1. A proton computed tomography (pCT) detector system, comprising: a first set of tracking detectors on a first side of an object to be imaged; a second set of tracking detectors on an opposite side of the object to be imaged; an imaging source configured to emit protons through the first set of tracking detectors, through and around the object, and through the second set of tracking detectors; a calorimeter configured to detect proton energy emitted from the imaging source; a computer cluster configured to reconstruct an image based on data recorded by the first set of tracking detectors, second set of tracking detectors and calorimeter; and wherein at least one of the first set of said tracking detectors and the second set of tracking detectors include plastic scintillation fibers packed in a row covering the full area of an imaging field and silicon photomultipliers.