Proof-of-Principle results of proton computed tomography

A proof of principle proton Computed Tomography (pCT) apparatus, based on a silicon microstrip tracker and a YAG:Ce calorimeter, has been manufactured. Tests with a 175 MeV proton beam at The Svedberg Laboratory (TSL, Uppsala, Sweden) aiming at collecting data for reconstructing a tomographic image have been carried out. Algebraic iterative reconstruction methods, together with the most likely path formalism, have been used to obtain non-homogeneous phantom images to eventually extract density and spatial resolutions. The heavy computation load required by the algebraic algorithms has been approached fully exploiting the high calculation parallelism of Graphics Processing Units. The dose delivered to the phantom during the tomographic data-taking has been estimated as well as spatial and density resolutions dependence on dose. An upgraded pCT apparatus with an extended field-of-view able to reconstruct objects of the size of a human head, thus suitable to be used in pre-clinical tests, is now at an advanced construction stage. Using this new apparatus radiographies of an anthropomorphic phantom have been taken at the proton experimental beam line of the `Trento Proton Therapy Center' (Trento, Italy).