3D dose reconstruction for narrow beams using ion chamber array measurements |
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Authors: | Karin Schombourg François O. Bochud René-Olivier Mirimanoff Raphaël Moeckli |
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Affiliation: | 1. Institute of Radiation Physics, University Hospital Centre and University of Lausanne, Grand-Pré 1, CH-1007 Lausanne, Switzerland;2. Radio-Oncology Department, University Hospital Centre and University of Lausanne, Lausanne, Bugnon 21, CH-1011 Lausanne, Switzerland |
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Abstract: | 3D dose reconstruction is a verification of the delivered absorbed dose. Our aim was to describe and evaluate a 3D dose reconstruction method applied to phantoms in the context of narrow beams. A solid water phantom and a phantom containing a bone-equivalent material were irradiated on a 6 MV linac. The transmitted dose was measured by using one array of a 2D ion chamber detector. The dose reconstruction was obtained by an iterative algorithm. A phantom set-up error and organ interfraction motion were simulated to test the algorithm sensitivity.In all configurations convergence was obtained within three iterations. A local reconstructed dose agreement of at least 3% / 3 mm with respect to the planned dose was obtained, except in a few points of the penumbra. The reconstructed primary fluences were consistent with the planned ones, which validates the whole reconstruction process. The results validate our method in a simple geometry and for narrow beams. The method is sensitive to a set-up error of a heterogeneous phantom and interfraction heterogeneous organ motion. |
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