Abstract: A medical imaging system includes a first tracking detector and a second tracking detector. The tracking detectors are spaced to allow for an object to be present between the first tracking detector and the second tracking detector. The system also includes a residual range detector adjacent the first tracking detector. The residual range detector includes: (1) a scintillator material having a first surface at least partially covered with an anti-reflection material and a second surface facing the first tracking detector and (2) at least one photon detector coupled to the scintillator material at a third surface of the scintillator material different than the first surface and opposite the second surface.