Quantitative proton imaging from multiple physics processes: a proof of concept
Résumé
Proton imaging is developed in order to improve the accuracy of charged
particle therapy treatment planning. It makes it possible to directly map the
relative stopping powers of the materials using the information on the energy
loss of the protons. In order to reach a satisfactory spatial resolution in the
reconstructed images, the position and direction of each particle is recorded
upstream and downstream from the patient. As a consequence of individual
proton detection, information on the transmission rate and scattering of the
protons is available. Image reconstruction processes are proposed to make use
of this information. A proton tomographic acquisition of an anthropomorphic
head phantom was simulated. The transmission rate of the particles was used
to reconstruct a map of the macroscopic cross section for nuclear interactions
of the materials. A two-step iterative reconstruction process was implemented
to reconstruct a map of the inverse scattering length of the materials using
the scattering of the protons. Results indicate that, while the reconstruction
processes should be optimized, it is possible to extract quantitative information
from the transmission rate and scattering of the protons. This suggests that
proton imaging could provide additional knowledge on the materials that may
be of use to further improve treatment planning.