Pencil beam approach to proton computed tomography: A performance study

Proton computed tomography (pCT) has the potential to improve the accuracy for proton therapy treatment planning. It will also be useful for pretreatment verification of patient positioning relative to the proton beam. The current approach to pCT requires that individual protons are tracked one by one. This requirement implies the development of fast detectors able to sustain a mean data rate of about 2 MHz. However accelerators used in the framework of hadrontherapy deliver beams of particles with a specific temporal structure, usually optimised for therapy purposes. In some cases a prohibitive data rate has to be handled if this parameter is included in the pCT design specification. Recently the pencil beam (PB) approach to pCT was proposed. Protons are not tracked one by one but a set of particle beams is considered instead. The mathematical formalism of such approach was previously defined however the achievable performances were not yet estimated. In this study these performances were evaluated for different beam parameters (beam size, number of particles per beam, and step-size raster scanning) and a comparison with the classical proton by proton approach is presented.