Dosimetry studies for radiation therapy with photons and radiobiology using low-energy protons

Resumen

This thesis work is based on the knowledge about the interaction of radiation with matter to develop new methods with the aim of applying them to the radiation therapy and radiobiology, specifically to dose measurements in radiation therapy, dose measurements with low energy proton beams and DNA damages caused by these protons on cancer cells. Thus, it presents two main parts: one regarding the presentation of a novel prototype based on silicon detector technology for treatment verification in radiotherapy, and the other, the instrumentation and the methodology for low energy proton beam characterization, dosimetry, with a special focus on the response of radiochromic films to protons, and finally the application on biological samples to study the DNA damage produced by protons. The first part of this work presents a novel system with improved performances with respect to a previous system which was filed for a patent in September Ministry of Industry, Tourism and Commerce, under reference number P201101009 [1]. This work was also published in specialized reviews and thesis works [2], [3], [4], [5]. The characterization of the response in terms of absorbed dose in standard conditions of this novel detector was presented in [6], [7] and [8]. Here, this study was repeated because of some modifications introduced in the electronics and in one of the detector's cables, which was modified due to a breakdown. In this thesis, the characterization of the system in treatment conditions has been studied, furnishing the calibration in absorbed dose to water needed for the The characterization and the calibration in absorbed dose to water of the system in treatment conditions, and subsequently, the application of this system for complex treatment verification providing a 2D dose map reconstruction in the axial plane is studied and presented for the first time in this thesis work. The second part of the work presents the installation of instrumentation for dosimetry and radiobiology studies using proton beams produced by the 3 MV Tandem accelerator at Centro Nacional de Acceleradores, Sevilla. The original work within this part can be divided into three main points: i) the elaboration of a protocol which allows to obtain a beam profile with low current and an homogeneous profile over the whole sample surface; ii) dosimetry with low energy protons using ionization chambers and radiochromic films; iii) study of the dosimetry at the Bragg peak. Last, the application of these studies to the irradiation of cell cultures is presented and preliminary results of the DNA damage produced by protons are shown. Part of this work was published in a peer-review journal [9]. Bibliography [1] Patent at the oemp - oficina española de patentes y marcas-- ministry of industry & commerce: Number p201101009 (13/09/2011). [2] Z. A. Haidar, A 2D Silicon Detector System for Complex Radiotherapy Treatment Verification. PhD thesis, University of Seville, 2012. [3] Z. Abou et al., Output factor determination for dose measurements in axial and perpendicular planes using a silicon strip detector, Phys. Rev. STAB, vol. 15, p. 042802, 2012. [4] M. A. Cortés-Giraldo, Desarrollos y aplicaciones de GEANT4 para radioterapia y microdosimetría en detectores y circuitos integrados. PhD thesis, University of Seville, 2011. [5] A. Bocci. et al. et al., Silion strip detector for a novel 2d dosimetric method for radiotherapy treatment verification, NIM A, vol. 673, pp. 98--106, 2012. [6] M. A. G. Alvarez et al., Novel dual single sided silicon strip detector chip for radiotherapy verification, Proceedings of Science, p. 049, 2013. [7] A. Selva, Characterization of a silicon strip detector for radiotherapy use, Master's thesis, University of Padova, 2014 [8] M. Ovejero, Perfeccionamiento de un Sistema para Verificar Tratamientos de Radioterapia y diseño del nuevo entorno VeRa. PhD thesis, University of Seville, 2015. [9] M. C. Battaglia et al., Dosimetric response of radiochromic films to protons of low energies in the bragg peak region, Physical Review Accelerators and Beams, 2016.