Recent results on the development of a proton computed tomography system

Proton Computed Tomography (pCT) is a medical imaging technique based on the use of proton beams with energies above 200 MeV to directly measure stopping power distributions inside the tissue volume. PRIMA (PRoton IMAging) is an Italian collaboration working on the development of a pCT scanner based on a tracker and a calorimeter to measure single protons trajectory and residual energy. The tracker is composed of four planes of silicon microstrip detectors to measure proton entry and exit positions and angles. Residual energy is measured by a calorimeter composed of YAG:Ce scintillating crystals. A first prototype of pCT scanner, with an active area of about 5 5cm2, has been constructed and characterized with 60 MeV protons at the INFN Laboratori Nazionali del Sud, Catania (Italy) and with 180 MeV protons at Svedberg Laboratory, Uppsala (Sweden). A new pre-clinical prototype with an extended active area up to 20 5cm2, real time data acquisition and a data rate up to 1 MHz is under development. A description of the two prototypes will be presented together with first results concerning tomographic image reconstruction.