Polynomial modelling of proton trajectories in homogeneous media for fast most likely path estimation and trajectory simulation.

Polynomial modelling of proton trajectories in homogeneous media for fast most likely path estimation and trajectory simulation.
Phys Med Biol. 2019 Aug 20;:
Authors: Krah N, Letang JM, Rit S
Abstract
Protons undergo many small angle deflections when traversing a medium, such as a patient. This effect, known as multiple Coulomb scattering (MCS), leads to degraded image resolution in proton radiography and computed tomography (CT) and to lateral spreading of the dose distribution in proton therapy. To optimally account for MCS in proton imaging, the most likely path (MLP) of a proton is estimated based on its position and propagation angle measured in front of and behind the object. In this work, we propose a functional which quantifies the likelihood of a proton trajectory and study how it can be used to model proton trajectories in a homogeneous medium. We focus on two aspects: first, we present an analytical method to quickly generate proton trajectories in a homogeneous medium based on the likelihood functional and validate it through Monte Carlo simulations. It could be used for fast generation of proton CT images without a full Monte Carlo simulation, or potentially to complement the components in a treatment planning Monte Carlo which simulate MCS. 
 Second, by maximising the likelihood functional, we derive an expression for the MLP which is equivalent to the conventional ones reported in the literature yet computa...

Source: Physics in Medicine and Biology - August 19, 2019 Category: Physics Authors: Krah N, Letang JM, Rit S Tags: Phys Med Biol Source Type: research