Evaluation of the range shifter model for proton pencil-beam scanning for the Eclipse v.11 treatment planning system.

Evaluation of the range shifter model for proton pencil-beam scanning for the Eclipse v.11 treatment planning system. J Appl Clin Med Phys. 2016;17(2):5798 Authors: Matysiak W, Yeung D, Slopsema R, Li Z Abstract Existing proton therapy pencil-beam scanning (PBS) systems have limitations on the minimum range to which a patient can be treated. This limitation arises from practical considerations, such as beam current intensity, layer spacing, and delivery time. The range shifter (RS) - a slab of stopping material inserted between the nozzle and the patient - is used to reduce the residual range of the incident beam so that the treatment ranges can be extended to shallow depths. Accurate modeling of the RS allows one to calculate the beam spot size entering the patient, given the proton energy, for arbitrary positions and thicknesses of the RS in the beam path. The Eclipse version 11 (v11) treatment planning system (TPS) models RS-induced beam widening by incorporating the scattering properties of the RS material into the V-parameter. Monte Carlo simulations with Geant4 code and analytical calcula-tions using the Fermi-Eyges (FE) theory with Highland approximation of multiple Coulomb scattering (MCS) were employed to calculate proton beam widening due to scattering in the RS. We demonstrated that both methods achieved consistent results and could be used as a benchmark for evaluating the Eclipse V-parameter model. In most cases, the V-p...
Source: Journal of Applied Clinical Medical Physics - Category: Physics Authors: Tags: J Appl Clin Med Phys Source Type: research