La proton terapia è analizzata nel dettaglio, insieme alle radiazioni gamma ed ai rivelatori di radiazioni, sia per imaging sia per spettroscopia. Il capitolo si conclude infine con un’introduzione al progetto GAMMA, punto di partenza per il modulo BENEdiCTE. • Capitolo 2 descrive la terapia di cattura neutronica, concentrandosi in particolare sul boro come agente di cattura. Segue una presentazione della tecnica NCEPT e del progetto ANSTO, con relative specifiche ed obiettivi. • Capitolo 3 definisce il cristallo ed i fotorivelatori usati. Dopo una panoramica dei diversi fotorivelatori disponibili, viene motivata la scelta dei NUV-HD Silicon Photomultipliers (SiPMs) descrivendo le loro caratteristiche. Infine, viene presentato l’ASIC di lettura. • Capitolo 4 descrive in dettaglio la struttura del sistema di rivela- zione, composto dal cristallo scintillatore, la matrice da 64 NUV- HD SiPMs, un involucro in alluminio ed il DAQ sviluppato. Inoltre, vengono mostrati anche la struttura del codice VHDL e la GUI sviluppata per l’acquisizione dei dati. • Capitolo 5 contiene la caratterizzazione e le misure effettuate con lo strumento sviluppato. Prima di tutto è testata la linea di anticoincidenza, successivamente vengono analizzate le capacita spettroscopiche del rivelatore. • Capitolo 6 presenta infine un riassunto dei risultati e offre una visione delle prospettive e delle sfide future del sistema sviluppato.
BENEdiCTE (Boron Enhanced NEutron CapTurE) gamma-ray detection module
Caracciolo, Anita
2019/2020
Abstract
Radiotherapy with high-energy charged particles has become an attractive therapeutic option for patients with several tumour types. The favourable physical properties of such particles justify their use. Unlike X-ray irradiation, the dose deposit of charged particles is characterized by a finite range in matter dependent on the starting energy, and by a sharp and narrow maximum reached towards the end of the range, the so called "Bragg peak". As a result, a high dose can be precisely delivered to the tumour area, while reducing the risk to surrounding healthy tissues. Because of these dosimetric benefits, charged particles such as protons, which are used in proton therapy, are currently being intensely investigated. Also neutrons, when used in neutron capture therapy, allow a highly selective therapeutic technique, providing an additional significant advantage due to their higher relative biological effectiveness (RBE). Neutron Capture Enhanced Particle Therapy (NCEPT), a new hybrid technique under development at The Australian Nuclear Science and Technology Organisation (ANSTO), arises from these considerations. This new type of radiotherapy is able to boost the effectiveness of particle therapy by capturing the thermal neutrons produced in and around the treatment site as a by-product of the particle therapy process, using neutron capture agent (10B or 157Gd-based) that concentrates in cancer cells. However, because of the large dose gradients which exist at the boundary between the treatment region and the surrounding healthy tissue, uncertainties in the determination of the range can heavily impact the applied dose distribution, preventing the techniques that used charged particles from exploiting their maximum potential. As regards NCEPT, the in vivo measurement can be performed by detecting the gamma rays emitted at highly specific wavelengths during the boron or gadolinium neutron capture reactions. Since they are emitted in situ and their emission rate is proportional to the reaction rate of the capture reactions, their detection makes it possible to monitor and quantify the delivered dose and its distribution during therapy. The goal of this thesis project is to design and develop a suitable detection system, the BENEdiCTE (Boron Enhanced NEutron CapTurE) module, capable of detecting the neutron-capture gamma photons, in order to estimate the dose delivered to the patient. The thesis is organized as follows: • Chapter 1 presents a brief overview on particle therapy, highlighting advantages and disadvantages of the different particles. Proton therapy is deeply explored, together with gamma radiation and radiation detectors, both for imaging and spectroscopy. It closes with an introduction of the GAMMA project, which has been the starting point for the BENEdiCTE module. • Chapter 2 describes neutron capture therapy, focusing in particular on boron neutron capture therapy. An introduction of the NCEPT technique follows, along with the ANSTO project and its main specifications and goals. • Chapter 3 defines the crystal and the photodetectors used. After an overview of the different photodetectors available, the choice of NUV-HD Silicon Photomultipliers (SiPMs) is justified, by describing their main figures of merit. Lastly, the readout ASIC is presented. • Chapter 4 describes in detail the detection system structure, composed of the scintillator crystal, the 64 NUV-HD SiPMs matrix, a metal enclosure and the DAQ system developed. Moreover, the VHDL firmware structure and the GUI developed for data acquisition are depicted. • Chapter 5 contains the characterizations and measurements performed with the instrument developed. First of all, the anticoincidence line is tested, then the spectroscopic capabilities of the detector are analyzed. • Chapter 6, lastly, presents a summary of the results and gives a view of the future perspective and challenges of the developed system.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/175786