Optimal Configuration of Proton Therapy Accelerators for Proton Computed Tomography RSP Resolution

TL;DR

This paper shows that reducing the proton beam energy spread in proton computed tomography significantly improves the accuracy of relative stopping power measurements, enhancing imaging quality for medical applications.

Contribution

It demonstrates that lowering the proton energy spread from 1.0% to 0.2% at 70MeV improves RSP resolution in pCT, supported by simulation results.

Findings

RSP resolution as low as 0.2% for cortical bone

RSP resolution up to 1% for lung tissue

Energy spread reduction feasible at clinical proton energies

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 70MeV) down to 0.2%, can be achieved at the proton currents needed for imaging at the Paul Scherrer Institut 230MeV 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.