Abstract: A radiation detector includes a plate-like monocrystal for converting a radiation ray radiated from an object to be examined to a visible ray, a glass plate provided on the monocrystal for transmitting the visible ray generated in the monocrystal and a plurality of photomultipliers arranged on the glass plate for converting the visible ray inputted through the glass plate from the monocrystal to an electrical signal.

Abstract: In a scintillation camera system, a total number of reference light sources such as LEDs is considerably reduced with reference to a total number of photomultiplier tubes, and a defect occurring in either the reference light source, or the photomultiplier tube can be detected. The scintillation camera system includes: a plurality of photomultiplier tubes (4A:4N) for outputting scintillation signals; at least three reference light sources (5A:5B:5C) positioned continuous to the plurality of photomultiplier tubes (4A:4N), one of these plural photomultiplier tubes (4A:4N) being separated from the three reference light sources at an equidistance; a signal processing unit (6) for processing the scintillation signal outputs from the plural photomultiplier tubes (4A:4N) to produce feedback signals; and a controlling unit (7) for controlling radiation from the reference light sources (5A:5B:5C) in response to the feedback signals.