A positron emission tomography (PET) scanner is provided which uses
information on the time-of-flight difference (TOF) between annihilation
radiations for image reconstruction. The scanner has detection time
correction information (memory) corresponding to information on
coordinates in a radiation detection element (e.g., scintillator
crystal), in the depth and lateral directions, at which an interaction
has occurred between an annihilation radiation and the crystal. Reference
is made to the detection time correction information, thereby providing
information on time-of-flight difference with improved accuracy. As such,
an improved signal to noise ratio and spatial resolution are provided for
image reconstruction using time-of-flight (TOF) difference.