Optimal Configuration of Proton-Therapy Accelerators for Relative-Stopping-Power Resolution in Proton Computed Tomography

Abstract

The determination of relative stopping power (RSP) via proton computed tomography (pCT) of a patient is dependent in part on the knowledge of the incoming proton kinetic energies; the uncertainty in these energies is in turn determined by the proton source-typically a cyclotron. Here, we show that reducing the incident proton beam energy spread may significantly improve RSP determination in pCT. We demonstrate that the reduction of beam energy spread from the typical 1.0% (at 70 MeV) down to 0.2% can be achieved at the proton currents needed for imaging at the Paul Scherrer Institut 250-MeV cyclotron. Through a simulated pCT imaging system, we find that this effect results in RSP resolutions as low as 0.2% for materials such as cortical bone, up to 1% for lung tissue. Several materials offer further improvement when the beam (residual) energy is also chosen such that the detection mechanisms used provide the optimal RSP resolution.

OPTIma: a tracking solution for proton computed tomography in high proton flux environments

“…The beam was modelled using a parameterization of the research beamline at The Christie. A 230 MeV beam was chosen to allow for penetration of up to 220 mm of water while still yielding a reasonable residual energy [15], with an expected beam energy spread of 𝜎 = 1 MeV. A total spot width of 40 mm (Gaussian with 𝜎 = 10 mm) was used based on trials performed by the Christie team to find the maximum scannable beam size.…”

OPTIma: simplifying calorimetry for proton computed tomography in high proton flux environments

“…A parameterization of the expected beam conditions at The Christie research line based on their internal studies was provided. A beam energy of 230 MeV (σ = 1 MeV) was chosen to have sufficient energy to penetrate head sized phantoms while providing an appropriate residual energy for the calorimeter (Herrod et al 2022).…”