title: A high-resolution large-area detector for quality assurance in cancer radiation therapy
Creators: name: Maia Oliveira, Andreia Cristina
Publisher: name: Universität Bern
Year: 2024
Subjects: subject: 000 Computer science, knowledge &amp; systems
subject: 530 Physics

description: Medical Physics is a branch of Applied Physics that uses physics principles, methods, and techniques in practice and research for the prevention, diagnosis, and treatment of human diseases with a specific goal of improving human health and well-being.
Physics and medicine have a history of a long-standing and successful symbiosis. Disciplines such as oncology and bio-mechanics, benefit from the improvement of medical practices due to the integration of physics knowledge. Additionally, new techniques emerged from this symbiosis and revolutionized some fields of medicine, such as radiotherapy. Its development was only possible with the discovery of radiation and radioactivity made by Röntgen, Becquerel, the Curies and many other scientists in the years 1895–1898.
Radiotherapy is one of the treatment modalities used to cure or control cancer. It is a field in continuous evolution aiming at prolonging substantially patient life expectancy, alleviating symptoms and improving the quality of life. The technological progress in the transformation of its practices and tools over the past decades is very remarkable. For instance, Cobalt-60 teletherapy machines dominated the X-ray teletherapy after their introduction in the early 1950s. Nowadays, more than 20,000 linacs are installed in hospitals worldwide and are the standard machines used for modern radiotherapy, making all Co-60 sources obsolete.
An advanced modality of cancer radiotherapy is hadron therapy. At the moment, it relies on cyclotrons and synchrotrons to accelerate predominantly protons and carbon ions. This technique offers compelling improvements to conventional treatments due to the possibility of better dose conformity to the tumor. However, treatment with hadrons requires not only an extremely accurate dose calculation but also a precise verification of the dose delivered to the patient with high spatial resolution. Therefore, it is critical to test and validate that the planned dose is delivered exactly where needed in order to deposit energy to each point of the tumor volume while sparing the nearby healthy tissue. This is in turn guaranteed by appropriate QA protocols and a proper set of detectors for measuring the beam parameters, in particular the beam position and the delivered dose distribution.
The present work aims at addressing the question: “How can we improve the QAprocedures by providing higher quality treatment for better patient outcomes and reducing healthcare costs?”. The answer to this question involves the development of advanced detector systems to improve current quality control protocols and dosimetry procedures. Improvements towards an all-in-one system offering precise and real-time measurements with sub-millimeter spatial resolution and uniform response to the beam energy are feasible today. The goal of this project is to facilitate the inclusion of all necessary information in the QA and treatment plan verification to enhance the quality of treatment for patients. A detector that combines a better performance than current commercial devices with significant time reduction at every step of the Machine and Patient QA chain leading to more efficient QA workflow is our ultimate goal. Hence, the purpose of the work presented in this thesis is to develop a novel large area GEM-based detector, the LaGEMPix, providing the 2D dosimetric imaging of ion beams with sub-millimetre spatial resolution. A large sensitive area is required in order to cover the typical radiation field size and evaluate the dose distribution in the entire area.
The research for this thesis was conducted in the context of the PhD in Medical Applications of Particle Physics at the Laboratory for High Energy Physics (LHEP) and Albert Einstein Center for Fundamental Physics (AEC) of the University of Bern. During my PhD, I was based at CERN and worked in HSE-RP-SP (Occupational Health & Safety and Environmental Protection Unit - Radiation Protection group - Special Projects section). This dissertation was carried out following the establishment of a contract for a Portuguese Trainee Programme (entitled Medical Applications Detector Engineering) between the PhD’s degree student, FCT (Portuguese national funding agency for science, research and technology) and CERN, which was carried out at the latter’s facilities. Moreover, this project has received funding from the ATTRACT project funded by the EC under Grant Agreement 777222, which allowed the development of the first LaGEMPix prototype in collaboration with TNO/Holst Center, Eindhoven, The Netherlands. Additionally, this project has been co-funded by the CERN Budget for Knowledge Transfer to Medical Applications.