Systems, methods, and devices involving segmented radiation detectors are provided. For example, a segmented radiation detector may include a segmented scintillator and an optical-to-electrical converter. The segmented scintillator may have several segments that convert radiation to light, at least one of which may detect radiation arriving from an azimuthal angle around an axis of the segmented scintillator. The optical-to-electrical converter may be coupled to the segmented scintillator. The optical-to-electrical converter may receive the light from the segments of the segmented scintillator and output respective electrical signals corresponding to the amount of radiation detected by each segment.