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La mesure et la modélisation des faisceaux de photons de petite taille pour l'IMRT et la radiochirurgie

Abstract : The advanced techniques of radiotherapy use very small fields in case small tumors such as in the brain to irradiate precisely the lesion. This work concerns the measurement absorbed dose in small field of 0.5×0.5cm² to 3×3cm². However, the measurement dose in small fields is characterized by high gradient dose and a leak of lateral electronic equilibrium. That requires use a detector having an adapted sensitive volume and adapted spatial resolution. The detectors marketed are not perfectly compatible with these conditions. Actually, there is no international methodological consensus, nor a metrological reference for measurement dose in small fields. The IAEA (International Atomic Energy Agency) protocol 398 used to calculate the absorbed dose at 10cm×10cm isn't suitable for small fields. In absence a referenced detector, the dosimetric data measurement is verified using a Gafcromic films due to its excellent spatial resolution. We measure using conventional detectors (ionization chambers and/or Gafcromic film) the leakage dose at a point outside of irradiated field. The dosimetric data such as output factor OF, depth PDD percentage depth dose and dose profile OAR were also carried out by the diode. The correlation between the on-axis dose and off-axis dose is the subject of our study. This study proposes an experimental method to calculate the on-axis dose in small field for stereotactic radiotherapy. The method is based on the out of field leakage measurement. This model can be used to validate dose and output factor measurement. The experimental validation of the present method was performed for square and rectangular fields with sizes ranging from 0.5cm×0.5cm to 10cm×10cm.
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https://tel.archives-ouvertes.fr/tel-01825782
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Submitted on : Thursday, June 28, 2018 - 3:57:39 PM
Last modification on : Tuesday, July 21, 2020 - 3:59:06 AM
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  • HAL Id : tel-01825782, version 1

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Talal Abdul Hadi. La mesure et la modélisation des faisceaux de photons de petite taille pour l'IMRT et la radiochirurgie. Traitement du signal et de l'image [eess.SP]. Université Paul Sabatier - Toulouse III, 2017. Français. ⟨NNT : 2017TOU30056⟩. ⟨tel-01825782⟩

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