Range-uncertainty imaging for obtaining dose perturbations in proton therapy

The proton dose distribution of a monoenergetic parallel proton beam in a biological sample (a sheep head in a mold) has been calculated using a Monte Carlo code. The calculations have been performed both including the effect of multiple Coulomb scattering of the protons at the atoms in the phantom and without it. The resulting dose distributions were subtracted from each other and their absolute value was integrated in the direction of the incident proton beam. This projected dose difference was compared to measurements of proton range uncertainties obtained using proton radiography data. A nearly linear relationship between the dose perturbations and the range variations was found which indicates that measured range variations can be used to predict dose perturbations in proton therapy.