The radiation detector (10) comprises a scintillator (15) having a first refractive index (ns) for converting incident radiation (RR) received at a first side (S1) of the radiation detector (10) into converted radiation (CR), a photosensor (20) for receiving the converted radiation (CR) from the scintillator (15), and an optical coating layer (25) arranged between the scintillator (15) and the photosensor (20). The scintillator (15) has regions (RR) arranged for being imaged, when impinged by the incident radiation (RR), onto corresponding regions of the photosensor (20). The optical coating layer (25) has a second refractive index (no) lower than the first refractive index (ns) for reflecting the converted radiation (CR) resulting from the incident radiation (RR) impinged on a particular region (A1) of the scintillator (15) and received by a region (A3) of the optical coating layer (25) corresponding to a photosensor region different from the imaged one (A2).