Influence de la composition chimique des tissus humains sur les dépôts de dose en hadronthérapie

Abstract : To compute the dose distribution, treatment planning systems require the exact anatomical location of tissues provided by computed tomography (CT) and the exact range of hadron beams in tissues based on the water equivalent ratio (WER). Since CT numbers are determined with x-rays and with an energy different from that used in hadrontherapy, a relation between CT numbers and the WER must to be established. We propose a determination of the WER with a Monte-Carlo simulation (GEANT4). We have determined the WER for 76 human tissues for a 135 MeV proton beam and for a 290 MeV/A carbon beam. The difference between the stoichiometric calibration and the simulated WER is lower than 1%. An additional 2% uncertainty that arises from the uncertainty in the CT numbers measurement should also be considered. The calculated WER were used to convert the deposited energy curve into the human tissue deposited energy curve for a 135 MeV proton beam and for a 290 MeV/A carbon beam. For both beams, the difference between the rescaled Bragg peak location and the one from the simulated curve is lower than 0.5 mm over the whole range of CT numbers. The differences between the maximum deposited energy can reach 3% for the proton beam in bones and vary between 1.5% and 3.5% for all tissues for the carbon beam. The scaling in two dimensions can be improved by using an additionnal factor that takes the scattering into account.
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Submitted on : Friday, July 11, 2008 - 10:36:28 AM
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E. Batin. Influence de la composition chimique des tissus humains sur les dépôts de dose en hadronthérapie. Physique Nucléaire Théorique [nucl-th]. Université de Caen, 2008. Français. ⟨tel-00295058⟩

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