Elevated LET components in clinical proton beams

摘要: This paper assesses the contribution of secondary particles to pencil and passively scattered proton beams, in particular when considering dose-averaged linear energy transfer (LET(d)) biological treatment planning. Proton Monte Carlo simulations are performed water phantoms for two patients, all primary particles, including recoils from inelastic nuclear interactions. Our results show that protons exhibit LET(d) values up a factor 10 higher than those at same depth. Thus, have significant impact on LET(d). Their increases by ∼50% along central axis even >200% penumbra. Furthermore, LET maximum after peak changes 12 15 keV µm(-1) adding contribution. is important modeling with analytical methods. The (A > 3) observed be 1.2% entrance region prostate case. degree damage inflicted remains hard quantify, but discussed basis detailed spectra. highlight role LET-based radiobiological effectiveness calculations therapy analyzing experiments. findings demonstrate inhomogeneities subtle between distributions actively scanned beams.