Pet device

A PET device comprising

• a detector portion having multiple detector rings on which multiple photon detectors each for detecting photons traveling from a measurement field of view containing a center axis are disposed on said slice plane perpendicular to said center axis, said multiple detector rings being stacked in layers in a direction parallel to said center axis,
• a rotating ceptor disposed rotatably about said center axis near said measurement field of view of part of said multiple photon detectors which constitute each of said multiple sets of detector rings, said rotating ceptor including multiple shield plates for collimating and passing therethrough only those photons that have traveled approximately parallel to said slice plane,
• radiation source support means for detachably supporting a calibration positron emission radiation source at a position at which photons produced by positrons emitted from the positron emission radiation source are collimated by said rotating ceptor in all directions parallel to said slice plane,
• rotating ceptor position determination means for determining whether said rotating ceptor is present near said measurement field of view of at least one of a pair of photon detectors when the pair of photon detectors of the photon detectors included in said detector portion simultaneously counts photon pairs,
• two-dimensional projection data accumulating means for accumulating simultaneous count information on photon pairs detected by said pair of photon detectors when said rotating ceptor position determination means has determined that said rotating ceptor is present near said measurement field of view of at least one of said pair of photon detectors,
• three-dimensional projection data accumulating means for accumulating simultaneous count information on photon pairs detected by said pair of photon detectors when said rotating ceptor position determination means has determined that said rotating ceptor is not present near any one of said measurement fields of view of said pair of photon detectors, and
• image reconstruction means for reconstructing an image representing a spatial distribution of frequencies of occurrence of photon pairs in said measurement field of view in accordance with the two-dimensional projection data produced by accumulating simultaneous count information by means of said two-dimensional projection data accumulating means and the three-dimensional projection data produced by accumulating simultaneous count information by means of said three-dimensional projection data accumulating means.