A radiation imaging device having a moisture impermeable metal layer compressed against a scintillator layer by compressible layer that is mechanically compressed against the scintillator layer. The metal layer is attached to the scintillator substrate by an adhesive ring surrounding the perimeter of the scintillator substrate. The adhesive can further include moisture getter particles. Preferably the metal layer is comprised of aluminum with a thickness between 25 μm and 100 μm to allow the layer to be flexible as free of pinholes to prevent ingress of moisture. The compressible layer can be compressed by the housing to maintain the metal layer in contact with the scintillator layer. The metal layer not only provides moisture protection for the scintillator but also increases the output of the scintillator by reflecting photons generated by the scintillator layer toward the photodetector array of the radiation imaging device.