PET system with a positron lifetime measurement function and positron lifetime measurement method in a PET system

A PET system with a positron lifetime measurement function, comprising:

• a first gamma ray detector configured to receive, from an imaging target containing a nuclide that goes into an excited state of a daughter nucleus by undergoing beta decay and that then, subsequently to emission of a positron resulting from the beta decay, emits a deexcitation gamma ray when transiting into a ground state of the daughter nucleus, three annihilation gamma rays resulting from the positron annihilating with an electron, the first gamma ray detector thereby detecting the three annihilation gamma rays;
• a second gamma ray detector provided separately from the first gamma ray detector and configured to detect the deexcitation gamma ray;
• and
• a processor configured
• to derive, in three dimensions, a distribution state of the nuclide in the imaging target and
• to determine information on a positron lifetime in association with a derived distribution position
• based on
• a detected energy and a detection position of each of the annihilation gamma rays as detected by the first gamma ray detector and
• a detection time point of the annihilation gamma rays as detected by the first gamma ray detector and a detection time point of the deexcitation gamma ray as detected by the second gamma ray detector, wherein
• the first gamma ray detector outputs a detection signal of a gamma ray that is incident on the first gamma ray detector, and
• in response to the second gamma ray detector detecting the deexcitation gamma ray, the processor acquires from the detection signal the detected energy and the detection position of each of the annihilation gamma rays and the detection time point of the annihilation gamma rays.