Conception et caractérisation d'un dosimètre à fibre scintillante pour des applications en imagerie diagnostique et interventionnelle

Authors: Boivin, Jonathan
Advisor: Beaulieu, LucGuillemette, Maxime
Abstract: This thesis deals with the development of a plastic scintillation detector for low energy photon eams. The main goal of the project consists in the design and characterization of this tool in the aim of measuring the radiation dose involved during diagnostic and interventional radiology examinations. The first section is devoted to the design of six different systems and to their performance evaluation when they are exposed to high and low energy radiation. For all photodetectors, the relative standard deviation (RSD) was less than 5% for dose rates higher than 3 mGy/s. This systematic approach identified the photomultiplier tube as the most appropriate photodetector for radiology specific beam qualities. Indeed, its RSD was less than 1% when the dose rate was below 0.10 mGy/s. The result analysis allowed the suggestion of some guidelines for the selection of an appropriate detector for a specific application. The second part was about this detector application to interventional radiology procedures by performing dose measurements at an anthropomorphic phantom surface. Several clinically relevant setups were reproduced to observe the detector’s accuracy and reliability. The RSD remained under 2% when the dose rate was more than 3 mGy/min and about 10% at the lowest dose rate (0.25 mGy/min). Phantom measurements showed a dose rate difference between the detector and the ion chamber of less than 4% when moving the table’s height or rotating the fluoroscope gantry. Moreover, this difference was below 2% for depth dose rate measurements. The last subject of this thesis was about the fundamental physics of scintillation within the plastic scintillators. The factors affecting the light emission were analyzed in order to identify their respective contribution. The detector’s response increased by a factor of about 4 when the tube potential varied between 20 kVp and 250 kVp. The clear optical response was below 0.5%of the scintillator’s light when the fibers were exposed on 10 cm-long by these beam qualities. he ionization quenching phenomenon was also investigated. The signal attenuation varied with the beam energy and reached about 20% for a 20 kVp beam quality. In conclusion, this study suggests that the plastic scintillation detectors can accurately measure the radiation dose involved in diagnostic and interventional radiology, but a rigorous calibration is essential.
Document Type: Thèse de doctorat
Issue Date: 2016
Open Access Date: 24 April 2018
Grantor: Université Laval
Collection:Thèses et mémoires

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