Master thesis and internship[BR]- Master's thesis : Vibratory disturbance of a medical device - experimental and numerical study[BR]- Internship

Abstract

Proton therapy is an advanced cancer treatment modality that demands precise dosimetry for effective and safe patient outcomes. This thesis investigates the ionization chamber (IC) within the IBA proton therapy machine, which is crucial for measuring the proton dosage administered to patients. However, vibration disturbances can cause significant measurement variations and saturation problems in the IC, potentially compromising treatment accuracy. The study is structured into three parts. The first part involves the numerical modeling the IC, focusing on the geometry and tension of the electrodes, which are configured as sheets. This model aims to understand the baseline behavior of the IC electrodes under pre-tension. The second part investigates the actual dynamic behavior of the IC through Experimental Modal Analysis (EMA). The third part correlates the numerical and experimental results by optimizing the numerical model using a surrogate-assisted genetic algorithm. Results indicate that the tension applied to the sheets significantly influences the modal analysis outcomes. Optimization of the numerical model determined optimal tensions of 77.2 N vertically and 40.1 N horizontally, achieving a global variation of 3.7% between the numerical and experimental natural frequencies. The dynamic analysis also reveals a significant vibratory influence of the IC casing on the measurement sheets, leading to perturbations in electrometer readings. This research contributes to medical physics by providing insights into the behavior of proton therapy dosimetry devices, with the aim of improving the performance and accuracy of proton therapy in clinical settings.