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Dose distributions of a proton beam for eye tumor therapy: Hybrid pencil‐beam ray‐tracing calculations
Author(s) -
Rethfeldt Ch.,
Fuchs H.,
Gardey K.U.
Publication year - 2006
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.2168067
Subject(s) - proton therapy , voxel , bragg peak , ray tracing (physics) , optics , path length , physics , pencil (optics) , monte carlo method , dosimetry , radiation treatment planning , beam (structure) , scattering , fluence , range (aeronautics) , pencil beam scanning , imaging phantom , computational physics , nuclear medicine , materials science , radiation therapy , mathematics , computer science , laser , statistics , medicine , composite material , artificial intelligence
For the case of eye tumor therapy with protons, improvements are introduced compared to the standard dose calculation which implies straight‐line optics and the constant‐density assumption for the eye and its surrounding. The progress consists of (i) taking account of the lateral scattering of the protons in tissue by folding the entrance fluence distribution with the pencil beam distribution widening with growing depth in the tissue, (ii) rescaling the spread‐out Bragg peak dose distribution in water with the radiological path length calculated voxel by voxel on ray traces through a realistic density matrix for the treatment geometry, yielding a trajectory dependence of the geometrical range. Distributions calculated for some specific situations are compared to measurements and/or standard calculations, and differences to the latter are discussed with respect to the requirements of therapy planning. The most pronounced changes appear for wedges placed in front of the eye, causing additional widening of the lateral falloff. The more accurate prediction of the dose dependence at the field borders is of interest with respect to side effects in the risk organs of the eye.