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Evaluation des algorithmes de calcul de dose pour les faisceaux d’électrons utilisés en radiothérapie : comparaison aux mesures par films radiochromiques

Abstract : In radiotherapy, the dose calculation accuracy is crucial for the quality and the outcome of the treatments. The purpose of our study was to evaluate the accuracy of dose calculation algorithms for electron beams in situations close to clinical conditions. A new practical approach of radiochromic film dosimetry was developed and validated especially for difficult situations. An accuracy of 3.1% and 2.6% was achieved for absolute and relative dosimetry respectively. Using this technique a measured database of dose distributions was developed to form the basis of several fast and efficient QualityAssurance tests. Such tests are intended to be used also when the dose calculation algorithm is changed or the Treatment Planning System replaced. Pencil Beam and Monte Carlo dose calculations were compared to the measured data for simple geometrical phantom setups. They both gave similar results for obliquity, surface irregularity and extended SSD tests but the Monte Carlo calculation was more accurate in presence of heterogeneities. The same radiochromic film dosimetry method was applied to film cuts inserted into anthropomorphic phantoms providing a 2D dose distribution for any transverse plan. This allowed us to develop clinical test that can be also used for internal Quality Assurance purposes. As for simpler geometries, the Monte Carlo calculations showed better agreement with the measured data than the Pencil Beam calculation, especially in presence of heterogeneities such as lungs, cavities and bones.
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https://tel.archives-ouvertes.fr/tel-00718649
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Submitted on : Tuesday, July 17, 2012 - 5:26:18 PM
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Jad El Barouky. Evaluation des algorithmes de calcul de dose pour les faisceaux d’électrons utilisés en radiothérapie : comparaison aux mesures par films radiochromiques. Ingénierie biomédicale. Université Paris Sud - Paris XI, 2011. Français. ⟨NNT : 2011PA11T002⟩. ⟨tel-00718649⟩

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