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Range precision of therapeutic proton beams
Author(s) -
Schaffner Barbara
Publication year - 1998
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 - 10.1118/1.598334
Subject(s) - monte carlo method , proton therapy , stopping power , range (aeronautics) , calibration , radiation treatment planning , beam (structure) , position (finance) , proton , dosimetry , computational physics , physics , mathematics , materials science , nuclear medicine , optics , statistics , radiation therapy , nuclear physics , medicine , finance , detector , economics , composite material
The precision of proton radiotherapy treatment planning is limited mainly by the precision achieved in the determination of relative stopping power values of human tissue and the accuracy of the analytical dose calculation model. A stoichiometric calibration curve for the conversion from CT values into relative proton stopping power values was defined theoretically and its accuracy was checked by measurements on biological tissue samples. Including the effects of beam hardening on the CT values an upper limit of 2–4 mm for the uncertainty in the position of the distal falloff of the dose distribution was estimated. Different dose calculation algorithms for the spot‐scanning technique have been developed. Their accuracy was evaluated by a comparison to Monte Carlo simulated dose distributions. Large errors due to inaccuracies of the planning algorithm are encountered mainly in the presence of density heterogeneities where the range of the protons is poorly defined. A quick estimation of the expected range dilution as a function of the beam incidence angle can be used to identify critical areas. Besides uncertainties in the treatment planning itself one has to consider the effects of setup uncertainties on the dose distribution. A suggestion is presented on how to deal with uncertainties during the treatment planning process.