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Dose delivered to a lung-like phantom in a ‘double dynamic system’

The success of radiation therapy critically depends on the ability to deposit a sufficient dose in the tumour to sterilize it while at the same time minimizing the dose in the surrounding healthy tissue to reduce the risk of clinically relevant complications. Proton therapy has physical advantages over the conventional photon therapy, as most of the dose is deposited at the end of the proton range (Bragg peak). This requires millimetre accuracy of the Bragg peak localization in order to avoid too high dose in healthy tissue and too low dose in the tumor. In practice, errors occur due to range uncertainties, positioning errors, organ motion and anatomical changes during the course of treatment. The correct delivery verification of the radiation dose is therefore essential to ensure high treatment quality. The treatment of moving tumors (e.g. in the lungs) with particle therapy is a real challenge as the motion can easily result in too low dose in the tumor and an associated too high dose in the surrounding healthy tissue. The verification is therefore even more important than for static tumors and faces the same challenge as the complex irradiation strategies for moving tumors that are currently being developed.

The goal of the project is to verify, by means of Geant4-based simulations, the dose distribution delivered in the ‘double dynamic system’, i.e. delivered by a dynamic (scanning) proton pencil beam on a dynamic inhomogeneous (PMMA with lung- and a tumor-like) target imitating the respiratory motion (breathing patient). It is expected that in treatment of lung cancer patient with a scanning proton beam the effect of motion in the accumulated dose needs to be taken into account.

The simulations will be performed with Geant4-based simulation toolkit and the results will be compared to the simulations performed with the RayStation Treatment Planning Software (available at UMCG Groningen) for the same geometry. Both simulation results will be verified with the experimental data obtained in February 2012 during the experiment at the KVI-CART/RuG, Groningen, in collaboration with researchers from Osaka University, Japan.

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Last modified:03 April 2014 1.36 p.m.