Conventional radiotherapy with photons and electrons is the more frequently used therapeutic treatment for malignant tumours. More recently, innovative techniques have been implemented aimed to improve the effectiveness of oncological treatments with ionizing radiations and to minimize the imparted dose to healthy tissue around the tumour. To this respect, binary techniques that combine both the effect of the primary beam and the of recoils products from the nuclear reaction of the beam and a specific target are under investigation as a potential enhancement of the treatment modality when the chemical compound used as a target is selectively deposited into the tumour. One of the most famous and most studied is the Boron Neutron Capture Therapy (BNCT), that exploits the reaction of thermal neutron on 10B. One of these binary techniques that exploits the proton therapy dose conformation and the proton reaction on 11B to enhance the biological effectiveness of the proton treatment is under investigation. In the framework of this scientific debate, the INFN has opened the call ‘NEPTUNE’ with the aim of investing under different points of view the feasibility of the implementation of the Proton Boron Capture Therapy (PBCT) as an enhancement technique for proton therapy. The PBCT radiation field is a mixed and complex field. To this aim, microdosimetry can be a useful technique able to characterize and discriminate its components. Tissue-equivalent Proportional Counters (TEPCs) are the reference devices in experimental microdosimetry. TEPCs with cathode walls loaded with natural boron were previously developed at the Legnaro National Laboratories of INFN for applications in BNCT. Two different detectors with boron have been used in the framework of this thesis, the first one (doped with 50 ppm of 10B and 200 ppm of 11B) is a miniaturized detector able to operate with high intensity beams of proton therapy, the second one (doped with 100 ppm of 10B and 400 ppm of 11B), is bigger and able to measure in medium intensity radiation fields. Thanks to the presence of 11B, both of them can be used to characterize PBCT radiation fields. The miniaturized detector was built several years ago and never used to measure in clinical facilities, for this reason it was needing some intervention in order to bring it back to operation and upgrade it to use it in the clinical environment. The aim of this thesis is the renovation of this existing TEPC to use it in clinical proton beams for the PBCT fields characterisation. During the first tests, some malfunctioning arose that needed some interventions. Moreover, a more compact data acquisition system was studied to reduce the encumbrance of the setup for measurements in clinics. In order to evaluate the success of the interventions, the TEPC has been tested in different radiation fields (gamma rays and neutrons) and its response compared to reference TEPCs of the LNL. The initial planning was to perform measurements in clinical facilities such as the protontherapy centre of Trento and the CNAO, but it was not possible due to the pandemic. The capability of microdosimetry of discriminating the different components of a complex radiation field was investigated on the thermal neutron column of MUNES (MUltidisciplinar Neutron Source for BNCT and Nuclear Waste characterization) at the CN accelerator of INFN-LNL. The methodology implemented for the determination of the BNC component can be exploited for the discrimination of the PBC components in future measurements. The good capability of microdosimetry of discriminating all the different component of a mixed radiation field paves the way to its use to investigate the radiation quality of PBCT radiation fields.
La radioterapia convenzionale che sfrutta fasci di fotoni ed elettroni (RT) rappresenta oggigiorno lo standard terapeutico nel trattamento dei tumori. Nel corso degli anni nuove tecniche sono state investigate ai fini di migliorare l’efficacia del trattamento con radiazioni ionizzanti nell’indurre la regressione del tumore e di minimizzare la dose impartita ai tessuti sani circostanti. A questo scopo sono state studiate tecniche binarie che sfruttano in primo luogo l’irraggiamento con un fascio primario e le capacità ionizzanti di altre particelle generate da una reazione del fascio primario con un particolare bersaglio, selettivamente assorbito dal tessuto tumorale. Una delle più note e studiate è la Boron Neutron Capture Therapy (BNCT), che sfrutta la reazione di neutroni termici sul 10B. Una nuova tecnica che sfrutta un fascio primario di protoni e la reazione di cattura del 11B è stata investigata ma l’aumento dell’efficacia biologica della radiazione ionizzante è una questione aperta e controversa. In questo ambito l’INFN ha indetto una call denominata “NEPTUNE”, un progetto di ricerca che ha come obiettivo l’approfondimento e lo studio della Proton Boron Capture Therapy (PBCT) e i relativi effetti biologici. Il campo di radiazione in PBCT è un campo misto e complesso. A questo proposito la microdosimetria rappresenta uno strumento utile nella caratterizzazione del campo essendo in grado di discriminare le diverse componenti della radiazione (gamma, protoni, particelle alpha e particelle ad alto Z). Contatori a gas tessuto-equivalenti (TEPCs) rappresentano gli strumenti di riferimento per la microdosimetria sperimentale. TEPCs con pareti borate precedentemente costruiti per applicazioni di BNCT, sono disponibili ai Laboratori Nazionali di Legnaro (LNL). In particolare, due TEPCs aventi le plastiche dei catodi caricati con boro naturale, sono stati usati in questo lavoro di tesi, uno dei quali miniaturizzato (dopato con 50 ppm 10B e 200 ppm 11B) costruito per lavorare con fasci clinici ad alta intensità, e il secondo più grande, (dopato con 100 ppm 10B e 400 ppm 11B) che consente di misurare in campi di radiazione di media intensità. Grazie alla presenza del 11B possono essere utilizzati entrambi per la caratterizzazione dei campi di radiazione e per lo studio della fisica della reazione nella PBCT con un approccio microdosimetrico. Il primo miniaturizzato, essendo stato costruito più di 10 anni fa e mai utilizzato per misure