Optimal Targeting of a Tumor through Proton Beam Therapy

Abstract

Publication date: March 2020 the prostate, esophagus, lung and liver. A large number of pediatric patients with central nervous system (CNS) tumors also benefit from PBT (Gondi et al., 2016). Protons interact with matter in three different ways: interactions with atomic electrons, interactions with the atomic nucleus, and interactions with the atom as a whole (Verhey et al., 1998). Protons that interact with the nucleus may produce Bremsstrahlung radiation, but this occurs so infrequently that its effects are negligible. There is also the possibility that protons will collide with an atom and produce secondary protons, neutrons, or excited nuclei, although these interactions are also rare. Protons primarily lose kinetic energy as they traverse matter via inelastic Coulombic interactions with atomic orbital electrons, which also deflect the proton trajectory (Newhauser and Zhang, 2015). The deflection due to a single interaction is generally quite small as the mass of a proton is much larger than that of an electron. However, the cumulative effect of many such interactions can be significant. The most complete theory of multiple Coulombic scattering was proposed by Molière (1947). Many simplifications of this theory have been proposed, although this simplicity often reduces the accuracy in modeling Coulombic scattering at large angles. Gottschalk et al. (1993) approximated Molière’s theory to take the form of a Gaussian function, assuming the small angle approximation in which sin(θ)≈θ: