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Développement et validation expérimentale d’un outil de détermination de la dose hors-champ en radiothérapie

Abstract : Over the last two decades, many technical developments have been achieved on intensity modulated radiotherapy (IMRT) and allow a better conformation of the dose to the tumor and consequently increase the success of cancer treatments. These techniques often reduce the dose to organs at risk close to the target volume; nevertheless they increase peripheral dose levels. In this situation, the rising of the survival rate also increases the probability of secondary effects expression caused by peripheral dose deposition (second cancers for instance). Nowadays, the peripheral dose is not taken into account during the treatment planification and no reliable prediction tool exists. However it becomes crucial to consider the peripheral dose during the planification, especially for pediatric cases. Many steps of the development of an accurate and fast Monte Carlo out-of-field dose prediction tool based on the PENELOPE code have been achieved during this PhD work. To this end, we demonstrated the ability of the PENELOPE code to estimate the peripheral dose by comparing its results with reference measurements performed on two experimental configurations (metrological and pre-clinical). During this experimental work, we defined a protocol for low doses measurement with OSL dosimeters. In parallel, we highlighted the slow convergence of the code for clinical use. Consequently, we accelerated the code by implementing a new variance reduction technique called pseudo-deterministic transport which is specifically with the objective of improving calculations in areas far away from the beam. This step improved the efficiency of the peripheral doses estimation in both validation configurations (by a factor of 20) in order to reach reasonable computing times for clinical application. Optimization works must be realized in order improve the convergence of our tool and consider a final clinical use.
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Submitted on : Friday, March 15, 2013 - 3:27:13 PM
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Igor Bessières. Développement et validation expérimentale d’un outil de détermination de la dose hors-champ en radiothérapie. Autre [cond-mat.other]. Université Paris Sud - Paris XI, 2013. Français. ⟨NNT : 2013PA112016⟩. ⟨tel-00801314⟩

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