A pencil beam approach to proton computed tomography.

Area of Science:

• Medical Imaging
• Particle Physics
• Computational Science

Background:

• Proton computed tomography (pCT) offers superior soft-tissue contrast compared to X-ray CT.
• Current pCT methods track protons individually, posing technical challenges.
• A new paradigm considering proton beams rather than individual particles is explored.

Purpose of the Study:

• To introduce a novel beam-by-beam approach for pCT.
• To redefine pCT reconstruction elements (residual energy, path) for this new approach.
• To propose an analytical image reconstruction algorithm for the beam-by-beam method.

Main Methods:

• Modeled proton beam (PB) propagation using generalized Fermi-Eyges theory with multiple Coulomb scattering (MCS).
• Integrated the PB model into pCT reconstruction, defining a mean beam path.
• Adapted filtered backprojection algorithm for the beam-by-beam approach and simulated image reconstruction.

Main Results:

• The PB model showed good agreement for mean values but depth-dependent discrepancies (2-8%) in distribution spread compared to Monte Carlo simulations.
• Images reconstructed with the beam-by-beam approach exhibited higher noise than those from the classical single-proton method.
• The study validated the analytical reconstruction algorithm's capability to incorporate MCS.

Conclusions:

• The beam-by-beam approach offers a potential solution to technical limitations of current pCT methods.
• An analytical algorithm is presented for this new approach, accounting for MCS during reconstruction.
• Further research is needed to fully assess the image quality and limitations of the beam-by-beam pCT method.