Gamma ray scintillation detector preserving the original scintillation light distribution

An apparatus to detect gamma rays, comprising:

• a scintillator, a position sensitive photo sensor and at least one scintillation-light-incidence-angle-constraining, SLIAC, element, wherein
• the scintillator has a plurality of faces;
• and
• wherein the position sensitive photo sensor is arranged to detect scintillation photons exiting a scintillation photons transparent face of the scintillator, and
• wherein at least a portion or the whole of at least one scintillator face is covered with an absorbing layer, which is arranged to absorb scintillation photons created by scintillation events due to the interaction of incoming gamma rays with the scintillator, and
• wherein the scintillation-light-incidence-angle-constraining, SLIAC, element is optically coupled between a scintillation photons transparent face of the scintillator and the position sensitive photo sensor and the scintillation-light-incidence-angle-constraining, SLIAC, element is configured to guide the scintillation photons exiting the scintillator towards the position sensitive photo sensor, and
• wherein the scintillation-light-incidence-angle-constraining, SLIAC, element restricts the maximum allowed half light acceptance angle for the scintillation light hitting the position sensitive photo sensor to less than 45°.