Abstract: A Proton Computer Tomography (pCT) system comprising: a position tracker, able to reconstruct the proton trajectory within the body; an energy detector, able to reconstruct the proton energy; wherein, the position tracker is made up of four Depleted Monolithic Active Pixel Sensors (DMAPS) placed in pairs at either side of a phantom, and the energy detector is a Super Thin Range Telescope located downstream comprising a plastic-scintillator made of layers of thin polystyrene bars oriented in alternate axis, perpendicular to the proton beam.