Patent Number: 
Section: abstract

By simultaneously administering a chemical using a nuclear species releasing a single photon (a first chemical) and another chemical using a nuclear species releasing a positron to a subject, the cumulative distributions of the respective chemicals are monitored. A plural number of γ-ray detectors, which are circularly located, and a collimator covering some of the γ-ray detectors and rotates along the front face of the γ-ray detectors are provided. Also, an energy discriminating means for discriminating signals having a single photon γ-ray energy (first signals) from signals having annihilation γ-ray energy (second signals) among all of the signals detected by the detectors is provided. Further, the cumulative position of the first chemical is specified based on the signals corresponding to the γ-ray detectors covered with the rotating collimator from the first signals. On the other hand, the cumulative position of the second chemical is specified by determining the signal almost simultaneously observed form the second signals and the positions thereof on the detectors.