in ambito clinico deve essere sottoposto ad interventi di manutenzione per ripristinare il funzionamento e devono essere apportate delle modifiche alle condizioni operative per renderlo adeguato all’uso in fasci clinici. L’obiettivo del progetto di tesi è l’ammodernamento e la rimessa in funzione di tale rivelatore già esistente per l’utilizzo in campi di radiazione usati in PBCT. Durante i primi test sono stati riscontrati dei malfunzionamenti che sono stati ripristinati con alcuni interventi. Inoltre, è stato necessario lo sviluppo di una catena elettronica ad hoc per l’utilizzo del rivelatore. Un nuovo sistema di acquisizione dati più compatto è stato testato al fine di minimizzare l’ingombro del set-up sperimentale per misurazioni in strutture cliniche. Per verificare che le operazioni effettuate sul rivelatore fossero stati risolutive, la sua risposta è stata caratterizzata in diversi campi di radiazioni (sorgente gamma di 137Cs e neutroni veloci) e confrontata con quella di TEPC di riferimento presenti ai LNL. Il prospetto iniziale del lavoro di tesi prevedeva campagne di misura con fasci di protoni terapeutici per applicazioni in PBCT, presso i centri di protonterapia di Trento e del CNAO ma a causa della pandemia non è stato possibile l’accesso a tali strutture. La capacità della microdosimetria sperimentale di discriminare le diverse componenti di campi di radiazione misti è stata testata con un campo di neutroni termici per applicazioni di BNCT, presso la colonna termica del progetto MUNES (MUltidisciplinar Neutron Source for BNCT and Nuclear Waste characterization) all’acceleratore CN dei LNL. Il metodo implementato durante tale campagna di misura per la determinazione della componente BNC potrà essere sfruttato per la determinazione della componente PBC in campi di radiazione per applicazioni in PBCT. La buona capacità della microdosimetria di discriminare varie componenti in campo di radiazione misto apre la strada al suo utilizzo per investigare il possibile uso clinico della PBCT.
A miniaturized tissue-equivalent proportional counter for characterizing boron capture therapy radiation fields
Giustiniani, Giulia
2020/2021
Abstract
Conventional radiotherapy with photons and electrons is the more frequently used therapeutic treatment for malignant tumours. More recently, innovative techniques have been implemented aimed to improve the effectiveness of oncological treatments with ionizing radiations and to minimize the imparted dose to healthy tissue around the tumour. To this respect, binary techniques that combine both the effect of the primary beam and the of recoils products from the nuclear reaction of the beam and a specific target are under investigation as a potential enhancement of the treatment modality when the chemical compound used as a target is selectively deposited into the tumour. One of the most famous and most studied is the Boron Neutron Capture Therapy (BNCT), that exploits the reaction of thermal neutron on 10B. One of these binary techniques that exploits the proton therapy dose conformation and the proton reaction on 11B to enhance the biological effectiveness of the proton treatment is under investigation. In the framework of this scientific debate, the INFN has opened the call ‘NEPTUNE’ with the aim of investing under different points of view the feasibility of the implementation of the Proton Boron Capture Therapy (PBCT) as an enhancement technique for proton therapy. The PBCT radiation field is a mixed and complex field. To this aim, microdosimetry can be a useful technique able to characterize and discriminate its components. Tissue-equivalent Proportional Counters (TEPCs) are the reference devices in experimental microdosimetry. TEPCs with cathode walls loaded with natural boron were previously developed at the Legnaro National Laboratories of INFN for applications in BNCT. Two different detectors with boron have been used in the framework of this thesis, the first one (doped with 50 ppm of 10B and 200 ppm of 11B) is a miniaturized detector able to operate with high intensity beams of proton therapy, the second one (doped with 100 ppm of 10B and 400 ppm of 11B), is bigger and able to measure in medium intensity radiation fields. Thanks to the presence of 11B, both of them can be used to characterize PBCT radiation fields. The miniaturized detector was built several years ago and never used to measure in clinical facilities, for this reason it was needing some intervention in order to bring it back to operation and upgrade it to use it in the clinical environment. The aim of this thesis is the renovation of this existing TEPC to use it in clinical proton beams for the PBCT fields characterisation. During the first tests, some malfunctioning arose that needed some interventions. Moreover, a more compact data acquisition system was studied to reduce the encumbrance of the setup for measurements in clinics. In order to evaluate the success of the interventions, the TEPC has been tested in different radiation fields (gamma rays and neutrons) and its response compared to reference TEPCs of the LNL. The initial planning was to perform measurements in clinical facilities such as the protontherapy centre of Trento and the CNAO, but it was not possible due to the pandemic. The capability of microdosimetry of discriminating the different components of a complex radiation field was investigated on the thermal neutron column of MUNES (MUltidisciplinar Neutron Source for BNCT and Nuclear Waste characterization) at the CN accelerator of INFN-LNL. The methodology implemented for the determination of the BNC component can be exploited for the discrimination of the PBC components in future measurements. The good capability of microdosimetry of discriminating all the different component of a mixed radiation field paves the way to its use to investigate the radiation quality of PBCT radiation fields.| File | Dimensione | Formato | |
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A Miniaturized Tissue-Equivalent Proportional Counter for Characterizing Boron Capture Therapy Radiation Fields.pdf
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https://hdl.handle.net/10589/178109