An imaging device includes: a scintillator layer； and an array of photodiode elements； wherein the scintillator layer is configured to receive radiation that has passed through the array of photodiode elements. An imaging device includes: a scintillator layer having a plurality of scintillator elements configured to convert radiation into photons； and an array of photodiode elements configured to receive photons from the scintillator layer, and generate electrical signals in response to the received photons； wherein at least two of the scintillator elements are separated by an air gap. An imaging device includes: a first scintillator layer having a plurality of scintillator elements arranged in a first plane； and a second scintillator layer having a plurality of scintillator elements arranged in a second plane； wherein the first scintillator layer and the second scintillator layer are arranged next to each other and form a non-zero angle relative to each other.
